Film formation from latex: Hindered initial interdiffusion of constrained polystyrene chains characterized by small-angle neutron scattering

Bulk polystyrene film samples were made from a 50% deuterated latex with a molecular weight of 5.85 × 10⁶ g/mol and 38 nm particle diameter. Because of the high molecular weight and small particle size, these chains are constrained in dimensions by a factor of four. Mildly molded (compacted to full density) samples were annealed for increasing time periods and their small-angle neutron scattering (SANS) patterns recorded. The radii of gyration increase with time as segmental diffusion proceeds during film formation. The initial diffusion was hindered, as shown by a slower than expected relaxation of the chains. Residual interfacial effects were postulated to be the main cause. Chain interdiffusion between latexes of about 110 Å is sufficient to develop a tough, coherent film.