CHAIN FRAGMENT DIFFUSION IN LIQUID AND GLASSY POLYMER BLENDS

A new technique for measurements of extremely slow chain diffusion in polymer blends is discussed. It involves the analysis of "chain fragment diffusion by small-angle neutron scattering (CFD-SANS)". The principle is that polymer chains are split in the glassy state in a condition where the chain conformation does not immediately respond to the fragmentation. The subsequent separation of chain fragments can then be followed with SANS. In order to obtain contrast for SANS measurements, chain fragmentation of a deuterated polymer was made in a hydrogenous matrix. Experiments are described on a copolycarbonate containing a thermosensitive comonomer in a matrix of tetramethyl polycarbonate. Diffusion coefficients in the range 10(-18)-10(-14) cm2/s were measured in a temperature range from 24 K below to 14 K above the glass transition. Evaluation of the data was based on a statistical analysis of the CFD process.