Design and synthesis of zero-zero-birefringence polymers in a quaternary copolymerization system

We designed and synthesized quaternary copolymers of methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), benzyl methacrylate (BzMA), and 3,3,5-trimethylcyclohexyl methacrylate (TMCHMA) and we investigated their birefringence, thermal properties, and other optical properties. When the copolymer composition was MMA/TFEMA/BzMA/TMCHMA = 50:38:8:4, 40:30:7:23, or 30:21:7:42 (wt%), a zero-zero-birefringence polymer that exhibited neither orientational nor photoelastic birefringence was obtained. We demonstrated that such zero-zero-birefringence polymers with a variety of compositions could be successfully prepared in the quaternary system by using the same compensation method as applied in ternary random copolymerization. We also demonstrated that the glass-transition temperature (T_g) and refractive index (n _D) of these copolymers could be controlled with high accuracy while retaining their zero-zero-birefringence property. We can therefore predict the type of birefringence, the T_g, and the n_D of a particular copolymer before polymerization. Zero-zero-birefringence polymers with the most appropriate characteristics can then be synthesized selectively by quaternary copolymerization.