MICROPHASE STRUCTURE IN RANDOM BLOCK-COPO LYMERS CONTAINING RIGID ANDFLEXIBLE BLOCKS

Specific features of microphase formation in films of polyblock copoly mers (cast from dilute solutions) containing randomly distributed rigi d blocks of aromatic polysulfone and flexible blocks of oligobutadiene were examined using small-angle X-ray scattering, radio-frequency spe ctroscopy, and IR spectroscopy. It was found that the mean density of the films increased in linear proportion to the fractional volume cont ent of the rigid blocks. The densities of the rigid and flexible micro phases did not stay constant but varied inversely: the density of the rigid phase decreased, while that of the flexible phase increased. In a certain region of compositions, the density of the flexible phase ma y be lower than that of the polybutadiene homopolymer. The existence o f excess free volume in the flexible phase of such materials, as compa red to homopolymers, was confirmed by spin-probe studies and by measur ing the local diffusion coefficients of low molecular-mass compounds.