bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of stoichiometry and diffusion on an epoxy/amine reaction mechanism
Authors: Finzel Mark C. , Delong John , Hawley Martin C.
Published: April 2003

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.
Polycarbonate synthesis by the melt phase carbonate‐ester interchange reaction of bisphenol‐A diacetate with dimethyl carbonate
Authors: Deshpande M. M. , Jadhav A. S. , Gunari A. A. , Sehra J. C. , Sivaram S.
Published: April 2003

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.
Synthesis of poly(4‐vinylbenzocyclobutene) and its reaction with dienophiles
Authors: Endo Takeshi , Koizumi Toshio , Takata Toshikazu , Chino Keisuke
Published: April 2003

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.
Biodegradable polymers derived from natural fatty acids
Authors: Domb Abraham J. , Nudelman Raphael
Published: April 2003

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.
Synthesis and characterization of new poly(arylene ether)s containing heterocyclic units. II.
Authors: Bottino Francesco A. , DiPasquale Giovanna , Leonardi Nicoletta , Pollicino Antonino
Published: April 2003

A series of new poly(arylene ether)s, containing naphthalene, pyridine, and quinoline units have been prepared by solution condensation polymerization. The synthesis involves nucleophilic displacement of aromatic dihalides with aromatic potassium bisphenates in an anhydrous dipolar aprotic solvent at elevated temperatures. The polymers, having inherent viscosity from 0.24 to 1.32 dL/g, were obtained in quantitative yield, have excellent thermal stability as shown by 10% weight loss temperatures in nitrogen and air (above 450 and 430°C, respectively) and high glass transition temperatures (in the range of 150–220°C). The introduction of quinoline moieties in the polymer backbone positively influences the thermal properties, such as high Tg/Tm ratios. © 1995 John Wiley & Sons, Inc.
Peroxide crosslinking of linear low‐density polyethylenes with homogeneous distribution of short chain branching
Authors: Sajkiewicz P. , Phillips P. J.
Published: April 2003

Extraction and swelling experiments were carried out in order to measure the crosslinkability by dicumyl peroxide (DCP) of new homogeneous linear low‐density polyethylenes (LLDPEs) with different molecular weight, branch content, and length of branches. Considering that the tertiary radicals are most probable macroradicals, our results indicate that tertiary carbons in LLDPEs could be either sites for scission reaction of effective coupling, depending upon degree of branching and to a lesser extent on degree of crosslinking. In the range of branching between 16 and n CH3/1000 C (n − 31 for low DCP concentration and decreases with DCP content approaching the value of 23 for the range above ca. 6 DCP moles per number average PE mole), the tertiary carbons seem to be rather the sites for effective coupling. In this range of branching an increase of crosslinkability with branch concentration and molecular weight of PE is due to the increase of crosslinking efficiency, but the scission probability is very low. At branch content exceeding the value of n CH3/1000 C, the dominant reaction on tertiary carbons is scission, leading to a small decrease of crosslinkability with increasing branch content. The possible mechanisms favoring tertiary carbons for either coupling or scission are discussed. © 1995 John Wiley & Sons, Inc.
Reactions of hydroxyl (HO•) and hydroperoxyl (HO) radicals generated chemically and photochemically with poly(ethylene oxide)
Authors: Kaczmarek H. , Lindén L. Å. , Rabek J. F.
Published: April 2003

Poly(ethylene oxide) (poly(oxy‐1,2‐ethanediyl) is rapidly oxidized by hydroxyl (HO•) and hydroperoxyl (HO) radicals generated by photolysis of hydrogen peroxide (H2O2) or by the catalytic decomposition of H2O2by metallic silver. This process is accompanied by a chain scission during which the molecular weight decreases and the polydispersity changes. As a result of this process, the crystalline structure of poly(ethylene oxide) disappears, and the polymer becomes completely amorphous. © 1995 John Wiley & Sons, Inc.
Spectrophotometric determination of thermal transition of polymeric systems using photochromic probes
Authors: Nayak Biswabimohan , Gupta Satyendra Nath
Published: April 2003

Mercury‐dithizone complex both free and bonded to a polymeric system has been synthesized and used to measure the thermal transition of polystyrene, poly(vinyl acetate), and some other polymers. The thermal relaxation rate of the activated complex in dark has been found to be dependent on the free volume of a polymer matrix. The rate goes through a maximum above Tg of a polymer. A very sensitive method, based on thermal recovery of activated photochromic probe chromophore has been devised to measure the thermal transition of both single and multicomponent polymer matrices. © 1995 John Wiley & Sons, Inc.
Changes in sol fraction during peroxide crosslinking of linear low‐density polyethylenes with homogeneous distribution of short chain branching
Authors: Sajkiewicz P. , Phillips P. J.
Published: April 2003

FTIR measurements of sol fractions were carried out in order to assess side reactions during dicumyl peroxide (DCP) crosslinking of linear low density polyethylenes (LLDPEs) with homogeneous distribution of short chain branching. The changes of methyl and olefinic unsaturation concentration were measured as a function of degree of branching and DCP content. The changes of methyl and vinylidene concentration indicate that the scission probability has greater significance for the samples with initial branch content above 31 CH3/1000 C and increases with increasing DCP concentration. The analysis of trans‐vinylene concentration indicates that the probability of disproportionation also increases with increasing DCP content. The changes of methyl concentration in the sol fraction of the sample containing initially ca. 23 CH3/1000 C with increasing DCP content could be interpreted using the dependence of crosslinking efficiency on branch content found previously for some range of branch concentration. © 1995 John Wiley & Sons, Inc.
Synthesis and polymerization of coupled compounds of 1,11‐dodecadiyne
Authors: Nezu S. , Walsh S. , Meille V. , Yoshida M. , Lando J. B.
Published: April 2003

The dimer, trimer, and tetramer of 1,11‐dodecadiyne, HCC(CH2)8CCH, were synthesized. The solid‐state polymerization of the dimer was investigated by infrared (IR) spectroscopy. IR bands due to the diacetylene moiety were identified through the comparison of the IR spectra of the dimer, trimer, and tetramer. The dimer was found to have two polymorphs, melt‐crystallized and solution‐crystallized. Both of the polymorphs undergo solid‐state polymerization by exposure to γ‐ray or UV irradiation. The former has higher polymerizability for the diacetylene moiety than the latter. The solid‐state polymerization of the terminal acetylene group was not observed. It is shown that the previously reported dimer structure in which both the diacetylene and terminal acetylene groups are polymerized to form an inherently electrically conducting polymer is incorrect. © 1995 John Wiley & Sons, Inc.
Swelling‐assisted modification of poly(ethylene terephthalate) by methacrylic acid
Authors: Xue Jianxian , Wilkie Charles A.
Published: April 2003

When a poly(ethylene terephthalate), PET, film is heated in an aqueous solution of methacrylic acid in the presence of hydrogen peroxide as an initiator, it is found that the weight of the film is increased. The amount of methacrylic acid that may be added onto the film is dependent upon the concentration of the monomer, the initiator, and the temperature at which the reaction occurs. Pretreatment of the film with 1,1,2,2,tetrachloroethane causes swelling and the amount of add‐on is increased as the swelling level increases. Methacrylic‐acid‐modified PET films hydrolyze at room temperature in aqueous sodium hydroxide; the rate of hydrolysis is dependent upon the amount of add‐on and the concentration of the base. This procedure leads to a chemically induced blend of polymethacrylic acid and poly(ethylene terephthalate), and grafting of the monomer onto the polymer film does not occur. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of new soluble aromatic polyamides from diaminotetraphenylimidazolin‐2‐one and various aromatic dicarboxylic acid chlorides
Authors: Park Ki Hong , Kakimoto Masa‐Aki , Imai Yoshio
Published: April 2003

Novel aromatic polyamides, having inherent viscosities of 0.76‐2.31 dL/g, were synthesized by the low temperature solution polycondensation of a new highly phenylated diamine monomer having an imidazolinone group, 1,3‐bis(4‐aminophenyl)‐4,5‐diphenylimidazoline‐2‐one (TPIDA), with various aromatic diacid chlorides. All the polymers were amorphous, and most of the polyamides were readily soluble in organic solvents such as N‐methyl–2‐pyrrolidone, N,N‐dimethylacetamide (DMAc), and m‐cresol. Flexible and tough films could be prepared from the DMAc solutions of these soluble aromatic polyamides. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the polyamides were in the range of 275–315°C and 430–505°C, respectively. © 1995 John Wiley & Sons, Inc.
Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo‐ and copoly(ether‐ester)s
Authors: Lai Wen Wei , Chang Teh Chou
Published: April 2003

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.
Synthesis and properties of aromatic polyamides derived from 1,6‐bis(4‐aminophenoxy)naphthalene and aromatic dicarboxylic acids
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei , Jang Chin‐Cheng
Published: April 2003

A new bis(phenoxy)naphthalene‐containing diamine, 1,6‐bis(4‐aminophenoxy)naphthalene, was synthesized in two steps from the condensation of 1,6‐dihydroxynaphthalene with p‐chloronitrobenzene in the presence of potassium carbonate, giving 1,6‐bis(4‐nitrophenoxv)naphthalene, followed by hydrazine hydrate/Pd—C reduction. A series of polyamides were synthesized by the direct polycondensation of the diamine with various aromatic dicarboxylic acids in the N‐methyl‐2‐pyrrolidone (NMP) solution containing dissolved metal salts such as CaCl2 or LiBr using triphenyl phosphite and pyridine as condensing agents. The polymers were obtained in quantitative yield with inherent viscosities of 0.78–3.72 dL/g. Most of the polymers were soluble in aprotic solvents such as N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), NMP, and they could be solution‐cast into transparent, flexible and tough films. The casting films had tensile strength of 102–175 MPa, elongation at break of 8–42%, and tensile modulus of 2.4–3.8 GPa. The polymers derived from rigid dicarboxylic acids such as terephthalic acid and 4,4′‐biphenyldicarboxylic acid exhibited some crystalline characteristics. The glass transition temperatures of the polyamides were in the range of 238–337°C, and their 10% weight loss temperatures were above 487°C in nitrogen and above 438°C in air. © 1995 John Wiley & Sons, Inc.
Kinetics and molecular weights distribution study of neodymium‐catalyzed polymerization of 1,3‐butadiene
Authors: Nickaf J. B. , Burford R. P. , Chaplin R. P.
Published: April 2003

The homopolymerization of 1,3‐butadiene in a stirred batch reactor with the catalytic system Nd octoate/diethyl‐aluminium chloride/triisobutyl‐aluminium in n‐heptane was studied. The effect of various reaction conditions on especially high conversion and molecular weight is reported. Polymerization is shown to be first order with respect to both monomer and neodymium. Molecular weights are high and broadly distributed. Chain transfer to triisobutylaluminium is the main factor governing molecular weight development. A mechanism of polymerization is presented with the chain transfer process incorporated. © 1995 John Wiley & Sons, Inc.
Synthesis of new polyimides by Diels–Alder reaction of bis(2‐pyrone)s with bismaleimides
Authors: Alhakimi Gamil , Klemm Elisabeth , Görls Helmar
Published: April 2003

The reaction of various substituted bis(2‐pyrone)s with bismaleimides in dilute solution was carried out to produce linear soluble polymers with coronand structure. The number‐average molecular weights of the polymers ranged from 7000 to 18,000 (vapor pressure osmometry). Polymer structures were identified by NMR spectroscopy and model reactions. The stereochemistry and the mechanism are discussed. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of hydrophilic thermotropic block copolyetheresters
Authors: Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing
Published: April 2003

The block copolyetheresters with a hard segment of poly (hexamethylene p,p′‐bibenzoate) and a soft segment of poly (ethylene oxide) were prepared by melt polycondensation of dimethyl‐p,p′‐bibenzoate, 1,6‐hexanediol, and polyethylene glycol (PEG) with molecular weights of 400, 1000, 2000, or 4000. These block copolyetheresters were characterized by intrinsic viscosity, GPC, FT‐IR, 1H‐NMR, and water absorption. The thermotropic liquid crystalline properties were investigated by DSC, polarized microscope, and x‐ray diffraction. The block copolyetheresters exhibit smectic liquid crystallinity due to the polyester segment. The transitions are dependent on the molar content and the molecular weight of PEG used. The block copolyetheresters show high water absorption due to the hydrophilic nature of the poly (ethylene oxide) segment. The water absorption increases with increasing PEG content. As the molecular weight of PEG increases, the water absorption increases significantly. The results indicate that the water absorption of the poly (ethylene oxide) segment in the block copolymers is affected by the presence of polyester segments. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins
Authors: Fyfe C. A. , Niu J. , Mok K.
Published: April 2003

An efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol‐A‐monocyanate monoglycidyl ether 3, has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol‐A 2, was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8, but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12, depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2‐allylphenyl cyanate 16, has also been synthesized and characterized. Like 3, 2‐allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2‐allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19. Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.
Studies on the chemical syntheses and on the characteristics of polyaniline derivatives
Authors: Mattoso L. H. C. , Manohar S. K. , Macdiarmid A. G. , Epstein A. J.
Published: April 2003

Syntheses of parent polyaniline and methyl, methoxy, and ethoxy ortho‐substituted polyanilines were performed using the conventional chemical methodology and monitored using the new open‐circuit‐potential (Voc) profile technique. The intermediate pernigraniline oxidation state was identified and isolated at the Voc maximum (A) during the conventional chemical synthesis of poly(o‐methoxyaniline) in the emeraldine oxidation state. The introduction of the substituent on the aniline ring leads to longer polymerization times and lower Voc values. Syntheses in the presence of two different monomers in solution were also investigated and showed preferential polymerization of the monomer with the lowest Voc potential. All polymers produced were characterized by elemental analysis, gel permeation chromatography, UV‐VIS spectroscopy, and cyclic voltammetry. The influence of the substituent on the Voc profile and on the polymer characteristics are rationalized in terms of steric and electronic effects. © 1995 John Wiley & Sons, Inc.
A simple assay for screening translational activity of non‐natural amino acids. Implications for polymer synthesis on messenger RNA templates
Authors: Kothakota Srinivas , Yoshikawa Eiichiro , Murphy Owen J. , Mason Thomas L. , Tirrell David A. , Fournier Maurille J.
Published: April 2003

The ability to incorporate unnatural amino acids into biologically synthesized proteins will greatly extend the impact of protein engineering on polymer materials science. The present report describes the use of a rapid cell‐free assay to assess the incorporation potential of unnatural amino acids in Escherichia coli. The assay features a coupled transcription‐translation system (‘Zubay system’) to screen incorporation of amino acid analogs into plasmid‐encoded proteins. Activity estimates are based on the ability of an analog to compete with a radiolabeled natural amino acid, and toxicity effects are screened by monitoring incorporation of a second, unrelated amino acid. The assay was established with analogs known to be active in vivo, using a common bacterial expression vector as template DNA. Positive results were obtained with the leucine analog 5,5,5‐trifluoroleucine, the proline analogs azetidine‐2‐carboxylic acid and thiazolidine‐4‐carboxylic acid, and three isomers of mono‐fluorophenylalanine (o,m,p). No activity was observed for the phenylalanine analogs 2‐thienylalanine and 3‐thienylalanine. The results suggest that the cell‐free assay will be a useful predictor of in vivo incorporation and a useful tool in the design and synthesis of genetically engineered materials. © 1995 John Wiley & Sons, Inc.
Rigid‐rod polymers with polysiloxane side chains. 2. Synthesis and characterization of aromatic polybenzobisoxazoles with polysiloxane side chains and composite formation with polysiloxane matrices
Authors: Sakakibara Akihito , Itoh Maki , Mita Itaru
Published: April 2003

Aromatic polybenzobisoxazoles, having polydimethylsiloxane side chains (SCPBOs), were prepared using terephthaloyl chloride‐terminated polydimethylsiloxane macromonomers and 3,3′‐bis(trimethylsiloxy)‐4,4′‐bis(trimethylsilylamino)biphenyl for the purpose of dispersing rigid‐rod molecules in silicone matrices for molecular reinforcement. The degree of polymerization of the side chain was varied from 7.8 to 45.4, and a small amount of (3‐butenyloxy)terephthaloyl chloride was copolymerized to give the polymers a functionality that can be linked to the matrices. For all the SCPBOs, the WAXD pattern showed only diffuse reflections, suggesting limited structural regularity, although the polymers were optically anisotropic. No melting transition was observed below the side chain decomposition temperature, 350°C. A polydimethylsiloxane/polybenzobisoxazole composite elastomer was obtained first curing the polysiloxane matrix containing the prepolymer of the SCPBO, followed by in situ thermal ring closure of the prepolymer. Some reinforcement was observed, but the presence of plasticizing effect by the unbound SCPBO was suggested at the same time. © 1995 John Wiley & Sons, Inc.
Propene polymerization using homogeneous MAO‐activated metallocene catalysts: Me2Si(Benz[e]Indenyl)2ZrCl2/MAO vs. Me2Si(2‐Me‐Benz[e]Indenyl)2ZrCl2/MAO
Authors: Jüngling Stephan , Mülhaupt Rolf , Stehling Udo , Brintzinger Hans‐Herbert , Fischer David , Langhauser Franz
Published: April 2003

Propene was polymerized at 40°C and 2‐bar propene in toluene using methylalumoxane (MAO) activated rac‐Me2Si(Benz[e]Indenyl)2ZrCl2 (BI) and rac‐Me2Si(2‐Me‐Benz[e]Indenyl)2ZrCl2 (MBI). Catalyst BI/MAO polymerizes propene with high activity to afford low molecular weight polypropylene, whereas MBI/MAO is less active and produces high molecular weight polypropylene. Variation of reaction conditions such as propene concentration, temperature, concentration of catalyst components, and addition of hydrogen reveals that the lower molecular weight polypropylene produced with BI/MAO results from chain transfer to propene monomer following a 2,1‐insertion. A large fraction of both metallocene catalyst systems is deactivated upon 2,1‐insertion. Such dormant sites can be reactivated by H2‐addition, which affords active metallocene hydrides. This effect of H2‐addition is reflected by a decreasing content of head‐to‐head enchainment and the formation of polypropylene with n‐butyl end groups. Both catalysts show a strong dependence of activity on propene concentration that indicates a formal reaction order of 1.7 with respect to propene. MBI/MAO shows a much higher dependence of the activity on temperature than BI/MAO. At elevated temperatures, MBI/MAO polymerizes propene faster than BI/MAO. © 1995 John Wiley & Sons, Inc.
Preparation and photocrosslinking behaviors of polyesters derived from trans‐2,2′‐dihydroxystilbene
Authors: Chen Yun , Tsay Cherng‐Jing
Published: April 2003

The monomer, trans‐2,2′‐dihydroxystilbene (DHS), has been prepared by asymmetric photocleavage (254 nm) of coumarin dimer acid derived from coumarin dimer. Four new polyesters are successfully synthesized by interfacial polycondensation of the DHS with adipoyl chloride, azelaoyl chloride, sebacoyl chloride, and dodecanedioyl dichloride, respectively. The reduced viscosities of the polyesters decrease from 0.32 to 0.11 dL/g as the number of methylene unit in diacid chlorides increases from 4 to 10. From DSC investigation, it is found that the polyesters are semi‐crystalline polymers with Tm = 39–192°C. Under 350 nm light, photocrosslinking behavior in solution and film‐state is investigated by UV spectral change with irradiation time (350 nm). The photoreactive stilbene chromophores in the main chain dimerize to form cyclobutane derivatives, and lead to crosslinking of the polyesters. Photosensitivity in the film state has also been evaluated by their characteristic curves. Polyester from dodecanedioyl dichloride (5d) exhibits the highest initial reaction rate and ultimate crosslinking ratio. © 1995 John Wiley & Sons, Inc.
Liquid crystalline block copolymers containing rigid units and flexible ethylene terephthalate segments
Authors: Ignatious Francis , Lu Caixia , Kim Jiheung , Kantor Simon W. , Lenz Robert W.
Published: April 2003

Liquid crystalline block copolymers containing different compositions of terephthaloyl bis(4‐oxybenzoyl) (triad) mesogen and flexible ethylene terephthalate (ET) units, were synthesized in tetrachloroethane/pyridine (TCE/Py) at 150°C and in 1‐chloronaphthalene (1‐CN) at elevated temperatures. Inherent viscosities of the PET block copolymers were always lower than 0.25 dL/g. By replacing the ET blocks with butylene terephthalate (BT) blocks, a copolymer of higher inherent viscosity (> 0.8 dL/g) was synthesized in 1‐CN at 220°C. Formation of low molecular weight PET copolymers was attributed to: (1) insolubility of the block copolymer in TCE/Py and (2) formation of side products which alter the stoichiometry of the reactants when the reaction was carried out in 1‐CN. The block copolymers were characterized by 1H and 13C‐NMR spectroscopy. Copolymer compositions were calculated from 1H and 13C‐NMR data. Thermal behavior of these copolymers was analyzed by DSC and polarizing optical microscopy. All copolymers exhibited a nematic liquid crystalline texture. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of amino‐terminated telechelic polybutadiene
Authors: Xu Jiangtian , Dimonie Victoria L. , Sudol E. David , El‐Aasser Mohamed S.
Published: April 2003

Butadiene was polymerized with water‐soluble 4,4′‐azobis(amidinopropane)dihydrochloride initiator in an ethanol‐water medium at 60°C. Important variables, such as the initiator concentration, monomer concentration, solvency, and polymerization time and temperature were studied. 13C‐NMR studies showed that no observable chain transfer to ethanol occurred during the polymerization. The conversion of monomer to polymer was significantly increased while maintaining a relatively narrow molecular weight distribution by intermittent feed of the initiator. The amidino end‐groups of the polymer were transformed into amino groups by reduction using lithium aluminum hydride in THF, so that amine‐terminated polybutadiene was obtained. The amino functionality of the polybutadiene was determined by titration to be 2.0. © 1995 John Wiley & Sons, Inc.
Electrical conductivity of poly(vinyl chloride) obtained by photodehydrochlorination from laminated poly(vinyl chloride)/polypyrrole films
Authors: Ogura K. , Kisaka K. , Furukawa H.
Published: April 2003

Poly(vinyl chloride) (PVC) has been converted to an electrically conductive structure by combined electrochemical and photochemical methods. PVC was cast on a polypyrrole (PPy) film electrode which had been electrochemically prepared. The PVC layer in the laminated PVC/PPy films was first dehydrochlorinated under the illumination of UV light, and the generated polyenes were subsequently doped with I2 and FeCl3. The maximum electrical conductivity achieved for such PVC film was 2.51 X 10−2 and 8.63 10−2 S cm−1 after I2 and FeCl3 doping, respectively. The temperature dependence of the electrical conductivity showed different behavior in higher and lower temperature ranges. In the former (T > 243 K), the T−1 law held, and the activation energy and bandgap were estimated as 0.25 and 0.49 eV, respectively. In the latter (T < 243 K), the conductivity mechanism followed the variable range hopping model (T−1/4 law) in which the radius of the localized state wave function and the density of the localized states at the Fermi level were 1.25 × 103 Å and 1.03 X 1015 eV−1 cm−3, respectively. © 1995 John Wiley & Sons, Inc.
Synthesis and cationic photopolymerization of 1‐butenyl ether monomers
Authors: Crivello J. V. , Yang B.
Published: April 2003

A new series of cationically polymerizable mono‐, di‐ and multifunctional 1‐butenyl ether monomers have been prepared in high yields by the ruthenium catalyzed isomerization of the corresponding crotyl (2‐butenyl) ethers. Their straightforward synthesis and high reactivity in photoinitiated cationic polymerization make these monomers highly attractive for a variety of applications. Cationic polymerization rate studies showed that these monomers exhibited comparable reactivity to their related vinyl and 1‐propenyl ether analogues. © 1995 John Wiley & Sons, Inc.
A novel way to study the initial stages of soap‐free emulsion polymerizations: The intercalation of polystyrene oligomers into hydrotalcite
Authors: Shouldice Grant T. D. , Choi Phillip Y. , Koene Bryan E. , Nazar Linda F. , Rudin Alfred
Published: April 2003

The dominant species in the early stages of an emulsifier‐free emulsion polymerization of styrene has been found to be an oligomer of two to three monomer units using a novel trapping technique. This involved the intercalation of charged primary oligomers between the layers of a hydrotalcite, [Mg4Al2(OH)12]2+[A]2‐ (where A = dianion). Hydrotalcites are an important class of lamellar, inorganic compounds whose interlayer spacing can be mod‐ified by anion exchange. Our approach first involved preparing a hydrotalcite precursor in which the layers were propped apart by an organic dianion (terephthalate = TA). This material was then used to capture the negatively charged polystyrene oligomers from the emulsion polymerization reaction mixture. We found that TA was rapidly ion‐exchanged for the charged oligomers.

The resulting pillared hydrotalcite material was characterized using XRD and SEC. We found that the interlayer spacing between the hydroxide layers increased to 23.2 Å on exposure to the emulsion reaction mixture. This represents an interlayer expansion of 18.3 Å (after subtraction of the hydroxide layer contribution), which is cnsistent with intercalation of oligomers with two to three monomer units arranged in a bilayer. This size estimate was confirmed by the results of size exclusion chromatography. © 1995 John Wiley & Sons, Inc.
Phosphoric acid diesters protonated polyaniline: Preparation, spectroscopic properties, and processability
Authors: Laska Jadwiga , Proń Adam , Lefrant Serge
Published: April 2003

Aliphatic and aromatic diesters of phosphoric acid were tested as dopants improving pro‐cessability of polyaniline (PANI) in its doped (conducting) state. It has been found that both aromatic and aliphatic diesters effectively protonate polyaniline, inducing at the same time its solubility. The protonated state has been confirmed by three independent spec‐troscopic methods (FTIR, Raman, and UV‐vis‐NIR). Both aromatic and aliphatic diesters of phosphoric acid plasticize polyaniline which, in turn, allows for the preparation of highly conducting films of PANI or highly conducting blends of PANI with classical nonconducting polymers by thermal processing. © 1995 John Wiley & Sons, Inc.
Crosslinking study of polyethers containing pendent double bonds
Authors: Reina J. A. , Serra A. , Mantecón A. , Cádiz V.
Published: April 2003

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.
Microemulsion polymerization of butyl acrylate. IV. Effect of emulsifier concentration
Authors: Capek Ignác , Potisk Pavol
Published: April 2003

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.
Polyether azomethines. I. Synthesis and characterization
Authors: Banerjee Susanta , Gutch Pranav K. , Saxena Chhaya
Published: April 2003

Six new polyether azomethines were synthesized by melt and solution polycondensation of six different diamines with 4,4′‐[1,4‐phenylene bis(oxy)] bisbenzaldehyde. The polymers synthesized by solution method are yellow to white in color and had inherent viscosities up to 0.59 dL/g in concentrated H2SO4. The polymers obtained by melt condensation show higher viscosity. Except polymer IV, others are insoluble in common organic solvents. The polymers were characterized by IR, x‐ray, elemental analysis, and DSC study. The thermal stability of the polymers was evaluated by TGA and IGA study. Polymers I‐III are highly thermally and thermooxidatively stable and exhibit no appreciable decomposition up to 420°C both in air and nitrogen atmosphere. It was shown that the curing of the polyazo‐methines takes place by opening up of the CHN linkages at higher temperature. The electrical conductivities of the virgin and iodine doped polymers were as high as 10−11−10−16 and 10−6−10−8S cm−1, respectively, at 30°C. Electronic spectra of the undoped polymers (I‐III) indicated a large bathochromic shift of the ⌅ – ⌅* absorptions band (376 nm) due to CN bonds of the model compound. This can be attributed to extensive delocalization of the electrons along the polymer chain. © 1995 John Wiley & Sons, Inc.
Amphiphilic graft copolymers with poly(oxyethylene) side chains: Synthesis via phthalimidoacrylate prepolymers
Authors: Berlinova Iliyana V. , Amzil Aissa , Vladimirov Nikolai G.
Published: April 2003

Amphiphilic graft copolymers of definite composition were obtained by grafting of amino‐functionalized poly(oxyethylene) monoether (MPEO–NH2) of M̌n = 750, 2000, and 5000 onto phthalimidoacrylate (PIA) homopolymer or its copolymer with styrene (St). The radical co‐polymerization of PIA and phthalimidomethacrylate (PIMA) with St was studied in dimeth‐ylformamide (DMF) at 60°C. The copolymer composition curves and the monomer reactivity ratios showed a high tendency of PIA to alternating copolymerization with St (r1r2 = 0.006). Hydrogen bonding between the functional groups leads to significant spectral modifications. The micellization of the graft copolymers was studied by GPC in aqueous‐methanolic eluent. The aggregation behavior of the graft copolymers depended on their composition and chromato‐graphic separation lead to the copolymers fractionation. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of α,ω‐bis(4‐hydroxybutyl) polydimethylsiloxanes
Authors: Lai Yu‐Chin , Ozark Richard , Quinn Edmond T.
Published: April 2003

α,ω‐Bis(4‐hydroxybutyl) polydimethylsiloxane (molecular weight 1500 to 4500) can be pre‐pared with well‐controlled molecular weight through the reaction of 1,3‐bis(4‐hydroxybu‐tyl)tetramethyl disiloxane and dimethoxydimethyl silane or diethoxydimethyl silane in the presence of a stoichiometric amount of water and hydrochloric acid. The molecular weight of these hydroxybutyl‐terminated polysiloxanes can be determined fairly consistently by a titration method. These polysiloxanes are stable toward cyclization. © 1995 John Wiley & Sons, Inc.
Syntheses and characterization of UV‐curable polysiloxane‐based polyurethane prepolymers
Authors: Lai Yu‐Chin , Quinn Edmond T.
Published: April 2003

UV‐curable polyurethane prepolymers were prepared from the following components: iso‐phorone diisocyanate, hydroxybutyl‐terminated polysiloxane, and 2‐hydroxyethyl meth‐acrylate with diethylene glycol or neopentyl glycol added as an optional chain extender. These prepolymers, with hard segments of different structures, were characterized by high resolution NMR, FTIR, and gel permeation chromatography. Model oligomers were prepared to confirm the structures of the prepolymers. The structure–property relationship of cured prepolymers were determined. © 1995 John Wiley & Sons, Inc.
Wavelength effect on the photoinduced reaction of polymethylmethacrylate
Authors: Torikai Ayako , Hattori Teruyuki , Eguchi Takuji
Published: April 2003

Polymethylmethacrylate (PMMA) containing benzophenone (BP) was photo‐irradiated with monochromatic radiation of wavelength 260–360 nm using the Okazaki Large Spec‐trograph (OLS). On irradiation of PMMA films containing BP in air, the sensitized main‐chain scission and photocrosslinking of PMMA took place simultaneously. These reactions are dependent on irradiation wavelength. The threshold wavelength for both reactions is found to be ca. 380 nm. The number of main‐chain scission and amount of gel increased with the increase of BP concentration in PMMA. Photosensitized main‐chain scission favors the irradiation of radiation at ca. 280 nm and photocrosslinking takes place efficiently with the exposure of 340 nm radiation. A possible mechanism for photosensitized reaction is proposed. © 1995 John Wiley & Sons, Inc.
Studies of synthesis and cationic photopolymerization of three isomeric monoterpene diepoxides
Authors: Crivello James V. , Yang Bo
Published: April 2003

The monoterpene diepoxides isoascaridole (III), γ‐terpinene diepoxide (V), and limonene diepoxide (VIII) were prepared from the corresponding hydrocarbons and their reactivity in photoinitiated cationic polymerization examined. Both V and VIII underwent facile and rapid polymerization to give crosslinked polyethers III, but although highly reactive, did not undergo crosslinking polymerization. With the aid of model compounds it was determined that the rearrangement of one of the epoxy groups of III takes place in the presence of photogenerated acid to give an epoxy ketone (XIII) as the primary product. XIII undergoes very sluggish polymerization. © 1995 John Wiley & Sons, Inc.
Hybrid inorganic/organic interpenetrating polymer networks based on zeolite 13x and polystyrene
Authors: Frisch H. L. , Xue Yongpeng
Published: April 2003

A hybrid inorganic/organic interpenetrating polymer network (IPN) of a three‐dimensional network structure zeolite crystal (13X, powder) and crosslinked or linear polystyrene (PS) was prepared and characterized by differential scanning calorimetry (DSC), solid‐state13C‐NMR, and scanning electron microscopy (SEM). The size and shape of the crystalline zeolite particles were revealed on SEM micrographs in both the pure zeolite and the IPNs. Solubility tests and the results of DSC with solid‐state 13C‐NMR confirm that some organic PS chains are incorporated within the internal three‐dimensional channels of the zeolite particles. We speculate that the internal PS chains may adopt an extended “one‐dimensional” conformation and exhibit no bulk polymer glass transition. These novel hybrid inorganic/organic IPNs are a new kind of IPN structure. © 1995 John Wiley & Sons, Inc.
Graft polymerization of arcylamide onto LLDPE film by electron beam pre‐irradiation in air or argon. I. Influence of dose, grafting temperature, and monomer concentration
Authors: Wirsén A. , Albertsson A.‐C.
Published: April 2003

Linear low density polyethylene (LLDPE) film was irradiated by electron beam in air or argon prior to grafting in aqueous solutions of acrylamide containing 0.05% of Mohr's salt. The grafting kinetics was studied with pre‐irradiation doses in the range of 2.5–25 Mrad and in the temperature range of 40–70°C. Grafting rates and final degrees of grafting were higher for LLDPE pre‐irradiated in air than for LLDPE pre‐irradiated in argon. The overall activation energies for the grafting reaction were dose‐dependent. Above 5 Mrad, the overall activation energies were higher for LLDPE pre‐irradiated in argon which is interpreted as being due to crosslinking of the LLDPE. © 1995 John Wiley & Sons, Inc.
Heptane‐soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer, polymerization catalysis, and effect of silica supports
Authors: Chen You‐Xian , Rausch Marvin D. , Chien James C. W.
Published: April 2003

Bis(1‐indenyl)‐di[1′S, 2′R, 5′S)‐methoxy]silane (1) was converted into a mixture of corresponding ansa‐diastereomeric zirconocenes. Further purification afforded a single dia‐stereomer, di[(1′S, 2′R, 5′S)‐methoxy] silylene‐bis[η5‐1(R, R)‐(+)‐indenyl] dichlorozirconium (2), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene‐hexene polymerizations were observed both in toluene and n‐heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ∼ 1.5×1010 (g of PE/((mol of Zr) · [C2H4] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph3CB(C6F5)4 exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (Tp) up to a conventional polymerization condition (50–70°C), and the 13C NMR study shows that the isotactic poly‐propylene obtained has fairly high [mmmm] methyl pentad distributions at high Tp (⩽25°C with [mmmm] ∼ 0.93–0.75) and a perfect stereoregularity at low Tp (⩽0°C with [mmmm] > 0.99). The catalyst precursors 2 and Et(Ind)2ZrCl2 (3) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph3CB(C6F5)4 free silica‐supported zirconocene system was found to be activated by triisobutylaluminum. © 1995 John Wiley & Sons, Inc.
Polymers with amino acids in their side chain: Conformation of poly(N‐methacryloyl‐L‐methionine)
Authors: Methenitis Costas , Pneumatikakis Georges , Pitsikalis Marinos , Morcellet Joëlle , Morcellet Michel
Published: April 2003

A homopolymer bearing L‐Methionine (PMet) in its side chain was synthesized by free radical polymerization of the corresponding vinyl monomer. Viscosimetric and pHmetric measurements indicate that PMet, in water at low pH, takes a compact conformation, which is destroyed (expanded) with increasing ionization of the carboxyl groups of the side chains. The influence of temperature and of some additives (neutral salt, urea, organic solvent, SDS) on the compact conformation and the pH‐induced conformational transition was investigated. It was concluded that hydrogen bonds are the main factors responsible for the existence of the compact conformation. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of aromatic polythiazole‐amides from new aromatic diamines containing phenyl‐pendant thiazole units
Authors: Inoue Kazuto , Imai Yoshio
Published: April 2003

New aromatic diamines containing phenyl‐pendant thiazole units were synthesized in three steps starting from p‐nitrobenzyl phenyl ketone. Novel aromatic polyamides containing phenyl‐pendant thiazole units were prepared by the low‐temperature solution polyconden‐sation of 1,4‐ (or 1.3‐) bis[5‐(p‐aminophenyl)‐4‐phenyl‐2‐thiazolyl] benzene with various aromatic dicarboxylic acid chlorides in N,N‐dimethylacetamide. High molecular weight polyamides having inherent viscosities of 0.5–3.0 dL/g were obtained quantitatively. The polythiazole‐amides with m‐phenylene, 4,4′‐oxydiphenylene, and 4,4′‐sulfonyldiphenylene units were soluble in N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, and pyridine, and gave transparent flexible films by casting from the solutions. These organic solvent‐soluble polyamides displayed prominent glass transition temperatures (Tg) between 257 and 325°C. On the other hand, the polythiazole‐amides with p‐phenylene and 4,4′‐biphenylene units were insoluble in most organic solvents, and had no observed Tg. All the polythiazole‐amides started to decompose at about 400°C with 10% weight loss being recorded at 450–525°C in air. © 1995 John Wiley & Sons, Inc.