Studies in chain transfer. III. Determination of chain transfer coefficients from catalyzed polymerization data

Abstract

Based on a general equation correlating DP and rate for catalyzed polymerization in the presence of solvents, an experimental method has been devised for determining all three transfer coefficients, viz. monomer transfer (C_M), solvent transfer (C_S), and catalyst transfer (C_I), in a simple and straightforward way. Three types of methods are possible for solvent transfer determination: (1) by determining the slope of [1/p-1/(A²M²)R_P] versus S/M (1) at constant 1(catalyst):M(monomer) ratio; (2) by determining the intercept of [1/p-1/(A²M²)R_P] versus 1/M (2) at constant S/M; and (3) by direct use of the general equation, especially using a catalyst whose C_I is known to be zero. It has been further shown that the existing method (slope of 1/P versus S/M) in uncatalyzed polymerization would give correct results for all solvents only over the range in which the rate of uncatalyzed polymerization is proportional to the square of monomer concentration. It has also been pointed out that, in systems in which the more usual rate equation, R_P=K_P (k_i/k_t)^1/2I^1/2M^3/2 is valid, the slope of 1/P versus S/M (at constant I/M) would give correct C_S values for catalyzed polymerization also.