Gamma-rays are effective in the dispersion polymerization of vinyl monomers such as methyl methacrylate (MMA) and 1,1 difluoroethylene (VF2) in CO(2)-based dense systems: the most relevant advantages by the use of this initiation method lie both in the possibility to have a very pure starting system and to operate at very mild temperature and pressure conditions. Moreover, y-rays sustain the polymerization up to high conversion in short reaction times.
The obtained polymer has a very high average molecular weight with a narrow distribution and a high degree of molecular complexity (branching and/or cross-linking) depending on the nature of the surfactant and on the adopted radiation intensity ; with a proper selection of the operative conditions the polymer properties (molecular weight and rheological behavior) are comparable to those obtained in conventional polymerizations carried out in the presence of AIBN at higher temperatures.