Specific refractive index increments of segmented poly(ester urethane)s

Segmented poly(ester urethane)s were obtained from aromatic diisocyanates with thiodiglycol or diethylene glycol and poly(ethylene glycol)adipate using a multistep polyaddition process. Specific refractive index increments of these segmented copolymers in N , N -dimethylformamide were determined by the Lorenz–Lorentz, Vogel and Gladstone–Dale equations and the corresponding group contributions to the molar refraction and to the molar volume. The results were compared with the experimental values. For the samples studied, the contribution of sulfur (from the thiodiglycol structure) and oxygen (from the diethylene glycol structure) atoms to the refractive index and specific refractive index increment was also determined.