SPINODAL DECOMPOSITION OF 2 HOMOPOLYMERS WITH THEIR BLOCK-COPOLYMER -A COMPARISON OF MODELS

The dynamics of phase separation in the presence of a diblock copolyme r have been studied using ternary and quaternary models of spinodal de composition. The ternary model treats the block copolymer as a third c omponent that is compatible with each of the mutually incompatible hom opolymers. The quaternary model treats the block copolymer as a pair o f specially constrained homopolymers. Both models predict core-shell m orphologies with the copolymer concentrated at the interface. Both mod els predict larger domain sizes and less sharp phase boundaries in the early stages of spinodal decomposition. In the late stages, domain si zes are largest for the system of homopolymers without copolymer and s mallest when a system containing copolymer is modeled as a quaternary blend. The scaling exponent observed for the quaternary model was s = 0.25 +/- 0.02 compared to s approximate to 0.3 for the homopolymers wi thout copolymer and for the ternary model. The quaternary model predic ts internal phase separation within a pure diblock copolymer, whenever the corresponding homopolymers are sufficiently incompatible. (C) 199 6 John Wiley & Sons, Inc.