Termination rate constants in radical polymerization

Abstract

AbstractA rate constant is generally derived by using Fick's equation corresponding to the spherical interdiffusion of particles. By using this rate constant, chain and primary radical termination rate constants can be approximated to rate constants for the bimolecular reactions between two radical chain ends, and primary radical and radical chain end, respectively. The former is given by ks = 8πNLDsLs exp { − Ls/Rs} × 10−3 1./mole‐sec. The latter is given by ksi = 4πNL(Ds + Di)Lsi exp { − Lsi/Rsi} × 10−3 1./mole‐sec. Here, NL is Avogadro's number; Ds and Di are the diffusion constants of radical chain end and primary radical, respectively; Ls and Lsi are, respectively, the distances between two radical chain ends and between a primary radical and a radical chain end at a thermal energy equal to the coulombic energy of interaction of the net charges; and Rs and Rsi are, respectively, the average distances between two radical chain ends and primary radical on a collision.