A THEORETICAL DESCRIPTION OF A METHOD FOR MODEL-INDEPENDENT DETERMINATION OF BIMOLECULAR CHAIN-LENGTH-DEPENDENT FREE-RADICAL-TERMINATION RATE COEFFICIENTS

摘要

A theoretical description is given of a method for model-independent determination of bimolecular chain-length-dependent free-radical-termination rate coefficients. By on-line determination of the monomer concentration versus time in a time-resolved pulsed laser polymerization, the value of the termination rate coefficient k(t)(i,i) of the termination reaction between species of identical chain length can be determined in a very simple fashion. The key assumption in this ht determination is that the radical chain-length distribution that is generated with a laser pulse is extremely narrow, such that all chains can be considered as being identical in chain length. With computer simulations the effects of several processes which could undermine this key assumption were investigated. For the monomer methyl methacrylate (MMA) the effects of(i) a Poisson distribution of the polymerization events, (ii) chain transfer to monomer, and (iii) the presence of a background initiation process were investigated. For MMA, none of these processes interfere with the model-independent determination of the termination rate coefficients, as long as suitable experimental conditions are chosen, which follow from the simulations. [References: 50]