Lattice model of equilibrium polymerization. IV. Influence of activation, chemical initiation, chain scission and fusion, and chain stiffness on polymerization and phase separation

The influence of thermal activation, chemical initiation, chain fragmentation, and chain stiffness on basic thermodynamic properties of equilibrium polymerization solutions is systematically investigated using a Flory-Huggins type lattice model. The properties treated include the average chain length L, extent of polymerization Phi, Helmholtz free energy F, configurational entropy S, specific heat C(V), polymerization transition temperature T(p), osmotic pressure Pi, and the second and third virial coefficients, A(2) and A(3). The dependence of the critical temperature T(c) and critical composition phi(c) (volume fraction of associating species) on the enthalpy Deltah(p) and entropy Deltas(p) of polymerization and on the strength epsilon(FH) of the FH effective monomer-solvent van der Waals interaction (chi=epsilon(FH)/T) is also analyzed as an illustration of the strong coupling between phase separation and polymerization. For a given polymerization model, both T(c) and phi(c), normalized by their values in the absence of polymerization, are functions of the dimensionless "sticking energy" h(epsilon)equivalent to(\Deltah(p)\/R)/(2epsilon(FH)) (where R is the gas constant) and Deltas(p). (C) 2003 American Institute of Physics.