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  • Chemistry  (38,506)
  • 1995-1999  (38,506)
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Year
  • 1
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
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  • 2
    Publication Date: 2019-03-27
    Description: Dissolved oxygen and carbonate system in seawater in the Gulf of Thailand and the east coast of Peninsular Malaysian September 1995 and April-May 1996 were determined. It was found that surface water was well in equilibrium with the atmosphere. The sub-pycnocline water in the Gulf had the chemistry that was distinctly different from the mixed layer as well as from sub-pycnocline water in the South China Sea near the mouth of the Gulf, even with the same depth. There were some evidences that intermediate water in the South China Sea might flow into the Gulf along the central axis and the coast of Vietnam and Cambodia, and exited the Gulf along the Thai-Malay Peninsular coast. The chemistry of deep water in the South China Sea off the coast of Western Malaysia varied its chemistry by a great deal among seasons which might be due to the prevailing monsoon. Seawater in the Gulf of Thailand and South China Sea was supersaturated with respected to the mineral calcite.
    Keywords: Chemistry ; Oceanography
    Repository Name: Aquatic Commons
    Type: Book Section , NonPeerReviewed
    Format: application/pdf
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  • 3
    ISSN: 0886-9383
    Keywords: Deconvolution algorithms ; Instrumental analysis ; Spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deconvolution algorithms for measurand reconstruction are considered. Their metrological and numerical properties are briefly characterized. Six algorithms most frequently used for instrumental applications are selected for closer analysis. Their comparative study is based on the use of spectrometric-type synthetic data, calorimetric-type synthetic data and spectrometric real-world data. Conclusions concerning computational complexity and accuracy of the compared algorithms as well as their metrological applicability are drawn.
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  • 4
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 69-89 
    ISSN: 0886-9383
    Keywords: chemometrics ; pattern recognition ; class modeling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different estimators of the Mahalanobis distance (such as that based on the Defrise - Gussenhoven correction) are studied and compared with respect to the bias on the distance and the characteristics (sensitivity and specificity) of the class model.Results obtained using estimators with critical values from χ2-statistics are compared with those obtained using estimators with critical values from β-statistics (training set) and Hotelling statistics (evaluation set).Tables are reported for D-statistics (useful for simulating populations of two categories with selectable theoretical sensitivity and specificity) and for critical values of the Mahalanobis distance obtained from β-statistics.For objects of the training set the estimator of the Mahalanobis distance based on the estimate of the covariance matrix produces models with the optimum sensitivity. The same model has too low a sensitivity for objects of the model category in the evaluation set, but good specificity for objects of outer categories.The estimator with the Defrise-Gussenhoven correction produces enlarged models with too high a sensitivity for objects in the training set, good sensitivity for objects of the model category in the evaluation set and low specificity for objects of outer categories.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 139-141 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 125-135 
    ISSN: 0886-9383
    Keywords: Procrustean analysis ; FT-IR spectroscopy ; NIR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Procrustean methods allow the fitting of a given matrix to another given matrix observed on the same objects. In the traditional approach orthogonal constraints are imposed upon the transformation matrix, whereas in the alternative approach Procrustean analysis may be performed without such constraints. The two methods (with and without constraints) were compared on data dealing with mid- and near-infrared spectra of oil. The aim was to reconstruct the mid-infrared spectral information using data from the near-infrared spectra. Unconstrained Procrustean analysis proved to be the more efficient for both the calibration and verification sets. Furthermore, the analysis of the transformation matrix between the two infrared ranges made it possible to indicate wavelengths and wave numbers corresponding to the same chemical groups.
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  • 8
    ISSN: 0886-9383
    Keywords: pattern recognition ; infrared spectra ; factor analysis ; maximum likelihood method ; entropy of information ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spectral region from 700 to 3600 cm-1 is subdivided into several wave number intervals. The peaks in each interval are summarized by means of three encoding algorithms. Using a factor model of kcommon factors, the total extractable variacnce (com) of a given set of intervals is calculated and correlated with the redundancy of information in all these intervals. The value of com is verified by analysis of the factor loadings aik (factor pattern). Finally, the information content of some chosen sets of intervals coded by the three selected feature algorithms will be correlated to the probability of information flow through a serial-parallel network. The encoding using only wave numbers was found to be the most effective.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 223-225 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 230-231 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 239-262 
    ISSN: 0886-9383
    Keywords: industrial experimentation ; parameter design ; quality by design ; robust design ; Taguchi method ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this paper is to present a simple structured review of the different approaches to robust process design to clarify their similarities and dissimilarities. It is primarily written for practitioners who wish to understand and compare the main ideas of each approach and to apply them to their work. Two examples are used to illustrate the different approaches and their corresponding data analysis strategies: the first one is a constructed example on a pigment kneading process and the second one is real example dealing with the validation of an HPLC method. A comparison of the different approaches is provided and some practical recommendations are formulated.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 9 (1995), S. 329-330 
    ISSN: 0886-9383
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 13
    ISSN: 0887-624X
    Keywords: poly(1-ethynylcyclohexene) ; conjugated polymer ; transition metal catalysts ; organoaluminum compounds ; thermal property ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Ethynylcyclohexene, an acetylene derivative having cyclohexenyl substituent, was polymerized by various W- and Mo-based catalysts. WCl6-EtAlCl2 catalyst system was found to be very effective for this polymerization. The effects of the monomer-to-catalyst mol ratio, the initial monomer concentration, the temperature, and the cocatalysts for the polymerization of 1-ethynylcyclohexene by WCl6 were investigated. The catalytic activity of Mo-based catalysts was found to be similar to that of W-based catalysts. The polymer structure was identified to have a conjugated polymer backbone carrying a cyclohexenyl substituent. The resulting polymers were light-brown powder and completely soluble in aromatic and halogenated hydrocarbon solvents such as chlorobenzene, benzene, chloroform, carbon tetrachloride, etc. Studies of the thermal properties and morphology of poly(1-ethynylcyclohexene) were also carried out. © 1995 John Wiley & Sons, Inc.
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  • 14
    ISSN: 0887-624X
    Keywords: bipolar amphiphiles ; bolaamphiphiles ; vesicles ; oligomeric phosphates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Certain phosphate bipolar amphiphiles, both monomeric (I and II) and polymeric or rather oligomeric (poly-I and poly-II), were used as basic materials for the preparation of simple and mixed vesicles. Specifically, it was found that oligomeric phosphate bipolar amphiphiles form stable vesicles in aqueous media. The same oligomeric bolaamphiphiles in mixture with their monomeric counterparts also form stable mixed vesicles with sonication; they are relatively less stable with the “thin film method.” Furthermore, it was shown that the method of spanning the membrane of didodecylphosphate vesicels with the dipolar amphiphile II is not effective for enhancing stability. © 1995 John Wiley & Sons, Inc.
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  • 15
    ISSN: 0887-624X
    Keywords: naphthalimide ; naphthalisoimide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of model compounds from 4-benzoyl-1,8-naphthalene anhydride and aromatic amines and diamines has been synthesized. The influence of the reaction conditions on the structure of the compounds obtained has been investigated to explain the high-temperature polycondensation reaction mechanism. It was found that at high-temperature polycondensation of 1,8-naphthalene-type anhydrides with aromatic amines, isoimides with cis and and trans structures are formed instead of amic acids. The only trans isoimides may isomerize to imide structure. © 1995 John Wiley & Sons, Inc.
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  • 16
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: maleic anhydride ; free radical grafting ; hydrocarbons ; polyethylene ; graft size ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Maleic anhydride has been grafted to eicosane and squalane at 60-80°C using 1,2-dichlorobenzene as solvent and benzoyl peroxide as initiator. These hydrocarbons are low molecular weight models for hydrocarbon polymers containing secondary and tertiary hydrogen atoms. In the absence of the hydrocarbon and with monomer concentrations of the order of 1M, low molecular weight poly(maleic anhydride) is formed. On addition of the hydrocarbon, the main product is grafted material and very little homopolymer is formed. The grafts consist primarily of single succinic anhydride units but some of them are short poly(maleic anhydride) chains. Ceiling temperature considerations control the formation of homopolymer in the absence of hydrocarbon substrate. In the presence of eicosane or squalane, initiation of grafting proceeds by hydrogen abstraction from the hydrocarbon. The main factor controlling graft length is then the ratio of the rates of intramolecular hydrogen abstraction and of monomer addition to succinic anhydride radicals © 1995 John Wiley & Sons, Inc.
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  • 17
    ISSN: 0887-624X
    Keywords: vanadium ; 51V-NMR ; polymerization ; catalysts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several VOCL3-based ethylene polymerization catalyst precursors were prepared on silica and studied by solid-state 51V-NMR. The structure of the vanadium species in these samples, as determined by 51V-NMR, did not have any significant effect on the resultant polyethylene MI or MWD. This result is significant since conventional wisdom says the attachment of the transition metal to the silica plays a key role in polymer properties. VOCl3 reacted with hexamethyldisilazane-treated silica and with 250°C dried silica results in double attachment of the vanadium to the silica, yet the catalysts which formed had different reactivities and produced polyethylene with different HLMIs. On the other hand, VOCl3 reacted with 600°C dried silica results in single attachment of the vanadium to the silica, yet this catalyst had a similar reactivity and produced polymer properties similar to the doubly attached vanadium on 250°C dried silica. Two theories are offered to explain the lack of correlation between catalyst precursor structure and catalyst performance. © 1995 John Wiley & Sons, Inc.
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  • 18
    ISSN: 0887-624X
    Keywords: 2-phenyl-4-methylene-1,d-dioxolane ; methylene-1,3-dioxolanes ; cationic photopolymerization ; poly(keto-ether)s ; poly(alkylene-ether-ketone)s ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 19
    ISSN: 0887-624X
    Keywords: propagating polymerization fronts ; frontal polymerization ; traveling waves ; conversion ; adiabatic polymerization ; temperature profiles ; ceiling temperature ; molecular weight distribution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several properties of propagating fronts of addition polymerization were studied. A power function could be fit to the velocity dependence on initiator concentration, but not with the exponents predicted by current models or in agreement with other published work. Bubbles from the volatile by-products of initiator decomposition were found to affect the front velocity and curvature. The front velocity for triethylene glycol dimethacrylate polymerization was found to depend linearly on temperature over a moderate range. The conversion of methacrylic acid in fronts varied greatly with initiator type and concentration. Benzoyl peroxide produced much lower conversion than t-butyl peroxide, but fronts with tBPO propagated slower. A dual initiator system of BPO and tBPO produced rapidly propagating fronts with good conversion but the contribution of each initiator to the velocity was not additive. The possibility of chain branching was considered. The apparent molecular weight distributions were very broad, often trimodal, and found to depend on initiator type and concentration as well as the tube diameter. The temperature profiles were measured and found to be very sharp for BPO and broader for tBPO but both had front temperatures in excess of 200°C, indicating a high ceiling temperature. © 1995 John Wiley & Sons, Inc.
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  • 20
    ISSN: 0887-624X
    Keywords: isotactic poly(acrylonitrile) ; UV-irradiation canal polymerization ; acrylonitrile/urea canal complex ; statistical analysis ; structure-properties relationships ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotactic poly(acrylonitrile) (PAN) has been prepared by means of a conventional ultraviolet (UV) irradiation apparatus without γ-ray sources; an acrylonitrile-urea canal complex was directly formed at the surface of the UV (Hg) emission tube at low temperatures (∼ -78°C). When the complex was UV-irradiated at this temperature, a stereoregular polymer was formed in the canal. The 13C-NMR analyses indicate that (1) these PAN are rich in isotactic configuration, (2) the extent of the isotactic triad is in the range of 56-71%, and (3) the penultimate unit effect, 4 (mm) (rr)/(mr)2, is linearly correlated with the ultimate unit effect, (mm)/(rr). From the plots of log{4(mm)(rr)/(mr)2} vs log{(mm)/(rr)}, the anomaly in the polymerization of AN is discussed. The molecular characteristics of the UV canal PAN such as molecular weight, etc., were briefly noted. © 1995 John Wiley & Sons, Inc.
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  • 21
    ISSN: 0887-624X
    Keywords: chain coupling reactions ; bisoxazoline ; bisoxazine ; carboxy end groups ; polyester ; polyamide ; bulk reaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2,2′-Bis(2-oxazoline) and 2,2′-bis[5,6-dihydro-(4H)-1,3-oxazine] have been used as chain coupling reagents (CC) and reacted in the bulk with α,ω-dicarboxy-poly(2,2′-oxydiethylene adipate) (PS) or with α,ω-dicarboxy-polyamide 12 (PA). The reactions have been followed by viscosimetry, titration of COOH groups and 1H- and 13C-NMR spectroscopy. Either with the PS/CC or PA/CC systems, or with the model system dodecanoic acid (DA)/CC, the reactions were fast, since in most cases 80% conversion was reached after 15 min reaction. The expected DA dimer or high molar mass PA or PS polymers were obtained. No significant side reaction has been detected. The thermal stability of the resulting polymers is higher than that of starting oligomers. Due to the introduction of CC units in the chains, the crystallinity of PA/CC is slower than that of starting PA. © 1995 John Wiley & Sons, Inc.
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  • 22
    ISSN: 0887-624X
    Keywords: polycarbonate ; polycondensation ; oligomer ; molecular weight ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular weight of polycarbonate formed by the carbonate-ester interchange reaction of bisphenol-A diacetate (BPAC2) and dimethyl carbonate (DMC) was found to depend on the composition of the oligomer formed in its first stage. At a [DMC] : [BPAC2] ratio of 2, an oligomer with relatively higher acetate end group concentration was formed. This upon further polycondensation yielded a polycarbonate of inherent viscosity, 0.2-0.25 dL/g. Upon addition of DMC at a later stage in the oligomer-forming reaction, an oligomer containing relatively higher carbonate end groups could be obtained. These oligomers gave polycarbonates higher inherent viscosity, 0.4-0.5 dL/g. It is therefore proposed that oligomers having carbonate end groups are more reactive in self-polycondensation than those containing acetate end groups. © 1995 John Wiley & Sons, Inc.
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  • 23
    ISSN: 0887-624X
    Keywords: epoxy/amine mechanism ; crosslinking ; rate law ; diffusion limit ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bulk phase kinetics of an epoxy (DGEBA) /amine (DDS) thermoset have been studied using DSC, FTIR, and 13C-NMR. In the absence of catalyst, the reaction was found to involve a main exothermic reaction between epoxide and amine hydrogen and a side reaction between tertiary amine formed in the main reaction and epoxide. The main reaction was exothermic while the side reaction had no discernable exotherm. Etherification did not occur to any significant extent. Since only the main reaction is exothermic, DSC was very useful for studying the main reaction kinetics. FTIR was used for determining whether epoxide and amine hydrogen were consumed at different rates as a way of following the side reaction. An IR band previously unused by other investigators was used to monitor the amine hydrogen concentration. NMR confirmed the above mechanism by identifying the formation of a quaternary ammonium ion/alkoxide ion pair as a reaction product of tertiary amine and epoxide. This mechanism has been successfully fit to a rate law valid over the entire extent of reaction. The rate constant for the epoxy/amine addition reaction was found to depend on hydroxide concentration (extent), reaction temperature, and glass transition temperature and included contributions from uncatalyzed and autocatalyzed parts. The side reaction (quaternary ammonium ion formation) formed weak bonds which did not affect the overall system Tg. Both reactions were second order. The rate constants for the main reaction first increase with increasing extent due to autocatalysis by hydroxide before decreasing due to the diffusion limit caused by gelation and vitrification. © 1995 John Wiley & Sons, Inc.
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  • 24
    ISSN: 0887-624X
    Keywords: benzocyclobutene ; o-quinodimethane ; radical polymerization ; Diels-Alder reaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4-Vinylbenzocyclobutene (1) was prepared by the nickel-catalyzed coupling reaction of 4-bromobenzocyclobutene with vinylbromide in 70% yield. Radical homopolymerization of 1 at 60°C for 24 h afforded poly(4 vinylbenzocyclobutene) [poly(1)] in 89% yield and radical copolymerizations of 1 with styrene (St) or methyl methacrylate (MMA) were carried out to obtain the corresponding copolymers. The Q = 1.07, e = 0.046. As a model reaction of the polymer reaction of the polymer reaction of poly(1) and poly(4-vinylbenzocyclobutene-co-styrene) [copoly(1-St)] with dienophiles, the Diels-Alder reaction of benzocyclobutene with N-phenylmaleimide (MI) or maleic anhydride (MANH) was carried out to determine the optimum reaction conditions. Under the optimum condition, the Diels-Alder reaction of poly(1) and copoly(1-St) with MI and MANH in the presence of 4-tert-butyl-catechol as an inhibitor were carried out to yield the corresponding polymers in good yields. The properties (solubilities, Tg, and temperature of 10% weight loss) of the products obtained from the polymer reaction were different from these of poly(1). © 1995 John Wiley & Sons, Inc.
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  • 25
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: biodegradable polymers ; polyanhydride ; fatty acid ester ; ricinoleic acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of polyanhydrides synthesized from nonlinear hydrophobic fatty acid esters, based on ricinoleic, maleic acid, and sebacic acid, possessed desired physico-chemical and mechanical properties for use as drug carriers. The polymers were synthesized by melt condensation to yield film-forming polymers with molecular weights exceeding 100,000. Their rate of elimination from rats in the course of about 2 months was faster than that found for similar polyanhydrides previously tested. In vitro studies showed that these polymers underwent rapid degradation in the first 10 days. The drug release followed first-order kinetics, showing a rapid drug release rate in the first 10 days which correlated with the degradation of the polymers. The fatty acid ester monomers underwent in vitro enzymatic degradation to the natural starting acids. Tests in rats demonstrated their toxicological inertness and biodegradability. © 1995 John Wiley & Sons, Inc.
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  • 26
    ISSN: 0887-624X
    Keywords: methyltrimethoxysilane ; hydrolytic polycondensation ; polysiloxane ; thin films ; structure ; tensile strength ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 27
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: EPDM rubbers ; hydroperoxide ; singlet oxygen ; anthracene ; dimethyl sulfide ; nitric oxide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three different ethylene/propylene/diene (EPDM) rubbers were allowed to react with singlet oxygen. This reaction leads to the production of polymeric pendant hydroperoxides only in one case. Terpolymer ethylene/propylene/5-ethylidene-2-norbornene reacts with singlet oxygen and isolated and associated secondary hydroperoxides are formed. Anthracene was used as a sensitizer for production of singlet oxygen under 365-nm irradiation. The course of hydroperoxide formation was similar in the solid state as well as in the toluene solution. Reactivity of hydroperoxides prepared was tested in their reaction with gaseous dimethyl sulfide (DMS). Both the isolated and associated hydroperoxides react with DMS by dual fast and slow process. Fast process is more significant in the case of the isolated hydroperoxides. © 1995 John Wiley & Sons, Inc.
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  • 28
    ISSN: 0887-624X
    Keywords: copolyamides ; nylons ; glycine ; x-ray diffraction ; NMR spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymers of glycine and 6-aminohexanoic or 12-aminododecanoic acid within a range of molar compositions from 80/20 to 5/95 were prepared by solution polycondensation of the adequate proportion of the respective pentachlorophenyl ester hydrobromides. Despite their random composition, the copolymers obtained were found to be highly crystalline. Intrinsic viscosities of 2/6 and 2/12 copolyamides were similar and rather low (Mn, ca. 3000-5000). Thermal post-polycondensation allowed to increase the molecular weight of 2/12 copolyamides, so that fibers could be prepared. The composition and sequence distributions were evaluated by means of 1H- and 13C-NMR spectroscopies. Copolyamides were also characterized in terms of thermal properties. Melting and glass transition temperatures are reported. Crystallinity was evaluated from heats of fusion. Crystalline structure was examined by infrared spectroscopy and wide-angle x-ray diffraction. The presence of structures related to the polyglycine I and to α/γ-nylons was confirmed depending on the molar composition. Highly oriented fibers with good tensile properties were obtained from the nylon 2/12 (10 : 90) copolymer. © 1995 John Wiley & Sons, Inc.
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  • 29
    ISSN: 0887-624X
    Keywords: tetra(maleimide) ; bismaleimide ; bis(2-pyrone)s ; intermediate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrafunctional products 3 and 6 were synthesized via Diels-Alder reaction of bis(2-pyrone) with bismaleimides in mol ratio 1:7. The chemical structure of these products was determined by 1H-NMR spectroscopy; the high degree of purity was confirmed by means of elemental analysis. The cyclization of the tetraimide 3 with 2 mol monopyrone 7 to the bicycle 8 was carried out. © 1995 John Wiley & Sons, Inc.
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  • 30
    ISSN: 0887-624X
    Keywords: polyamide ; amine ; anhydride ; equilibrium ; molecular weight ; melt reaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyamide 6 (PA6) and poly(metaxylene adipamide) (PAmXD6) were blended in a batch mixer with anhydrides such as phthalic anhydride, n-octadecyl succinic anhydride, and anhydride-grafted ethylene propylene rubber. The melt viscosity, the solution viscosity, and chain end concentration were studied during the mixing. PA was first mixed 5 min to get an homogeneous melt prior to the anhydride addition. The introduction of the anhydride to the molten polyamide resulted in large decreases of melt and solution viscosities and of amine chain end concentrations. The anhydride units react with amine chain ends to form imide groups. The resulting low amine chain end concentration causes hydrolysis reaction to maintain the condensation equilibrium. As a consequence an increased carboxylic chain end concentration is observed. The imide concentration was studied by IR. It was shown that when most of the amine chain ends are consumed, the remaining anhydride reacts with amino groups formed by polyamide hydrolysis. © 1995 John Wiley & Sons, Inc.
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  • 31
    ISSN: 0887-624X
    Keywords: radical polymerization ; methyl trans-β-vinylacrylate ; kinetics propagation radical ; monomer reactivity ratios ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl trans-β-vinylacrylate (MVA) undergoes radical polymerization with α,α′-azobis(isobutyronitrile) (AIBN) in bulk and solution. The polymer obtained consists of 85% trans-1,4 and 15% trans-3,4 units. Poly(MVA) (PMVA) is readily soluble in common organic solvents, but insoluble in n-hexane and petroleum ether. PMVA exhibits a glass transition at 60°C, and loses no weight up to 300°C in nitrogen. The kinetics of MVA homopolymerization with AIBN was investigated in benzene. The rate of polymerization (Rp) can be expressed by Rp = k[AIBN]0.5[MVA]1.0, and the overall activation energy has been calculated to be 94 kJ/mol. The propagation radical of MVA at 80°C was detected by ESR spectroscopy, which indicated that the unpaired electron of the propagating radical was completely delocalized over the three allyl carbons. Furthermore, the steady-state concentration of the propagating radical of MVA at 60°C was determined by ESR spectroscopy, and the propagation rate constant (kp) was calculated to be 1.25 X 102 L/mol ·s. Monomer reactivity ratios in copolymerization of MVA (M2) with styrene (M1) are r1 = 0.16 and r2 = 4.9, from which Q and e values of MVA are calculated as 4.2 and -0.32, respectively. © 1995 John Wiley & Sons, Inc.
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  • 32
    ISSN: 0887-624X
    Keywords: polyurea-amides ; N,N′-dimethylurea-based aromatic diamines ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aromatic polyurea-amides having inherent viscosities of 0.36-0.67 dL/g were synthesized by the low temperature solution polycondensation of new N,N′-dimethyl-N,N′-bis(aminophenyl)ureas with various aromatic dicarboxylic acid chlorides. All the polymers were amorphous, and most of them were soluble in a variety of organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc), m-cresol, and pyridine. Some of the polymers could be cast from the DMAc solutions into transparent and flexible films having good tensile properties. The glass transition temperatures of the polyurea-amides obtained from the bis(4-aminophenyl)-substituted ureas were 244-272°C. The temperatures of 10% weight loss under nitrogen of the polymers were in the range of 430 and 480°C. © 1995 John Wiley & Sons, Inc.
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  • 33
    ISSN: 0887-624X
    Keywords: alternating copolymer ; carbazole ; phenanthrene ; energy migration ; excimer formation ; fluorescence quenching ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alternating and random copolymers of 9-phenanthrylmethyl methacrylate or 2-(9-carbazolyl)ethyl methacrylate with styrene were synthesized and their fluorescence properties were examined. There was no noticeable difference in the spectral features of the alternating and random copolymers in tetrahydrofuran (THF), demonstrating that this type of polymers have no quenching sites in the polymer chains. The fluorescence quenching studies indicated that the alternating copolymers permitted singlet-state energy migration as efficiently as the corresponding random copolymers but less efficiently than the random copolymers with higher chromophore contents. These results strongly suggest that to be chromophores close to each other is most important for facilitation of an intramolecular energy migration. © 1995 John Wiley & Sons, Inc.
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  • 34
    ISSN: 0887-624X
    Keywords: crosslinkable ; liquid crystalline poly(ether ester) ; vinyl monomer ; photoirradiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.
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  • 35
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysis ; zirconocene catalysts ; molecular modeling ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syndiospecific propylene polymerizations catalyzed by isopropylidene(cyclopentadienyl)(fluorenyl)- and (2,2-dimethylpropylidene)(cyclopentadienyl)(fluorenyl)-zirconocenium (1+ and 2+) have been investigated theoretically and compared with experimental observations. With the ab initio calculated structures for the transition state (TS) of 1+(M)P and 2+(M)P (M = propylene, P = 2-methylpentyl), their steric energies (E°) have been computed using MM2 force-field. The difference between steric energies E°(m) and E°(r) for the meso and racemic enchainment of propylene, respectively, is defined as the stereocontrol energy [δE°(m - r)] for syndiotactic propagation. The δE°(m - r) for the TS of 1+ (M)P is about 2.1 kcal/mol, the value is 1 kcal/mol greater for 2+(M)P. The observed steric pentad distributions of the syndiotactic poly(propylene) obtained by these catalysts are consistent with smaller effective stereocontrol energy, which is about two-third as large as δE°(m - r) values calculated for the MM2 optimized structure. Syndiotactic enchainment is favored over isotactic enchainment for all combinations of site configurations in the catalyst. α-Agostic interaction seems to enhance syndioselectivity, whereas γ-agostic interaction changes the stereoselectivity to meso enchainment. The mirror plane symmetry of the syndiotactic propagating species renders the stereoselectivity of the polymerization insensitive to reaction conditions. These catalysts are also highly regiospecific. © 1995 John Wiley & Sons, Inc.
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  • 36
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: grafting ; poly(styrene-graft-ethylene oxide) ; styrene-oxirane graft copolymers ; ethoxylation ; alkylation ; anionic polymerization of ethylene oxide ; poly(styrene-co-acryl-amide) ; crystallinity ; water absorption ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(styrene-graft-ethylene oxide), having alkyl chains (C12 or C18) on the polystyrene main chain or on the poly(ethylene oxide) (PEO) side chains, were synthesized. The main chain was alkylated by first ionizing amide groups in a styrene/acrylamide copolymer with tert-butoxide, and then using the amide anions as sites for reactions with 1-bromoalkanes. An excess of amide anions was used in the reaction, and the remaining anions were subsequently utilized as initiator sites for the anionic polymerization of ethylene oxide (EO). Synthesis of poly(styrene-graft-ethylene oxide) with alkylated side chains was accomplished by polymerization of EO onto the ionized styrene/acrylamide copolymer, followed by an alkylation of the terminal alkoxide anions with 1-bromoalkanes. The alkylated graft copolymers were structurally characterized by using elemental analysis, 1H NMR, GPC, and IR spectroscopy. DSC analysis showed that only graft copolymers with PEO contents exceeding about 50 wt % and side chain crystallinities comparable to those of homo-PEO. Main chain alkylated graft copolymers generally had higher crystalinities, as compared to nonalkylated and side chain alkylated samples. The graft copolymers absorbed water corresponding to one water molecule per EO unit at low PEO contents. The water absorption increased progressively at PEO contents above 30 wt % for main chain alkylated samples and above 50 wt % for non-alkylated samples. © 1995 John Wiley & Sons, Inc.
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  • 37
    ISSN: 0887-624X
    Keywords: methacrylate bearing donor and acceptor moieties ; polymer effect ; intra-molecular charge-transfer interaction ; spacer length ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-[3,5-Bis(N,N-dimethylamino)phenoxy]-ω-(2,4,6-tricyanophenylthio)alkanes (1a-c), where an electron-accepting 2,4,6-tricyanophenylthio group and an electron-donating 3,5-bis(N,N-dimethylamino)phenoxy one are linked with a spacer such as ethylene, trimethylene, and tetramethylene, were prepared in order to examine an effect of the spacer chain length on intramolecular charge-transfer interaction between the 2,4,6-tricyanophenylthio and 3,5-bis(N,N-dimethylamino)phenoxy groups. From the UV-vis spectra measurements of 1a-c, 1-[3,5-bis(N,N-dimethylamino)phenoxy]-3-(2,4,6-tricyanophenylthio)Propane (1b) carrying the trimethylene chain as a spacer was found to have the strongest intramolecular charge-transfer interaction. A new methacrylate-type monomer carrying the 1b unit as a side chain, 1-(2,4,6-tricyanophenylthio)-3-[3,5-bis(N,N-dimethylamino)phenoxy]-2-propyl methacrylate (2), was prepared successfully in 9.2% total yield in seven steps. The monomer 2 homopolymerized in benzene, tetrahydrofuran, acetone, and dimethyl sulfoxide in the presence of 2,2′-azobis(isobutyronitrile) at 60°C to give polymers [poly(2)] with molecular weights of 6,000 to 98,000. An intramolecular charge-transfer interaction in the poly(2) was found to be larger than that in the monomer 2 and to increase with an increase in the degree of polymerization of the poly(2), suggesting that there is an existence of polymer effect other than the polymer effect due to the high local concentration of the donor-acceptor pair. © 1995 John Wiley & Sons, Inc.
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  • 38
    ISSN: 0887-624X
    Keywords: saccharic acid ; dilactone ; polyaddition ; polyurethane ; diisocyanate ; deg-radation ; hydrolysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyaddition of saccharic acid dilactones prepared from D-glucose and D-mannitol, D-glu-caro-, and D-mannaro-1,4:6,3-dilactones (1 and 2, respectively), with hexamethylene di-isocyanate (3a) and methyl (S)-2,6-diisocyanatocaproate (3b) was carried out by using dibutyltin dilaurate as a catalyst at 50, 25, and 0°C to give polyurethanes (4 and 5) having dilactone moieties in the main chains. The resulting polymers were found to decompose easily in phosphate buffers under neutral or slightly basic conditions (pH 7 or 8). Therefore, the polyurethanes may be used as novel degradable polymeric materials. © 1995 John Wiley & Sons, Inc.
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  • 39
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polyesterification ; unsaturated polyesters ; ethylene glycol ; adipic acid ; fumaric acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of unsaturated polyesters using adipic acid, ethylene glycol, and fumaric acid in the absence and presence of a foreign acid (phosphoric acid) as catalyst was carried out by a two-stage method under constant reaction temperatures of 160-180°C and at different ratios of diol to diacid. The experimental data fit the Chen-Wu rate equations for self-catalyzed and acid-catalyzed reactions. The reaction rate constants and activation energies for both systems were calculated. The rate constants of fumaric acid-ethylene glycol systems were found to be nearly constant and had negligible variations with increasing chain length of polymer. © 1995 John Wiley & Sons, Inc.
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  • 40
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: dispersion polymerization ; micron-size monodisperse polymer particles ; sty-rene ; butyl acrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the nitrogen purge, monomer purification, type of agitation, and presence of costabilizer on the particle size distribution (PSD) was investigated in the dispersion po-lymerization of styrene in ethanol and in the dispersion copolymerization of styrene and butyl acrylate in a water-ethanol mixture. Purging with nitrogen and, to a lesser extent, monomer purification, were of paramount importance to achieve monodispersity. The type of agitation had a week effect on the PSD, whereas the presence of costabilizer had no effect on the PSD. © 1995 John Wiley & Sons, Inc.
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  • 41
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 42
    ISSN: 0887-624X
    Keywords: phenylethynylphenol ; endcap ; thermosets ; arylene ether matrix resins ; processing window trace metals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 3-phenylethynylphenol, and its applicability as a high temperature cross-linking endcap for high Tg polyarylene ethers is described. It was synthesized in high yields and purity using the palladium catalyzed coupling reaction between the protected 3-bromo or iodo phenol and phenylacetylene. The yield of the reaction was found to be highly dependent on the structure of the halide used, the reaction temperature, and the concentration of phenylacetylene. The use of the protected phenol in the palladium catalyzed reaction was also extended to the high yield synthesis of 3-ethynylphenol and protected 4-ethynylphenols. The complete synthesis of 3-phenylethynylphenol, 3-ethynylphenol, and protected 4-ethynylphenol in high yields has been demonstrated and is discussed herein. Three new phenylethynyl functionalized arylene ether matrix resins have been synthesized in high yields and purity by reacting 3-phenylethynylphenol with 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorobenzophenone, and bis(4-fluorophenyl)phenyl phosphine oxide, via nucleophilic poly(arylene ether) synthesis conditions. These low molecular weight materials undergo thermally induced chain extension/branching to yield an insoluble three-dimensional network at reaction temperatures of around 380°C. The low molecular weight arylene ethers endcapped with the phenylethynyl group demonstrate excellent flow characteristics and a wide processing window of about 250°C. Crosslinking of the 4,4′-bis(3-phenylethynyl phenoxy)diphenyl sulfone system for 30 min at 350°C in air afforded a Tg value of 265°C by differential scanning calorimetry measurements. Trace metal analysis for palladium and copper showed absence of these metals that would otherwise detract from the excellent thermal stability. The synthesis and characterization of these phenylethynyl endcapped arylene ether matrix resins is discussed. © 1995 John Wiley & Sons, Inc.
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  • 43
    ISSN: 0887-624X
    Keywords: olephins ; crosslinking kinetics ; polyethers ; differential scanning calorimetry ; thermogravimetric analyses ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article studies the crosslinking reactions of some polyethers containing double bonds on the side chains. Thermal crosslinking takes place in all cases, but is overlapped by the degradation process. So, a catalyst has to be used to obtain the cured material and avoid degradation. The best initiator appears to be dicumyl peroxide and the maximum cross-linking degree is achieved only with 5% (w/w). Thermogravimetric analyses are used to test the quality of the cured materials. IR spectroscopy shows that crosslinking actually takes place by polymerizing pendent double bonds. Furthermore, activation energies for thermal and radical initiated crosslinking are determined by means of dynamic DSC studies. © 1995 John Wiley & Sons, Inc.
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  • 44
    ISSN: 0887-624X
    Keywords: AIBN decomposition ; radical initiation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition rate constant of AIBN (kd) in N,N-dimethylformamide (DMF)/methyl methacrylate (MM) mixtures of various compositions at 60°C is studied. The kd value is 6.45 × 10-4min-1 for pure DMF and 7.20 × 10-1 min-1 for pure methyl methacrylate. The kd values of DMF/MM mixtures were found to be dependent on the mixture composition. This dependence is not a linear function of the monomer mole fraction, but has a minimum at ca. 20 30 mol% of MM. The relationship between the AIBN decomposition rate constant and the monomer mole fraction was interpreted on the basis of solvation of the initiator molecules. © 1995 John Wiley & Sons, Inc.
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  • 45
    ISSN: 0887-624X
    Keywords: binaphthyl dianhydride ; polyimides ; synthesis ; property ; fluorescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,4′-Binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride was synthesized from 4-chloro-1,8-naphthalic anhydride and polymerized with aromatic and pliphatic diamines in m-cresol or N-methyl-2-pyrrolidinone (NMP). The polyimides, except for two derived from p-phenylenediamine and hydrazine, are soluble in 1,1,2,2-tetrachloroethane and NMP. Their intrinsic viscosities ranged from 0.36 to 2.20 dL/g. The polymers showed excellent thermal and thermooxidative stabilities and displayed weak glass transition temperatures. Young's moduli of some polymer films were in the range of 2.5 and 5.4 GPa at 30°C. The aliphatic polyimides exhibited a stronger fluorescence than the aromatic polyimides. © 1995 John Wiley & Sons, Inc.
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  • 46
    ISSN: 0887-624X
    Keywords: photopolymerization ; metathesis ; cycloolefin ; ROMP ; PROMP ; ruthenium ; polymerization ; catalysis ; photoinduction ; arene complexes ; ring opening ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon UV irradiation, the complexes [(η6-arene1)Ru(η6-arene2)]2+ (toluene-4-sulfonate or trifluormethane-sulfonate as counter ion; examples for arene: benzene, toluene, mesitylene, hexamethylbenzene, anisole, biphenyl, naphthalene) and [Ru(NC-R)6]2+ (tosylate or triflate as counter iron; R = methyl, ethyl, phenyl) are transformed into active catalysts for ring opening metathesis polymerization (ROMP) of strained bicyclic olefins. The photoinduced ring opening metathesis polymerization (PROMP) is most efficient with sandwich complexes having high quantum yields for the photochemically induced solvation of [(η6-arene1)Ru(η6-arene2)]2+ to [Ru(solvent)6]2+. With most of the complexes no (or only low) catalytic activity is observed in the absence of light. After the photolysis step, the mechanism of the polymerzation is identical to ROMP reactions with thermally activated ruthenium catalysts. Good yields and high molecular weights are obtained with a catalyst concentration of 0.1-1%. A mechanistic model for the initiation is presented. © 1995 John Wiley & Sons, Inc.
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  • 47
    ISSN: 0887-624X
    Keywords: microemulsion ; polymerization ; butyl acrylate ; ammonium peroxodisulfate ; dibenzoyl peroxide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oil/water microemulsion polymerizations of butyl acrylate initiated by a water (ammonium peroxodisulfate, APS) or oil (dibenzoyl peroxide, DBP) soluble radical initiator at different emulsifier concentrations were investigated. The rate of polymerization vs. conversion curve shows two intervals. The rate of polymerization is found to decrease with the emulsifier concentration. This finding was discussed in terms of the decrease of both radical and monomer concentration, the chain transfer to emulsifier, desorption of chaintransferred radicals, and the contribution of solution polymerization. The polymerization is faster with APS. In the APS system the rate per particle or the number of radicals per particle increases exponentially with increasing particle size. The particle size and number increase during the whole polymerization. This behavior was discussed in terms of the nucleation of monomer-containing micelles and agglomeration of primary particles during the whole polymerization. © 1995 John Wiley & Sons, Inc.
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  • 48
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: radical polymerization ; initiation ; AIBN decomposition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvation effect in the thermal decomposition of a radical initiator (AIBN) in monomer-solvent mixtures is discussed. Equations were derived which comprise the initiator decomposition constant as a function of the monomer mole fraction for chosen types of solvation. In addition, equations were deduced presenting the concentrations and partial relative decomposition rates for the solvated initiator species as a function of the monomer mole fraction. The equations obtained were compared to the experimental literature data and possible dependences of decomposition constants on monomer concentration were simulated for various solvated species. The simulated relationships were found to be straight lines, curves of saturated type (possessing a plateau), S-shaped curves, and maximum or minimum curves. © 1995 John Wiley & Sons, Inc.
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  • 49
    ISSN: 0887-624X
    Keywords: solid electrolytes ; poly(ethylene oxide) ; poly(2vinylpyridine) ; conductive polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(ethylene oxide) (MW 600,000)/poly(2vinylpyridine) (MW 200,000)/LiClO4 blends have been prepared by the solution blending process. The ionic conductivities of the blends containing lower weight fractions (15, 17.5, 20 and 22.5%) of poly (2vinylpyridine) initially increases as the salt content is increased, reaches a maximum at an ethylene oxide/Li+ mole ratio of 10 and decreases as the salt content is further increased. Blends, which have higher weight fractions of poly(2vinylpyridine) (25 and 35%) display different electric behavior, i.e., the ionic conductivity continously increased as the salt content is increased to an ethylene oxide/Li+ mole ratio of 2. Thermal, 7Li solidstate NMR and semiempirical MNDO molecular orbital studies indicate that this contrasting behavior may be explained by the structure and ratios of the solvates (mixed solvate or homosolvate) of LiClO4 present in the blends. © 1995 John Wiley & Sons, Inc.
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  • 50
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: viologen polymer ; lyotropic ; critical concentration ; synthesis ; characterization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [no Abstrat]
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  • 51
    ISSN: 0887-624X
    Keywords: polycondensation ; palladium-catalyzed ; π-conjugated polymer ; copolymer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 52
    ISSN: 0887-624X
    Keywords: poly(aryl ether)s ; poly(dicyanopyrazine ether)s ; amorphous ; bisphenol ; 2,3,9,10,16,17,23,24-octaphenyltetrapyrazinoporphyrazine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermooxidatively stable amorphous poly(dicyanopyrazine ether)s with high glass transition temperatures are synthesized and converted into poly(aryl ether)s bearing covalently bound zinc(II) 2,3,9,10,16,17,23,24-octaphenyltetrapyrazinoporphyrazine units. They are soluble in common organic solvents and can be cast into strong and flexible films. The maximum absorption wavelength of the poly(aryl ether)s bearing zinc (II) 2,3,9,10,16,17,23,24-octaphenyltetrapyrazinoporphyrazine units in chloroform is 654 nm. © 1995 John Wiley & Sons, Inc.
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  • 53
    ISSN: 0887-624X
    Keywords: glycidyl methacrylate ; poly(glycidyl methacrylate) ; carbon disulfide ; cyclic dithiocarbonate ; polymer reaction ; aminolysis ; thiol ; auto-oxidation ; cross-linking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 5-(Methacryloyloxy)methyl-1,3-oxathiolane-2-thione (3) was synthesized from glycidyl methacrylate (GMA) and carbon disulfide in the presence of lithium bromide in 93% yield. The radical polymerization of 3 in DMSO initiated by AIBN at 60°C afforded corresponding polymethacrylate 4 quantitatively. Copolymerization of 3 with MMA was also carried out. 5-Phenoxymethyl-1,3-oxathiolane-2-thione (6), model dithiocarbonate, reacts with benzylamine at room temperature to afford O-(1-mercapto-3-phenoxy-2-propyl)N-benzyl-thiocarbamate (7) and 1,1′-dithiobis[3-phenoxy-2-(benzylaminothiocarbonyloxy)-propane] (8) in 89% and 7% yield, respectively. Polymer 4 reacted with butylamine or dipropylamine to afford a corresponding polymethacrylate bearing thiol group, which immediately turned to insoluble gel by facile auto-oxidation of the thiol group. © 1995 John Wiley & Sons, Inc.
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  • 54
    ISSN: 0887-624X
    Keywords: molecular orbital method ; MOPAC ; transition state ; addition polymerization ; ethylene ; methyl acrylate ; methyl methacrylate ; dimethyl itaconate ; N-methyl itaconimide ; differential photocalorimetry ; DPC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition states (TSs) of radical addition homopolymerization reactions of methyl acrylate, methyl methacrylate, dimethyl itaconate, and N-methyl itaconimide were examined with two-unit radical models using MOPAC (PM3 UHF) semiempirical method. Calculated activation energies (Eas) show good correlations with experimental values. Calculated activation entropies (-ΔS
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  • 55
    ISSN: 0887-624X
    Keywords: α-(t-butylperoxymethyl)styrene ; chain transfer agent ; thermal decomposition ; addition-fragmentation ; styrene polymerization ; epoxide end groups ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epoxy-terminated polystyrene has been synthesized by radical polymerization using α-(t-butylperoxymethyl) styrene (TPMS) as the chain transfer agent. The chain transfer constants were found to be 0.66 and 0.80 at 60 and 70°C, respectively. The presence of epoxy end groups was confirmed by functional group modification of epoxide to aldehyde by treatment with BF3.Et2O. Thermal stability of TPMS was followed by differential scanning calorimetry and iodimetry. Thermal decomposition of TPMS in toluene follows first order kinetics with an activation energy of 23 kcal/mol. © 1996 John Wiley & Sons, Inc.
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  • 56
    ISSN: 0887-624X
    Keywords: thermotropic ; liquid crystalline poly(amide-ester) elastomer ; direct polycondensation ; two-phase morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three series of novel poly(amide-ester) (PAE) elastomers were prepared by direct poly-condensation from terephthalic acid (TPA), polyols (Mn = 1000 or 2000), and various diamines. The structures and thermal properties of the synthesized PAEs were examined by FTIR spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calo-rimetry (DSC), thermal optical polarized microscopy, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The effects of kinds and amount of diamines and the molecular weight of polyols on the thermal properties of PAEs were studied. By introducing long flexible spacers (PE-1000 or PE-2000) into the polymer main chain, all polymers showed two-phase morphology under the thermal optical microscopic observation. It was interesting that most of the synthesized polymers exhibited only one melting transition corresponding to the soft segments. The melting transition of hard segments could not be detected due to decomposition of the soft segments. However, a thermotropic liquid crystalline PAE (TLCPAE) prepared from methylhydroquinone and 2-chloro-5-methyl-phenylenediamine with PE-1000 could be obtained by lowering the melting transition temperature of the hard segment. © 1995 John Wiley & Sons, Inc.
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  • 57
    ISSN: 0887-624X
    Keywords: aromatic polyamides ; ether-dicarboxylic acids ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 4,4′-(1,4-Phenylenedioxy)dibenzoic acid (3), 4,4′-(2,5-tolylenedioxy)dibenzoic acid (Me-3), and 4,4′-(2,5-biphenylenedioxy)dibenzoic acid (Ph-3) were prepared by the nucleophilic substitution reaction of p-fluorobenzonitrile with hydroquinone, methylhydroquinone, and phenylhydroquinone, respectively, followed by alkaline hydrolysis. Several aromatic polyamides having inherent viscosities of 0.66-1.34 dL/g were directly prepared by a Yamazaki phosphorylation polyamidation technique from dicarboxylic acids 3, Me-3, and Ph-3, respectively, with aromatic diamines using triphenyl phosphite and pyridine as condensing agents. The solubility of methyl- or phenyl-substituted polyamides was remarkably enhanced when compared to that of nonsubstituted analogues. Most of the substituted polyamides revealed an amorphous nature and were readily soluble in a variety of organic solvents including N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, dimethyl sulfoxide, and m-cresol. Transparent, flexible, and tough films of these polymers could be cast from the DMAc or NMP solutions. These films had tensile strength of 60-100 MPa, elongation to break of 6-11%, and tensile modulus of 1.68-2.25 GPa. The glass transition temperatures (Tg) of most polyamides could be determined by differential scanning calorimetry (DSC) and were in the range of 200-232°C. Thermogravimetric analyses established that these polymers were fairly stable up to 450°C, and the 10% weight loss temperatures were recorded in the range of 458-535°C in nitrogen and 468-528°C in air atmosphere. In general, the phenyl-substituted polyamides exhibited relatively higher Tg, thermal stability, and solubility. © 1996 John Wiley & Sons, Inc.
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  • 58
    ISSN: 0887-624X
    Keywords: side-chain liquid crystalline polymers ; azobenzene mesogens ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of azo monomers for polycondensation have been synthesized and characterized. These monomers, which contain electron-donor or acceptor substituents, have been condensed with aliphatic monomers to obtain two different series of aliphatic main-chain polyesters with pendant mesogenic groups. The polymers display nematic or smectic phases depending on the structural modifications of pendant mesogenic groups and the length of the flexible main-chain. In addition to these series, two polyesters with a high concentration of side pro-mesogenic groups have been synthesized. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 59
    ISSN: 0887-624X
    Keywords: two-component ; polyurethane coatings ; flame retardancy ; modified polyester ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-component polyurethane flame-retardant coatings were prepared by blending chlorine-containing modified polyesters (DCAOs) and polyisocyanate. DCAOs used were synthesized by polycondensation of dichloroacetic acid, a flame-retardant aliphatic carboxylic acid, with 1,4-butanediol, trimethylolpropane, and adipic acid. The content of dichloroacetic acid was varied in 10, 20, and 30 wt % for the polycondensation reaction. Various physical properties of these new flame-retardant coatings were comparable to nonflame-retardant coatings. They showed desirable properties for flame-retardant coatings such as rapid drying and 8-10 hours of pot-life. Coatings with 30 wt % dichloroacetic acid were not fired by the vertical burning test. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 60
    ISSN: 0887-624X
    Keywords: 1,7-bis(4-aminophenoxy)naphthalene ; poly(amic acid) ; polyimide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel diamine, 1,7-bis(4-aminophenoxy)naphthalene (1,7-BAPON), was synthesized and used to prepared polyimides. 1,7-BAPON was synthesized through the nucleophilic displacement of 1,7-dihydroxynaphthalene with p-fluoronitrobenzene in the presence of K2CO3 followed by catalytic-reduction. Polyimides were prepared from 1,7-BAPON and various aromatic tetracarboxylic dianhydrides by the usual two-step procedure that included ring-opening polyaddition to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s had inherent viscosities of 0.74-2.48 dL/g. Most of the polyimides formed tough, creasible films. These polyimides had glass transition temperatures between 247-278°C and their 10% weight loss temperatures were recorded in the range of 515-575°C in nitrogen atmosphere. © 1995 John Wiley & Sons, Inc.
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