Due to its inertness and solubility in vinylidene fluoride, (VF2), supercritical carbon dioxide is used as a replacement solvent for producing polyvinylidene fluoride (PVDF). tert-butyl peroxyacetate (TBPA) was evaluated for the first time as a free radical initiator for radical chain polymerization of VF2 producing PVDF without use of a dispersion agent in a semibatch reactor using supercritical carbon dioxide. Diethyl peroxydicarbonate (DEPDC) at 75 degrees C has been evaluated in many publications as an initiator in batch and continuous reactors for polymerization of VF2 in supercritical carbon dioxide. The effects of monomer and initiator concentration, agitation, and reaction time upon average molecular weight and polydispersity were evaluated using TBPA as an initiator at 104 degrees C and compared with DEPDC initiated polymerization. It was found that as agitation rate, monomer concentration, and reaction time increased, the average molecular weight of PVDF using TBPA as an initiator increased. Lower concentrations of TBPA were needed compared to DEPDC to produce comparable molecular weights of PVDF. Using TBPA as an initiator at the conditions investigated resulted in lower polydispersity at similar monomer concentrations compared to DEPDC. Average molecular weights using TBPA ranged from 49,900 g/mol to 1.3 million g/mol and polydispersity ranged from 1.3 to 5.4. POLYM. ENG. SCI., 56:435-440, 2016. (c) 2016 Society of Plastics Engineers