New approaches to statistical thermodynamics of blends containing copolymers

Abstract

For thermodynamic description of homopolymer blends several theories exist nowadays whose conclusions are in reasonable agreement with experimental data available. Sophisticated approaches employed in such theories normally are not so efficient when considering blends of copolymers. The reason is that a specimen of a synthetic copolymer involves enormous (practically infinite) set of molecules differing in number of monomeric units, composition andsequence distribution. Just this circumstance is likely to be responsible for the absence of a universal thermodynamic theory of blends comprising copolymers with an arbitrary chemical structure. We managed to solve within the framework of the simplest model the fundamental problem of this theory which consists in deriving equations for the calculation of cloud-point curve, spinodal and critical points for any blend of linear copolymers with known characteristics of their primary molecular structure [I]. In terms of this unified approach it is possible to examine phase behavior of either statistic copolymers or block copolymers showing microphase separation. Covering wide range of polymer blends our theory is convenient for the construction of theoretical phase diagrams of particular blends since the equations derived comprise minimal number of thermodynamic parameters (like the Flory 1 -parameters) experimentally found for a number of polymers.