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Digitale Medien

Post-gamma-irradiation grafting of polypropylene. Part II. Butadiene: E.S.R. experiments (1986)

Busfield, W. Ken ; Buchanan, Tracey Morley ; Pomery, Peter J.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 3089-3099

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ISSN: 0887-624X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: ESR spectra of gamma irradiated annealed and quenched forms of polypropylene film have been studied at the temperatures used for post-irradiation grafting experiments with butadiene, described in Part I. On warming from low temperature there is radical loss by termination and some radical transformation to radicals with optimum stability in annealed polypropylene at approximately 45°C. These radicals, which may be allyl type, are sited at the crystal faces, and decay more rapidly at higher temperatures in annealed polypropylene; in quenced polypropylene their concentration never exceeds one third the optimum observed in annealed polypropylene. Correlation with the grafting experiments suggests that allyl radicals are important for long-term grafting. Effects on the ESR spectrum of adding butadiene to the system show that in the long-term butadiene adds exclusively to the allyl radicals and that alkyl radicals still present at that stage are precursors to the allyl radicals. They do not react directly with butadiene presumably because they are sited in the inaccessible crystal core. Experiments at lower temperature show that butadiene does react with alkyl radicals in accessible regions.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pola.1986.080241133

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Probing changes in the structure and performance of a lithium nickel oxide catalyst by in situ X-ray diffraction during the high temperature oxidative coupling of methaneWe thank the Science and Engineering Research Council for a studentship (to I J P), a fellowship (to P J M) and an equipment grant (to J M T). (1989)

Pickering, Ingrid J. ; Maddox, Peter J. ; Thomas, John M.

Weinheim : Wiley-Blackwell

Advanced Materials 1 (1989), S. 194-196

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ISSN: 0935-9648

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/adma.19890010604

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3

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Two-Dimensional NMR studies of [Pro-10] atrial natriuretic factor [7-23] (1988)

Gampe, Robert T. ; Connolly, Peter J. ; Rockway, Todd ; [weitere]

New York : Wiley-Blackwell

Biopolymers 27 (1988), S. 313-321

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The conformational properties of an analog of atrial naturiuretic factor, [Pro-10] ANF(7-23), were examined in H2O, H2O/DMSO-d6 (2/1), and DMSO-d6 using two-dimensional nmr techniques. The sequence differs from the native peptide by the absence of the exocyclic N- and C-terminal residues, and the substitution of a proline for a glycine at position 10 - a modification expected to reduce the conformational flexibility of this analog. The backbone proton nmr resonances were assigned from two-dimensional correlated spectroscopy (2D-COSY), relayed COSY, and 2D nuclear Overhàuser enhancement (NOE) experiments, and the solution conformation was evaluated from vicinal spin-spin coupling constants and NOE data. Despite the substitution of a proline in the sequence, [Pro-10] ANF(7-23) exhibits a considerable amount of flexibility in all of the solvents employed.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.360270210

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Polydispersity effects on diffusion in polymers: Concentration profiles of d-polystyrene measured by forward recoil spectrometry (1986)

Mills, Peter J. ; Green, Peter F. ; Palmstrøm, Christopher J. ; [weitere]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 1-9

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ISSN: 0887-6266

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Forward recoil spectrometry is shown to be a useful technique for measuring diffusion of d-polymer chains in h-polymer melts. Concentration profiles of a deuterated diffusing species may be determined with a depth resolution of 80 nm and a sensitivity of 0.1 vol % d-polymer in h-polymer. Consequently diffusion coefficients as small as 10-16 cm2/s can be readily measured. If polymer chains diffuse by a reptation mechanism, the concentration profile ø(x) of diffusing polydisperse polymer should be quite different from øm(x), the Fickian solution, which one obtains for monodisperse polymer. This idea was tested by measuring ø(x) of polydisperse d-polystyrene (d-PS) diffusing into h-PS. The results are in excellent agreement with the ø(x) predicted from the reptation model and the experimentally determined molecular weight distribution.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/polb.1986.180240101

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5

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Hydrogen-bonding. Part 4. An analysis of solute hydrogen-bond basicity, in terms of complexation constants (log K), using F1 and F2 factors, the principal components of different kinds of basicityPart 3. M. H. Abraham, P. P. Duce, D. V. Prior, R. A. Schulz, J. J. Morris and P. J. Taylor, J. Chem. Soc. Faraday Trans. 1, 84, 865 (1988). (1989)

Abraham, Michael H. ; Grellier, Priscilla L. ; Prior, David V. ; [weitere]

Chichester : Wiley-Blackwell

Journal of Physical Organic Chemistry 2 (1989), S. 243-254

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ISSN: 0894-3230

Schlagwort(e): Organic Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The principal components factors F1 and F2 in the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ \log K = {\rm BDP}_0 + S_1 F_1 + S_2 F_2 $$\end{document} have been used to obtain S1 and S2 values for sets of hydrogen-bond bases against 32 reference acid/solvent systems. The constants S1 and S2 define an angle θ = tan-1 S2/S1 that is a measure of the electrostatic:covalent bonding ratio in the hydrogen-bond complex. It is shown that θ can vary from 53 (4-fluorophenol in CH2Cl2)to 86 degrees (Ph2NH in CCl4) depending on the reference acid and solvent. This variation in θ can lead to family dependent behaviour in plots of log K for bases against a given reference acid system vs log K for bases against another reference acid system, and precludes the construction of any general scale of hydrogen-bond basicity using log K values. Amongst a quite wide range of reference acid/solvent systems θ varies only from 64 to 73 degrees, and for bases against these reference systems a ‘reasonably general’ scale could be set up. Such a scale could be extended to bases against reference acid/solvent systems outside the 64-73 degree range provided that certain classes of base (e.g. pyridines, alkylamines) were excluded from the additional reference acid/solvent systems.

Zusätzliches Material: 6 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/poc.610020307

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6

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Hydrogen-bonding 8.Part 7; M. H. Abraham, P. L. Grellier, D. V. Prior, P. P. Duce, J. J. Morris and P. J. Taylor. J. Chem Soc., Perkin Trans. 2, (in press). Possible equivalence of solute and solvent scales of hydrogen-bond basicity of non-associated compounds (1989)

Abraham, Michael H. ; Buist, Gabriel J. ; Grellier, Priscilla L. ; [weitere]

Chichester : Wiley-Blackwell

Journal of Physical Organic Chemistry 2 (1989), S. 540-552

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ISSN: 0894-3230

Schlagwort(e): Organic Chemistry ; Physical Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Using the solvatochromic indicator method, a scale of solvent hydrogen-bond basicity, β1 (General), has been set up using a series of double regression equations, \documentclass{article}\pagestyle{empty}\begin{document}$$ \nu = \nu _0 + s\pi _1^* + b\beta _1 $$\end{document} for 11 aniline-type indicators. A similar solvent scale, β1 (Special), has been constructed by the homomorphic comparison method using only results by Laurence et al. on the indicators 4-nitroaniline and 4-nitro-N,N-dimethylaniline. Results are available from our previous work on a general solute scale, β2H, and we have also obtained a special solute scale, β2 (pKHB) from available log K values for hydrogen-bond complexation of bases with 4-fluorophenol in CCl4. However, the two solute β2 scales are virtually identical.It is shown that there is a general connection between β1(General) and β2H, with r = 0·9775 and s.d. = 0·05 for 32 compounds, and between β1(Special) and β2H, with r = 0·9776 and s.d. = 0·06 for the same 32 compounds. The latter correlation over 60 compounds yields r = 0·9684 and s.d. = 0·07. However, there are so many compounds in these regressions for which the differences in the solvent and solute β values are larger than the total expected error of 0·07 units that the use of β1 to predict β2 or vice versa is a very hazardous procedure. About 70 new β1 values obtained by the double regression method are also reported.

Zusätzliches Material: 6 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/poc.610020706

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ESR study of reactions of cellulose initiated by the ceric ion methodPaper presented in part at the IUPAC International Symposium on Macromolecular Chemistry, Tokyo and Kyoto, Japan, September 28-October 4, 1966. (1966)

Arthur, Jett C. ; Baugh, Peter J. ; Hinojosa, Oscar

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 10 (1966), S. 1591-1606

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The ESR spectra of microcrystalline cellulose and purified cotton cellulose reacted with ceric ammonium nitrate in nitric acid were determined. The effects of the concentration of ceric ion, atmosphere, temperature, and graft copolymerization with acrylonitrile on the rates of formation and decay of radicals in the cellulose molecule were determined under both static and dynamic conditions. Under static conditions, after the desired conditions of reaction, the samples were frozen at -100 or -160°C., and then the concentration of free radicals was determined. Under dynamic conditions ceric ion solution was continuously flowed through the celluloses while these determinations were being made at 25°C. In the presence of oxygen the rate of decay of free radicals was decreased. On initiation of copolymerization reactions with acrylonitrile, there was an increase in radical concentration, then a decrease. Apparently, during graft copolymerization the radical site initially on the cellulose molecule was retained on the end of the growing polymer chain. Then additional ceric ion coordinated with the hydroxyl groups of the cellulose, leading to the formation of additional radical sites. An Arrhenius interpretation of the effect of temperature on the formation of these additional radical sites gave apparent activation energies for radical formation on cotton cellulose as 34 kcal./mole and on microcrystalline cellulose as 29 kcal./mole.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1966.070101015

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ESR spectra of copper complexes of cellulose (1968)

Baugh, Peter J. ; Hinojosa, Oscar ; Arthur, Jett C. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 12 (1968), S. 249-265

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The ESR spectra of complexes of fibrous cotton cellulose and cupriammonia dihydroxide or cupriethylene diamine dihydroxide under various experimental conditions were determined. The spectra of both complexes with cotton cellulose were almost identical at -100 and 25°C. The spectrum of the complex of cupriethylene diamine dihydroxide with cellulose was stable to temperatures as high as 100°C. The sum of the linewidths of the hyperfine components of the spectra for each complex was about 180 gauss. Cotton fibers were combed and aligned with their axes (lengths) parallel to the magnetic field (B∥); after formation of either of the complexes with cellulose a minumum of hyperfine structure of components centered at H∥ was observed. A maximum of hyperfine structure of these components was observed when the complexed fibers were aligned with their axes perpendicular to the magnetic field (B⊥). The opposite was true of components centered at H⊥. For a complex of cupriethylene diamine dihydroxide and cellulose at 25°C. and at high pH the g∥ was 2.2127 and the g∥ was 2.0476. It was suggested that the alignment of most of the complex was its axis of symmetry at a maximum angle to the axes of the cotton fiber, when the axes of the fibers were in the parallel alignment with the magnetic field. At high pH these observations were even more marked. When ramie was used with cupriethylene diamine dihydroxide at high pH, the contribution of components centered at H∥ to the spectra was zero. Spectra for the copper compounds alone and complexed with cellobiose are also reported.

Zusätzliches Material: 16 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1968.070120202

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Water immersion of polysulfide sealants. II. An interpretation of the influence of curing systems on water resistancePresented at Adhesives, Sealants and Encapsulants 85 (Network Events), London, U.K., November 1985. (1986)

Hanhela, Peter J. ; Huang, Robert H. E. ; Paul, D. Brenton ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 32 (1986), S. 5415-5429

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Dichromate cured polysulfide sealants have superior resistance to swelling in hot water than those cured with manganese dioxide and examinations to identify the reasons for this difference were undertaken. The commercial sealants PR-1422, PR-1750, and Pro-Seal 899 were shown to contain similar types and loading of fillers. Crosslink densities were compared through a procedure involving an oscillating disc cure meter modified to accommodate mobile mixtures. No relationship between stability and crosslinking was observed. Formation of large voids in MnO2-cured sealants after prolonged immersion at 70-90°C, suggests the formation of a water-soluble acid which then reacts with the CaCO3 filler, and this was supported by pH measurements. The acid was shown to arise through autoxidation of formal groups in the polysulfide, and this process can be suppressed by radical scavengers (including ammonium dichromate). When PR-1750 was examined under nitrogen or with carbon black as filler, a similar time-swell curve to that of PR-1422 was produced. It was concluded that abnormal swell does not result simply from autoxidation: a filler capable of reacting with the acid must also be present.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1986.070320614

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ESR study of post-irradiation reactions of cellulose and acrylonitrile (1967)

Baugh, Peter J. ; Hinojosa, Oscar ; Arthur, Jett C.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 11 (1967), S. 1139-1153

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: An ESR study of the free-radical mechanisms of the post-irradiation reactions of cotton cellulose with acrylonitrile is reported. The effects of atmosphere, moisture content, and solutions of acrylonitrile on the yield and stability of free-radical sites in irradiated cellulose were determined. On interaction of γ-radiation from a 60Co source with cotton cellulose, long-lived free-radical sites were found within the molecular lattice. Short-lived free-radical sites were apparently also formed on chain cleavage, gave strong singlet spectra, and were readily accessible to interaction with water. Other free-radical sites were formed within regions of the cellulosic fiber which were inaccessible to moisture or aqueous solutions even after contact times as long as three days. It was suggested that long-lived free-radical sites in cellulose I (containing regain moisture) resulted from dehydrogenation at C5, and in cellulose II (containing regain moisture) resulted from dehydrogenation at C5 and dehydrogenation of the OH group or dehydroxylation at C6. When irradiated cellulose was contacted with a solution of acrylonitrile (15%) in 75% aqueous zinc chloride, the initial rate of decrease in spin concentration was higher than the rate of decrease as the time of contact increased. The ESR spectrum of the reacted cellulose, observed at -100°C., as compared with the spectrum for the irradiated cellulose, had decreased in signal strength with increase in time of contact and changed from a three-line spectrum to an ill-defined spectrum. The free radical being observed was probably due to unreacted sites in the cellulose. The extent of the graft copolymerization reaction was directly related to the initial spin concentration in the irradiated cellulose.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1967.070110712

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