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We clarified the birefringence properties of poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate), poly(cyclohexyl methacrylate), poly(isopropyl methacrylate), and poly(tert‐butyl methacrylate). We demonstrated that the conformational change in polymer molecules that causes orientational birefringence differs from that causing photoelastic birefringence. Orientational birefringence depends mainly on the orientation of the main chains of the methacrylate polymers above Tg. On the other hand, photoelastic birefringence in elastic deformation below Tg depends mainly on the orientation of the side chains while the main chains are scarcely oriented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2029–2037, 2010

Zero-zero-birefringence polymers which exhibit no orientational birefringence and no photoelastic birefringence may be suitable candidates for the components of optical devices. To develop zero-zero-birefringence polymers, a novel copolymerization system is required. We investigated two types of birefringence of poly(N-methylmaleimide) (PMeMI) and showed that PMeMI exhibits positive orientational and photoelastic birefringence. On the basis of the results, we calculated the optimal composition for compensating both types of birefringence by solving three equations which describe the relationship between birefringence properties and weight fraction of monomers. When the copolymer compositions were MMA/BzMA/MeMI 5 86/8/6 and 88/8/4 (wt %), zero-zerobirefringence polymers were obtained. By using MeMI as a comonomer, these zero-zero-birefringence polymers have a much higher glass transition temperature (T g ) than those of previous researches. Also, this polymer film has high transparency comparable with that of PMMA film. Therefore, we conclude that we successfully prepared zero-zero-birefringence polymers using N-substituted maleimide and that N-substituted maleimide is a promising material for zero-zero-birefringence polymers for optical devices.

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. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013