SLOW DYNAMICS OF SEGREGATION IN HYDROGEN-BONDED POLYMER BLENDS

Time-resolved small-angle neutron scattering has been used to study th e dynamics of phase separation in hydrogen-bonded polymer blends under a variety of shallow-quench conditions. Above a well defined cutoff w ave vector q(c), the structure factor S(q,t) is described by an expon ential or a stretched exponential decay. The early-stage growth rate R (q) appears to change sign precipitously at the cutoff, however, whic h is not consistent with a linear theory. Below the cutoff, S(q,t) exh ibits nonlinear growth with a characteristic time scale t(m)(q), and s cales as q(-D)f(t/t(m)) with a scaling exponent D that is often differ ent from the universal value d=3.