Structure relaxation after temperature jumps in homogeneous polystyrene/poly(styrene-co-bromostyrene) blends

Abstract

Concentration fluctuations in polymer blends and their change after a temperature jump were studied by time-dependent small angle X-ray scattering experiments. Measurements were conducted on homogeneous mixtures of polystyrene and a partially brominated derivative. Structure factors in thermal equilibrium show the form given by the random phase approximation, thus enabling a direct determination of thez-parameter and the mean radius of gyration. The T-dependence of Z can be understood as the result of superposed enthalpic contributions and a free volume term. In the T-jump experiments, samples were quenched to temperatures near Tg. Relaxation occurs on the time scale of minutes and is nonexponential, becoming slower with time. Initial relaxation rates increase with increasing scattering vectors q in accordance with theoreticalpredictions.

Measuring the binodal by interdiffusion in blends of deuterated polystyrene and poly(styrene-co-4-bromostyrene)

“…The bromination of the polystyrene was carried out following a procedure described elsewhere.lS The degree of bromination x was computed from the mass densities, which were measured by a suspension method and a calibration table of mass density versus degree of bromination x. 12 Blends obtained from bilayers of these polymers are labeled in the following manner (see Table I): blend 1 = polymer A and polymer D, blend 2 = polymer B and polymer D, blend 3 = polymer C and polymer E. Diffusion couples of blend 2 and blend 3 were formed by first spinning a solution of the copolymer in chloroform onto a polished silicon wafer. This gives about 300-500-nm-thick films after drying.…”

Concentration dependence of the flory‐huggins interaction parameter of a polymer blend as determined by small‐angle X‐ray scattering experiments

“…Equation (6) R: is an average with inverse weights of the radii of gyration of the two components6 R: = (1 -+ ) R i + +Ri (8) Analysis of scattering curves on the basis of eq. (6) enables a direct determination of R: and x.…”

Segregation at the Interface between a Homopolymer and a Binary Polymer Blend

“…To calculate the volume fraction profiles using the SCF method, the numbers of segments for A, B, and C, the bulk volume fraction of B, and the interaction parameters x AB , x AC , and x BC must be known. The values of x AB and x AC were determined by interpolating the previously measured PS:PBr x S interaction parameters [13] to x 0.093 and 0.131. Interdiffusion experiments on B͞C couples were carried out to determine the mutual diffusion coefficient.…”