bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical analysis of sorption of a binary solvent in a polymer phase. I. Occurrence and character of inversion in preferential sorption
Authors: Živný A. , Pouchlý J. 
Published: April 2003

AbstractOsmotic and sorption equilibria in the system polymer–binary solvent can be represented with advantage in coordinates (u1, v3), where v3 is the volume fraction of the polymer and u1 gives the composition (volume fraction) of the binary solvent in the polymer phase. The coexistence lines and osmotic isobars are plotted; the former are used to read the preferential sorption ε of one of the solvent components in the polymer. The newly formulated equilibrium condition for the preferential sorption is applied to the Flory–Huggins theory extended by the ternary interaction parameter χT. This is used as a starting point for analyzing the conditions under which inversion of preferential sorption takes place, i.e., the sign of ε changes. The existence of inversion and the course of the inversion line in the v3 versus u1 plot are affected in a decisive manner by the extent to which the effect of the mutual interaction of solvent components prevails over the effect of the relative difference between their molar volumes and of the difference in strength of their interaction with the polymer. The effect of the ratio of molar volumes upon the preferential sorption increases with the concentration of the polymer, so that for v3 not too far from unity the component having the smaller molecule is necessarily sorbed preferentially. If, therefore, both types of small molecules are not of the same size, the inversion vanishes for large v3 even in systems where it actually occurs if v3 is small. On the contrary, the same effect can in other cases have as its consequence an inversion at moderate values of v3, even if it does not appear as v3 approaches zero; a similar effect can also be produced by a nonzero value of the interaction parameter χT. The neighborhood of the inversion line can have a “divergent” or a “convergent” character, depending on whether the component being preferentially sorbed is that present in excess. The former case is observed with negative and the latter for the positive values of the binary solvent–solvent interaction parameter χ12. The inversion with the divergent neighborhood has not yet been confirmed experimentally, owing to the small number of systems investigated.
Theoretical analysis of sorption of a binary solvent in a polymer phase. II. Occurrence of maxima and minima in the curve of total sorption
Authors: Pouchlý J. , Živný A. 
Published: April 2003

AbstractIt has been shown that sorption equilibrium in the system polymer–mixed solvent and the total sorption as one of its manifestations can be derived from osmotic equilibrium. The equilibrium relation for the dependence of the osmotic pressure II (as the potential for total sorption) on the composition of the ternary polymer‐containing phase also includes the preferential sorption ε. This complication leads to difficulties in the analysis of the dependence of II on composition: for this reason, analysis has been limited to the case of a very dilute polymer phase. If preferential sorption is neglected, the occurrence of an extremum on the curve representing the dependence of the total sorption on the composition of the mixed solvent is affected by the Flory‐Huggins parameters as in the occurrence of an inversion in preferential sorption, with the exception that in the former case the difference in the molar volumes of the solvent components contributes a term smaller by a factor of two. In the general case, however, the contribution of preferential sorption to the osmotic pressure (which has always a negative sign) also plays its role. Consequently, while total sorption, at a low preferential sorption and at a large positive value of the solvent–solvent interaction parameter χ12, can exhibit a maximum, a larger preferential sorption can overcompensate the effect of the parameter χ12, so that a minimum appears. The coexistence of a minimum with a maximum on the same curve is possible in some cases with positive χ12. The latter theoretical predictions have not yet been confirmed experimentally. At a negative χ12 the extremum is always a minimum.
Studies on crystalline forms of nylon 6. II. Crystallization from the melt
Authors: Kyotani Mutsumasa , Mitsuhashi Shigenobu 
Published: April 2003

AbstractThe relative amounts of the α and the γ crystalline forms of nylon 6 obtained from the melt under different crystallization conditions have been studied by an x‐ray diffraction procedure by comparison with a calibration curve obtained from the diffraction of standard samples. The weight fraction of the α form decreases with increasing crystallization temperature and that of the γ form increases. Growth of the α form is predominant in crystallization at 100°C and of the α form at 200°C. The amount of the α form tends to increase on annealing at 200°C for specimens crystallized at any temperature.
Bulk modulus and density of polyethylene to 30 kbar
Authors: Heydemann P. L. M. , Houck J. C. 
Published: April 2003

AbstractThe results of bulk modulus and density measurements on low‐density polyethylene to 30 kbar are presented. From these data the pressure coefficient dTt/dp of the glass transition temperature is obtained, and a comparison is made with data calculated from Pastine's theoretical equation of state for polyethylene.
Side‐chain crystallinity. IV. Mechanical properties and transition temperatures of copolymers of methyl methacrylate with higher n‐alkyl acrylates and N‐n‐alkylacrylamides
Authors: Jordan Edmund F. , Riser George R. , Artymyshyn Bohdan , Pensabene John W. , Wrigley A. N. 
Published: April 2003

AbstractMechanical properties were correlated with glass transition temperatures for a series of random copolymers of methyl methacrylate with comonomers selected from the higher n‐alkyl acrylates and N‐n‐alkylacrylamides. The plasticizing comonomers were the n‐butyl, 2‐ethylhexyl, n‐octadecyl, and oleyl acrylates, and the N‐n‐butyl‐, N‐n‐octyl‐, N‐n‐octadecyl‐, and N‐oleylacrylamides. The complete range of compositions was investigated. However, the bulk of the data was obtained on compositions in the glassy region below the onset of the vitreous transition. In this region it was found that the decrease in tensile and flexural moduli and strengths with increase in internal plasticizer for all of the systems was directly proportional to the decrease in Tg. It was concluded that the additive contribution to the free volume made by each side‐chain methylene group was alone responsible for the magnitude of the rate of change of properties. However, polar contributions of the amide group to stiffening the main chain exceeded those of the ester, so that the amides were less efficient plasticizers. An empirical equation was derived which described, with fair accuracy, the decrease in the mechanical parameters with composition for the amorphous copolymers. It was reasonably successful in predicting properties even into the composition range where the ambient testing temperature corresponded to or exceeded the transition temperature. In this transition region an accelerated decrease in the magnitude of the physical properties was observed. All samples exhibited brittle fracture except those tested in the transition region. Here the strain was largely irrecoverable flow. Side‐chain crystallinity did not interfere significantly with the mechanical properties because moduli and strengths had already decayed to small values near the compositions where crystallinity commenced. Non‐random copolymers of vinyl stearate and methyl methacrylate showed no internal plasticization, apparently because of macrophase aggregation.
Effect of the reference chain dimensions in the molecular theory of viscoelastic behavior of polymer networks
Authors: Ilavský M. , Hasa J. , Havlíček I. 
Published: April 2003

AbstractMooney's version of the molecular theory of polymer networks has been generalized to the case when the external strain applied in the isotropic state is different from that at network formation. As in the theory of equilibrium behavior of the polymer networks, this generalization allows inclusion in the viscoelastic functions of effects connected with the temperature dependence of internal energy of the chains and with the strain effect of the solvent. From viscoelastic functions thus generalized, it is possible to derive a relation for calculation of the monomeric friction coefficient. It also suggests the possibility of superposing data obtained at various temperatures, degrees of swelling, and condition of network formation.
Characterization of polymers under large deformation. I. Repeated chemical stress relaxation of vulcanized rubbers
Authors: Kusano Takae , Murakami Kenkichi 
Published: April 2003

AbstractIn this investigation, repeated chemical stress relaxation measurements were carried out to observe the relaxation behavior at large deformation. It was found that the repeated chemical stress relaxation curves were affected by both measurement temperature and the extension ratio of rubber. It was suggested on the basis of the results that temperature and mechanical stimulus have a similar effect on the stress relaxation curves. Thus we propose the following Arrhenius type equation for high extension ratios:

where α is the extension ratio and A, B are constants determined experimentally. On the other hand, from this equation and the usual Arrhenius equation, a universal equation for the extension ratio and the temperature was derived as follows:

where, T0 is voluntary temperature. The curves obtained by this equation were quite consistent with those obtained experimentally at different temperatures and extensions at large deformation.
Photopolymerization with the use of titanocene dichoride as sensitizer
Authors: Kaeriyama Kyoji , Shimura Yukio 
Published: April 2003

AbstractTitanocene dichloride sensitized photopolymerization of vinyl ethers and styrene but did not polymerize methyl methacrylate and vinyl acetate. In the case of 2‐chloroethyl vinyl ether, polymerization started rapidly some time after the color of the liquid had changed from orange to green. Polymerization was also achieved by heating the monomer at 60°C after stopping the irradiation at the end of the induction period. On the basis of the reactivity of the monomers and the effect of additives, polymerization is considered to proceed cationically. In case of the polymerization of styrene, conversion increased linearly with time. The k/kt value of 6.3 × 10−5l./mole‐sec obtained for the polymerization of styrene agrees well with the value reported for radical polymerization. The agreement of the value and ineffective inhibition of polymerization in the presence of pyridine indicates the polymerization follows a radical mechanism. Copolymerization of styrene (M1) and 2‐chloroethyl vinyl ether (M2) proceeded radically, and the reactivity ratios were r1 = 2.5 and r2 = 0.6.
Long branching in poly(vinyl acetate) and poly(vinyl alcohol). III. Kinetic study of the branching reaction in the radical polymerization of vinyl acetate
Authors: Nozakura Shun‐Ichi , Morishima Yotaro , Murahashi Shunsuke 
Published: April 2003

AbstractThe branching reaction in the radical polymerization of vinyl acetate was studied kinetically. Branching occurs by polymer transfer as well as terminal double‐bond copolymerization. The chain‐transfer constants to the main chain (Cp,2) and to the acetoxy methyl group (Cp,1) on the polymer were calculated on the basis of the experimental data described in the preceding paper giving Cp,2 = 3.03 × 10−4, Cp,1 = 1.27 × 10−4 at 60°C, and Cp,2 = 2.48 × 10−4, Cp,1 = 0.52 × 10−4 at 0°C. Chain transfer to monomer is important with respect to the formation of the terminal double bond. The total values of transfer constants to the α‐ or β‐position in the vinyl group and the acetoxymethyl group in vinyl acetate was determined to be 2.15 × 10−4 at 60°C. The transfer constant to the acetyl group in the monomer (Cm,1) was also evaluated to be 2.26 × 10−4 at 60°C from the quantitative determination of the carboxyl terminals in PVA. These facts suggest that the chain‐transfer constant to the α‐ or β‐position in the monomer (Cm,2) is nearly equal to zero within experimental error. Copolymerization reactivity parameters of the terminal double bond were also estimated. In conclusion, it has become clear that the formation of nonhydrolyzable branching by the terminal double‐bond reaction can be almost neglected, and hence that the long branching in PVA is formed only by the polymer transfer mechanism. On the other hand, a large number of hydrolyzable branches in PVAc are prepared by the terminal double‐bond reaction rather than by polymer transfer.
Organolithium cleavage of aliphatic polyethers, polysulfides and polyimines
Authors: Vandenberg E. J. 
Published: April 2003

AbstractOrganolithium compounds and other Group IA organometallics cleave high molecular weight poly(alkylene oxides) very rapidly at room temperature in dilute benzene solution. This reaction also works on a dimeric polyepoxide such as bis(2‐n‐butoxyethyl)ether and much less readily on a monomeric one as 1,2‐dimethoxyethane. On the other hand, a simple aliphatic monoether such as di‐n‐butyl ether is not cleaved under conditions several orders of magnitude more drastic than were effective on the polyethers. The mechanism for this facile polyether cleavage is proposed as a β‐elimination in which the organolithium is greatly activated by chelation with the main‐chain oxygen atoms of the polyether. This cleavage method has been used broadly on high molecular weight polyethers to obtain quantitative yields of hydroxyl‐ended, amorphous, and crystalline polyethers (Mn = 500–10,000), many of which cannot be made by direct polymerization. Aliphatic polysulfides and an N‐substituted aliphatic polyamine cleave by this same method to, respectively, mercapto‐ended and secondary amine‐ended polymers. The mechanism aspects of these results are discussed.
Theoretical reaction kinetics of reversible polymerization with a linear time dependence of the rate constant
Authors: Huang Ching‐Rong , Wang Huei‐Hsiung 
Published: April 2003

AbstractThe theoretical kinetics of reversible polymerization of a live polymer solution is studied. The initiation, transfer, and termination reactions are assumed to be negligible. An analytic solution in a closed form is obtained which gives the transient monomer concentration after perturbation of the polymer system. The disturbance is assumed to impose a linear change of the depropagation rate constant with respect to time. It is more realistic physically than the assumption of a sudden change of rate constants. Also discussed in the paper is the application of the solution to cases which have a nonlinear change of the rate constant.
Preparation and thermal degradation of polyperfluorobut‐2‐yne
Authors: Jackson J. A. 
Published: April 2003

AbstractPolyperfluorobut‐2‐yne has been prepared by the fluoride ion‐catalyzed polymerization of hexafluorobut‐2‐yne. The thermal stability of the polymer was monitored by TGA and DTA in air, argon, and vacuum environments. The major breakdown route appears to be depolymerization into fragments of lower molecular weight. Copolymerization of the acetylene with fluoroolefins was attempted; however, homopolymerization of the acetylene occurred at a far greater rate than the copolymerization reaction.
Preparation and properties of polymers from aryl cyclic sulfonium zwitterions
Authors: Schmidt D. L. , Smith H. B. , Yoshimine M. , Hatch M. J. 
Published: April 2003

AbstractA new class of zwitterionic monomers were prepared in which the positive and negative sites are cyclic sulfonium and phenolate. Thermal polymerization occurs by phenolic anionic attack upon the aliphatic carbon α to the sulfonium sulfur. Polymerization proceeds with ring opening and net loss of charge to form nonionic polymers. The monomeric zwitterions are generally hydrated, crystalline solids that are soluble in water or alcohol. Chlorination of the aromatic portion of the molecule yields nonhydrated species. The polymerizations of 1‐(4‐hydroxy‐3‐methylphenyl)tetrahydrothiophenium hydroxide inner salt (dihydrate) and 1‐(3,5‐dichloro‐4‐hydroxyphenyl)tetrahydrothiophenium hydroxide inner salt were studied. The latter monomer gave a polymer with M̄n of 46,000 when a nucleophile was present as an initiator. The physical properties of this polymer were determined. Cyclization appears to be the main mechanism of termination in the polymerization of zwitterions.
Radical terpolymerization of sulfur dioxide, hexene‐1, and methyl acrylate or methyl methacrylate
Authors: Iino Masashi , Seki Kiichiro , Matsuda Minoru 
Published: April 2003

AbstractThe radical terpolymerization of sulfur dioxide, hexene‐1, and methyl acrylate has been investigated, and from the dilution effects on composition of the terpolymer it would seem reasonable to rule out the possibility of the participation of the charge‐transfer complex in the propagation process. We have also carried out terpolymerization of sulfur dioxide, hexene‐1, and methyl methacrylate and obtained a terpolymer having the block nature.
γ‐Radiation‐initiated post‐polymerization of methacrylic acid in the solid state
Authors: Lando J. B. , Semen J. 
Published: April 2003

AbstractThe solid‐state postpolymerization of slowly crystallized methacrylic acid was studied at 0°C with 60Co γ‐radiation as the initiator. The yield, molecular weight, molecular weight distribution, and stereosequencing of the polymer product were determined as a function of polymerization time. The narrow molecular weight distribution and the linear dependence of molecular weight on polymer yield were attributed to a polymerization mechanism characterized by both independent chain propagation and essentially no termination step. The overall polymerization rate was substantially faster than that reported previously for shock‐crystallized monomer, a result which was attributed to termination by the occlusion of propagating radicals at defects in the shock‐crystallized monomer. Although largely atactic, the polymer synthesized in the solid state contained a secondary kind of stereosequencing; the meso triad probability was highest at the end of the chain, where propagation had initiated and decreased continuously with chain growth. The gradient in stereosequencing along the chains was attributed to defects that were introduced into the monomer crystals by the growing polymer chains.
Alternating copolymer of butadiene and ethylene. I. Copolymerization by TiCl4–R3Al catalyst systems
Authors: Furukawa Junji , Hirai Ryuichi 
Published: April 2003

AbstractAlternating copolymerization of butadiene and ethylene was investigated by the TiCl4−R3Al system as catalyst with the use of toluene solutions of monomers of various compositions or by introducing a 1:1 gaseous mixture of both monomers into the reaction system. It was found that the copolymer composition is much influenced by the monomer composition or by the flow rate of monomer. Copolymers containing sequences of alternating monomer arrangement are formed by the polymerization of a monomer mixture having a butadiene: ethylene ratio of 4:1. A suitable catalyst for the alternating copolymerization was found to consist of R3Al−TiCl4 at a ratio of 2. The addition of amine was found to modify the catalyst to favor the alternating copolymerization but was accompanied by a decrease in catalyst activity.
Radiation‐induced heterogeneous polymerization of ethylene in the presence of ethyl alcohol
Authors: Wada Takeshi , Watanabe Terutaka , Takehisa Masaaki 
Published: April 2003

AbstractThe radiation‐induced heterogeneous polymerization of ethylene in ethyl alcohol was carried out in a reactor with a capacity of 100 ml under the following reaction conditions: temperature, 24 ± 3°C; pressure, 200–400 kg/cm2; amount of ethyl alcohol, 30–70 ml; dose rate, 3.7 × 104−1.05 × 105 rad hr. The effects of amount of ethyl alcohol, pressure, and dose rate on the rate of polymerization at the steady state, the amount of polymerized monomer, the molecular weight of polymer, and the number of polymer chains were studied compared with the results obtained in the polymerization in tert‐butyl alcohol. It was found that there is an acceleration period in the early stage of reaction followed by a steady state. The rate of polymerization was maximum when about 50 ml of ethyl alcohol was used. The molecular weight of polymer increased with a decrease in the amount of ethyl alcohol. The dependences of pressure (p) and dose rate (I) on the rate of polymerization at steady state (Rs) and the molecular weight of polymer (M̄n) were expressed as follows; Rs ∝ p0.74, M̄n ∝ p0.3−0.4, Rs ∝ I0.9 and M̄n ∝ I−0.1 −0.0. The results were analyzed by a kinetic treatment based on a reaction mechanism containing both first‐and second‐order terminations. The rate constant of first‐order termination by radical occlusion was considerably larger than that in the polymerization in tert‐butyl alcohol, because the affinity of ethyl alcohol for polyethylene is smaller than that of tert‐butyl alcohol. It was found that chain transfer to ethyl alcohol takes place easily and the G value of ethyl alcohol for initiation is larger than 1.5.
Molecular weight distributions in radiation‐induced polymerization. VII. γ‐ray‐induced polymerization of “wet” styrene in the solid state
Authors: Westlake John F. , Huang Robert Y. 
Published: April 2003

AbstractIn the present paper kinetic and molecular weight distribution results are reported for the γ‐ray‐initiated polymerization of styrene in the solid state. “In‐source” polymerization over the temperature range −35°C to −55°C and post‐polymerization at −35°C have been investigated for “wet” styrene samples (water concentration ≈ 10−3 mole/l.). An interesting feature of the solid‐state polymerization of styrene is the bimodal nature of the molecular weight distribution. On a qualitative basis the results resemble those obtained previously for the polymerization of rigorously dried (“dry”) styrene. However, there are noticeable differences on a quantitative basis resulting from the considerable difference in the water content between wet and dry samples. On the basis of these studies, the kinetic and molecular weight distribution data have been interpreted as being indicative of polymerization occurring simultaneously via free‐radical and cationic mechanisms.
Catalytic action of calcium acetate and the manganese acetate–sodium acetate mixture in the pre‐esterification of dimethyl terephthalate with ethylene glycol
Authors: Dimov K. , Terlemezyan E. 
Published: April 2003

AbstractProducts of pre‐esterification of dimethyl terephthalate with ethylene glycol at various times carried out with two catalysts, i.e., calcium acetate and a mixture of manganese and sodium acetates, were studied. Thin‐layer chromatography was used to follow the fundamental reaction and determine the type and degree of oligomerization. It was established that the manganese–sodium acetate mixed catalyst is more efficient both with regard to pre‐esterification and oligomerization.