bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation of poly(methylphenylsilylene) and poly(di‐n‐hexylsilylene)
Authors: Kim Hwan Kyu , Matyjaszewski Krzysztof 
Published: April 2003

AbstractDegradation of poly(methylphenylsiylene) and poly(di‐n‐hexylsilylene) was studied by chemical and mechanical methods at ambient and higher temperatures. Purely thermal degradation in solid state starts as a slow process at 150°C and provides soluble and insoluble products which include cyclosilanes as well as various siloxanes. Sonication at ambient temperatures leads to the mechanical degradation of high molecular weight polymers by homolytic cleavage induced by shear forces. No cyclics are formed under these conditions. Polysilanes in the presence of strong nucleophiles degrade exclusively to cyclic oligomers. Rate of this back‐biting chain reaction depends on substituents at silicon atom, alkali metal, solvents, and temperature. Electrophiles degrade polysilanes to various α,ω‐difunctional oligosilanes. © 1993 John Wiley & Sons, Inc.
Novel polycationic biocides: Synthesis and antibacterial activity of polymeric phosphonium salts
Authors: Kanazawa Akihiko , Ikeda Tomiki , Endo Takeshi 
Published: April 2003

AbstractVarious polymeric phosphonium salts and the corresponding low‐molecular‐weight model compounds were prepared and their antibacterial activities against Staphylococcus aureus and Escherichia coli were explored by the viable cell counting method in sterile distilled water. Antibacterial activity of the polymers was found to be higher than that of the corresponding model compounds, particularly against S. aureus. Furthermore, the polymeric phosphonium salt exhibited a higher activity by 2 orders of magnitude than the polymeric quaternary ammonium salt with the same structure except the cationic part. Compounds with the longest alkyl chain (octyl) studied were found to exhibit particularly high activity, and this finding may be ascribed to the contribution of the increased hydrophobicity of the compounds to the cidal activity. © 1993 John Wiley & Sons, Inc.
Approaches to novel AB heteroaromatic polyamides based on cyanoimidazoles
Authors: Thurber Ernest L. , Rasmussen Paul G. 
Published: April 2003

AbstractWe report the synthesis of several AB monomers based on 2‐amino‐4,5‐dicyanoimidazole. Polymerization of the monomers to poly(imidazoleamide)s, by several methods is described. Amino acids 2‐amino‐4‐cyano‐1‐methyl‐5‐imidazolecarboxylic acid and 2‐amino‐5‐cyano‐1‐methyl‐4‐imidazolecarboxylic acid were prepared by mono‐ethanolysis of 2‐amino‐4,5‐dicyanoimidazole followed by methylation of the 1‐nitrogen. The resulting regioisomeric mixture of ethyl esters was separated by fractional crystallization and hydrolyzed to the desired amino acids. The regioisomeric structure was determined by NOE studies of the decarboxylated amino acids. The corresponding acid chlorides were prepared with thionyl chloride and isolated as the HCl salts. Activated esters were prepared by reacting the acid chlorides with alcohols such as 1,1,1‐trifluoroethanol and 2‐chlorophenol. Model compounds were prepared by the acylation of aminocyanoimidazoles but yields were low. The low nucleophilicity of the aminocyanoimidazolecarboxylic acids was partially overcome by the use of the acylation catalyst 4‐dimethylaminopyridine (DMAP) and the activating agent silicon tetrachloride. The acid chlorides were polymerized in amide solvents such as hexamethyl phosphoramide with pyridine and DMAP. A copolyamide consisting of both regioisomers was prepared from a regioisomeric mixture of the acid chlorides. In addition, aminolysis of 2‐chlorophenyl 2‐amino‐4‐cyano‐1‐methyl‐5‐imidazolecarboxylate resulted in a low yield of poly(imidazoleamide). Poly(imidazoleamide)s were red to tan which suggest conjugation along the polymer backbone. The solubility of the polyamides varied from amide solvents to sulfuric acid depending on the regioisomeric structure and molecular weight. The molecular weight of the heteroaramids was in the range from 1500 to 4000 based on viscosity measurements in sulfuric acid. The poly(imidazoleamide)s were thermally stable in excess of 300°C under air and nitrogen atmosphere. © 1993 John Wiley & Sons, Inc.
Ethylene–vinyl acetate semi‐batch emulsion copolymerization: Experimental design and preliminary screening experiments
Authors: Scott P. J. , Penlidis A. , Rempel G. L. 
Published: April 2003

AbstractEthylene–vinyl acetate emulsion copolymers are useful materials for paint, adhesive, and coating applications. The kinetics of their production remain largely unstudied, probably due to the inherent difficulties associated with pressure polymerizations. Polymerizations at elevated pressures are in general more difficult to understand and control, and relatively more expensive since one has to consider the added cost of increased safety precautions. Reported here are the preliminary results of an extensive experimental investigation of the variables which govern the ethylene–vinyl acetate emulsion process. Two redox initiator systems have been identified as more suitable for the polymerization process. Two buffer systems, namely sodium acetate/acetic acid and potassium phosphate, have been used to effectively control pH. The addition of n‐hexane has offered an effective method of enhancing the ethylene content in the copolymer produced. Several other important variables including agitation/mixing and emulsifier type and concentration have been identified and are discussed. These screening experimental observations have aided in the selection of suitable design levels for future, more focused experimentation to quantify the effects of reaction variables on the latex and copolymer properties of interest. A review of the existing literature on ethylene–vinyl acetate copolymer properties and processes is also included. © 1993 John Wiley & Sons, Inc.
Photo‐thermal properties of poly(4‐tert‐butoxycarbonyloxystyrene) bearing imino sulfonate units
Authors: Shirai Masamitsu , Kinoshita Hirotaka , Tsunooka Masahiro 
Published: April 2003

AbstractCopolymers of 4‐tert‐butoxycarbonyloxystyrene (BOS) and 9‐fluorenilideneimino p‐styrenesulfonate (FISS) were synthesized. FISS units in copolymers became p‐styrenesulfonic acid units upon ultraviolet irradiation. The irradiated copolymers thermally decomposed to poly(hydroxystyrene) by liberating tert‐butoxycarbonyl (BOC) units at temperatures where the unirradiated copolymers were stable. The thermal decomposition of the copolymers catalyzed by sulfonic acid formed photochemically was studied by thermogravimetry. The pseudo first‐order rate constant (k) and the activation energy for the acid catalyzed thermal decomposition of BOC units in copolymers were evaluated. The thermolysis of the irradiated copolymer system was compared with that of the irradiated blended system of poly(4‐tert‐butoxycarbonyloxystyrene) (PBOCST) and 9‐fluorenilideneimino p‐toluene‐sulfonate (FITS). © 1993 John Wiley & Sons, Inc.
Characterization of water‐soluble oligomers formed during the emulsion polymerization of styrene by means of isotachophoresis
Authors: Morrison Bradley R. , Maxwell Ian A. , Napper Donald H. , Gilbert Robert G. , Ammerdorffer Joop L. , German Anton L. 
Published: April 2003

AbstractThe concentrations and probable nature of charged oligomers formed by aqueous‐phase termination in the persulfate‐initiated emulsion polymerization of styrene were measured by isotachophoresis. Isotachophoresis has some advantages over other techniques (e.g., GPC, UV spectroscopy) in that it separates species according to their molecular weight, geometry, and charge. The charged water‐soluble oligomeric species were detected in experiments in which particles were nucleated in a surfactant‐free environment. Identification of the moieties present was made by comparison with model compounds. Evidence was found for bimolecular combination as a major mechanism of termination in the aqueous phase, although the possibility of disproportionation could not be ruled out. The species formed in the aqueous phase under saturated monomer conditions were found to be subject to further reaction towards the end of polymerization. The surface adsorption characteristics of the compounds formed were compared with those of known surfactants and showed good agreement with the assumptions in the model of Maxwell et. al. [Macromolecules, 24, 1629 (1991)] for initiator efficiencies in emulsion polymerization. The relatively large concentrations of nonradical aqueous–soluble oligomeric compounds demonstrate conclusively that initiator efficiencies are not 100%, as is often assumed in such systems. © 1993 John Wiley & Sons, Inc.
Squid chitin as a potential alternative chitin source: Deacetylation behavior and characteristic properties
Authors: Kurita Keisuke , Tomita Koji , Tada Tomoyoshi , Ishii Shigeru , Nishimura Shin‐Ichiro , Shimoda Kayo 
Published: April 2003

Abstractβ‐Chitin was isolated from squid pens, and the characteristic chemical and physical properties were elucidated in comparison with those of shrimp chitin, α‐chitin. Deacetylation behavior of the squid chitin was first studied to look into the reactivity of β‐chitin and also to establish an efficient procedure for preparing squid chitosan. The squid chitin proved to show much higher reactivity in alkaline deacetylation than shrimp chitin. Although it was deacetylated quite easily, the product assumed a dark brown color under the ordinary reaction conditions for shrimp chitosan. Squid chitosan was successfully prepared by repeated alkaline treatments under mild conditions, particularly with high concentration alkali at low temperatures, without appreciable discoloration. The structural characteristics of the squid chitin were discussed on the basis of the IR and x‐ray analysis data. The crystalline structure of squid chitin was destroyed easily on deacetylation compared to that of shrimp chitin, and moreover, the resulting squid chitosan was amorphous unlike crystalline shrimp chitosan. The squid chitin was characterized by the remarkable affinity for organic solvents and water. Squid chitin and chitosan also showed much higher hygroscopicity and retention of the absorbed water than shrimp chitin and chitosan and are considered to be useful as highly hydrophilic materials. © 1993 John Wiley & Sons, Inc.
Swelling of interpenetrating polymer networks
Authors: Rogovina L. , Zhou Peiguang , Frisch H. L. 
Published: April 2003

AbstractWe have studied the densities, kinetics, and equilibrium degree of swelling in a number of different solvents of poly(carbonate urethane)/poly(methyl methacrylate) and poly(carbonate urethane)/poly(vinyl pyridine) interpenetrating polymer networks (IPN's). The kinetics of solvent uptake are often anomalous. The equilibrium extent of swelling reflects, among other factors, the number of phases present. © 1993 John Wiley & Sons, Inc.
A study of polyesters synthesized from an arylsilane and its carbon analog
Authors: Thames S. F. , Malone K. G. 
Published: April 2003

AbstractBis(4,4′‐benzoyl chloride) dimethylsilane (SiCO) and 2,2‐bis(4,4′‐benzoyl chloride) propane (CCO) were synthesized and polymerized with butanediol, resorcinol, or hydroquinone. The polymers of SiCO–hydroquinone (SiCO–Hyd) and SiCO–resorcinol (SiCO–Res) possess glass transition temperatures 25°C lower than their carbon analogs but the less aromatic SiCO–butanediol (SiCO–BDO) and CCO–butanediol (CCO–BDO) polymers have similar glass transitions. Silicon containing polymers are superior to their carbon counterparts in thermal stability. Furthermore, polyarylates of excellent thermal stability and solubility were synthesized from SiCO/terephthaloyl chloride and hydroquinone. © 1993 John Wiley & Sons, Inc.
Graft polymerization of methyl methacrylate initiated by pendant azo groups introduced onto γ‐poly(glutamic acid)
Authors: Tsubokawa Norio , Inagaki Masatoshi , Endo Takeshi 
Published: April 2003

AbstractThe grafting of poly(methyl methacrylate) (PMMA) onto biosynthesized γ‐poly(glutamic acid) (γ‐PGA) initiated by pendant azo groups introduced onto γ‐PGA was performed. The introduction of pendant azo groups onto γ‐PGA was achieved by the reaction of carboxyl groups of γ‐PGA with azo initiators having hydroxyl or amino groups, such as 2,2‐azobis[2‐(hydroxymethyl)propionitrile] (AHP), 2,2′‐azobis[2‐methyl‐N‐(2‐hydroxyethyl)propionamide] (AMHP), and 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane] (AIP), using N,N′‐dicyclohexylcarbodiimide. The amount of pendant AHP groups introduced onto γ‐PGA was estimated to be 0.15 mmol/g. Untreated γ‐PGA failed to initiate the polymerization of MMA. On the contrary, the polymerization of MMA was found to be initiated in the presence of γ‐PGA having azo groups: the polymerization rate was proportional to the square root of the concentration of γ‐PGA having pendant azo groups. During the polymerization PMMA was grafted onto γ‐PGA; the percentage of grafting of PMMA onto γ‐PGA obtained from the graft polymerization initiated by pendant AHP, AMHP, and AIP groups was evaluated to be 65.0, 53.1, and 29.0%, respectively. Differential scanning calorimetric analysis shows that the endotherm transition point of γ‐PGA at 220°C disappears by the grafting of PMMA onto the polymer. © 1993 John Wiley & Sons, Inc.
In‐situ direct polycondensation in polymer matrices. II. In‐situ direct polycondensation in styrene–butadiene block copolymers
Authors: Sanui Kohei , Ogata Naoya , Kamitani Kazuyuki , Watanabe Masayoshi 
Published: April 2003

AbstractDirect polycondensation of 3‐substituted‐4‐hydroxybenzoic acid was carried out in solutions of styrene‐butadiene block copolymers (SBS) at room temperature in the presence of triphenylphosphine and hexachloroethane as an initiator for the direct polycondensation of these monomers. Solution casting after the direct polycondensation provided opaque films in which the aromatic polyester was finely dispersed within the matrix of SBS. Mechanical properties of these films were examined by tensile tests. A great improvement of tensile strength was achieved by the incorporation of phenyl substituent in the resulting polyester. In‐situ direct polycondensation leads to the formation of new composites of rigid polymers and flexible polymers. © 1993 John Wiley & Sons, Inc.
Gamma‐oxidation of linear low density polyethylenes: Ethylene–butene and ethylene–hexene copolymers
Authors: Tidjani Adams , Arnaud René 
Published: April 2003

AbstractDifferent linear low density polyethylenes (LLDPEs) based on hexene and butene comonomer were irradiated with γ‐rays under air. The oxidation products have been quantified using NO and SF4 treatments by IR spectroscopy. An FTIR examination displayed unexpected products such as free hydroperoxides and trans‐vinylenes. It was found that the type of α‐olefin used to process LLDPE films may influence the mechanism of oxidation. Parameters such as the melt index and the density seem to affect the γ‐oxidation rate. © 1993 John Wiley & Sons, Inc.
Synthesis and some properties of a polyamide containing trans‐2,5‐linked tetrahydropyran rings in the main chain
Authors: Okada Masahiko , Hayakawa Toshiyuki 
Published: April 2003

AbstractA novel polyamide containing trans‐2,5‐linked tetrahydropyran rings in the main chain, poly(trans‐tetrahydropyran‐2,5‐diyliminocarbonyl) (trans‐polyamide 6), was synthesized by the two‐stage polycondensation of ethyl or 2,2,2‐trifluoroethyl trans‐5‐aminotetrahydropyran‐2‐carboxylate (5b or 5c). The polycondensation was carried out first in m‐cresol at 180°C. The isolated polymer of a relatively low molecular weight was then allowed to react further in a solid state at different temperatures between 180 and 230°C under vacuum. The trans‐polyamide 6 thus obtained was soluble only in protic solvents such as m‐cresol, 2,2,2‐trifluoroethanol, 1,1,1,3,3,3‐hexafluoro‐2‐isopropanol, and trifluoroacetic acid. The viscosity numbers of 6 were up to 0.46 dL/g in m‐cresol at 25°C. DSC and TGA analyses of 6 showed that the thermal decomposition occurred at about 350°C in nitrogen, whereas a rapid weight decrease due to the thermooxidative decomposition started at about 300°C in air. The moisture sorption isotherm was determined on coarsely ground samples of 6 at 25°C and compared with those for the structurally‐related polyamides 2 and 4. © 1993 John Wiley & Sons, Inc.
Free radical copolymerization of furfuryl acrylate and 2‐hydroxyethyl‐methacrylate
Authors: Zaldívar Dionisio , Peniche Carlos , Bulay Anna , Román Julio San 
Published: April 2003

AbstractCopolymers of furfuryl acrylate (F) and 2‐hydroxyethyl methacrylate (H) were prepared by free radical polymerization in DMF solution at 50°C, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were calculated according to the general copolymerization equation using the Fineman‐Ross and Kelen‐Tüdös linearization methods, as well as the Tidwell and Mortimer nonlinear least‐squares treatment. The reactivity ratios obtained were rF = 0.93 and rH = 1.42. The microstructure of copolymer chains is described on the basis of first‐order Markov statistics, and the copolymer glass transition temperatures were determined calorimetrically. The variation of Tg with the copolymer composition is discussed according to modern methods, considering the sequence distribution of monomeric units along the copolymer chains. Also the Tg of the corresponding homopolymers was determined giving the values Tg(F) = 321 K and Tg(H) = 358 K, whereas the Tg of the corresponding alternating diad has an average value of TgFH = 326 K. © 1993 John Wiley & Sons, Inc.
Monoesterification of styrene–maleic anhydride copolymers with alcohols in ethyl benzene: Catalysis and kinetics
Authors: Hu G. H. , Lindt J. T. 
Published: April 2003

AbstractA kinetic investigation on the monoesterification reaction of the maleic anhydride residue (MA) in styrene‐maleic anhydride copolymers with aliphatic alcohols was carried out in ethyl benzene solution. By comparison to classic catalysts such as tributylamine (TBA) and pyridine, 4‐dimethylaminopyridine (4DMAP) is by far the most effective catalyst for this reaction. While both general base and nucleophilic mechanisms contribute to the reaction catalyzed by TBA or pyridine, a nucleophilic mechanism prevails with 4DMAP. This reaction is reversible, and its chemical equilibrium constant decreases significantly with increasing temperature. Both kinetic and thermodynamic results showed that in the presence of 4DMAP, the forward and reverse reactions are second and first order, respectively. The existence of side reactions, reactivity of two styrene‐maleic anhydride copolymers of different MA contents as well as two aliphatic alcohols of different lengths are also addressed. © 1993 John Wiley & Sons, Inc.
Fire‐ and heat‐resistant matrix resins based on ethynyl‐substituted aromatic cyclotriphosphazenes
Authors: Kumar Devendra , Gupta Alka D. , Khullar Mrignaini 
Published: April 2003

AbstractA novel class of fire‐ and heat‐resistant matrix resins has been synthesized by thermal polymerization of ethynyl‐substituted aromatic cyclotriphosphazenes. Thermal polymerization of new tris[4‐(4′‐ethynylbenzanilido)phenoxy]tris(phenoxy) cyclotriphosphazene (III) and tris[4‐(4′‐ethynylphthalimido)phenoxy]tris(phenoxy)cyclotriphosphazene (VII) at 250°C for 1–1.5 h gave tough polymers. The thermal stabilities of the polymers were evaluated in nitrogen and in air by thermogravimetric analysis (TGA). The synthesised polymers were stable to 400–410°C and showed char yield of 78–65% at 800°C in nitrogen and of 78–69% at 700°C in air. The ethynyl‐substituted polymer precursor (III) was synthesised by the reaction of tris(4‐aminophenoxy)tris(phenoxy)cyclotriphosphazene (I) with 4‐ethynylbenzoyl chloride. The polymer precursor (VII) was synthesised by a solution condensation of I with 4‐ethynylphthalic anhydride followed by in situ thermal cyclodehydration at 150°C. The structure of polymer precursors was characterized using proton nuclear magnetic resonance (1H‐NMR), infrared (IR) spectroscopy, and elemental analysis. The curing of polymer precursors was monitored by differential scanning calorimetery (DSC) and IR spectroscopy. The synthesised matrix resins are potential candidates for the development of heat‐ and fire‐resistant fiber‐reinforced composites. © 1993 John Wiley & Sons, Inc.
Photocrosslinking of acrylated natural rubber
Authors: Le Xuan H. , Decker C. 
Published: April 2003

AbstractPhotocrosslinkable elastomers with pendent acrylate groups have been synthesized by ringopening reaction of epoxidized natural rubber with acrylic acid. The kinetics of the acrylation reaction has been studied by infrared spectroscopy and shown to obey a simple first‐order law. The acrylated natural rubber undergoes a fast crosslinking‐polymerization when it is exposed to UV radiation in the presence of an aryl ketone photoinitiator, with formation of a tridimensional polymer network within a few seconds. The cure kinetics has been studied in real time by monitoring the disappearance of the IR absorption of the grafted acrylate double bond. The rate of polymerization was found to increase linearly with the degree of acrylation of the rubber, reaching values up to 3 mol kg−1 s−1. The isoprene double bond, which is inactive in virgin natural rubber, also undergoes polymerization upon UV exposure when epoxy or acrylate groups are present. The UV‐cured polymer becomes totally insoluble in the organic solvents and exhibits remarkable mechanical properties, such as hardness, flexibility, and impact resistance. The gel fraction and the hardness were both shown to increase with the degree of acrylation and with the cure extent. © 1993 John Wiley & Sons, Inc.
Syntheses and some fluorescence properties of poly(2‐methacrylamido‐3‐arylpropionic acid)
Authors: Morishima Yotaro , Tominaga Yukio , Nomura Shigeki , Kamachi Mikiharu 
Published: April 2003

Abstract2‐Methacrylamido‐3‐arylpropionic acid, where aryl is 1‐naphthyl (M1NpPA), 2‐naphthyl (M2NpPA), or 1‐pyrenyl (M1PyPA), was synthesized. Free radical polymerization gave polymers which were soluble in water at pH > 6. In aqueous solution, poly(M1NpPA) and poly(M2NpPA) exhibited strong excimer fluorescence as a dominant component, whereas poly(M1PvPA) showed weak monomer fluorescence as a main component. Excitation spectra and fluorescence quenching by Tl+ ions suggested that naphthyl groups in poly(M1NpPA) and poly(M2NpPA) interacted so as to form excimer sites, by which migrating excited singlets were trapped, leading to the strong excimer emission. It was suggested, however, that pyrenyl groups in poly(M1PyPA) were sterically so constrained that they could not attain the full‐overlap excimer conformation but could only interact to form self‐quenching sites, to which energy migration occurred, leading to weak fluorescence. © 1993 John Wiley & Sons, Inc.