ALBERT

Notes: Polymerization of butadiene by bis(h3-allylnickel trifluoroacetate) in benzene and o-dichlorobenzene solvents yields an equibinary 1,4-polybutadiene, containing equal amounts of cis and trans isomers. Initiation proceeds by addition of the allylic moiety of the initiator to a butadiene molecule. The rate of initiation is high enough to ensure complete consumption of the catalyst for a monomer/catalyst molar ratio of about 10 at 5°C. The propagation exhibits the characteristics of a “living” polymerization: the molecular weight is proportional to the conversion, and at the end of the reaction, the average degree of polymerization is equal to the monomer/catalyst molar ratio. Living polybutadienyl-nickel trifluoroacetate is able to reinitiate not only butadiene polymerization but also allene polymerization. However, for high [monomer]/[catalyst] ratios, conversion-dependent transfer reactions limit the molecular weight to 7000 in benzene and to 70,000 in bulk polymerization in the presence of small amounts of o-dichlorobenzene.

Notes: In bulk polymerization and copolymerization of trioxane with ethylene oxide, it has been shown that p-chlorophenyldiazonium hexafluorophosphate is a superior catalyst as compared to boron trifluoride dibutyl etherate (BF3 · Bu2O). Polymers and copolymers of significantly higher molecular weight have been obtained. The higher molecular weight has been attributed primarily to less inherent chain transfer during propagation, which in turn can be attributed to the superior gegenion PF6-.The polymerization proceeds via a clear period followed by sudden solidification. Faster polymerization and higher molecular weight polymers have been observed for homopolymerization than for copolymerization. The polymer yield obtained after solidification is determined by both rate of polymerization and rate of crystallization of polymers. These rates, in turn, are dependent on the catalyst concentration. The molecular weight is determined both by polymer yield and extent of inherent chain transfer. In the range of monomer to catalyst mole ration [M]/[C] = (0.5-20) × 104 investigated, it has been found that in the higher range, the polymer yield is independent of the catalyst concentration and the extent of inherent chain transfer is inversely proportional to the half power of catalyst concentration: [M]/[C] = (0.5-8) × 104 for homopolymerization and (0.5-3) × 104 for copolymerization with 4.2 mole % ethylene oxide. In the lower range, the yield decreases with catalyst concentration and the extent of inherent chain transfer is inversely proportional to higher power of catalyst concentration. The dependence of molecular weight of polymers on catalyst concentration has been shown to be a complex one. The molecular weight goes through a maximum as the catalyst concentration is decreased. The maximum molecular weights have been obtained at [M]/[C] ≈ 8 × 104 for homopolymerization and ∼3 × 104 for copolymerization with 4.2 mole % ethylene oxide. Prior to reaching maximum the molecular weight is inversely proportional to the half power of catalyst concentration indicating it is primarily controlled by inherent chain transfer. Upon further decrease of catalyst, molecular weight decreases as a result of both a decrease in polymer yield and an increase in inherent chain transfer.In copolymerization of trioxane and ethylene oxide, it has been ascertained that methylene chloride exhibits a favorable solvating effect. Although higher inherent chain transfer takes place in copolymerization than in homopolymerization, the extent of chain transfer is independent of ethylene oxide concentration. The difference in polymer yield and molecular weight a t different ethylene oxide concentrations is attributed primarily to the difference in kp/kt ratio. It also has been demonstrated that end capping of polymer chains can be accomplished by the use of a chain transfer agent - methylal.

Notes: A theoretical description of chain-growth polymerization is presented in terms of a distributed parameter model. Analysis of molecular distributions of macromolecular materials results in graphical procedures capable of yielding absolute values for kinetic constants. A steady-state analysis of styrene polymerizations initiated with 2,2′-azobisisobutyronitrile in toluene yielded the following rate information, which is in qualitative agreement with previously published results: f = 0.4; Ki = 1.58 × 1015 exp {-30,800/RT} Ktc/K2p = 1.10 × 10-5 exp {13,200/RT}.

Notes: The concentration of water in purified and BaO-dried α-methylstyrene was found to be 1.1 × 10-4M. The radiation-induced bulk polymerization of the α-methylstyrene thus prepared was studied in the temperature range of -20°C to 35°C. The polymerization rate varied as the 0.55 power of the dose rate. The theoretical molecular weights and molecular weight distribution were calculated from a proposed kinetic scheme and these values were then compared with those found experimentally. The agreement between these two was reasonably close, and therefore it was concluded that, from the molecular weight distribution point of view, the proposed kinetic scheme for the cationic polymerization of α-methylstyrene is an acceptable one. The rate constant for chain transfer to monomer kf changed with temperature and was found to be responsible for the decrease in the molecular weight of the polymer with increase in temperature. kf and kp at 20°C were found to be 0.95 × 104 l./mole-sec and 0.99 × 106 l./mole-sec, respectively.

Notes: When a chain length dependence of polymer-polymer termination is given by kt,ns = const. (n-2a + s-2a) where n and s are the chain lengths for the polymer radicals and a is parameter, an instantaneous weight fraction of the non-reacting polymers is derived as: \documentclass{article}\pagestyle{empty}\begin{document}$$ g(n) = \frac{{n^{2 - 2a} \exp \left\{ { - [phn^{1 - 2a} /(1 - 2a)] - h\bar kn} \right\}}}{{p_n \int_1^\infty {n^{1 - 2a} \exp \left\{ { - [phn^{1 - 2a} /(1 - 2a)] - h\bar kn} \right\}dn} }} $$\end{document} where h and k̄ are the kinetic parameters, p is a parameter depending on a, and pn is instantaneous number-average chain length. Such a weight fraction corresponds to the experimental one over a wide range of conversion in the polymerization of styrene. On the scope of this correspondence, the polymer-polymer termination rate is estimated as: k̄t = 8πR0D1/100 ( = 4πRsDs) where R0 is reaction radius between monomer radicals and D1 is the diffusion coefficient of the monomer; Rs is reaction radius between segment radicals with n ≅ 100 and Ds is the diffusion coefficient of the segment. The Fujita-Doolittle theory applies to such a rate. Further, the rate also yields 1.5 × 1071./mole-sec, which is the observable extent at conversions less than 0.2.

Notes: The radiation-induced polymerization of methyl methacrylate (MMA) absorbed on such inorganic substances as silica gel, white carbon, silicic acid anhydride, zeolite, and activated alumina was carried out to compare with the case of styrene. The rate of radiation-induced polymerization adsorbed on inorganic substances was high compared with that of radiation-induced bulk state polymerization, as was the case with styrene. Inorganic substrates which contain aluminum as a component element are more likely to be grafted than those which consist of SiO2 alone, as with styrene. The molecular weight distribution of unextractable polymer and extractable polymer differs, depending on the type of inorganic substance. Experiments by a preirradiation method were carried out in case of silica gel, white carbon, and silicic acid anhydride. GPC spectra of the polymer obtained were different from those of polymer formed by the simultaneous irradiation method. It appears that all the unextractable polymer is grafted to the inorganic surface with chemical bond.

Notes: The photopolymerization of vinyl fluoride, in the presence of peroxide, was studied in dimethyl sulfoxide (DMSO) solution and in bulk. It was found that high rates of reaction could be obtained in spite of the fact that the polymer precipitates at an early stage. By continuous supply of monomer the precipitated polymer was converted into a transparent bulk polymer.

Notes: A method based on infrared spectral changes in thin films was devised and used to evaluate the relative effectiveness of various types of additives on photodegradative processes in an olefinically unsaturated polymer. Nickel chelates of the thiobisphenol-amine complex type are shown to be quantitatively more effective in retarding the photodegradation of these polymers than other additives having greater singlet oxygen quenching efficiencies, ultraviolet absorption, or radical antioxidant properties. Photosensitization with a singlet oxygen sensitizer (fluoranthene) rapidly produces degradative effects in the polymer which are identical with those of its direct degradation by light. The sensitized effects are also retarded by the nickel chelates. Photosensitization by a hydrogen atom-abstracting sensitizer (a benzophenone) proved considerably less effective. The effectiveness of the nickel complexes appears to be due to a combination of their ability to quench singlet oxygen and precusor excited states and their relative stability under photoexposure conditions.

Notes: A soluble and self-crosslinkable linear copolymer with pendant epoxy and pyridyl groups was obtained from glycidyl methacrylate (M1) and 2-vinylpyridine (M2) or 2-vinyl-5-ethylpyridine (M2) by the action of azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C: r1 = 0.510, r2 = 0.620 with 2-vinylpyridine and r1 = 0.57, r2 = 0.62 with 2-vinyl-5-ethylpyridine. These were consistent with the calculated values with the reported Q and e values for these monomers. The intrinsic viscosities of the copolymers with 2-vinylpyridine and with 2-vinyl-5-ethylpyridine were found to be 0.17-0.19 and 0.26-0.38, respectively, in tetrahydrofuran at 30°C; they were independent of the copolymer composition. The copolymers were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents.

Notes: 1,3-Bis(p-phenoxybenzenesulfonyl)benzene and 4,4′-diphenoxydiphenyl sulfone were polymerized with isophthaloyl and terephthaloyl chloride in Friedel-Crafts type polymerizations. These polymers had 2,4-diphenoxyacetophenone in the backbone. The acetyl group was then converted into an acetylene group. They were crosslinked effectively by cyclization of the acetylene groups with a catalyst or by cyclo-addition with bisnitrile oxides.

Notes: Poly(vinyl alcohol) (PVA) films having different crystallinities were prepared by elongating PVA films to different degrees and heating the films with and without elongation treatment at several temperatures between 60 and 200°C. Then, they were dehydrated by heating from 80°C to 230 or 330°C in hydrogen chloride gas. Infrared spectral measurements were made on the dehydrated PVA films obtained. Absorbances of the absorption bands due to several groups seen in the infrared spectra depended only on the density of original PVA films, regardless of its degree of elongation. From these dependences, it was found that the dehydration reaction progressed more easily in the crystalline region than in the amorphous region, that the aromatic rings with four or five adjacent hydrogen atoms were formed mainly in the amorphous region and those with two adjacent hydrogen atoms in the crystalline region, and that the aromatic rings with two isolated hydrogen atoms were formed in both the amorphous and crystalline regions. Relative concentrations of the groups of which the dehydrated PVA were composed were estimated. Comparison of the numbers of carbon atoms among the composing groups indicated that the main groups were the methylene group and the aromatic ring.

Notes: 2-Pentene and 2-hexene were found to undergo monomer-isomerization copolymerizations with 2-butene by Al(C2H5)3-VCl3 and Al(C2H5)3-TiCl3 catalysts in the presence of nickel dimethylglyoxime or transition metal acetylacetonates to yield copolymers consisting of the respective 1-olefin units. For comparison, the copolymerizations of 1-pentene with 1-butene and 1-hexene with 1-butene by Al(C2H5)3-VCl3 catalyst were also attempted. The compositions of the copolymers obtained from these copolymerizations were determined by using the calibration curves between the compositions of the respective homopolymer mixtures and the values of D766/D1380 in the infrared spectra. The monomer reactivity ratios for the monomer-isomerization copolymerizations of 2-butene (M1) with 2-pentene and 2-hexene, in which the concentrations of both 1-olefins calculated from the observed isomer distribution were used as those in the monomer feed mixture, and for the ordinary copolymerizations of 1-butene (M1) with 1-pentene and 1-hexene by Al(C2H5)3-VCl3 catalyst were determined as follows: 2-butene (M1)/2-pentene (M2): r1 = 0.14, r2 = 0.99; 1-butene (M1)/1-pentene (M2): r1 = 0.30, r2 = 0.74; 2-butene (M1)/2-hexene (M2): r1 = 0.11, r2 = 0.62; 1-butene (M1)/1-hexene (M2): r1 = 0.13, r2 = 0.90.

Notes: Highly active catalysts for low pressure ethylene polymerization are formed when chromocene, bis (benzene)- or bis (cumene)-chromium or tris- or bis (allyl)-chromium compounds are deposited on high surface area silica-alumina or silica supports. Each catalyst type shows its own unique behavior in preparation, polymerization, activity, isomerization, and response to hydrogen as a chain transfer agent. The arene chromium compounds require an acidic support (silicaalumina) or thermal aging with silica to form a highly active catalyst. At 90°C polymerization temperature arene chromium catalysts produced high molecular weight polyethylene and showed, in contrast to supported chromocene catalysts, a much lower response to hydrogen as a chain transfer agent. An increase in polymerization temperature caused a significant decrease in polymer molecular weight. Addition of cyclopentadiene to supported bis (cumene)-chromium catalyst led to a new catalyst which showed a chain transfer response to hydrogen typical of a supported chromocene catalyst. Polymerization activity with tris- or bis (allyl)-chromium appears to depend on the divalent chromium content in the catalyst. Changes in the silica dehydration temperature of supported allyl chromium catalyst have a significant effect on the resulting polymer molecular weight. High molecular weight polymers were formed with catalysts that were prepared using silica dehydration temperatures below about 400°C. Dimers, trimers, and oligomers of ethylene were usually formed with catalysts that were prepared on silica dehydrated much above 400°C. The order of activity of the different types of catalysts was chromocene/silica 〉 chromocene/silica-alumina 〉 bis (arene)-chromium/silica-alumina ≃ allyl chromium/silica.

Notes: The radiation induced copolymerization of chlorotrifluoro ethylene (CTFE) with various butenes was studied at temperatures between -20°C and +40°C using 60Co-γ rays.In the case of isobutene (IB) an almost alternating crystalline copolymer is formed in a heterogeneous reaction. At high IB-concentrations a cationic homopolymerization of this olefin occurs simultaneously to the radical copolymerization. The copolymerization rate increases with increasing temperature and degree of conversion. The highest rates are obtained for monomer mixtures with about 80 to 90 mole % CTFE. The decrease in rate for monomer mixtures with still higher CTFE concentrations is assumed to be partly due to the low IB-concentration and partly to degradative chain transfer by the isobutene. In support of this assumption molecular weights and melting points of the copolymer have been determined.Similar results were obtained for butene-1 but in this case, no cationic homopolymerization was observed and the reaction proceeded homogeneously.Cis- and trans-butene-2 only acted as polymerization inhibitors.

Notes: Poly-p-benzamide of high molecular weight (ηinh = ∼ in H2SO4) was obtained by the direct polycondensation reaction of p-aminobenzoic acid (p-ABA) by means of diphenyl and triaryl phosphites in N-methylpyrrolidone (NMP)-pyridine solution containing lithium and calcium chlorides. Molecular weight of polymer varied with the amount of these salts, showing maximum values at the concentration of about 4 wt-% of LiCl or about 8 wt-% of CaCl2 in the reaction mixture. The reaction temperature at around 80°C gave a polymer of the highest viscosity. The polycondensation reaction was also affected by monomer concentration, solvents, and tertiary amines like pyridine. Similarly, aromatic polyamides with high molecular weight (ηinh values up to 1.34 in H2SO4) were prepared from isophthalic acid and aromatic diamines, whereas terephthalic acid gave only low-viscosity polymers.

Notes: Gel-permeation chromatography is an excellent tool for obtaining polymer fractionation data. Inasmuch as chromatograms are functions of instrument operating conditions, an interpretation procedure must be employed to yield correct molecular distributions of macromolecular materials. A procedure is described that corrects for imperfect resolution. Extensive experimental testing of polymeric materials with kinetically known molecular distributions demonstrates its validity in regions where poor resolution is experienced.Applications will allow one to utilize equipment with inherently poor resolution or to operate instruments with high resolution in regions of poor resolution (e.g., rapid analysis).

Notes: Dynamic-mechanical properties of mixtures of polymers with low molecular weight substances containing six- and eight-membered rings were studied. Secondary relaxations have been found and interpreted by means of the theory of conformational motions. There is good agreement of the results with literature data.

Notes: The chemical nature of starch xanthate (SX)-polyethylenimine (PEI) reaction products has been studied because of their effectiveness as wet-end additives for improving strength properties of paper. Model compounds, in conjunction with ultraviolet, infrared, and chemical analyses, served to elucidate SX-PEI reaction mechanisms. Aqueous solutions of SX (degrees of substitution 0.1-0.5) were titrated with PEI at pH 5-7 (25-30°C) to form SX-PEI flocculent precipitates that were determined to be polyelectrolyte complexes. However, when solutions of SX-PEI were kept at pH 10-12, products were formed that included dithiocarbamic acid salts in major quantities, PEI thioureas, and minor quantities of O-starch PEI thinocarbamate. Acid precipitation of these SX-PEI polymeric reaction products from their alkaline solutions, which contained residual xanthate and PEI, also yielded polyelectrolyte complexes. Model systems suggest that PEI thiuram disulfide and starch xanthide, possible products of air oxidation, could be present in minor amounts and would react rapidly with PEI to yield thioureas and thioncarbamates, respectively. Apparently, mixtures of xanthate and amine gave (1) dithiocarbamic acid salts from both xanthate groups and CS2 (decomposition from xanthate), (2) thioureas from both dithiocarbamic acid salts and thiuram disulfide, and (3) thioncarbamates, principally from xanthate as opposed to xanthide.

Notes: The polymerization of α-amino acid N-carboxy anhydrides (NCAs) initiated by 4-aminoethylimidazole (histamine) was studied in order to synthesize poly(amino acids) containing an imidazole nucleus at the end of polymer chain. On the basis of the kinetical measurements, it was found that the rate of polymerization is proportional to the first order in both NCA and initiator concentrations and that the initiation reaction is predominantly caused by the primary amine with the highest basicity in a histamine molecule. Binding of the histamine fragment to the end of polymer chain was confirmed by elementary analysis, nuclear magnetic resonance spectroscopy, and measuring the number-average molecular weight of the resulting polymers. It was thus possible to prepare poly(amino acids) with a pendant histamine. In addition, the lowering of the number-average degree of polymerization of the polymers prepared was observed under the condition that the initial molar ratio of NCA to histamine was larger. It was caused by the reinitiation of polymerization by the imidazole nucleus at the chain end.

Notes: The synthesis and characterization of new bigraft copolymers poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-styrene-g-α-methylstyrene] (Nordel-g-PSt-g-PαMeSt) and poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-isobutylene] (Nordel-g-PSt-g-PIB) are described. The synthesis involves the use of a polyhydrocarbon backbone containing allylic chlorines and bromines (chlorobrominated Nordel) in conjunction with a suitable alkylaluminum compound to initiate selectively the polymerization of a monomer (generally styrene) from the chloride sites and subsequently to initiate the polymerization of another monomer (α-methylstyrene or isobutylene) from the bromide sites. Conditions conductive to selective and sequential initiation have been worked out. The pure bigrafts are obtained by selective solvent extraction and their homogeneity (by gel permeation chromatography), overall composition (by nuclear magnetic resonance spectroscopy) and molecular weight (by osmometry) are determined.

Notes: The synthesis of a new class of block polymers that contain alternating polyimidothioether “hard” blocks and polysulfide elastomer “soft” blocks is described. Compositions with 70% and greater polysulfide component are solvent-resistant, thermoplastic elastomers exhibiting room temperature tensile strengths of up to 1500 psi and ultimate elongations of nearly 800%. The physical properties are a strong function of test temperature due to relatively short polyimidothioether blocks, 850 ≤ M̄n ≤ 3500 g/mole. These short polyimidothioether blocks were necessary to minimize degradation of the polysulfide elastomer blocks during thermal processing at temperatures ∼100°C above the “hard” block domain Tg.

Notes: 300 MHz proton magnetic resonance spectroscopy was applied to the determination of triad structures of three poly(alkyl α-chloroacrylates) of widely varying stereoregularities. Assignments and quantitative analyses were made for all of the tetrad peaks in the backbone methylene resonance of poly(methyl α-chloroacrylate), poly(ethyl α-chloroacrylate), and poly(isopropyl α-chloroacrylate). In addition the methyl singlet peaks of poly(methyl α-chloroacrylate), the methyl triplet peaks of poly(ethyl α-chloroacrylate) which had not been amenable previously to resolution at 220 MHz, and the methyl doublet peaks of poly(isopropyl α-chloroacrylate) were resolved, and the triad values which were obtained from these pendant ester group resonances compared favorably with triad values calculated from experimental tetrad values. As a demonstration of the internal agreement of the triad and tetrad peaks assignments, statistical calculations of the stereochemical structures of the actic and syndiotactic polymers were generally described well or to a first approximation by random selection statistics (Bernoullian) while the stereochemical statistics of the moderately to highly isotactic polymers were consistent with a nonrandom statistical process (first-order Markovian), as expected.

Notes: Techniques for measuring gel contents of elastomers by liquid exclusion chromatography are described. Chromatographic methods are based on solubilizing aqueous latex in a water-miscible elastomer solvent. The resulting mixture of solubilized elastomer and dispersed gel particles is separated and analyzed by liquid chromatography, columns packed with porous glass particles and a differential refractometer detector being used. Applicability of these techniques is illustrated with results for typical nitrile elastomers in methyl ethyl ketone. Chromatographically measured gel contents in the range 30-80% gel were in good agreement with those measured by a classical, 3-day static method. Repeatability of chromatographic measurement was ±1.35% gel. The entire analysis, including solution preparation, required less than 1 hr and can be as short as 10-20 min.

Notes: 1,4-Cyclohexadiene underwent monomer-isomerization polymerization to yield poly(1,3-cyclohexadiene) with a Ziegler-Natta catalyst comprising TiCl4-Al(C2H5)3 catalyst with Al/Ti molar ratios of 0.5-3.0 at 60°C for 96 hr. Good yields of polymer were obtained (49.5% yield at Al/Ti = 3.0; [η] = 0.04 dl/g). The infrared and NMR spectra of the polymer were identical to those of poly-(1,3-cyclohexadiene), confirming that 1,4-cyclohexadiene first isomerizes to 1,3-cyclohexadiene and then homopolymerizes to give poly-1,3-cyclohexadiene. 1,3-Cyclohexadiene polymerized without isomerization easily in the presence of TiCl3-Al(C2H5)3 catalyst at Al/Ti molar ratios of 0.5-3.0 at 60°C for 3 hr (76.3% yield at Al/Ti = 3.0; [η] = 0.06 dl/g).

Notes: The copolymerization of propylene oxide (PO) with tetrahydrofuran (THF) in dichloroethane (DCE) has been studied at -10, 0, +10, and +20°C. The reactions were initiated by triphenylmethyl cations associated with the following gegenions: PF6-, SbF6-, and AsF6-. The overall energies of activation (Eα of PO and Ea of THF) obtained with the three gegenions increase as one passes from PF6- to AsF6- then to SbF6-, though the magnitude of the increase in each case is not substantial. On the other hand, the associated frequency factors A show a considerable variation with the gegenion. The bimodal distributions of the molecular weights, obtained by GPC with the copolymer produced from reactions initiated with triphenylmethyl hexafluorophosphate, show that the proportions of the lower molecular weight component (L) decrease as the solvent is changed from DCE to toluene, and this is even more marked when bulk polymerization conditions are adopted. The proportions of the higher molecular weight component (H) however increase, as does its molecular weight. The GPC molecular weight distributions of the copolymers initiated with triphenylmethyl hexafluorophosphate in DCE to which water has been added, show that the molecular weight of component H decreases with increasing concentration of water, while that of component L remains practically unchanged at a value of 308. This corresponds to an average degree of polymerization (DP) of 4 to 5. The NMR and infrared spectra of copolymers prepared in the presence of still higher initial water concentrations indicate that the PO-based polymer segments are present in excess of those required for a 1:1 copolymer.

Notes: Because diisocyanates are widely used raw materials in the production of urethane elastomers and foams, it is of particular interest, to know the contribution of secondary reactions to the overall reaction between diisocyanates and polyether glycols, because of the well known influence of crosslinks on the physicochemical properties of polyurethanes. A mathematical method is suggested to calculate rate constants for the primary and secondary reactions, the hypothesis being that the allophanate group is the main secondary product. The method has been verified with experimental data obtained by reacting models. In addition, the influence of the [NCO]/[OH] ratio and of temperature on the formation of the allophanate group has been studied. The method has been applied to the reaction of 4,4′-diphenylmethane diisocyanate with poly(oxytetramethylene) glycol, a polyether glycol specifically designed for use in preparing polyurethanes. The results are in complete agreement with the experimental data.

Notes: The ring-opening polyaddition reaction of N,N′-disubstituted bisisomaleimides with various diamines in N-methyl-2-pyrrolidone at room temperature afforded polymaleamides having inherent viscosity up to 0.7 in almost quantitative yield. These polymers are a new class of homopolymaleamides and ordered alternating copolymaleamides. Almost all of the polyamides were soluble in a wide range of solvents such as dimethylsulfoxide, dimethylacetamide, m-cresol, and formic acid. They did not show any melt temperature, and began to decompose at a temperature ranging between 200 and 300°C.

Notes: In order to elucidate the mechanism of radiation-induced polymerization of styrene adsorbed on silica gel, the effect of p-benzoquinone and ammonia was investigated. The high molecular weight GPC peaks of both graft polymers and homopolymers decreased with increasing p-benzoquinone concentration, while the low molecular weight peaks of both graft copolymers and homopolymers decreased with increasing ammonia concentration. The results indicate that the high molecular weight peaks of both graft and homopolymers are formed as a result of a radical mechanism and that the low molecular weight peaks of both types of polymers are formed by a cationic mechanism. In formation of both graft polymers and homopolymers both radical and cationic polymerization take place at the same time.

Notes: The polymerization of methyl α-ethylacrylate was carried out in toluene by n-BuLi at various temperatures. The yield of the polymer decreased with increase in the polymerization temperature and at 30°C and above no polymer was obtained, indicating that the ceiling temperature of this monomer lay between 0 and 30°C. The isotacticity increased with an increase in the polymerization temperature and at 0°C a highly isotactic polymer was obtained. The fractionation of the polymer obtained at -78°C showed that the polymer was a mixture of isotactic and syndiotactic ones. Upon the addition of a small amount of methanol or water in the polymerization mixture the isotacticity of the polymer increased while the yield decreased. Syndiotactic polymer was obtained in the polymerization by n-BuLi in tetrahydrofuran as well as by diisobutyl aluminum diphenylamide in toluene.

Notes: The present work is concerned with the influence of the polymerization temperature on the propagation mechanisms of polyisoprenyl- and polybutadienyl-alkali metals. The thermodynamic parameters of the contact ion pairs and free ions propagations have been calculated. With Li+ in dioxane solvent, the vinyl propagation is stereospecific (for isoprene, the propagation is mainly 4-3). In comparison with benzene, the vinyl propagation of the polydienyl-Li contact ions pairs should be due to complexation of Li+ by dioxane, an electron donor having a weak dielectric constant. In general, the stereospecificity of the propagation of contact ion pairs decreases with increasing counterion size; little difference has been observed with K+ and Cs+ ion pairs in dioxane and benzene media. For isoprene, the methyl substituant should have chiefly a steric effect in the propagation of free ions, whereas it should confer a polar character to the isoprene molecule in the presence of ions pairs.

Notes: A kinetic model for the formation of polyene sequences during the thermal degradation of poly(vinyl chloride) in nitrogen is proposed. The model includes a propagation step of the “zipper” type and termination by crosslinking. The initiation can occur randomly or at weak links in the polymer chain. The rate of polyene growth increased with increasing polyene sequence length and passed through a flat maximum at n = 7. The average polyene sequence length was almost constant up to about 0.5% conversion, but then slowly decreased with increasing conversion. This was the result of a larger extent of termination reactions (crosslinking) at higher conversions. At 0.2-0.5% conversion an average polyene sequence length of about 6 was observed. The degradation was carried out in nitrogen at 190°C. The experimental results were obtained from ultraviolet-visible spectrophotometric measurements.

Notes: Ring-opening polymerization and copolymerization of the cis and trans isomers of 1,4-dichloro-2,3-epoxybutane has let to an interesting 50% Cl. This family of polymers is expected to acquire commercial importance.

Notes: The syntheses of poly(styrene-b-isobutylene), poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-styrene-g-α-methylstyrene], and poly[(ethylene-co-propylene-co-1,4-hexadiene)-g-styrene-g-isobutylene] have been accomplished by using the principle of selective sequential initiation. This method makes use of the large differences in initiation rates that exist between labile organic chlorides and bromides when these halides interact with alkylaluminum compounds. Synthesis conditions have been worked out which allow composition control. These new AB blocks and bigrafts exhibit unusual mechanical and solubility properties, some of which will be described. For example, the Nordel-g-PSt-g-PIB bigraft exhibits only one low temperature transition (DSC, Rheovibron), suggesting an intimate aggregation of Nordel and polyisobutylene phases.

Notes: The condensation of bisketomethylene monomers with either 4,6-dibenzoyl-1,3-phenylenediamine or 2,5-dibenzoyl-1,4-phenylenediamine catalyzed by acid affords high molecular weight polymers containing the anthrazoline and isoanthrazoline units in the polymer main chain. Base is not an effective catalyst for the production of high molecular weight polymer. The phenyl substitution on the anthrazoline and isoanthrazoline units increases the solubility of these polymers over those in which phenyl substitution is absent. The rodlike character of these polymers, which can be altered by positional isomerism in the chain, has an effect on the solution properties.

Notes: Pyrolysis, in combination with gas-chromatography technique, was used in the determination of the structure and study of the thermal degradation mechanism of the condensation polymers obtained by Friedel-Crafts reactions of poly(vinyl chloride) with benzene, toluene, and naphthalene. The separation of the pyrolysis products was made using a column packed with chromosorb W (80-100 mesh) coated with 15% silicone SE-52. The identification of the pyrolysis products resulted as a consequence of the thermal decomposition of condensation polymers and their semiquantitative estimation led to the final conclusion that the initial normal chlorine substitution in the macromolecular chain of poly(vinyl chloride) is followed by an important intramolecular cyclization reaction yielding 1,3-methyleneindan units.

Notes: The kinetics and molecular weight distributions (MWD) of the gamma-ray induced polymerization of styrene in methanol were studied at 35°C, at low conversions and over a dose rate range of 2.76 × 103 to 2.74 × 104 rad/hr. The data obtained at low initial methanol content agreed with previously obtained results and the MWD of the polystyrene formed yielded a single unimodal peak with M̄n in the range of 35,000-480,000. However, at high initial methanol content and low dose rates, at least three peaks were clearly discernible over wide molecular weight distributions. The existence of these peaks is related to the kinetic data and the formation of three distinguishable regions in the polymerization system.

Notes: We have investigated the optical rotatory dispersion of a stereo-irregular polyelectrolyte when neutralized with alkaline and N-tetraalkylammonium hydroxides, both in water and aqueousacetone mixtures.The variations of the optical activity properties during the neutralization can be well related to potentiometric and viscosity measurements. They are interpreted by assuming two kinds of solvation of the chiral centers located on the main chain, to which two partial optical rotary dispersions (ORD) of opposite signs are associated. The observed optical activity changes and specifically the discontinuity occurring in the neutralization range where a conformational transition between a compact structure and a more extended one is initiated, are thus accounted for in terms of the corresponding changes in the state of solvation of chains.

Notes: We have shown previously that the free-radical polymerization kinetics of maleimide can be explained by a scheme for retarded polymerization. The steps involve tautomerization of a growing maleimidyl chain to succinimidyl, the retarded addition of maleimide to the latter, and termination solely by resonance-stabilized succinimidyl radicals. Combination termination is preferred, since this yields a very stable N,N′-bisuccinimidyl structure. Other authors also invoke tautomerization to succinimidyl radicals which they believe terminate by disproportionation with growing maleimidyl chains to generate polymer with unsaturated endgroups. Free-radical-initiated polymaleimides are colored in the presence of base. Our measurements of the absorbance of polymaleimides at 387 and 500 nm in the presence of excess strong organic base show there is essentially no dependence on molecular weight. This suggests that the chromophoric groups are intramolecular and that color does not arise from the ionization of allylic protons associated with terminal double bonds. The near-ultraviolet spectra of polymaleimides in slightly acidic media contain absorption bands at about 288, 320, and 360 nm. The structural impurities that account for these bands cannot be terminal unsaturation. We propose that the origin of these bands is pyrrolinone type structures which are formed by a retarded polymerization step through succinimidyl oxygen.

Notes: A study has been carried out on the kinetics of persulfate-initiated emulsion polymerization of styrene in the presence of an anionic (oleate) or mixed anionic-nonionic emulsifier. In both cases it appears that Smith-Ewart kinetics are obeyed, i.e., there is a constant-rate period up to 40-50% conversion, during which there is a concomitant constant molecular weight development. The sharp increases in molecular weight with conversion reported by Grancio and Williams appear to be an artifact resulting from the use of an impure emulsifier (Triton X-100), which acts as a chain transfer agent to reduce the molecular weight by approximately an order of magnitude. Hence there does not appear to be any kinetic justification for assuming an inhomogeneous swollen latex particle (“core-shell” morphology), and normal thermodynamic considerations should still apply to this swelling phenomemon.

Notes: ESR spectra of purified and ferric ion-sensitized celluloses irradiated with ultraviolet light in vacuo at 45, 20, -80, and -196°C were recoreded and compared. Generally, several kinds of spectra, viz., singlet, three-line, five-line, and seven-line spectra, were observed. At higher temperatures, only singlet and three-line spectra of stable free-radical species were detected, whereas at lower temperatures such as at -196°C, two doubled spectra of formyl radicals and hydrogen atoms were also detected in addition to cellulose radicals. It is believed that the intricate spectra observed at low temperatures are superimposed upon spectra generated by free radicals which may or may not be stable at high temperatures. During reirradiation at -196°C with an alternative light sources, i.e., λ 〉 2537 Å and λ 〉 3400 Å, of samples which were irradiated at 20°C or at -196°C, phenomena indicative of radical transformation and formation of new radicals or of decay of radicals in terms of ultraviolet bleaching were observed on studying the changes of line-shapes and relative signal intensities of the spectra.

Notes: A novel class of polypyrimidoquinazolinetetraones was synthesized by the polymerization of N,N′-bis(mesyloxy)pyromellitimide with aromatic diamines in N-methyl-2-pyrrolidone in the presence of triethylamine as an acid acceptor. The polymerization proceeded probably through the formation of ring-opened adducts, followed by elimination and rearrangement yielding polyamide-isocyanates, which in turn were cyclized to give polypyrimidoquinazolinetetraones. These polymers, which were soluble in strong acids, had inherent viscosities in the range of 0.17-0.27. Thermogravimetric analyses indicated that they began to decompose at around 450°C in air.

Notes: Syntheses and radical ring-opening polymerization of spiro o-carbonates(I-IV) were investigated. These polymers were yellow powders and soluble in common organic solvents. The infrared and NMR spectra indicated that the polymers were alternate copolymers of either and carbonate containing double bonds. The polymerization mechanism is discussed.

Notes: The synthesis of a series of Polybis(arylamino)phosphazenes is described. The polymers usually were prepared by treatment of polydichlorophosphazene in benzene-tetrahydrofuran with arylamines/triethylamine at reflux for 48-144 hr. The polymers, having viscosities of 0.3-1.4dl/g, are essentially free of active chlorine sites, as shown by elemental analysis and their longterm hydrolytic stability. Thermal analysis revealed glass transition temperatures between 53 and 105°C and decomposition temperatures between 243 and 266°C. Analysis by differential scanning calorimetry revealed no first-order endothermic transitions. For comparison with the arylamino polymers, polydiethylaminophenylaminophosphazene, polybis(benzylamino)phosphazene, and polybis(β-phenethylamino)phosphazene were prepared and are described.

Notes: The effect of conditions of polycondensation on the structure of polymers formed from monomers with symmetric and asymmetric functional groups by nonequilibrium polycondensation has been studied for the system with acceptor-catalytic polyesterification of β-hydroxyethyl ethers of bisphenols and terephthalic acid chloride in the presence of triethylamine. Polymers with statistical or regular arrangement of diol residues in the chain can be produced in such systems, depending on the way in which starting compounds are introduced in the reactor. A difference in the reactivity of functional groups in an asymmetric monomer is not sufficient to produce polycondensation polymers with a regular structure. Gradual introduction of the symmetric monomer is essential to yield polymers with predominant “head-to-head” (“tail-to-tail”) configurations. Some properties of the resulting polymers have been studied. Polymers with ordered residues of the asymmetric monomers in the macromolecules have higher softening temperatures and an increased tendency for crystallization than the statistic polymers.

Notes: Sodium bisulfite-soda lime glass has proved to be a good initiator for polymerization and graft polymerization onto cellulose of some vinyl monomers. A scheme dealing with the mechanism of initiation has been proposed assuming trapping of the bisulfite radical inside the glass frame-work to form a so-called sulfur-impregnated solid. Such a solid has paramagnetic properties and acts on the vinyl monomers and cellulose as any free-radical-producing source thus leading to polymerization and graft polymerization onto cellulose. Other radicals containing sulfur, such as sulfite, sulfate, and persulfate failed to give such property with soda lime glass. With the sodium bisulfite-soda lime glass system the reactivity decreases in the order methyl methacrylate 〉 ethyl acrylate 〉 acrylonitrile which is inconsistent with the arrangement of acceptor monomers with decreasing electron-donating ability. This may reflect interference of the addition reaction which may take place between the monomer and bisulfite and the rate of which may depend on the activation energy of the monomer.

Notes: In the sodium bisulfite-soda lime glass initiating system, crude and true grafting yields increased with increasing ratio of methyl methacrylate to cellulose up to a limit; beyond this limiting value, grafting yields decreased due to the increase of the rate of sodium bisulfite-monomer addition over that of polymerization. Limitation was also achieved on increasing the glass to cellulose ratio through increased termination rates by coupling and disproportionation reactions, as the free radicals are increased. In addition, a limiting value was reached with increasing sodium bisulfite concentration; this may be related to the formation of a nonfunctioning disulfite ion at the expense of bisulfite radicals at high concentrations of sodium bisulfite. The temperature plays a role in this initiating system. Maximum rates of conversion and grafting were achieved at the ceiling temperature. Dissociation of the sodium bisulfite, which decreases with temperature, also has an effect.

Notes: The mechanism of dehydrochlorination of 2,3-dichlorobutane and chlorinated polybutadiene which are model compounds of head-to-head poly(vinyl chloride) has been investigated by pyrolysis, thermal, and ultraviolet-induced decomposition. The activation energy of dehydrochlorination for head-to-head poly(vinyl chloride) in nitrogen was 23 kcal/mole at temperatures of 150-190°C, which is slightly smaller than that (29 kcal/mole) for head-to-tail poly(vinyl chloride). The conjugated double bonds were formed by thermal and radiation decomposition of head-to-head poly(vinyl chloride), similar to head-to-tail poly(vinyl chloride). The probability of polyene formation by radiation-induced dehydrochlorination is larger than that by thermal decomposition and is affected by the conformation and the molecular motion of the main chain. This may be due to the alternative mechanism of dehydrochlorination in the thermal and radiation decomposition. The amount of head-to-head linkage of poly(vinyl chloride) samples prepared with various catalysts is dependent on polymerization temperature rather than the kinds of catalyst. Commercial poly(vinyl chloride) has 6-7 head-to-head linkages per 1000 monomeric units.

Notes: The ring-opening polyaddition reaction of N,N′-biisomaleimide with a dihydrazine and dihydrazides was carried out in polar aprotic solvents at room temperature to afford a new class of polyhydrazides having inherent viscosities in the range of 0.1-0.5 in nearly quantitative yields. Almost all of the polyhydrazides were soluble in dimethylformamide, dimethyl sulfoxide, and other polar aprotic solvents. They did not show any clear melt temperature and began to decompose at around 200-300°C.

Notes: The irradiation of nonconjugated bichromophoric systems, diaryl ketones, with ultraviolet light in the presence of hydrogen donors, such as isopropanol or bisbenzhydrol, yields high polymers. Two series of arylketones were investigated, namely bisbenzophenones and bisketotriazoles. The cage reaction, which arises from the cross combination between the acetone ketyl and bisbenzophenone ketyl radicals, was estimated to be very small but may constitute a chain termination reaction in the photopolymerization in isopropanol. The photopolymerization of bisdiketone-dihydrol systems was found to yield polymers with much higher molecular weights than those obtained from the photopolymerization of bisdiketone-isopropanol systems. The photolysis of some binary mixtures of aromatic diketones in the presence of isopropanol yielded statistical copolypinacols. In some favorable cases, the NMR spectrum of the copolymer obtained showed three distinct linkages and from the infrared spectrum intensities the copolymers composition and the number average length of the sequences may be determined.

Notes: Experimental data for the stresses and the deformations for crosslinked rubbers at uniaxial and symmetrical and asymmetrical biaxial extension and pure shear are given. Stressed states up to 100% extension are described by a single parameter, the highly elastic potential of Bartenev and Khazanovich. The classical statistical potential of Kuhn-James-Guth-Treloar is not in agreement with experimental data, as shear modulus G has different values for different types of stressed states.

Notes: Diallyl o-phthalate (DAP) has been polymerised by γ-radiation from a 60Co source and the kinetics of polymerization have been studied at several dose rates and temperatures. The results show that the rate of polymerization was proportional to I0.68, where I is the radiation dose rate. The net activation energy of the polymerization reaction (Ep - 1/2Et) was 5.02 kcal/mole, where Ep and Et are the activation energies for the propagation and termination steps, respectively. The radical yield GR for DAP was measured by the loss of diphenyl picryl hydrazyl (DPPH) used as a radical scavenger. GR in the solution after irradiation was 3.12. The ratio of the rate constants kp2/kt was calculated to be 4.09 times; 10-7 at 25.8°C and 15.0 × 10-7 at 55.4°C. At room temperature, the ratio of degradative chain transfer constant to kp, i.e., ku/kp was found to be 0.065 and ktr/ku as 0.032, where ktr is the nondegradative chain-transfer constant. Molecular weights of these polymers as determined by vapor pressure osmometry showed that the degree of polymerization was between 8 and 10. Infrared spectra of the polymers indicated that intramolecular cyclization took place during polymerization.

Notes: The radical polymerization of vinyl monomers initiated by Cr2+-RX in the presence of various amines was studied in DMF at 30°C. Polyamines able to form the chelate complex with Cr2+ accelerated the rate of polymerization of styrene in the following order: ethanolamine 〉 triethylenetetramine 〉 diethylenetriamine 〉 ethylenediamine. However, aliphatic monoamine, hexamethylenediamine, and aromatic diamine did not have any effect on the polymerization. These results suggest that the effect of multidentate ligands may be associated with chelating effects which affect the electron transfer ability of the metal complex. An apparent activation energy of 8.2 kcal/mole for the polymerization of styrene was obtained in the presence of ethanolamine. With the Cr2+-CHCl3 system, on addition of ethanolamine, the polymerization of methyl methacrylate was accelerated, and acrylonitrile and vinyl chloride, could be polymerized.

Notes: Allyloxyacetaldehyde (AOA) was synthesized by the Williamson reaction between sodium allyl alcoholate and bromoacetaldehyde dimethyl acetal. Highly reactive crystalline poly(allyloxymethyl)oxymethylene was obtained from AOA by using organoaluminum compounds as initiators at low temperature. The influence of initiators, solvents, and temperature on the polymerization was examined. Conspicuous exothermal behavior of the resulting polymer observed in the temperature range of 110-140°C in air with a differential scanning calorimeter, was not only due to an oxidative scission of the polyoxymethylene chain but also due to a chain reaction of neighboring allyl side groups in the polymer chain.

Notes: Ion-Exchange membranes containing aminoacetic, iminodiacetic, and ethylenediamine-triacetic acid groups were prepared on the basis of polyethylene modified with styrene and divinylbenzene. The polyethylene modified was in the form of a film. Optimum parameters of the membranes were determined by using both the method of statistical planning of the experiments and nonlinear optimization technique. Physical and chemical properties of the membranes were investigated as well. Some observations were also made concerning the structure of the prepared membranes.

Notes: Cyclic tests in tension were performed on PMMA and PC center-notched plate specimens. Frequencies between 0.1 and 100 Hz at temperatures from -78 to +55°C were investigated. Correlations between crack growth rates, described in the terms of stress intensity K, and the appropriate values of the loss factor tan δ were studied. It was concluded that, in the investigated conditions, a direct correspondence exists between the crack growth rate and tan δ.

Notes: The dependence of the polymerization rate on initiator concentration over a wide range of conversion is analyzed by an equation derived on the assumption that the primary radical termination is important and another equation derived on the assumption of the chain length dependence of the termination. The analytical result by the former equation, is nearly equivalent to the result by the later when transfer predominates. Fujita-Doolittle theory is applicable to both results. In the apparent termination, small polymer radicals not exceeding the size of the segment play an important role.

Notes: Experimental data are presented for the polymerization of commercial styrene in a γ-radiation flux of 20-51 rad/sec in the temperature range of 150-200°C. At radiation intensities above 20 rad/second, conversion rate is independent of dose rate over the range. Above 165°C, radiation does not enhance the conversion rate but does produce more rapid elimination of residual monomer. Molecular weights of polymer product in this temperature range are too low to be of commercial interest. An optimal temperature range of 110-120°C is suggested for the process.

Notes: The crosslinked copolymerization of methyl methacrylate with ethylene dimethacrylate (EDMA) in bulk and in toluene has been investigated by differential scanning calorimetry. The appearance of a second peak, in addition to that arising from the gel effect, noted in curves of bulk copolymerization rate (fraction of EDMA mE = 0.20) is explained by the formation of microgels during the copolymerization. With mE = 0.50-1.00, copolymerization proceeds heterogeneously at first, providing opaque microgels, which become transparent polymer in a later stage at a weight fraction of toluene wT ≦ 0.20 and independent polymer particles at wT ≧ 0.30. A diagram is given which illustrates three types of copolymerization depending on initial composition of monomers and toluene. Final conversions for mE ≦ 0.10 agree well with predictions. Copolymerization at mE ≧ 0.20 ceases because of reduction of segmental mobility due to dense network formation in microgel, though the whole system is not yet in glassy state. Data of final conversions in solution copolymerization also support the above mechanism.

Notes: The inclusion of minor amounts of methyl isopropenyl ketone in polyacrylonitrile and its copolymers with methyl acrylate and vinyl acetate causes the polymer to become sensitive to ultraviolet light in the 290-320 nm region. Both films and fibers show decreases in molecular weight on irradiation which are attributable to C—C bond scission by the Norrish type II reaction. In addition to bond cleavage, decarbonylation occurs, presumably by a type I radical process which also leads to the formation of ketonitrile groups. Fibers spun from such polymers lose most of their tensile strength and elongation after a few months outdoor exposure to natural sunlight, whereas control samples not containing carbonyl groups will retain their strength for much longer periods. Quantum yields both for chain scission and for carbonyl loss in these systems are estimated to be of the order of 0.005.

Notes: α-Methylstyrene (MS) and isobutyl vinyl ether (VE) readily polymerize, styrene (S) polymerizes to a small extent, and isobutylene (IB), butadiene (BD), and isoprene (IP) fail to polymerize in the presence of catalytic amounts of AlCl3 when propionitrile, ethyl propionate, and methyl isobutyrate are used as reaction media. MS polymerizes readily and S polymerizes with difficulty in the presence of AlCl3 to yield homopolymers when acrylonitrile (AN) is present and copolymers with ethyl acrylate (EA) and methyl methacrylate (MMA). VE readily homopolymerizes, while IB, BD, and IP fail to polymerize in the presence of AlCl3 and the acrylic monomers. VE readily homopolymerizes, S and MS polymerize to a very small extent, and IB, BD, and IP do not polymerize in the presence of ethylaluminum sesquichloride (EASC) in polar solvents. VE readily homopolymerizes in the presence of EASC and the acrylic monomers. MS polymerizes to a small extent in the presence of EASC and the acrylic monomers to yield equimolar copolymers with EA and MMA and a mixture of cationic homopolymer and equimolar copolymer with AN. S yields equimolar copolymers in low yield in the presence of EASC and the acrylic monomers. IB, BD, and IP in the presence of EASC do not polymerize to any significant extent when EA is present, form AN-rich copolymers and yield poly(methyl methacrylate) in the presence of MMA. A revised mechanism is presented for the formation of cationic, radical, random, and alternating copolymers as well as alternating copolymer graft copolymers in the copolymerization of donor and acceptor monomers.

Notes: The paper is concerned with the kinetics of radical conversions in solid polystyrene (PS) induced by decomposition of free-radical initiators over the temperature range of 60-90°C. A complex quantitative study of PS oxidation was carried out. The kinetics of initiator decomposition and of hydroperoxide accumulation, the variations in chemiluminescence (CL) intensity accompanying polymer oxidation were studied. The CL spectrum and the changes in molecular weight in the course of oxidation were measured. A method for determination of the relative antiradical activity of antioxidants, based on the competition between the antioxidant and the stable radical for the active radical was proposed. The activity of valence-saturated antioxidants in the solid phase was found to become more uniform compared to the liquid phase, whereas that of stable nitroxide radicals was abnormally high. Initiated solid PS oxidation occurred by a chain mechanism with formally linear termination of the chain. The chain length of 3.0 ± 0.5 was independent of temperature. A model of initiated PS oxidation is proposed. It implies structural inhomogeneity of the sample, resulting in different probabilities of radical formation in the polymer bulk in the course of initiator decomposition in various sample zones. The model permits quantitative description of the kinetics of hydroperoxide accumulation, stable radical consumption, and of variations in CL intensity during initiated and inhibited PS oxidation.

Notes: Radical polymerization of methacrylic acid (MAA) and acrylic acid (AA) in the presence of a positively charged macromolecular matrix was studied. In the presence of a matrix, the rates of polymerization were remarkably increased, especially in high pH region. This suggests that electrostatic interaction between the macromolecular matrix and the growing chains and/or the monomer molecules plays an important role in the process of polymerization reaction. The kinetic orders were greatly influenced by the relative matrix concentration (PC) as follows: for (PC)0 〉 [M]0, Rp = k[M]0.9 [PC]0.3 [I]0.8≤ [M]0 Rp = k[M]0.3[PC]0[I]0,8 where [M] and [I] are monomer and initiator concentration, respectively, and k is a constant. The mechanism of the interaction of matrix with monomer and/or growing chains in the process of the propagation is discussed. The complex formed in the matrix polymerization could be easily made into fiber by spinning.

Notes: Representative aliphatic and aromatic polyurethanes undergo degradation upon treatment with hexamethyldisilazane (HMDS) at elevated temperatures. The course of the reaction is dependent on the nature of the polyurethane. Thus heating poly-[ethylene methylene bis(4-phenylcarbamate)] with HMDS in a sealed tube at 197°C gives high yields of 4,4′-diaminodiphenylmethane, trimethylisocyanatosilane, and 1,2-bis(trimethylsiloxyethane) along with lesser amounts of hexamethyldisiloxane, bis-(trimethylsilyl)carbodiimide, and ammonia. Under the same conditions, poly(ethylene N,N′-hexamethylenedicarboxylate) gives no diamine, but good yields of polyhexamethyleneurea and 1,2-bis(trimethylsiloxy)ethane together with smaller quantities of the other named products are obtained. In the course of this study, two novel routes to polyalkyleneureas were developed. For example, polyhexamethyleneurea is obtained in good yield by treatment of 1,6-hexanediamine with trimethyklisocyanatosilane at elevated temperatures in a sealed tube. The reaction of 1,1′-hexamethylenediurea with HMDS under these conditions results in formation of the same product. A mechanism rationalizing the foregoing results is proposed which involves initial nucleophilic attack by HMDS on the polyurethane to give an intermediate disilylated urea. Thermal decomposition of this intermediate by alternative routes would give the observed products.

Notes: Experimental conditions have been defined for the steady-state combustion of vertically positioned polymer rods burning at the top surface. Temperature and composition profiles through solid and gas phases of the system, polymer consumption rate, and flame height were measured, and the response of these parameters to changes of the oxygen concentration in the environment were determined. Measurements showed that unreacted oxygen diffused from the environment to the burning surface and was absorbed into the polymer, forming a well defined oxygen-rich layer. Concentration of chemically bound oxygen at the surface of this layer were high, e.g., with polypropylene ca. 26 wt-%, and identical with the stoichiometry of the gases leaving the surface and serving as fuel for the flame. The composition of the gas phase at the surface indicated the conversion of 11.4% of the hydrocarbon fuel to CO, CO2, and H2O. An energy balance for the system confirmed that fuel production in this surface layer takes place via simultaneous oxidative and pyrolytic degradation of the polymer, with exothermic processes supplying the energy for endothermic processes. Conductive and radiative contributions from the gas phase were found to play a minor role in maintaining fuel formation. The rate of degradation of a polymer to fuel, normalized to the area of the burning surface, was found to be independent of polymer supply rate and to increase with the oxygen concentration in the environment. The degradation process was successfully modeled in TGA experiments at temperatures and oxygen concentrations representative of the burning surface. The existence of an oxidative surface layer was confirmed and the TGA degradation rate related to the surface-to-volume ratio of the polymer sample. Compositional analysis of a methane diffusion flame of a geometry identical to that of the polymer flame, revealed the presence of unreacted oxygen throughout the preheating zone and at the surface of the burner. Conversion of fuel to final combustion products at the surface was 6.3%. Temperature and composition changes as a function of oxygen concentration in the environment were determined and compared with the polymer diffusion flame. It was concluded that a polymer flame, because of its autogenerative fuel production, possesses only one degree of freedom, viz., the oxygen concentration in the environment, in contrast to the conventionally fueled diffusion flame for which fuel supply rate is an additional independent parameter. Due to this single degree of freedom, the sensitivity of the polymer flame to environmental influences is increased. Effects caused by these extrinsic factors will be the subject of a separate report.

Notes: The condensation of dimethylamine with epichlorohydrin gave an almost quantitative yield of 2-hydroxy-3-dimethylaminopropyl chloride which was polymerized via the Menschutkin reaction to give 2-hydroxy-3-ionene chloride. This cationically charged polymer was obtained in greater than 90% yields as a white to tan solid when precipitated into acetone. Number-average molecular weights of up to 10,000 and intrinsic viscosities of up to 0.11 dl/g in 0.4M potassium bromide were found. These low molecular weights were attributed to several impurities that were identified as being produced by side reactions. Thermal analysis of the polymers showed an endothermic transition at 32-39°C with the onset of decomposition occuring at about 200°C.

Notes: The effects of triphenyl phosphite (TPP) on the radical polymerization of styrene (St) and methyl methacrylate (MMA) initiated with α,α,-azobisisobutyronitrile (AIBN) was investigated at 50°C. The rate of polymerization of St and MMA at a constant concentration of TPP was found to be proportional to the monomer concentration and the square root of the initiator concentration. The rate of polymerization and the degree of polymerization of both St and MMA increased with increasing TPP concentration. The accelerating effect was shown to be due to the decrease of the termination rate constant kt with an increase in the viscosity of the polymerization systems. The chain transfer constant Ctr of TPP in St and MMA systems was determined from the degree of polymerization system. The Ctr of TPP was almost zero in the St system and 6.5 × 10-5 in the MMA system.

Notes: A study designed to ascertain the role of singlet molecular oxygen in the photodegradation of plastics established that most classes of dye chromophores are sensitizers in polymer films, absorbing light and transferring the absorbed energy to ambient triplet ground state molecular oxygen, generating metastable reactive singlet molecular oxygen. Unsaturated polymers containing polybutadiene, polyisoprene, etc. are highly reactive to singlet oxygen produced through photosensitization, generating hydroxylic and carbonyl derivatives and losing their rubbery properties as consequences of such reactions. Many types of transition metal chelates are singlet oxygen quenchers. The relationships of the structures and spectroscopic properties of these chelates to their efficiency in quenching singlet oxygen are examined and discussed.

Notes: Polyureas of high molecular weight were obtained by the direct polycondensation reaction of carbon dioxide with diamines at 40°C for several hours under a pressure of carbon dioxide (below 30 atm) by use of diphenyl phosphite in pyridine. Optimal temperature and pressure were 40°C and 20 atm of carbon dioxide. The polycondensation reaction was also affected by solvents and type and amounts of tertiary amines. Pyridine was most effective as tertiary amine and solvent as well. Of the phosphorous compounds used, triaryl phosphites and diphenyl phosphite were most effective, but trialkyl phosphites failed to give polymer. The reaction was assumed to proceed via a carbamyl N-phosphonium salt of pyridine formed by dephenoxylation of phosphites. Similarly, polythioureas were prepared by heating a mixture of carbon disulfide, diamines, and diphenyl phosphite in pyridine at 40°C for 6 hr under nitrogen.

Notes: Polymerization of THF in CCl4 solvent was initiated with 1,3-dioxolan-2-ylium eations with AsF6-, PF6-, and SbF6- anions as well as with esters of fluorosulfonic and trifluoromethanesulfonic acids. With these esters polymerization proceeds with a marked acceleration period, due to slow initiation. The corresponding rate constants of initiation and their dependence on the polarity of the THF/CCl4 mixture were determined. The rate constant of propagation on the macroion-pairs (kp±) of the polytetrahydrofurylium cation with AsF6-, PF6-, and SbF6- and CF3SO3-, anions was found to be independent in CCl4 solvent on the anion structure and given by the expression: kp± = 2.93 × 10-2 exp {-4.7 × 103/T} at [THF]0 = 8.0M. This constant depends on the polarity of the polymerization mixture, and at 25°C for the THF-CCl4 system, kp± = 1.78 × 10-2 exp {-4.9/D}; thus, in CCl4 at [THF]0 = 8.0M, and at 25° kp± = 4.0 × 10-21/mole-sec. In the polymerization with derivatives of CF3SO3H (able to form the corresponding macroester) the overall polymerization rate is much lower than that with complex anions because of the reversible conversion of the macroion-pairs into the macroester (internal return). The macroester is much less reactive than the macroionpair (102-103 times) in the monomer addition reaction. At [THF]0 = 8.0M and at 25°C, 96.5% of the growing species exists in the macroester form.Polymerization of THF initiated with derivatives of CF3SO3H is a subject of a strong special salt-effect. At a sufficiently high ratio of [AgSbF6] to [I]0, where the initiator I is C2H5OSO2CF3, the overall polymerization rate is equal to that observed for the polymerization of THF on the macroion-pairs, since the internal return within the triflate ion-pair (the macroester formation) is eliminated and polymerization proceeds on the macroion-pairs with SbF6- anions exclusively.

Notes: This study deals with the copolymerization of trioxane (TO) and 1-chloro-2, 3-epoxypropane (epichlorohydrin, ECH) catalyzed by EtB⊖F3 A⊕lEt2 in toluene. The rate of exhaustion of monomers during copolymerization was measured by gas chromatography. It was established that no homopolymers were formed. The copolymers obtained show a high alkali resistance, indicating a statistical distribution of the ECH in the polymer chain. During the first stages of the copolymerization the ECH is exhausted almost instantaneously, whereas TO is gradually exhausted, finally reaching a certain equilibrium depending both on the quantity of the initial ECH and on the temperature at which the process was carried out. Copolymerization is inhibited at increased ECH levels, and only homopolymerization occurs at a certain critical concentration of ECH.

Notes: The fracture toughness of PVC has been measured by using three-point bend specimens tested over a wide range of strain rate and temperature. A method has been described of deriving fracture load indirectly by measurement of stiffness from a preliminary “low blow” test in instrumented impact testing. Some limitations of the method, when used with semi-ductile material of low stiffness, have been discussed. Fracture toughness results have also been evaluated by an alternative energy method, which is however more suitably applied to the lower speed impact test. The curves of K1c versus temperature for PVC contain a weak maximum at a temperature below Tg, the location of which varies with testing speed. The position of the maximum in the time-temperature field has been compared with the locus of the β damping peak derived from mechanical (flexural vibrations, torsion pendulum) and dielectric loss measurements, with reasonable agreement. Static toughness was higher than dynamic, and this correlated with fracture surface appearance, thereby indicating a real difference in toughness probably associated with crack tip craze development.

Notes: The effect of the catalytic amount of H2O was investigated with the EtnAlCl3-n-VOCl3 catalyst system on the alternating copolymerization of acrylic monomers with diolefins and styrene. The presence of the catalytic amount of H2O produced an improvement in the yield and in the molecular weight as well as the structure of copolymer with the EtnAlCl3-n-VOCl3 catalyst system. The efficiency of the aluminum components in the EtnAlCl3-n-VOCl3 system appears with AlEt3 and especially with Et1.5AlCl1.5. The catalytic activity was found to depend upon the H2O EtnAlCl3-n molar ratio and was also affected by the order of mixing of the catalyst components and the monomers. Effective catalyst could be prepared when the catalyst components (except VOCl3) were premixed without presence of monomers. The possible catalytic behavior of H2O was discussed.

Notes: Pyrolysis of a commercial flexible urethane foam in an inert atmosphere was investigated by use of GCMS and chemical ionization mass spectroscopy. Pyrolysis products were identified and quantified at four pyrolysis temperatures. A mechanism is discussed in terms of the identified products.

Notes: Ring-opening polyaddition of 4,4′-disubstituted bisazlactones with various diamines was carried out in N-methyl-2-pyrrolidone to afford polyamides with pendant amide group having inherent viscosities of 0.17-0.51 in quantitative yields. The solution polymerization with aliphatic diamines was almost complete at room temperature within 24 hr. Nearly all of the polyamides were soluble in polar in polar aprotic solvents and in acidic solvents. These polymers began to decompose at around 200-300°C as determined by DTA and TGA under nitrogen.

Notes: Seven crosslinked polydimethylsiloxanes were prepared from carboxyl-terminated siloxane oligomers of different average lengths and a trifunctional imine. The 10-sec torsion modulus was measured as a function of temperature, and compression-deflection data were obtained on swollen specimens. Polymer-solvent interaction parameters were calculated from equilibrium swelling ratios and modulus data. The plots of modulus versus temperature show two distinct transitions for all the crosslinked polymers. The low-temperature transition corresponds to the siloxane chains, whereas the high-temperature transition should be attributed to the portion of the network chain derived from the crosslinking agent and the organic part of the oligosiloxane. On shortening the siloxane blocks, both transitions shift to successively higher temperatures and higher modulus levels. However, the siloxane transition temperature shows only a limited rise even when the average block length becomes quite small. The low siloxane polymers seem to exhibit two swelling maxima, each corresponding to one of the constituents. The studied materials from nonrandom copolymeric structures typical of block polymers. Such microphase systems can probably be expected in crosslinked polymers whenever the crosslinking agent participates significantly in the network chains and its compatibility with the flexible chains species is poor.

Notes: Bis(2-carb-n-butoxyethyl)methylphosphine oxide was prepared and condensed with 1,2-diaminoethane, 1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane, and 1,12-diaminododecane to form polyamides with an increasing number of methylene groups between the amide moieties. Polyamides made from the 1,10- and 1,12-diaminoalkanes were shown by x-ray and DSC to be semicrystalline, while those based on the 1,6- and 1,8-diaminoalkanes were amorphous to x-ray and revealed no first-order transitions. The repeat distances of the crystalline polymers were determined, and an extended planar zigzag conformation was excluded as a possible conformation for these polymers. The thermal stability of the phosphorus-containing polyamides, in both oxygen and nitrogen, was studied by TGA and the results were correlated with the chemical structure.

Notes: Polyesters were made with aromatic diacid chlorides and 4,4,-thiodiphenol. Isophthaloyl chloride and/or terephthaloyl chloride were used as acid chlorides alone or together with 5-cyanoisophthaloyl chloride or [2.2]p-cyclophane-3,9-dicarboxylic acid chloride. The latter components were incorporated in order to make the polymers useful for crosslinking. A polyether could be obtained by polycondensation of 2,4-dichloro-benzonitrile and 4,4′-thiodiphenol. The polycondensations were run in nitrobenzene as solvent.

Notes: The polymerization of picryl (PMA), 2,4-dinitrophenyl (2,4-DNMA),2,6-dinitrophenyl (2,6-DNMA), 2-methyl-4,6-dinitrophenyl (MDNMA), and 2,6-dimethylphenyl methacrylates (DMMA) was carried out in benzene at 60°C. PMA, 2,6-DNMA, and MDNMA did not undergo radical homopolymerization, while 2,4-DNMA and DMMA did. The results suggest that the growing radical readily attacks the oxygen atom of the nitro group at the 2 position of the terminal phenyl group due to the steric effect of the substituent at the 6 position, resulting in chain termination. PMA formed a charge-transfer complex with 2-naphthyl methacrylate (NMA). The stoichiometric composition of this complex was shown to be 1:1 molar complex. PMA was readily copolymerized with NMA. The amount of solvent affected the composition of the copolymer obtained at a given same mole fraction in feed. The results suggest that charge-transfer interaction between the ester groups affects the copolymerization mechanism.

Notes: ESR spectra and optical absorption spectra of γ-irradiated poly(methyl methacrylate) (PMMA) at 77°K and the photo- and thermal bleaching behavior have been studied. γ-Irradiation of PMMA yields a singles spectrum with a line width of 6 G which is bleachable with visible light. This species is assigned to the polymer cation. The unbleached species consists mainly of a four-line spectrum and is assigned to a polymer radical having a different CH2 conformation from the usual nine-line spectrum. On subsequent warming to room temperature, the spectrum changes into the nine-line spectrum. γ-Irradiation of PMMA containing biphenyl as an additive at 77°K gives biphenyl cation. Yield of polymer radical is reduced by the addition of biphenyl and 2-methyltetrahydrofuran. A mechanism is proposed which is consistent with the experimental results.

Notes: The polyfluoroethers \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \rlap{--}[OCH}_{\rm 2} {\rm XCH}_{\rm 2} {\rm OCH}_{\rm 2} ({\rm CF}_{\rm 2} )_3 {\rm CH}_{\rm 2} \rlap{--} ]_n $\end{document} (X = O, 1,3-C6H4, 1,4-C6H4 or 4,4′-C6H4OC6H4) and copolymers (X = 1,3- and 1,4-C6H4) having inherent viscosities in acetone 〉0.5 dl/g were prepared in good yields by treatment of the mixture of sodium salts obtained from 2,2,3,3,4,4-hexafluoropentanediol and an excess of sodium hydride in tetramethylene sulfone (TMS)-tetrahydrofuran or TMS-petroleum ether with the appropriate bishalomethyl compound. The polymers varied from highly extensile elastomeric gums when X = O or 1,3-C6H4 to a leathery material when X = 4,4′-C6H4-OC6H4. Glass transition temperatures ranged from -43°C when X = 0 to 6°C when X = 4,4′-C6H4OC6H4. The polymers started to lose weight (by thermogravimetry) at 220-250°C in oxygen and at 250-290°C in nitrogen. However, the xylylene polymers underwent structural changes even at room temperature, as reflected by changes in solution viscosity. Attempts to cure the polymer when X = O with peroxides were unsuccessful.

Notes: Critical surface tensions γc of poly(vinyl butyral) and poly(vinyl benzal) multilayers built up by the Langmuir-Blodgett method were measured with polyhydric alcohols and n-alkanes. The γc values of both polymer multilayers increased with increasing pressures of the piston oils used to control pressures of polymers on the water surface during deposition. The γc value of poly(vinyl butyral) multilayers built up to lower pressure of the piston oil was approximately consistent with a crystalline hydrocarbon surface, while the γc value of the multilayer built up to higher pressure of the piston oil was approximately consistent with a - CH3 rather than a —CH2 —CH2— surface. All results for γc values of poly(vinyl benzal) multilayers were very close to the γc value of benzene ringrich surface. The γc value of the multilayer built up to lower pressure of the piston oil almost coincided with the γc value for amorphous polystyrene, while the γc value for the multilayer built up to higher pressure of the piston oil was in fair agreement with γc for an aromatic ring edge in the crystalline state. Values of γsd, the dispersion force contribution to the surface free energy of multilayers calculated by Fowkes' relation, were in fair agreement with the corresponding observed γc values, respectively. It is concluded from these measurements that orientations and surface structures in both polymer multilayers are affected by pressure change of piston oils. The properties on monolayers of two polymers at a air-water interface and on barium stearate multilayers are also presented.

Notes: Neighboring monomer units cause significant shifts in the infrared absorption peaks attributed to cis- and trans-1,4 units in conjugated diene-acceptor monomer copolymers. Conjugated diene-maleic anhydride alternating copolymers apparently have a predominantly cis-1,4-structure, while alternating diene-SO2 copolymers have a predominantly trans-1,4 structure. Alternating copolymers of butadiene, isoprene, and pentadiene-1,3 with α-chloroacrylonitrile and methyl α-chloroacrylate, prepared in the presence of Et1.5AlCl1.5(EASC), have trans-1,4 unsaturation. Alternating copolymers of chloroprene with acrylonitrile, methyl acrylate, methyl methacrylate, α-chloroacrylonitrile, and methyl α-chloroacrylate prepared in the presence of EASC-VOCl3 have trans-1,4 configuration. The reaction between chloroprene and acrylonitrile in the presence of AlCl3 yields the cyclic Diel-Alder adduct in the dark and the alternating copolymer under ultraviolet irradiation. The equimolar, presumably alternating, copolymers of chloroprene with methyl acrylate and methyl methacrylate undergo cyclization at 205°C to a far lesser extent than theoretically calculated, to yield five and seven-membered lactones. The polymerization of chloroprene in the presence of EASC and acetonitrile yields a radical homopolymer with trans-1,4 unsaturation.

Notes: Free-radical copolymerizations of N-methylpyridazinone (I) and N-phenylpyridazinone (II) with styrene (M1) were carried out in various solvents. The copolymerization rates were found to increase linearly with increasing viscosities of the reaction mixtures. Monomer reactivity ratios were strongly affected by the reaction media. This might be due to solvation of the carbonyl group of the pyridazinone ring, because linear relationships between log 1/r1 and vc=o of the pyridazinones were obtained. It was also found that monomer concentration influences these copolymerizabilities.

Notes: Polymerization of MMA was carried out in presence of visible light (440 nm), quinoline-bromine charge-transfer complex being used as the photoinitiator. The initiator exponent was observed to be 0.5 up to 0.014 M initiator concentration; when chloroform was used as the solvent, the monomer exponent was found to be unity. The polymerization was inhibited in presence of hydroquinone but little inhibitory effect was observed in the presence of air. An average value of k2p/kt for this photopolymerization system was found to be (1.08 ± 0.22) × 10-2. Kinetic and other evidence indicates that the overall polymerization takes place by a radical mechanism.

Notes: The effect of moisture content upon free radical formation in celluloses irradiated with ultraviolet light has been studied by means of ESR spectroscopy at 77°K. As studied from the variation of the line-shape and the relative signal intensity of the spectra observed, it is clear that moisture content in the sample greatly influences the formation of free radicals when irradiated with ultraviolet light. The moisture content in the range of 5-7% leads to a significant decrease of radical formation; and alternatively, when moisture content is lower or higher than this range, the formation of free radicals is increased.

Notes: The technique of microozonolysis followed by gas chromatography has been used to determine the amount of 1,2-structures occurring as 1,4-1,2-1,4 sequences in n-butyl-lithium-initiated polybutadienes. The product obtained from the ozonolysis of these sequences, 3-formly-1,6-hexanedial, was directly proportional to the 1,2 (vinyl) content of the polymers as measured by infrared or NMR spectroscopy. An unusual ozonolysis product, 4-octene-1,8-dial, has been found in the ozonolysis products of high-1,4 poly-butadienes. Ozonolysis has also been used to determine alternating structures in propylene-butadiene copolymers. The product obtained from ozonolysis of such structures is 3-methyl-1,6-hexanedial. Ozonolysis of a polyisoprene containing equal amounts of 1,4 and 3,4 structures indicated it to have a nonalternating structure with long blocks of 1,4-isoprene units. Gas chromatographic separation was accomplished by using sucrose acetate isobutyrate with Carbowax 20M as the liquid phase. Retention times were established by using model compounds where possible.

Notes: Thermosetting arylimides were prepared by reaction of sulfone ether diamines with maleic anhydride followed by chemical imidization of the intermediate polyamic acid with acetic anhydride/sodium acetate. These arylimides could be thermally cured to afford heat stable systems possessing high glass transition temperatures (Tg) and moderate to high modulus plateaus above the Tg, depending upon the molecular weight between maleimide sites. The addition type curing process alleviates problems associated with the fabrication of other polyimide systems, since volatiles are not liberated and lowviscosity, high-solids solutions can be prepared in common organic solvents. Thermal, mechanical, adhesive and fabrication characteristics are reported for the sulfone-based arylimides, which indicate utility in spectrum of high-temperature applications.

Notes: A variety of techniques were used to follow the thermal degradation of a poly(parabanic acid) (PPA-M). The kinetic data associated with the weight loss as a function of time at elevated temperatures indicates a random initiation process followed by depolymerization. Infrared and mass spectral techniques further confirmed the kinetic data by showing the presence of isocyanate and amide groups in addition to CO, CO2, and nitric oxide gases being evolved. Incipient gelation occurs simultaneously with the formation of the amide. A reverse Hoffman rearrangement mechanism has been proposed which appears to be consistent with the available experimental data.

Notes: The pyrolysis of chlorinated polybutadienes (CPB) was investigated by using a pyrolysis gas chromatograph. CPB corresponds to poly(vinyl chloride) (PVC) constructed with head-head and tail-tail linkages of the vinyl chloride unit. Benzene, toluene, ethyl-benzene, o-xylene, styrene, vinyltoluene, chlorobenzenes, naphthalene, and methylnaphthalenes were detected in the pyrolysis products from CPB above 300°C, and no hydrocarbons could be detected at 200°C. The pyrolysis products from CPB were similar to those from PVC and new products could not be detected. Lower aliphatics, toluene, ethylbenzene, o-xylene, chlorobenzenes, and methylnaphthalenes were released more easily from pyrolysis of CPB than from PVC; amounts of benzene, styrene, and naphthalene formed were small. These results support the conclusion that recombination of chlorine atoms with the double bonds in the polyene chain takes place and that scission of the main chain may depend on the location of methylene groups isolated along the polyene chain during the thermal decomposition of PVC.