CHARACTERIZATION OF FILM FORMATION FROM POLYSTYRENE LATEX-PARTICLES VIA SANS .1. MODERATE MOLECULAR-WEIGHT

Deuterated and protonated polystyrene latexes of 275- Å radius and 250 000 g/mol were mixed together to give 6 mol % of deuterated polystyrene. After removal of the aqueous phase and surfactants, the dry latex particles were sintered to full density at 110 °C under a pressure of 9.0 MPa by using a vacuum hot press for 40 min. These sintered films were annealed at 144 °C from 5 min to 48 h. Small-angle neutron scattering, SANS, measurements were made to evaluate the interdiffusion through an apparent increase in size of the deuterated polystyrene-rich particles, while tensile strength measurements were carried out on the corresponding protonated samples. For the present system, the minimum depth of molecular diffusional penetration for full tensile strength (3.04 X 107 N/m2) was found to be about 110-120 Å, comparable to the weight-average radius of gyration, Rgw, of the whole polystyrene chain. An elbow in the tensile strength-penetration depth relationship was found at 45-50 Å, corresponding to the critical molecular weight for entanglement. After an apparent induction period, the tensile strength increased with time to the one- fourth power, as predicted by Wool et al. After 48 h of annealing at 144 °C, complete molecular mixing was achieved via interdiffusion of deuterated and protonated species. © 1990, American Chemical Society. All rights reserved.