Photooxidation of blends of polystyrene and poly (vinyl methyl ether)

Photooxidation of blends of polystyrene and poly (vinyl methyl ether) was studied at 30°C. The oxygen uptake by PS was negligible but PVME oxidized readily. The induction period of oxidation of PVME was prolonged by the presence of PS. The steady state rate of oxidation of the blend was strongly influenced by the segmental mobility of the blend which also governed the kinetics and morphology of phase separation. The molecular weight of PVME decreased more slowly in the blend as PS content increased. It was believed that the reaction between PVME radicals and PS resulted in less reactive PS radicals which retarded oxidation. The PS radicals eventually underwent chain scission reactions.     

ABA triblock copolymer containing two crystallizable components

A triblock copolymer of the ABA type in which both components were crystallizable was synthesized. The A block was poly(ethylene oxide), PEO, and the B block, poly(dimethyl siloxane), PDMS. Upon cooling from the melt to liquid nitrogen temperature, the PEO block crystallized at around 40°C. When the copolymer was heated from ?170°C after quenching, glass transition, crystallization and melting of the PDMS middle block were identified in the thermogram at ?117°C, ?74°C and ?42°C, respectively. The degree of crystallinity of the PDMS block was estimated from the heat of fusion to be about 27%. The growth rates of the PEO spherulites were reduced by the presence of the middle block.     

Viscoelasticity of crosslinked epoxy polymer in the transition region

The dynamic mechanical properties of highly crosslinked epoxyamine polymer networks with nonrandomly distributed crosslinks were investigated. The transition temperatures of these polymers can be correlated with the number of CH₂ groups between crosslink junctions in the aliphatic amine portions of the network. The steepness of the modulus-temperature curve is also a function of crosslink density. This is in contrast with the case of natural rubber crosslinked by sulfur or by electron irradiation, where the modulus-temperature curves have similar shapes although the glass transition temperature increases with the degree of crosslinking. An empirical distribution function, similar to the one used by Tobolsky for stress relaxation distributions, was used to describe the temperature dispersion of the dynamic moduli. Two parameters, h_g and h_r, are used to characterize the steepness of the dispersion curve below and above the transition temperature, respectively. It is tentatively concluded that h_g correlates with the length of the CH₂ sequences in the amine portion of the polymer. The quantity h_r may be related perhaps to the motion involving the trifunctional nitrogen junction.     

Insights into the Kramers’ flux‐over‐population rate for chemical reactions in liquid phases through the matrix transport equation

Kramers’ equation models a chemical reaction as a Brownian particle diffusing over a potential barrier under the influence of medium viscosity. In the case of high viscosity, the equation reduces to a simpler Smoluchowski equation. In this report, we have contrived an equivalent matrix‐transport equation that relates the ordered pair (activity, flux) of the output (activated complex) to that of the input (reactant). With an initial condition of the Dirac delta type placed at the location of the reactant, and a reflecting boundary condition set on the reactant state, and an absorbing boundary condition on the activated complex state, we are able to prove the equality relation between the mean first passage time, , for the diffusion and the inverse of the rate constant, k^?1, for the reaction counterpart. We have also derived , where λ_i is the ith eigenvalue of the Smoluchowski differential operator stipulated with the above‐mentioned boundary conditions. We have also deduced that, in the long time limit, the number of particles remaining inside the diffusion domain decays exponentially with a relaxation time just the same as the concentration of the reactant does for a first‐order reaction system.     

Studies on and with Functionalized Polystyrenes

A number of useful functionalized polystyrenes have been prepared. Studies on fluoroalkyl ketone, fluoroalkyl carbinol, and hydroxy-contain polystyrenes, as well as polystyryl pyridine-based polymers, in regard to a variety of properties were made. These are discussed individually in regard to their reactions with alcohols to form hemiketals, miscibilization by hydrogen bonding, improvements in the thermostability of blends, and char formation at elevated temperature, respectively. In addition, enhancements of polystyrene and copolymers of modified polymers in regard to the oxidative stabilization of blends are discussed.     

Estimation of the Moments of the Residence Time and First Passage Time from Experimentally Measurable Permeation Parameters via a New Formulation of the Transmission Matrix

Siegel's analysis on membrane transport in the Laplace domain [J. Phys. Chem. 95 (1991) 2556] in terms of transmission matrix, T(s), has been extended to a more useful formulation. This is achieved by combining uses of the matrix transport equations appropriate for void initial condition, or for saturated equilibrium, or of Dirac delta functional type and the theorem det[T(s)] = 1. This formulation enables us to expand T(s) in power series of the Laplace variable, s, with the expansion coefficients as the algebraic functions of the experimentally measurable transport parameters. Utility of the formulation is illustrated in the estimation of the experimentally inaccessible time moments for the first passage or residence times. It was also applied to the percutaneous drug delivery to obtain from the experimental data. The higher moments of the time lag or time lead using a graphic method.     

Polymer Compatibilization Through Hydrogen Bonding

Partially modified polystyrene containing vinyl phenyl hexafluorodimethyl carbinol was mixed with a number of counterpolymers containing poly(vinyl-acetate), poly(methyl methacry1 ate), poly(ethy] methacrylate, poly (n-butyl methacry late), poly(viny] methyl ether), poly(2,6 dimethyl-1,4 phenylene oxide), bisphenol A polycarbonate poly(styrene-co-acryloni-trile), poly (dimethyl siloxane), a crystallizable polyester, an amorphous polyamide and two amorphous polyamides. Hydrogen bonding interactions to effect miscibility were related to the number of proton donating groups in the modified polystyrene, and these were studied in regard to lower critical solution temperatures and the glass transition temperatures of the hydrogen bonded blends.     

Head to Head Polymers. 42. Head to Head Poly(Vinyl Halide) Blends: Thermal and Degradation Behavior

Abstract

Improved halogenation techniques for poly(1, 4-butadiene) have made well-defined head to head poly(vinyl chloride) and head to head poly(vinyl bromide) accessible in larger quantities. This allowed the preparation and study of blends of poly(vinyl chloride) or poly(vinyl bromide) with polycaprolactone and poly(methyl methacrylate); blends were also prepared between the poly(vinyl halides). The thermal behavior and the thermal degradation behavior of these blends were investigated. It was confirmed that head to head and head to tail poly(vinyl chloride) are immiscible over almost the entire range of compositions.