Design of zero–zero‐birefringence polymers in methacrylate copolymer systems containing trichloroethyl methacrylate

Polymers that exhibit neither orientational nor photoelastic birefringence, called zero–zero‐birefringence polymers, are candidate materials for preparing optical components of liquid crystal displays (LCDs). Analyzing the birefringences for various methacrylate polymers is an issue of current importance in developing zero–zero‐birefringence polymers with appropriate characteristics for LCDs. The researchers have investigated different types of birefringence for poly(2,2,2‐trichloroethyl methacrylate) (PTCEMA) and have shown that PTCEMA exhibits negative orientational and photoelastic birefringences. By using TCEMA as a comonomer, a zero–zero‐birefringence polymer having much higher glass transition temperature (Tg) compared with previous researches has been prepared by ternary copolymerization. Moreover, the researchers have fabricated zero–zero‐birefringence polymers in a quaternary system containing TCEMA. The property analyses indicate that Tg can be controlled while maintaining the zero–zero‐birefringence property, which shows that designing a quaternary zero–zero‐birefringence polymer permits selective synthesis with the most appropriate characteristics.