| Fluoropolymers; have high chemical and thermal stabilities, making them desirable for a number of applications, yet limit their broader applicability. To enhance processability and solubility in organic solvents, new fluoropolymers incorporating partial hydrocarbon functionality were synthesized.;In one approach, three new trifluorovinyl ether monomers (TFVEs), having hydrocarbon pendant groups were polymerized: 1-[2-(2-ethoxy-ethoxy)-ethoxy]-1,2,2-trifluoroethene (Et-TFVE), 1-[2-(2-tert-butoxy-ethoxy)-ethoxy]-1,2,2-trifluoroethene (tert-Bu-TFVE) and 1-(2-phenoxy-ethoxy)-1,2,2-trifluoroethene (Ph-TFVE). The TFVEs were homo- and copolymerized with ethyl vinyl ether (EVE) and vinyl acetate (VAc) by redox-initiated aqueous emulsion polymerization. Et-TFVE was also homo- and copolymerized with tetrafluoroethylene (TFE) in carbon dioxide (CO2).;As a result of TFVE structure and low reactivity, relatively low molar mass homopolymers; and TFE copolymers resulted (on the order of 10,000 g mol -1). The polymerization mechanism was complicated because of beta-scission termination/chain transfer for all TFVE homopolymers and copolymers with TFE. Furthermore, radical hydrogen abstraction chain transfer was observed in polymers incorporating Et-TFVE and tert-Bu-TFVE but not poly(Ph-TFVE). Interestingly, abstraction in poly(TFVE)s was a localized intramolecular process, occurring from the pendant group adjacent to the propagating macro-radical.;TFVE copolymerization with EVE and VAc resulted in significantly higher molar mass polymers (typically ≥100,000-g mol-1) because of higher rates of TFVE cross-propagation. However, abstraction from the oligo-ether pendant group of Et-TFVE was still evident. The frequency of abstraction was more significant for copolymers having a greater fraction of (Et-TFVE), in the monomer feed. Reactivity ratios were estimated for a series of bulk copolymerizations of Ph-TFVE with EVE or VAc and confirmed azeotropic copolymerization.;In a second approach to processable fluoropolymers, TFE and VAc were copolymerized in supercritical CO2. High molar mass poly(TFE-co-VAc)s incorporating up to 71 mo1% TFE were synthesized and were organic solvent soluble. Previous syntheses in aqueous emulsions resulted in a branched structure as a result of TFE radical hydrogen abstraction from VAc with continued propagation of the resulting macro-radical. Consequently, at least a 10-fold decrease in molar mass was observed following hydrolysis. Only a small decrease in molar mass was observed after hydrolysis for poly(TFE-co-VAc)s synthesized in CO2. This suggested that abstraction was suppressed in carbon dioxide relative to propagation, thereby yielding predominantly linear polymers. |
