The laser flash‐initiated polymerization as a tool of evaluating (individual) kinetic constants of free radical polymerization, 1. Outline of method and first results

Abstract

Abstract A method is presented which allows the determination of k p / k t ‐values in free radical polymerization. It is based on measurements of the (average) rate of polymerization under pseudostationary conditions, the polymerization being initiated by laser flashes of short duration. For ρ k t t 0 ≫ 1 (ρ being the additional polymer radical concentration produced by each laser flash, k t the bimolecular termination constant between polymer radicals, k p the rate constant of chain propagation, t 0 the time separating two successive laser flashes) k p / k t may be obtained as the slope of a linear plot of the fractional conversion per flash vs. ln t 0 . Dividing the intercept by the slope yields ln ( pk t ). Thus, if p is accessible, separation of k p / k t ‐data into its individual constituents may be accomplished without making any use of stationary polymerization data. Application of this method to the polymerization of styrene sensitized by benzoin or AIBN at 25°C gives k p / k t ‐values of 1,0 · 10 −6 which are in fair agreement with those obtained by other methods.