ENTHALPIC INTERACTION OF DIBLOCK COPOLYMERS WITH IMMISCIBLE POLYMER BLEND COMPONENTS

An attempt is made to extend the model of Leibler for the emulsifying activity and Interfacial properties of A-b-B diblock copolymers in inc ompatible blends of the homopolymers A and B - which are identical wit h the respective copolymer components - to enthalpically interacting C -b-D diblock copolymers, the block C being thermodynamically compatibl e with A and D with B. Due to the attractive enthalpic interaction the A/C-b-D/B compatibilized blends are promising for optimum phase adhes ion (bold types for thermodynamically compatible partners). Thus, the extended model for a plane interfacial layer includes the enthalpic in teraction of the compatible polymer pairs beside the entropic effects. The approach starts with the equilibrium supposition, not taking into consideration enthalpy driven migration effects of the block copolyme r from the bulk to the Interface. The model confirms a dominant role o f the enthalpic interaction between blocks of the diblock copolymer an d the respective homopolymers to the compatibilization of incompatible blend components. It is applicable also for blends compatibilized wit h block copolymers of unfavourable repulsive type interaction, A/C-b-D /B, and for blend systems with mixed type interactions, e.g. A/C-b-B/B or A/C-b-D/B.