Effect of water absorption on the structure and properties of isosorbide-based polycarbonate

The structure and properties of isosorbide-based polycarbonate (ISB-PC), and its responses to water absorption were investigated. Although the glass transition temperature of an ISB-PC film decreased as its water content increased, its Young's modulus increased as the strain at break decreased. The tensile yield stress of the polymer decreased following water absorption. Optical properties such as the refractive index and the photoelastic coefficient in the glassy state were also affected by water absorption. The refractive index increased with the water content, although the refractive index of water is lower than that of the polymer. The photoelastic coefficient reached a maximum at a specific water content. These phenomena can be explained by the interaction between water molecules and the carbonyl groups in the polymer, which affect the segmental mobility and polarizability anisotropy of ISB-PC. Basic properties such as entanglement molecular weight were also determined.