Active sites of gamma-irradiated silica initiating surface polymerization of tetrafluoroethylene

EPR and low-temperature calorimetry were used to demonstrate that active si tes of ionic type are responsible for the initiation of the postradiation p olymerization of tetrafluoroethylene at the surface of a macroporous glass. A heat-release peak in the DSC curve within 180-220 K was attributed to po lymerization. The presence in of spectral features belonging to the termina l similar to CF2-CF2. radical in the EPR spectrum of the system suggests th at polymer chains grow by the radical mechanism. It was assumed that the fi rst stage of the polymerization is the formation of radicals by the interac tion between ionic species of the silica support and adsorbed monomer molec ules.