PHASE-TRANSITIONS IN POLYDISPERSE POLYMER MELTS

The order-disorder transition in a lattice hole model of a polydisperse dense system of semiflexible chain macromolecules is studied within the mean-field approximation and by Monte-Carlo methods. The polymer chains consist of 'stiff' or 'flexible' monomer units which associate at a given density and temperature in the process of reversible equilibrium polymerization. The system goes from an ordered state of parallel infinite rods into a lower density state of differently long disoriented chains at a temperature which is influenced by the chain stiffness and by the ratio between inter- and intrachain interactions. The mechanism of the transition is different from that of Flory and represents rather a polymerization transition.