Compensation of the photoelastic birefringence of a polymer by doping with an anisotropic molecule

We report on a method to compensate the photoelastic birefringence of a polymer. In this method, a rod-like molecule that has a polarizability anisotropy was chosen and doped in a polymer. We demonstrated this method by compensating the negative photoelastic birefringence of poly(methylmethacrylate) at a wavelength of 633 nm. Homogeneous doping with 2.2 wt.∈% of trans-stilbene almost eliminated the photoelastic birefringence of the polymer. The photoelastic coefficient of the synthesized zero-photoelastic birefringence polymer was 0.057×10^-12 Pa^-1. We found that the photoelastic birefringence of poly(methylmethacrylate) was compensated by the motion of trans-stilbene in the polymer by the analysis of the infrared absorption spectrum.