Synthesis and properties of copolymers of methyl methacrylate with 2,3,4,5,6-pentafluoro and 4-trifluoromethyl 2,3,5,6-tetrafluoro styrenes: An intrachain interaction between methyl ester and fluoro aromatic moieties

2,3,4,5,6-Pentafluoro and 4-trifluoromethyl 2,3,5,6-tetrafluoro styrenes were readily copolymerized with methyl methacrylate (MMA) by a free radical initiator. The copolymers were soluble in tetrahydrofuran and acetone. The films obtained were transparent and flexible. The glass transition temperatures (T_gs) of the copolymers were found positively deviated from the Gordon-Taylor equation. The positive deviation could be accounted for by dipole-dipole intrachain interaction between the methyl ester group of MMA and the highly fluorinated aromatic moiety, which resulted in a decrease in the segmental mobility of the polymer chains and the enhanced T_g values of the copolymers. The water absorption of PMMA was greatly decreased by copolymerization of MMA with the highly fluorinated styrenes. With as little as 10 mol % of pentafluoro styrene content in the copolymer, the water absorption was decreased to one-third of that for pure PMMA. The fluorinated styrenes-MMA copolymers were thermally stable up to 420 °C under air and nitrogen atmospheres. With 50 mol % of MMA in the copolymer, the copolymer was still stable up to 350 °C. Since these copolymers contain a large number of fluorine atoms, the light absorption in the region of the visible to near infrared is decreased in comparison with nonfluorinated polymers. Thus, these copolymers may be suitable for application in optical devices, such as optical fibers and waveguides.