bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multichain copoly(α‐amino acid). II. Preparation and properties of multi‐Nϵ‐poly(γ‐benzyl‐L‐glutamyl)copoly(L‐lysine γ‐methyl‐L‐glutamate)
Authors: Sakamoto Munenori , Kuroyanagi Yoshimitsu , Sakamoto Ryuichi 
Published: April 2003

AbstractA number of multi‐Nϵ‐poly(γ‐benzyl‐L‐glutamyl)copoly(L‐lysine γ‐methyl‐L‐glutamate)s with branches having various degrees of polymerization and with various intervals of the grafting sites in the core molecule were prepared in N,N‐dimethylformamide containing dimethyl sulfoxide by the reaction of N‐carboxy anhydride of γ‐benzyl L‐glutamate with random copoly(L‐lysine γ‐methyl‐L‐glutamate)s of different composition with various anhydride‐initiator ratios. The relationship between the intrinsic viscosity measured in a coil solvent, dichloroacetic acid (DCA), and the number‐average molecular weight determined by osmometry was found to be expressed by the Mark–Houwink–Sakurada equation for the multichain copoly(α‐amino acid)s which were made from the same polymeric initiator. The observed α values of the multichain copoly(α‐amino acid)s in the equation were lower than that of linear poly(γ‐benzyl‐L‐glutamate). The solvent induced helix–coil transition of the multichain copolymer was investigated in the chloroform‒DCA system by the ORD technique. Two kinds of transition regions were clearly distinguished: The α‐helices of the core molecules underwent the transition at lower DCA concentration and those of the branch chains at higher DCA concentration. The reduced viscosity of the multichain copoly‐(α‐amino acid) increased slightly between the two transition regions, in contrast to the large decrease in the reduced viscosity of linear poly(γ‐benzyl‐L‐glutamate) during the helix–coil transition.
Modification of poly(vinyl chloride). XXXI. Crosslinking of poly(vinyl chloride) with 2‐R‐4,6‐dithiol‐s‐triazine and metal activators
Authors: Mori Kunio , Nakamura Yoshiro 
Published: April 2003

AbstractCrosslinking of poly(vinyl chloride) (PVC) with 2‐R‐4,6‐dithiol‐s‐triazine (R‐DT) and metal activators has been studied to determine crosslinking rate constants, induction periods, and apparent activation energy and the final efficiency of crosslinking agents. The rate constants were about 1.4–7.5 min−1 and the induction periods were about 6.8–24.3 min for various kinds of R‐DT at 180°C. The activation energy was about 16.6–33 kcal/mol over the temperature range 160–195°C.The rate constants were strongly influenced by 2‐substituted groups (R) in R‐DT and increased in the order R′O‐≪ R′NH‐< (R′)2N, where R′ is an alkyl or aryl group. Further, the rate constants increased in the order of: metal carboxylates < metal carboxylates < metal oxides for the activators and in the order of: Pb < Mg < Ca < Ba < Na for metal atoms.The final efficiency was about 75–80% for the activators such as MgO, MgCO3, PbO, and SnO. The activators containing Na, Ca, and Ba atoms, however, gave final efficiency of more than 100%.
Oxidative stress relaxation and the measurement of sol fraction in rubber vulcanizates
Authors: Kaeriyama Akitoshi , Ono Katsumichi , Murakami Kenkichi 
Published: April 2003

AbstractA simple method to determine the chain scission mechanism of the oxidative degradation of rubber vulcanizates is proposed. The method involves the measurement of oxidative stress decay and the change in sol fraction, which allow us to distinguish whether scission occurs randomly along the main chain, near crosslinks or of crosslinks. The applicability of this method was well established using natural rubber vulcanizates as the reference samples. The chain scission of cis‐1,4‐polyisoprene vulcanizaties was proved to take place randomly along the main chain irrespective of their crosslink structure. On the other hand, the chain scission of dicumyl peroxide cured cis‐1,4‐polybutadiene takes place selectively near crosslinks. It is suggested that the unusual behavior of cis‐1,4‐polybutadiene vulcanizates is due to the characteristic structure of the crosslinks.
Four‐center‐type photopolymerization in the crystalline state. IX. Characteristic features of topochemical process and polymer properties thus obtained
Authors: Hasegawa Masaki , Nakanishi Hachiro , Yurugi Tadashi 
Published: April 2003

AbstractChanges in TG‐DSC diagrams and X‐ray diffraction patterns in the course of four‐center‐type photopolymerization of 2,5‐distyrylpyrazine (DSP) and thermal depolymerization of poly‐DSP were investigated. It has been found that as‐polymerized poly‐DSP crystal with high molecular weight does not melt but depolymerizes into the oligomer in the crystalline state. The crystal change found in the depolymerization was just the reverse of that in the polymerization. From the results a reversible topochemical process, which comprises monomer lattice‐controlled photopolymerization and polymer lattice‐controlled thermal depolymerization, has been established between DSP and poly‐DSP. Quantitative thermal analysis reveals that both of the two endotherms of poly‐DSP crystal include the heat of crystallization as well as that of depolymerization. Several specific properties of a topochemical product of as‐polymerized poly‐DSP crystal, such as nonreproducibility of the original crystal structure by recrystallization and superior stabilities to thermal depolymerization and photooxidation, are discussed in comparison with natural cellulose.
Aromatic polyamides. II. Synthesis, wet‐spinning, and fiber thermal characterization of poly(4,4′‐oxanilideterephthalamide) and copolymers with 4,4′‐oxydianiline or isophthalic acid
Authors: Silver Frank M. , Dobinson Frank 
Published: April 2003

AbstractPoly(4,4′‐oxanilideterephthalamide) (coded A‐202) was prepared from 4,4′‐diaminooxanilide (DAO) and terephthaloyl chloride (TCI) in N,N‐dimethylacetamide (DMAc)/5% LiCl and DMAc (5% LiCl)/hexamethylphosphorictriamide (HMPA) solvents. Fiber with tenacity/elongation/modulus at 1% extension (t/e/m) of 5.2 grams per denier (gpd)/1.9%/316 gpd was obtained. The all‐para A‐202 tended to precipitate from solution. More soluble copolyamides were prepared from DAO and TCl in combination with either 4,4′‐oxydianiline (A‐202/ODA) or isophthaloyl chloride (A‐202/I) in DMAc (5%LiCl). A‐202/ODA solutions were spun to fiber with t/e/m of 11.2 gpd/6%/217 gpd; A‐202/I gave fiber with t/e/m of 6.4 gpd/1.3%/432 gpd. Dynamic mechanical analyses (Vibron) and dilatometric measurements of A‐202, A‐202/ODA, and A‐202/I showed no glass transition temperature below 200°C. Differential thermal analyses (DTA) revealed no transitions below 400°C. Thermogravimetric analyses (TGA) at 15°C/min exhibited substantially no weight loss in air at temperatures up to 400°C.
Study of kinetic regularities and mechanism of methyl methacrylate radical polymerization in the presence of orthophosphoric acid
Authors: Garina E. S. , Olenin A. V. , Zubov V. P. , Kuchanov S. I. , Povolotskaya E. S. , Kabanov V. A. 
Published: April 2003

AbstractPhotoinitiated homophase polymerization of methyl methacrylate (MMA) at 25°C in the presence of a complexing agent, orthophosphoric acid (H3PO4), was studied. It was found that in addition to the increase in initial polymerization rates and molecular weights of PMMA the system MMA/H3PO4 reveals postpolymerization that does not retard with time and is accompanied by an increase on average molecular weight. Macroradicals, lifetimes of which grow considerably in the presence of the complexing agent, are shown to be responsible for the termination‐free postpolymerization in this system by the living chain mechanism. The effect of various factors on the kinetics of postillumination polymerization was studied. A drastic decrease in the rate of bimolecular termination of poly(methyl methacrylate) radicals was shown to be related to the change in conformational properties and to the association of propagation chains via complexing with H3PO4. The mechanism of polymerization in this system was discussed.
Poly(β‐amino acid)s. IV. Synthesis and conformational properties of poly(α‐isobutyl‐L‐aspartate)
Authors: Yuki Heimei , Okamoto Yoshio , Taketani Yutaka , Tsubota Tetsuo , Marubayashi Yoshizo 
Published: April 2003

AbstractPoly(α‐isobutyl‐L‐aspartate) was prepared by the polycondensation reaction of p‐nitrophenyl ester of α‐isobutyl‐L‐aspartate and the conformation of the poly(β‐amino acid) was investigated by X‐ray diffraction, polarized infrared, circular dichroism (CD), optical rotatory dispersion (ORD), and NMR spectroscopy. α‐Isobutyl β‐p‐nitrophenyl‐L‐aspartate hydrochloride and hydrobromide were used as monomers and dimethylformamide, chloroform, and chlorobenzene, as solvents. A high‐molecular‐weight polymer with [η] 1.0 dl/g (dichloroacetic acid, 25°C) was formed in the polymerization of the hydrochloride in chloroform at 25°C. The X‐ray diagram and polarized infrared spectrum of the stretched polymer film obtained from a chloroform solution suggested a cross‐β‐form as the most probable structure in the solid state. The CD spectra of the polymer in a 2,2,2‐trifluoroethanol (TFE) solution and its film cast from the solution showed a peak at 205 nm and a trough at 190 nm which were assigned to a β‐structure. The polymer was associated in chloroform. The NMR and ORD spectra in chloroform were similar to those in TFE, which suggests that the polymer also exists in the β‐structure in chloroform. The addition of small amounts of dichloroacetic acid and sulfuric acid to chloroform and TFE solutions, respectively, destroyed the β‐structure. A random copolymer of α‐isobutyl‐L‐aspartate with β‐alanine was also prepared by polycondensation reaction. The copolymer apparently did not form an ordered structure in the solid state or in solution.
Equilibrium cyclotrimerization of ether oxygen‐substituted aliphatic aldehydes
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi , Kawase Sanshiro 
Published: April 2003

AbstractThis article describes the equilibrium cyclotrimerization of β‐methoxypropionaldehyde (MPA), 4,7‐dioxaoctanal (DOA), and n‐octanal (OA) initiated by boron trifluoride etherate in toluene at a temperature range of −10 to 25°C. The enthalpy and entropy changes corresponding to the conversion of 1 mole of the monomers to 1/3 mole of their cyclic trimers in toluene solution, at the initial monomer concentration of 1 mole/liter, were evaluated as follows: ΔHss = −5.9 ± 0.3 kcal/mole and ΔSss = −19.1 ± 1.3 cal/mole deg for the MPA system; ΔHss = −7.4 ± 0.4 kcal/mole and ΔSss = −24.1 ± 1.7 cal/mole deg for the DOA system; ΔHss = −6.1 ± 0.4 kcal/mole and ΔSss = −21.2 ± 1.5 cal/mole deg for the OA system. The comparison of these values with those in their polymerization indicates that the cyclotrimerization of aldehydes is thermodynamically of greater advantage than their polymerization. The effects of long and polar substituents are discussed from the view‐point of the intermolecular interactions by the polar groups in monomers and their cyclic trimers.
Hydrogen chain transfer in olefin polymerization with organometallic catalysts
Authors: Mortimer George A. , Ort Morris R. , Mottus Edward H. 
Published: April 2003

AbstractHydrogen has been shown to be a true chain‐transfer agent with some organometallic olefin polymerization catalysts. However, the Mayo equation for chain transfer in free‐radical polymerization does not fit quantitative data from organometallic catalysts. There appear to be two reasons for the lack of fit. First, the Mayo equation considers the competition between hydrogen and olefin for the growing chain but does not account for their competitive absorption on the catalyst (coordination with vacant orbitals on the transition metal). Second, some organometallic catalysts gradually absorb hydrogen irreversibly to give a new catalyst species of altered behavior.
Photodegradation of aramids. I. Irradiation in the absence of oxygen
Authors: Carlsson D. J. , Gan L. H. , Wiles D. M. 
Published: April 2003

AbstractThe photolysis reactions of a series of isomeric fully aromatic polyamides (aramids) have been investigated in the absence of oxygen by ultraviolet and luminescence spectroscopy. Several of the aramids were found to undergo photo‐Fries rearrangements to give 2‐aminobenzophenone backbone units when irradiated either as films, fibers, or dissolved in liquids. Quantum yields for this rearrangement were low, < 1 × 10−6 mole/einstein, and increased with decreasing aramid glass transition temperature and increasing backbone mobility. The formation of gel, carbon monoxide, and a strong ESR signal were consistent with a free‐radical mechanism for the rearrangement.
Urea‐formaldehyde resins. III. Constitutional characterization by 13C fourier transform NMR spectroscopy
Authors: Tomita Bunichiro , Hatono Shiro 
Published: April 2003

Abstract13C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of 13C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a 13C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated.Measurement of a 13C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a 13C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde.
Distribution of polymer deposition in plasma polymerization. III. Effect of discharge power
Authors: Yasuda H. , Hirotsu T. 
Published: April 2003

AbstractDistribution of polymer deposition in an inductively coupled rf discharge system is studied as a function of level of discharge power with acetylene and styrene as monomers. When a fixed flow rate is used, the discharge power has a relatively small effect on the pattern of distribution of polymer deposition as long as values of W/FM, where W is discharge wattage, F is flow rate, and M is molecular weight of monomer, are maintained above a critical level to maintain full glow in the reaction tube. It has been shown that plasma polymerization of two monomers which have different molecular weights can be compared in a fair manner by selecting conditions to yield similar value of W/FM.
Radiation effect on polystyrene deposited and grafted on silica gel
Authors: Kusama Yasuo , Udagawa Akira , Takehisa Masaaki 
Published: April 2003

AbstractThe effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with GPC. Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. Part of the deposited polymer bonded to silica gel by radiation; the G value for graft‐chain formation is in the range of 0.01–0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation‐induced polymerization of styrene adsorbed on silica gel is due to a secondary effect of radiation on the polymer.
Quasi‐equilibrium states of copolymers that simultaneously crystallize and interchange structural units
Authors: Theil Michael H. 
Published: April 2003

AbstractA quasi‐equilibrium model of a step‐growth copolymer that crystallizes and interchanges structural units simultaneously is presented. Equilibrium values of counit‐sequence‐length distribution in the amorphous phase and degree of crystallinity are calculated in a system for which crystallite thickness is determined by nucleation. When applied to calculations, the model predicts that the counits of the amorphous phase will tend to be ordered in blocks. The crystalline content of the whole polymer and the extent of ordering counits along the chain decreases with increasing temperature. The model predicts temperature ranges for some whole copolymers in which one of two similarly stable, disparate combinations of crystallinity and sequence‐length distribution may prevail.
Functionality and structure of polymers. II. Photodimerization of polymer‐bound anthryl groups and thermal dissociation of the photodimers
Authors: Tazuke Shigeo , Hayashi Naoya 
Published: April 2003

AbstractAnthryl groups bound to various polyesters and polyesterurethanes as side groups were photodimerized in solid state in a nitrogen atmosphere. The rate of photodimerization is strongly affected by polymer structure as observed in the photodimerization of dilute solutions. The results revealed the importance of segment mobility rather than local concentration of anthryl groups. Temperature effects on the rate of photodimerization indicated that the rate jumped above the glass transition temperature (Tg). A definite difference in photodimerization behavior was apparent between polyesters and polyesterurethanes. Anthryl groups in polyesters were to some extent photodimerized at Tg, whereas polyesterurethanes did not react at all. Hydrogen bonding in polyesterurethanes restricted the movement of anthryl groups and consequently additional energy was required to liberate them and allow photodimerization to proceed. The anthryl groups can be recovered from the photodimerized polymers by heating to 80–100°C. The activation energy of thermal dissociation of the photodimer depends to a great extent on polymer structure. These results were interpreted as being due to the strain brought about by photodimer formation exhibited this dependence. The photodimerization–thermal dissociation cycle was reversible (reversibility: 95–100% under nitrogen). A novel principle of reversible photomemory, based on dry unit processes that consisted of image recording above Tg, fixation of image by cooling below Tg, and image erasure at elevated temperature, was proposed.
Radical‐cationic photoinitiated copolymerization of isobutylene with isoprene in the presence of vanadium (IV) chloride
Authors: Toman Luděk , Pilař Jan , Spěváček Jiří , Marek Miroslav 
Published: April 2003

AbstractEPR spectra of isoprene and isobutylene‐isoprene mixture has been studied in the presence of VCl4 in dark and under irradiation, respectively. Analogously, as with isobutylene, a radical‐cation of isoprene is formed under irradiation, and in a mixture of both monomers radical‐cations of isobutylene and isoprene are formed side by side. Formation of the isoprene radical‐cation prevails even in an excess of isobutylene, that is, in an isobutylene‐isoprene ratio of 8:1. Peroxy radicals which inhibit the photochemical copolymerization of isobutylene with isoprene were recorded in the presence of oxygen in isoprene and in the isobutylene‐isoprene mixture. The copolymers of isobutylene with isoprene prepared photochemically (unsaturation 1.5–2 mole %) at −30 to −78°C had a considerably higher viscometric molecular weight than copolymer samples prepared under the same conditions with AlCl3 or BF3 catalysts. According to NMR measurements of butyl rubber samples prepared by photochemical copolymerization, all isoprene is incorporated in the polymer chain as 1,4‐structural units.
Adsorptionsmodifizierung der oberfläche von mineralischen polymerfüllstoffen als die methode deren aktivierung
Authors: Tolstaja S. N. , Taubman A. B. , Mikhailova S. S. 
Published: April 2003

AbstractThe process of modifying the surface of particles of dispersed polymer fillers, using tensides, has been studied. The main principles were established with regard to the effect of modification of titanium dioxide and kaolin on the structure formation in solutions and block formations of chlorinated poly(vinyl chloride) resin and rubber, depending on the nature and concentration of the modifier. The decisive part played by chemisorption of the tenside in lyophilization (water‐repellency treatment) of the surface of the filler and its activation, as a structure former, has been elucidated.
Block copolymers of ethylene. I. Butadiene
Authors: Hay J. N. , McCabe J. F. 
Published: April 2003

AbstractBlock copolymers of ethylene and butadiene have been prepared to study their properties. The method of preparation of polybutadiene, polyethylene, and block copolymers of ethylene and butadiene with n‐butyl lithium‐tetramethyl ethylene diamine complex is outlined. Kinetic studies have been reported elsewhere and these are assessed to determine that suitability of the system to produce monodispersed “living” chains so that simple correlations between physical properties and molecular weight can be made. The properties were somewhat restricted by the 1,2‐microstructure of the butadiene block.
Copolymerization of vinyl monomers with irradiated acrylamide crystals
Authors: Kücükyavuz Savas , Baysal Bahattin M. 
Published: April 2003

AbstractLiquid vinyl monomers (styrene and methyl methacrylate) were copolymerized with γ‐irradiated acrylamide in a two‐phase system. The products obtained were mainly diblock copolymers of acrylamide and the vinyl monomer used, but small amounts of homopolymers were also formed. The effects of radiation dose, copolymerization temperature, initial molar ratio of monomers, crystal size of acrylamide, mode of irradiation, and the existence of a solvent were investigated. In addition to the conventional methods, the reaction was studied by electron spin resonance spectroscopy. A mechanism was proposed and a kinetic rate equation was established for this copolymerization. Characterization of the copolymers was made by physical and mechanical testing.
Study of associated reaction variables in the synthesis of titanium (IV) polyamines and a comparison of synthesis by different techniques
Authors: Carraher Charles E. , Jorgensen Steven 
Published: April 2003

AbstractSynthesis of titanium polyamines was accomplished with “inverse” and “normal” interfacial and aqueous solution systems. Yield was independent of the usual reaction parameters for substituents
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on p‐phenylenediamine for the interfacial systems but might be dependent on the particular diffusion rates of the diamines. Yield decreases as the nucleophilicity of the diamine decreases for the aqueous solution systems. Yield is independent of pH, decreases with reduction in reactant concentration and increases with increases in the amine: Cp2TiCl2 ratio for both normal interfacial and aqueous solution systems.