Charge-Transfer Complexes and Their Role in Copolymerization.

摘要

A new theoretical approach to charge-transfer complex formation is presented. The overall process is seen as a result of two processes; solvation and actual complexation, each having a distinct equilibrium constant. The complex concentration can be determined for any donor and solvent concentration. The theory is applied to the fumaronitrile/styrene complex in four solvents, with dielectric constants ranging from 2.24 to 24. Styrene and fumaronitrile polymerize with a pronounced alternating tendency. Since the two monomers also have very different polarities (eplison values), they provide a convenient system to test the charge-transfer complex compolymerization model developed by Seiner and Litt. For this purpose two series of polymerizations were run: one in ethanol at low total monomer concentration (conditions unfavorable for the formation of the charge-transfer complex), the other in dichloroethane at high total monomer concentration (conditions favoring the charge-transfer complex). It is shown that the polymerization is both solvent and dilution dependent as predicted by the model. This dependence is related to charge-transfer complex concentrations.