γ-radiation-initiated polymerization of vinylidene fluoride in dense carbon dioxide

The gamma-ray-initiated batch polymerization of vinylidene fluoride (VF2) has been investigated in dense carbon dioxide under relatively mild operative conditions (T less than or equal to 40 degreesC and P < 25 MPa). When the initial VF2 molar concentration was increased from 3.4 to 6.4 mol/L, monomer conversion increased from 20 to 73%; a similar trend was observed for the number-average molecular weight and the molecular complexity of synthesized poly(vinylidene fluoride) (PVDF) as determined from rheological measurements. Under all adopted experimental conditions, a synthesized PVDF polymer was collected in the form of a white powder. Despite the inherent heterogeneous character of the polymerization process, a homogeneous free-radical chain kinetics model can be used to fit kinetic data collected at 30 degreesC and 3.4 mol/L VF2 loading, with evidence of heterogeneous-phase polymerization being constituted by the onset of an acceleration period.