bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of two‐phase bulk polymerization. II. The influence of dissolved polymer
Authors: Ludwico W. A. , Rosen S. L. 
Published: April 2003

AbstractThe effect of dissolved polybutadiene on the initial rate of polymerization of styrene was investigated by using high‐precision dilatometric techniques. The dissolved polymer reduced the rate of polymerization by amounts greater than can be accounted for by a reduction in monomer concentration. Rate reductions increased with the amount of dissolved polybutadiene and with its molecular weight and were greater for benzoyl peroxide initiator than for equal concentrations of azobisisobutyronitrile. Surprisingly, analogous rate reductions were observed when polystyrene were substituted for the polybutadienes, except that at high polystyrene concentrations, the expected autoacceleration was observed. These rate reductions showed no correlation with the viscosity of the reaction mass, nor did the dissolved polymer affect initiator efficiency. At a given level of a particular dissolved polybutadiene, rate reductions were diminished by increasing levels of each initiator, and by adding a chain‐transfer agent. Good quantitative agreement was obtained with the number‐average length of the growing polymer chains, whether varied by using different initiators, changing initiator level, or adding chain‐transfer agent. These results are inconsistent with a chemical mechanism, but they are explained by a proposal originated by North and Reed whereby the dissolved polymer makes the reaction mass a “poorer” solvent for the growing polymer chains, reducing their overall coil dimensions and enhancing their rate of diffusion together for termination.
Acidic dehydration as an analytical method for evaluating ethylene oxide–propylene oxide copolymers
Authors: Cervenka A. , Merrall G. T. 
Published: April 2003

AbstractAcidic dehydration by p‐toluenesulfonic acid at 250°C converts poly(alkylene oxides) into dioxane derivatives which can be separated by gas–liquid chromatography. This procedure has been developed as an analytical technique for characterizing some aspects of the molecular structure of polymers of ethylene and propylene oxides. Experimental data on homopolymers, their blends, and some model copolymers have shown that the method is capable of distinguishing between copolymers of different structures, giving correct overall comonomer contents and also ranking copolymers according to their degrees of blockiness.
Cationic polymerization of p‐substituted α‐methylstyrenes. III. Effect of polymerization conditions on tacticity and molecular weight for p‐chloro‐α‐methylstyrene
Authors: Lenz Robert W. , Westfelt Lars C. 
Published: April 2003

AbstractThe cationic polymerization of p‐chloro‐α‐methylstyrene was investigated for the effect of initiator and solvent on polymer tacticity, molecular weight, and molecular weight distribution. The products were generally crystalline polymers of 80–90% syndiotactic content with fairly high molecular weights and broad molecular weight distributions. Tacticities and molecular weight distributions followed similar patterns suggesting that the effect of reaction conditions on ionpair end‐group structures was the dominant factor.
Mechanism of thermal decomposition of peroxide radicals formed in polytetrafluoroethylene by γ‐ray irradiation
Authors: Hagiwara Miyuki , Tagawa Toru , Amemiya Hideo , Araki Kunio , Shinohara Isao , Kagiya Tsutomu 
Published: April 2003

AbstractThermal decomposition of polymer peroxide radicals formed in γ‐irradiated polytetrafluoroethylene, ∼CF2CF(OO·)CF2∼ (radical I) and ∼CF2CF2(OO∼) (radical II), was studied by mass spectral analysis of the gas evolved in comparison with their photolysis with ultraviolet light. In the thermal decomposition of radicals I and II, CO2 was the most abundant component, with smaller amount of CO, CF2O, and gases present. In the photolysis, CO instead of CO2 was the most abundant in the case of radical I, while in the case of radical II, CO2 was again the main product. When a labeled polymer peroxide radical, ∼CF2CF(18O‐18O·)CF2∼, was treated with heat or ultraviolet light, C18O16O was detected as a main component. In the treatment with ultraviolet light, a large amount of C18O comparable to that of C18O16O was also obtained. The mechanism of main‐chain scission of radicals I and II is discussed.
Effects of the acid chain length and copolymer crosslinking on the acylation of N‐hydroxysuccinimide copolymers with carbobenzoxyoligo‐ϵ‐aminocaproic acids
Authors: Akiyama M. , Narita M. , Seida K. , Osawa T. 
Published: April 2003

AbstractN‐Hydroxysuccinimide‐type soluble copolymer with styrene and three similar divinylbenzene (3–4 mole‐%) crosslinked copolymers with styrene, N‐vinylpyrrolidone, and N,N‐dimethylacrylamide were prepared from their precursor copolymers of N‐acetoxymaleimide. Acylation of these N‐hydroxyl polymers with carbobenzoxyoligo‐ϵ‐aminocaproic acids was conducted in dimethylformamide at room temperature by using dicyclohexylcarbodiimide as condensing agent. The soluble styrene copolymer was acylated in good conversions (76–89%) in every case (n = 1–3), whereas the acylation of the crosslinked copolymers decreased slightly from n = 1 to n = 2, and dropped suddenly to only small conversions (4.7–7.4%) with n = 3, showing a marked inhibitory effect of crosslinking when the acids became longer. The effect of the microenvironment of the polymer did not appear significant. All the acyl polymers, including the precursor polymers, yielded the corresponding cyclohexylamides when treated with cyclohexylamine.
Synthesis and structure of the p‐hydroxybenzoic acid polymer
Authors: Economy James , Storm R. S. , Matkovich V. I. , Cottis S. G. , Nowak B. E. 
Published: April 2003

AbstractThe synthesis and structure of the p‐hydroxybenzoic acid polymer is described. The polymer was successfully prepared from either the phenyl ester of p‐hydroxybenzoic acid or from p‐acetoxybenzoic acid. With highly purified acetoxybenzoic acid, single crystals of the polymer could be prepared. The structure of the polymer was determined and shown to consist of a double helix where the two chains are in a reversed head‐to‐tail order. The unit cell dimensions are: a = 17.8 Å and c = 18.4 Å, where c corresponds to the chain length with a repeat distance of three units. The mechanism of polymerization and formation of the single crystal is discussed. The polymer displays a reversible high‐temperature crystalline transition at 325–360°C (not a melting point). The transition was characterized by differential thermal analysis, differential calorimetry, thermal expansion coefficient measurements, high‐temperature x‐ray scans, and dielectric constant determinations. Orientation of the polymer chains during fabrication and changes in the mechanism of oxidative degradation above the crystal transition are described.
Glass transition temperature of low molecular weight styrene–isoprene block copolymers
Authors: Toporowski P. M. , Roovers J. E. L. 
Published: April 2003

AbstractDifferent series of poly(styrene–isoprene) diblock and poly(styrene–isoprene–styrene) triblock copolymers were prepared. In each series, the low molecular weight polystyrene block was kept constant, and the molecular weight of the polyisoprene block varied. The glass transition behavior of these polymers was studied and their glass transition temperatures compared with those of the random copolymers of styrene and isoprene. It is concluded that some low molecular weight styrene‐isoprene block copolymers form a single phase. Krause's thermodynamic treatment of phase separation in block copolymers was applied to the data. One arrives at a polystyrene–polyisoprene interaction parameter χ1,2 ≈ 0.1. The experimental and theoretical limitations of this result are discussed.
Studies of methyl methacrylate–glycidyl methacrylate copolymers: Copolymerization to low molecular weights and modification by ring‐opening reaction of epoxy side groups
Authors: Paul Swaraj , Rånby Bengt 
Published: April 2003

AbstractThe copolymerization of methyl methacrylate (MMA) with glycidyl methacrylate (GMA) at 60°C with 2,2′‐azobisisobutyronitrile (AIBN) as radical initiator and in the presence of thiophenol (TP) as chain‐transfer agent has been investigated. Monomer reactivity ratios for MMA and GMA are found to be r1 (MMA) = 0.80 ± 0.015 and r2 (GMA) = 0.70 ± 0.015, from which Q and e values are calculated to be 0.68 and −0.36 for GMA. The initial rate of copolymerization Rp at 60°C with AIBN (0.02 mole/l.) and TP (0.1, 0.01 mole/l.) were found to increase nonlinearly with increasing GMA concentration in the monomer feed. Homopolymerizations of MMA and GMA monomers were studied in the presence and in the absence of thiophenol. The values of δ (= kt1/2/kp) for MMA and GMA were determined to be 10.25 and 3.00 (mole‐sec/l.)1/2, respectively. Using the values r1 (MMA), r2 (GMA), δ1 (MMA), δ2 (GMA), and Rp, the cross‐termination constants ϕ for MMA–GMA monomers were determined (average value ϕ = 0.42). The increase in Rp values with increasing GMA content has been attributed to the cross‐termination of MMA–GMA radicals. The transfer constant of TP has also been determined for GMA and found to be 1.00. A MMA–GMA copolymer of low molecular weight, containing 2.01% of oxirane oxygen, was modified by opening of the oxirane ring of GMA by reaction with diethanolamine (DEA). The reaction was carried out at 70 ± 1°C, the copolymer content of epoxy groups and the amine being assumed to be in the molar ratio of 1:4. Addition of a hydrogen‐bond acceptor like nitrobenzene decreases, while addition of a hydrogen‐bond donor like phenol increases the rate of epoxy ring opening with DEA. This indicates that a hydrogen‐bonded intermediate is involved in this reaction and that it weakens the epoxy ring and enhances the rate of its opening with DEA. From the studies of the conversion rates, existence of a “nonspecific” side reaction has been shown which involves the reaction of the terminal epoxy groups of the copolymer and the hydroxyl groups of DEA or formed in the reaction with DEA (involves a chain coupling). DEA can be trifunctional in this reaction. This has been further confirmed from the increase of number‐average molecular weights M̄n of the copolymers resulting from this coupling and the nitrogen content in the copolymers after modification with DEA.
Cyclic acetal‐photosensitized polymerization. II. Photopolymerization of styrene in the presence of various monocyclic acetals
Authors: Ouchi Tatsuro , Hamada Masao 
Published: April 2003

AbstractThe polymerization of styrene (St) in benzene solution in the presence of 1,3‐dioxane (DON), 1,3‐dioxepane (DOP), trioxane (TRON), or tetraoxane (TEON) by means of photoirradiation of the system at 40°C has been studied kinetically from the standpoint of photosensitized polymerization. The rate of photosensitized polymerization Rp increased in the order: DOP < DON < TRON < TEON, as shown by the rate constant of decomposition of cyclic acetals, and then could be expressed by Rp = k[monocyclic acetal]0.5[St]1.0. The polymerization was confirmed to proceed via a radical mechanism.
Preparation of block copolymers from occluded vinyl acetate macroradicals
Authors: Seymour Raymond B. , Stahl G. Allan 
Published: April 2003

AbstractStable vinyl acetate macroradicals were produced by polymerization in a nonviscous poor solvent, a viscous good solvent and a viscous poor solvent. These macroradicals were then allowed to react with a second vinyl monomer to produce block copolymers. The formation of block copolymers was monitored for rate and yield data. The block copolymers produced were poly(vinyl acetate‐b‐methyl methacrylate), poly(vinyl acetate‐b‐acrylic acid), poly(vinyl acetate‐b‐vinylpyrrolidone), poly(vinyl acetate‐b‐acrylonitrile), poly(vinyl acetate‐b‐styrene), and poly(vinyl acetate‐b‐methyl acrylate). The block copolymers were characterized by yield, precipitation in selected solvents, pyrolysis gas chromatography, and differential scanning calorimetry.
The nature of active centers of a polymeric catalase analog
Authors: Pshezhetskyǐ V. S. , Ikryannikov S. G. , Kuznetsova T. A. , Kabanov V. A. 
Published: April 2003

AbstractThe decomposition of hydrogen peroxide by a polymer complex of Fe3+ and poly(acrylic acid) partially amidated by diethylenetriamine has been studied. The molecular mechanism of catalysis is discussed. The rate constant of the reaction is k = 6.9 × 107 exp {−2.300/RT}. Decomposition of hydrogen peroxide proceeds via activation by the diethylenetriamine which is a cofactor.
Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. II. Salt effect on the relative reactivity in the cationic copolymerization of styrene derivatives with 2‐chloroethyl vinyl ether initiated by iodine
Authors: Yamamoto Kenji , Higashimura Toshinobu 
Published: April 2003

AbstractTo determine the effect of the dissociation of propagating species on the relative reactivity of monomers, 2‐chloroethyl vinyl ether was copolymerized with p‐methoxystyrene or with p‐methylstyrene by using iodine in various solvents at 0°C. A common‐ion salt (tetra‐n‐butylammonium iodide or tetra‐n‐butylammonium triiodide) was added to these copolymerization systems in a polar solvent to depress the dissociation of the propagating species. The addition of a common‐ion salt increased the vinyl ether content in the copolymer. The more the dissociation of propagating species was depressed, the more the vinyl ether content in the copolymer increased. This effect of common‐ion salt was in agreement with that of decreasing solvent polarity which yielded vinyl ether‐rich copolymer as well. Therefore, the change of the monomer reactivity ratio by the solvent polarity, which used to be explained in terms of a selective solvation, must be reconsidered from the viewpoint of varying degrees of the dissociation of propagating species.
Syntheses and properties of phosphorus‐containing copolyamides
Authors: Shalaby S. W. , Sifniades S. , Sheehan D. 
Published: April 2003

AbstractCaprolactam was copolymerized with 1,5‐dioxo‐1‐methyl‐4‐azaphosphepane or methylphosphacaprolactam. The molecular weight of the resulting copolymers decreased with increasing concentration of the thermally labile phosphorus moieties. Copolymers based on ≥40% caprolactam were shown to be crystalline by differential scanning calorimetry and x‐ray techniques. As the concentration of the phosphorus structures in the copolymers increased, the glass transition and crystallization temperatures increased while the melting temperatures, crystallinities, and thermal stabilities decreased. Melt blends of nylon 6 and polymethylphosphacaprolactam were shown by differential scanning calorimetry, a selective extraction technique, and elemental analysis to contain appreciable amounts of block copolyamides, and no crystalline random structures were detected. The thermal stabilities of the melt blends were similar to those of random copolymers having comparable concentrations of the phosphorus‐containing sequences.
Solvent effects on the radiation‐induced graft polymerization of styrene onto poly(isobutylene oxide)
Authors: Omichi Hideki , Araki Kunio 
Published: April 2003

AbstractThe graft polymerization of styrene onto preirradiated poly(isobutylene oxide) (PIBO) with methanol and benzene was studied. The order of grafting yield and of the number‐average molecular weight of graft chains decrease in the order; undiluted styrene > styrene–methanol (1:1) solution > styrene–benzene (1:1) solution. A kinetic treatment to calculate rate constants from the rate of grafting and the molecular weight of the graft chain was proposed. The propagation rate constant kp was 0.2–0.3 l./mole‐sec and the termination rate constant kt was 1.0–16.0 l./mole‐sec. The ratio kp/kt in this heterogeneous system was larger than that in homogeneous system by a factor of about 104–105.
Para‐ordered polybenzimidazole
Authors: Kovar Robert F. , Arnold F. E. 
Published: April 2003

AbstractA series of novel AB monomers such as 2‐[p‐carboxyphenyl]‐5,6‐diaminobenzimidazole hydrochloride have been synthesized. In addition, a new aromatic monomer, 1,3‐diamino‐4,6‐bis(p‐toluenesulfonamido)benzene has been prepared in high purity and substituted for 1,2,4,5‐tetraaminobenzene in a polymerization with terephthalic acid. Homopolymerization of the AB monomers, and polycondensation of monomer with terephthalic acid in polyphosphoric acid, produced the rod‐like para‐oriented polymer, poly[1,7‐dihydrobenzo(1,2‐d: 4,5‐d)diimidazole‐2,6‐diyl‐1,4‐phenylene]. The yellow polymer was completely soluble in methanesulfonic acid (MSA) and PPA, exhibiting intrinsic viscosities as high as 5 dl/g in MSA, and a blue opalescence in solution. Polymerization at temperatures above 225°C caused crystallization and subsequent precipitation to occur. Polymer thus obtained was completely insoluble in MSA and possessed a high degree of crystallinity as demonstrated by x‐ray analysis.
Photodegradation of polyacetaldehyde in solution. I. Direct photolysis
Authors: Marsh Dana G. 
Published: April 2003

AbstractThe quantum yields measured for the random scission of main‐chain bonds of polyacetaldehyde in benzene solution by 254 nm irradiation at 298°K are on the order of 10−3–10−4 scissions per quantum absorbed by the polymer. The quantum yields are unaffected by oxygen but are dependent upon initial polymer concentration and upon the inverse square root of absorbed light intensity. The direct photochemistry involves excitation of carbonyl chromophores in their 1nπ* bands, and a Norrish type I process is believed to be responsible for subsequent free‐radical random‐chain scissions. It has been established that direct photoexcitation processes do not lead to sequential depolymerization of polyacetaldehyde to monomer.
Sulfur‐containing polymers. XVIII. Preparation and properties of thiuram polysulfide polymers
Authors: Kobayashi Norio , Osawa Akiko , Kimoto Hisao , Hayashi Yasuo , Shimizu Kiwako , Fujisawa Tamotsu 
Published: April 2003

AbstractThiuram polysulfide polymers have been prepared from alkali metal bisdithiocarbamates either by oxidation with ammonium persulfate or by polycondensation with sulfur chlorides. In some cases, isothiocyanate formation and/or thiourea formation were noticed. The polymer properties were significantly affected by the diamines used. Polymers derived from p‐phenylenediamine decomposed gradually at room temperature with the liberation of elemental sulfur. Polymers based on aliphatic primary diamines were more stable. Piperazine gave the most stable polymer.
Synthesis of polyamides by ring‐opening polyaddition of 4,4′‐disubstituted bis(3‐buten‐4‐olide) with aliphatic diamines
Authors: Ueda Mitsuru , Yabuuchi Masahiko , Imai Yoshio 
Published: April 2003

AbstractAn investigation of the reaction of 4‐phenyl‐3‐buten‐4‐olide with benzylamine was conducted as a model for the polymerization, and some ethers and acidic solvents were found to be favorable reaction media for formation of the ring‐opened amide as the sole product. By using m‐cresol as the polymerization medium, linear polyamides having inherent viscosities up to 0.67 were readily prepared by the ring‐opening polyaddition of 4,4′‐oxydi‐p‐phenylenebis(3‐buten‐4‐olide) with aliphatic diamines at room temperature. These polymers were soluble in m‐cresol and gave transparent, flexible films by the solution casting technique. They did not show any melt temperature, and began to decompose at around 200°C, both in air and under nitrogen.
Linear polybenzyls. III. Sterically assisted linear polymerization of 2,5‐dimethylbenzyl chloride and α‐methylbenzyl chloride
Authors: Kuo Jeffrey , Lenz Robert W. 
Published: April 2003

AbstractThe low‐temperature Friedel‐Crafts step‐growth polymerization reactions of 2,5‐dimethylbenzyl chloride with TiCl4—(C2H5)2AlCl catalyst, and of α‐methylbenzyl chloride with AlCl3 catalyst were investigated for the effect of reaction conditions on polymer molecular weight, linearity, glass transition temperature, and crystalline properties. Premature precipitation of highly crystalline poly(2,5‐dimethylbenzyl) prevented the preparation of high molecular weight products from this monomer, while most likely an indanyl‐type termination reaction limited the molecular weight of poly(α‐methylbenzyl). Model reactions indicated that, under proper conditions, the latter could be prepared with 99% para substitution, and these polymers were crystalline.
Factors affecting electrical conductivity of carbon black‐loaded rubber. I. Effect of milling conditions and thermal‐oxidative aging on electrical conductivity of haf carbon black‐loaded styrene–butadiene rubber
Authors: Abdel‐Bary E. M. , Amin M. , Hassan H. H. 
Published: April 2003

AbstractStyrene–butadiene rubber (SBR‐1502) loaded with 50 phr carbon black (HAF) was prepared. The electrical conductivity of rubber vulcanizates was measured. It was found that milling conditions have a marked effect on the temperature dependence of the electrical conductivity σ(T) of test samples. In this case, the resistivity of prepared samples increases with remilling and has a minimum value on the σ(T) curve. Thermal‐oxidative aging of such vulcanizates decreases the conductivity of the prepared samples.
Photopolymerization of methyl methacrylate with the use of tetrahydrofuran–bromine charge‐transfer complex as the photoinitiator
Authors: Ghosh Premamoy , Banerjee Amar Nath 
Published: April 2003

AbstractThe polymerization of MMA was kinetically studied in the presence of visible light (using a 125‐W high‐pressure mercury vapor lamp with fluorescent coating, without a filter), a THF—bromine charge‐transfer complex being used as the photoinitiator. The initiator exponent was 0.5 in bulk polymerization. The monomer exponent varied from about 1.2 to about 2.5, depending on the nature of the solvent used; the initiator exponent also varied in diluted systems, depending on the nature and proportion of the solvent, the variation being from a value of 0.5 in bulk system to zero or almost zero at about 25% (v/v) solvent concentration. Other kinetic parameters, viz., kp2/kt and the activation energy for polymerization, were determined and are reported. Kinetic and other evidence indicates that the photopolymerization takes place by a radical mechanism and termination is bimolecular in nature in bulk systems; in dilute systems, termination by initiator complex assumes predominance, particularly at high solvent concentrations (≥25% v/v).