PRIMITIVE MODELS OF CHEMICAL ASSOCIATION - III - TOTALLY FLEXIBLE STICKY 2-POINT MODEL FOR MULTICOMPONENT HETERONUCLEAR FIXED-CHAIN-LENGTH POLYMERIZATION

A multidensity integral-equation theory for polymerization into freely jointed hard-sphere homonuclear chain fluids proposed earlier [J. Che m. Phys. 106, 1940 (1997)] is extended to the case of multicomponent h eteronuclear chain polymerization. The theory is based on the analytic al solution of the polymer Percus-Yevick (PPY) approximation for the t otally flexible sticky two-point (S2P) model of associating fluids. Th e model consists of an n-component mixture of hard spheres of differen t sizes with species 2,...,n-1 bearing two sticky sites A and B, rando mly distributed on its surface, and species 1 and n with only one B an d A site per particle, respectively. Due to some specific restrictions imposed on the possibility of forming bonds between particles of vari ous species, the present version of the S2P model represents an associ ating fluid that is able to polymerize into a mixture of heteronuclear chain macromolecules. The structural properties of such a model are s tudied in the complete-association limit and compared with computer-si mulation results for homonuclear hard-sphere chain mixtures, symmetric al diblock copolymers, alternating copolymers, and homonuclear hard-sp here chains in a hard-sphere solvent. Some results for the case of par tial association are also presented. The PPY theory represents a quant itatively successful theory for the mixtures of short homonuclear chai ns and the short copolymer systems studied here. We also expect that t he theory will prove to be of the same order of accuracy in investigat ing the case of partial association. (C) 1998 American Institute of Ph ysics. [S0021-9606(98)51315-9].