Control of optical anisotropy at large deformations in PMMA/chlorinated-PHB (PHB-Cl) blends: Mechano-optical behavior

There is a continuing need to produce polymer films with high optical clarity with ability to dial in the optical properties including refractive indices and optical anisotropies. In this research, we investigated the mechano-optical behavior of PMMA/PHB-Cl blend films during uniaxial deformation and mapped out the composition-birefringence-processing relationships. The results indicate the presence of a broad glass transition for the composition range investigated that indicates the development of micro-heterogeneities particularly at the higher concentration of PHB-Cl. However, this did not detrimentally influence the optical transparency of the solvent cast films as the size of these micro-heterogeneities remains well below the size range to affect the transparency. Optical retardation behavior of the films can be altered from negative to positive by increasing the PHB-Cl concentration from 0 to 20 wt%. The films with 18 wt% PHB-Cl are predicted to exhibit zero birefringence even when they are stretched to large deformations. This dialability of optical properties makes these materials suitable for optical device applications such as CD and DVDs as well as optical retarder films for liquid-crystal display applications.