Chain transfer for vinyl monomers polymerized in N‐allylstearamide

Abstract

AbstractApparent transfer constants have been determined for styrene, methyl methacrylate vinyl acetate, and diethyl maleate polymerized in N‐allylstearamide at 90°C. Regression coefficients for transfer were: methyl methacrylate, 0.301 × 10−3; styrene, with no added initiator, 0.582 × 10−3; styrene, initiated with benzoyl peroxide, 0.830 × 10−3; vinyl acetate, 62.01 × 10−3; and diethyl maleate, 2.24 × 10−3. Rates of polymerization were retarded for both styrene and methyl methacrylate. Vinyl monomer and comonomer disappearance followed an increasing exponential dependence on both initiator and monomer concentration. Although degradative chain transfer probably caused most of the retardation, the cross‐termination effect was not eliminated as a contribution factor. Rates for the vinyl acetate copolymerization were somewhat retarded, even though initiator consumption was large because of induced decomposition. The kinetic and transfer data indicated that the reactive monomers added radicals readily, but that rates were lowered by degradative chain transfer. Growing chains were terminated at only moderate rates of transfer. Unreactive monomers added radicals less easily, producing reactive radicals, which transferred rapidly, so that molecular weights were lowered precipitously. Although induced initiator decomposition occurred, rates were still retarded by degradative chain transfer. A simple empirical relation was found between the reciprocal number‐average degree of polymerization, 1/X̄n1 and the mole fraction of allylic comonomer entering the copolymer F2, which permitted estimation of the molecular weight of copolymers of vinyl monomers with allylic comonomers. This equation should be applicable when monomer transfer constants for each homopolymer are known and when osmometric molecular weights of one or two copolymers of low allylic content have been determined.