Radical Copolymerization of Various Vinyl Esters and the Cotacticities of the Copolymers

Radical copolymerizations of vinyl acetate (VAc) with vinyl butylate (VBu), vinyl isobutylate (ViBu), vinyl trifluoroacetate (VTFAc), and vinyl benzoate (VBz), and those of vinyl pivalate (VP) with VTFAc were carried out at 0°C by UV irradiation. The cotacticities were determined from the 1HNMR spectra of poly (vinyl alcohol) s (PVAs) obtained by saponification of the copolymers, they varied with the monomer combination and feed monomer composition. The cotacticities of VAc/VBu and VAc/VTFAc copolymers could be expressed by coisotactic parameters derived on the basis of the terminal model, but those of VAc/ViBu copolymer could not be expressed by the terminal model and could be expressed well by the penultimate model. In the cases of VAc/VBz and VP/VTFAc copolymers, both of the terminal and penultimate model were not enough to explain the cotacticities indicating a new model.