The heat capacity relaxation and the enthalpy decrease in mass and diffusion-controlled polymerization reaction kinetics

Abstract

To gain insight into the diffusion control kinetics during the course of a linear chain polymerization reaction, the heat capacity relaxation time and (polymerization) reaction rate coefficient have been studied by measuring the real and imaginary components of the complex heat capacity and the enthalpy release simultaneously in real time by means of an instrument designed for the purpose. Polymerization of a stoichiometric mixture of cyclohexylamine with diglycidyl ether of bisphenol-A into linear chains occurring isothermally has been studied at five temperatures, and the extent of polymerization α, and the heat capacity relaxation time τ, have been determined. The stretched exponential distribution parameter for the latter is 0.42 ± 0.01, and is found to remain constant with increase in α over a narrow range. A criterion for determining the extent of polymerization α, as well as the temperature at which mass-controlled reaction kinetics gradually changes to diffusion-controlled kinetics is used here for determining the temperature and α conditions at which this change occurs.