Water-absorption properties of an acetal copolymer

The kinetics of sorption from the liquid phase to equilibrium and desorption were studied over the temperature range 0–80°C. Equilibrium uptake was found to increase linearly with concentration in this range. Sorption-desorption kinetics showed the diffusion coefficients to decrease with increasing concentration, although the extent of this dependence did not appear in itself to be temperature-dependent. The apparent diffusion coefficient obeyed the law D = D₀ exp {? E/RT} over the temperature range studied, giving E = 9.9 kcal./mole and D₀ = 0.45 cm.² sec.^?1. These values are compared with corresponding values for other polymers.     

Electrorheological properties of PMMA-b-PSt copolymer suspensions

In this study, a block copolymer of methyl methacrylate (MMA) and styrene (St) synthesized by combined ultrasonic irradiation and reverse atom transfer radical polymerization (RATRP) processes was used. PMMA-b-PSt was partially hydrolyzed and converted to a lithium salt, PMMA-b-PSt-Li, before the electrorheological (ER) measurements carried out. Average particle diameter of PMMA-b-PSt-Li polymeric salt was determined by dynamic light scattering (DLS) as 22 mum. Suspensions of PMMA-b-PSt-Li polymeric salts were prepared in silicone oil. ER properties of PMMA-b-PSt-Li/silicone oil suspensions were studied as a function of electric field strength, dispersed phase concentration, shear rate, shear stress, temperature, frequency, and polar promoter. Further dielectric properties of PMMA-b-PSt-Li ionomer were also investigated.     

Transport properties of polyphenylquinoxalines

The correlation between chemical structure and gas transport properties is considered for a new class of membrane materials based on structurally similar polyphenylquinoxalines that are characterized by different numbers of flexible-O-ether bonds in the repeating unit and different chain rigidities. Permeability, diffusion, and solubility coefficients have been estimated for the gases H₂, He, O₂, N₂, CO, CO₂, and CH₄; separation factors for various gas pairs have been determined. For the materials with a similar level of cohesive energy density, which characterizes interchain interactions, permeability decreases with a decrease in chain rigidity, whereas selectivity of gas separation increases.     

Characterization of the porosity of a hydrophobic-hydrophilic electrode

Three types of channels determining the porosity of a hydrophobic—hydrophilic indicator electrode of a sensor were considered. A method for determining the porosity coefficient of the hydrophobic matrix was proposed assuming complete filling of the porous electrode.P. I. Magdich participated in the experimental portion of this work.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 6, pp. 548–552, November–December, 1993.     

Effect of plasticization by amines on the physical properties of an acidic styrene copolymer

The dynamic mechanical properties of partly sulfonated (8.1 mole%) polystyrene were investigated at a frequency of ca. 1 Hz, following neutralization with various low molecular weight flexible and rigid amines. IR spectroscopic evidence suggested that the protonated amine units were possibly H-bonded to the sulfonate anion. Neutralization with flexible amines was found to result in a decrease in the glass transition temperature T_g by an amount proportional to the number of carbon atoms in the amine, while neutralization with rigid amines was found to result in an increase in T_g. It was also observed that the amines were more miscible with the sulfonated material than with polystyrene. It was concluded that the changes in properties observed upon neutralization are similar to those expected from a graft.     

Transport properties of chrysazine-type molecules

Electronic transport properties are presented for the three lowest-energy conformers of the chrysazine molecule. The current–voltage characteristics of these isomers are calculated for two different connections of the molecule to gold leads. The results for the various structures differ so significantly from each other that the specific conformer and its connection to the leads can be identified by its transport characteristics. The calculated transport properties suggest that chrysazine may be used as a molecular optical switch.     

Transport properties of quantum-classical systems

Correlation function expressions for calculating transport coefficients for quantum-classical systems are derived. The results are obtained by starting with quantum transport coefficient expressions and replacing the quantum time evolution with quantum-classical Liouville evolution, while retaining the full quantum equilibrium structure through the spectral density function. The method provides a variety of routes for simulating transport coefficients of mixed quantum-classical systems, composed of a quantum subsystem and a classical bath, by selecting different but equivalent time evolution schemes of any operator or the spectral density. The structure of the spectral density is examined for a single harmonic oscillator where exact analytical results can be obtained. The utility of the formulation is illustrated by considering the rate constant of an activated quantum transfer process that can be described by a many-body bath reaction coordinate.     

Transport properties of asymmetric-top molecules

Kinetic theory of gases is extended from linear molecules to asymmetric tops. The integration over the velocity of the centre of mass is carried out explicitly and the results are expressed in a form suitable for classical evaluation. These results can also be employed for spherical and symmetric tops.     

Transport properties of chitosan films

Effect of the history of chitosan films on their transport characteristics in relation to elimination of drugs from the body is studied.     

Styrene-acrylate copolymer plastisols with stable colloidal properties

Methods for the synthesis of emulsion-polymerized styrene-methyl methacrylate-methacrylic acid copolymers with different compositions and structures are proposed. Stable plastisols are obtained from these copolymers and phthalate plasticizers. Factors that affect the colloidal stability and rheological properties of the plastisols were studied. These are the polymer particle size, the type of surfactants used in emulsion copolymerization, the distribution of methacrylic acid units over the latex particle volume (uniform or gradient, with concentration rising from the particle center to periphery), the degree of carboxyl group neutralization with a base, and the nature of plasticizers. The plastisols obtained are characterized by a pseudoplastic flow. However, as the degree of carboxyl group neutralization in the copolymers is increased, the rheological properties of the plastisols approach those of Newtonian liquids.     

Domain structure and viscoelastic properties of graft copolymer

Summary The domain structures of film specimens cast from benzene solutions of a series of graft copolymer of poly(methyl acrylate) with styrene with different degrees of grafting, from 10 to 80 vol% of styrene component, were investigated with phase-contrast and dye-staining microscopy. The graft copolymers were synthesized by coupling polystyryllithium, obtained by anionic polymerization technique, onto a well-fractionated PMA, so that the coupling density of the grafted segment along the backbone segment was varied but the molecular weights of the grafted and backbone segments were kept constant to cover the above range of volume fraction of styrene component for the series of graft copolymer.It was found that with an increase of the volume fraction of styrene component (grafted segment) the domain structure changes from spheres of styrene component dispersed in a matrix of MA component, to alternating lamellae of the two components, and to spheres of MA component dispersed in a matrix of styrene component. Two types of rodlike domains, usually found for block copolymers as the intermediates between the spherical and lamellar domains, were missed.The domain formation mechanism was discussed in terms of a quasi-equilibrium phenomenon of micelle formation, microphase separation between the grafted and backbone segments, at a critical micelle concentration. TheGibbs free energies of five types of micelle formations; anA sphere in aB shell micelle, anA rod in aB sheath micelle, alternating lamellar micelle ofA andB, aB rod in anA sheath, and aB sphere in anA shell micelle, were discussed in terms of molecular and thermodynamic parameters. Comparing the free energy levels of the five types of micelle formations with each other, it was revealed that the free energy levels for forming the two types of rodlike micelles can not be the lowest at any volume fraction of grafted segment.Dedicated to Prof.R. Hosemann on the occasion of his 60th birthday.A part of M. S. thesis ofT. Ono, presented to the Department of Polymer Chemistry, Faculty of Engineering, Kyoto University, March 11, 1969; presented before the 18th Annual Meeting of the Society of Polymer Science, Japan, Kyoto, May 20, 1969.     

苯乙烯-异戊二烯-丁二烯三元集成橡胶的合成、表征及性能研究

以正丁基锂为引发剂、环己烷-己烷混合溶剂为溶剂,采用二元结构调节剂,对S-SIBR(溶液苯乙烯-异戊二烯-丁二烯共聚物)三元共聚进行了研究,考察了不同单体含量,以及苯乙烯微嵌段含量对SIBR性能的影响.在500 L全流程中试装置中采用湿法充油技术批量制备了充油型集成橡胶,对充油集成橡胶的结构、性能以及在轮胎中的应用进行了研究.结果表明,充油型SIBR的混炼行为、硫化速度、机械性能、滚动损失及抗湿滑性能均较优异,机械性能完全符合轮胎胎面胶的性能要求,并且具有优异的抗湿滑性和滚动阻力,是一种理想的轮胎胎面材料.     

Examining the frictional forces between mixed hydrophobic-hydrophilic alkylsilane monolayers

Monolayers presenting methyl-terminated (hydrophobic) and hydroxyl-terminated (hydrophilic) surfaces on silica have been studied by molecular dynamics simulation and the effects of hydrogen bonding, chain length, and chain mixing on the frictional properties determined. The hydroxyl-terminated monolayers were found to show large adhesion zones as a result of strong interfacial interlayer hydrogen bonds; the interfacial sliding forces observed in the hydroxyl-terminated monolayers being one order of magnitude higher than the interfacial forces for the hydrophobic surfaces at the characteristic point of zero-load. Mixed hydroxyl- and methyl-terminated monolayers of equal length were found to exhibit intermediate shear stress values between those observed for pure monolayers, with the magnitude of the shear stress depending on the surface content of the hydroxyl-terminated chains. For mixed monolayers of unequal chain lengths, at high loads a maximum in the magnitude of the shear stress as a function of the length of the methyl-terminated chain was observed due to the creation of a buffer zone between the hydroxyl-terminated chains that produces strong hydrogen-bonding interactions. The effect of a constant normal load or constant separation simulation ensemble on the results has also been studied and in general found to have minimal influence on the observed behavior, although some differences are observed for the shear stress at intermediate normal loads due to the formation of stronger hydrogen bond networks at constant load compared to constant separation.     

PVT properties of polyethylene copolymer melts

PVT properties of four polyethylene random copolymers (ethylene-propylene, ethylene-1-butene, ethylene-1-hexene, and ethylene-1-octene) and linear polyethylene were measured at temperatures from 313 to 493 K and pressures up to 200 MPa. Dependence of properties such as specific volume, thermal expansion coefficient, isothermal compressibility, and characteristic parameter of equations of state on the length of the polymer branched chains were examined. It was found that the length of the branched chain did not affect the thermal expansion coefficient and isothermal compressibility. The specific volume of copolymers having longer branched chains were slightly larger than those copolymers with short branched chains.     

Transport properties of boron and aluminum

Transport cross sections and collision integrals are tabulated for a wide range of energies and temperatures for the interactions B–B and Al–Al. For aluminum, a semiclassical approximation was used to determine the scattering phase shifts from which the transport cross sections were calculated. For boron, the smaller reduced mass and the deep potential wells required the phase shifts at lower energies to be determined from a numerical solution of the time-independent Schroedinger equation; the semiclassical approximation was used at higher energies where the two methods agree. The variations of the collision integrals for viscosity and diffusion are presented graphically as a function of temperature. The results are applied to estimate the transport properties of gallium. Received: 9 July 1999 / Accepted: 18 August 1999 / Published online: 2 November 1999     

Investigation of structure and properties of divinylbenzene-styrene copolymer films

A method for preparation of divinylbenzene-styrene copolymer porous layer on the inner wall of a fused silica capillary was developed. Capillary gas chromatography was used to investigate the sorption capacity of copolymer film toward substances of various classes.