Synthesis of ultrahigh molecular weight poly(vinylidene fluoride) via emulsion polymerization initiated by the combination of silver nanoparticles with trichloroacetic acid

Ultrahigh molecular weight (UHMW) polymers, as high-performance materials, have great potential applications in many aspects. However, the synthesis of UHMW poly (vinylidene fluoride) (PVDF) remains challenging. To achieve the synthesis of UHMW polymers, we developed a novel route to synthesize UHMW PVDF successfully and then investigated the effects of varying conditions and reactants on molecular weight and dispersity ( Đ ). The combination of Ag nanoparticles (Ag NPs) and trichloroacetic acid (TCA) represented a highly effective system for initiating the emulsion polymerization of vinylidene fluoride (VDF). Under pressures up to 70 bar, the PVDF with a number-average molecular weight up to 1.72 × 10 6  Da ( Ð  = 1.62) was obtained in the presence of 28.5 ppm Ag NPs at 50 °C. Systematic investigation revealed that the molecular weight and distribution were significantly influenced by the composition of the initiating system, reaction temperature, and surfactant concentration. Preliminary investigation of the mechanism revealed that emulsion polymerization of VDF was initiated by carbon radicals generated from the reaction of Ag NPs and TCA. Furthermore, the separation of radicals in different polymer particles decreases the probability of bimolecular termination, thereby leading to an increase in the molecular weight of polymers. The synthesis of UHMW PVDF using metal nanoparticles and halogenated acids provides significant insights for future development of high-performance fluorinated polymers.