SPINODAL DECOMPOSITION IN MULTICOMPONENT POLYMER BLENDS

Spinodal decomposition in multicomponent mixtures of two homopolymers and a block copolymer was studied by a combination of neutron and ligh t scattering experiments. Mixtures of nearly monodisperse polyolefins- polymethylbutylene (M(w) = 1.7 x 10(5) gm/mol), polyethylbutylene (M(w ) = 2.2 x 10(5) gm/mol), and a symmetric polymethylbutylene-block-poly ethylbutylene (M(w) = 4.6 x 10(4) gm/mol) were studied, following rela tively deep quenches into the spinodal region (-)chi/chi(s) ranged fro m 1.7 to 2.4 (chi is the Flory-Huggins interaction parameter at the ex perimental temperature and chi(s) is the Flory-Huggins interaction par ameter at the spinodal temperature). The ratio of homopolymer volume f ractions was kept constant at unity, and the block copolymer volume fr action was varied from 0.0 to 0.2. The evolution of structure was foll owed over five decades of real time-1 min to 1 month. During this time , the characteristic length scale of the phase separated structure inc reased from 10(-1) to 10 mu m. The early stages of spinodal decomposit ion, captured by time-resolved neutron scattering, were compared with theoretical predictions based on the random phase approximation (RPA). Qualitative agreement was obtained. The intermediate and late stages, studied by light scattering, followed classic signatures of binary sp inodal decomposition. Experimental evidence indicates that the block c opolymer is uniformly distributed throughout the sample during all sta ges of the decomposition. (C) 1995 American Institute of Physics.