This paper discusses two closely relative areas, including the borane-mediated radical polymerization mechanism and the formed fluoropolymers used as the dielectrics thin films in high energy density capacitors for energy storage. The system of borane/oxygen control radical initiators are surprisingly effective for initiating polymerization of fluoromonomers, such as vinylidene fluoride (VDF), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), etc., at ambient temperature. Mechanistic study indicates that the in situ formed alkyl radical (C*) is responsible for the initiation, and the borinate radical (B-O*) forms a reversible bond with the propagating radical to prolong the polymerization. The control polymerization is characterized by predictable molecular weight, narrow molecular weight distribution, formation of diblock copolymer and chain end functionalized polymers, and tolerance to many functional groups that usually cause chain transfer reactions in regular free radical polymerization. The other aspect of this paper is to apply this control polymerization to prepare a whole family of PVDF copolymers. By systematically tuning the polymer chain conformation and crystal structure, we have identified the most suitable fluoropolymer for thin film capacitor that exhibits high energy density and low energy loss.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)