Degradation of vinyl polymers in solution

Abstract

AbstractThe degradation of high polymers was studied in dilute solution (1%) in the presence of an equivalent amount of benzoyl peroxide in a temperature range from 65 to 100°C.The reaction was followed dynamically by a viscometric method, and from a static point of view by determining the polydispersity of the samples after degradation, and also by spectrophotometric measurements. The viscometric method allows examination of the influence of the polymer concentration, of the degree of polymerization, of the initiator concentration, of the temperature, and of the chemical structure of the polymer on the rate of degradation. These rate constants were obtained under the same experimental conditions, and permit the classification of the polymers in the following decreasing order: polychloroacrylate, polymethyl methacrylate, and polystyrene. Under the same conditions, polyvinyl chloride and acetate are stable and not affected. These results are discussed as a function of the lability of some atoms present in the polymeric chain and as a function of the relative stability of the intermediate radicals produced during the reaction. Statically, the degradation was followed by determining the variation of polydispersity before and after degradation in the case of a sample of polymethyl methacrylate. On the other side, ultraviolet spectrophotometry shows the presence of monomer by degradation of a polystyrene sample; this spectrophotometric method also allows proof of the microreversibility of the polymerization process. The use of this technique makes it necessary to carry out the experiments under experimental conditions that differ from the preceding ones (lauroyl peroxide, and chloroform as solvent).