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Tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), and vinylidene fluoride (VDF) were copolymerized with vinyl acetate (VAc) in supercritical fluid CO2 by a free radical mechanism and without the use of a surfactant. A series of copolymers were synthesized with yields as high as 83% for TFE-VAc, 91% for CTFE-VAc, and 70% for VDF-VAc copolymers. Their weight-average molar masses, relative to polystyrene, were between 120 and 290 kg mol -1 , and polydispersity was between 1.6 and 2.4. A range of compositions was prepared with the amount of fluorocarbon in the copolymer varying from 13 to 84 mol %, as determined by elemental analysis. Monomer reactivity ratios were estimated using the error-in-variable method to be rCTFE ) 0.014 ( 0.05, rVAc ) 0.44 ( 0.03; rTFE ) -0.009 ( 0.06, rVAc ) 0.95 ( 0.08; and rVDF ) -0.4 ( 0.04, rVAc ) 1.67 ( 0.6. Proton NMR was used to estimate copolymer composition, based on triad sequences. These data, together with the reactivity ratio data, indicate that the fluorocarbons cross-propagate with VAc and that VAc propagates randomly. All samples were characterized by DSC for Tg with P(CTFE-co-VAc) having a Tg between 42 and 53°C, P(TFE-co-VAc) between 34 and 41°C, and P(VDF-co-VAc) between 20 and 33°C. Hydrolysis of vinyl acetate to vinyl alcohol (VA) in P(TFE-co-VAc) yielded terpolymers, P(TFE-co-VAc-co-VA), with >80% of VAc hydrolyzed to VA, thereby providing a reactive functional group for further modification. Interestingly, only a small decrease in molar mass was observed after the hydrolysis of vinyl acetate to vinyl alcohol, reflecting the loss of acetic acid and suggesting that these polymers are linear. The results presented herein are particularly interesting because no surfactant (or dispersion agent) was required for apparent solubility in CO 2. The fluoropolymers prepared herein may find utility in coatings or paint applications.

Supercritical carbon dioxide was used as a reaction medium to synthesize statistically random (i.e., no specific correlation between the location of the monomers on the polymer) copolymers of tetrafluoroethylene (TFE) and vinyl acetate (VAc) with similar molar mass and 11.6-63.3 mol % TFE content. The solubility of the copolymers at 25°C in CO 2 reduced after reaching a maximum value at a TFE molar concentration of 19.3 mol %. The 46.7 mol % TFE copolymer only dissolved in CO2 at elevated temperatures, whereas the 63.3 mol % TFE copolymer did not dissolve in CO2 even at temperatures in excess of 144°C and pressures of 210 MPa. The molecular modeling results show that the interaction of CO2 with acetate side group was not affected by presence of fluorine in the polymer backbone; therefore, the enhanced solubility of the semifluorinated copolymers is attributable to the enhanced binding between CO2 and the semifluorinated backbone of the copolymer when the CO2 molecule can access both the fluorinated (Lewis base) and hydrogenated (Lewis acid) parts of the backbone simultaneously.

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