Influence of hard segments to specific refractive index increments of segmented poly(ester urethane)s

The segmented poly(ester urethane)s were obtained from 4,4'-methylene diphenylene diisocyanate and 2,4-tolylene dissocyanate with thiodiglycol, diethylene glycol, or 4,4-dihidroxydiethoxydiphenyl sulfone as chain extender, and poly(ethylene glycol)adipate using a multistep polyaddition process. Specific refractive index increments of these segmented copolymers in N,N-dimethyl-formamide have been determined by the Lorenz-Lorentz and Gladstone-Dale equations and the corresponding group contributions to the molar refraction and to the molar volume. The results are compared with the experimental values. Also, for studied samples we can observe the contribution of composition of hard segments to the refractive index and specific refractive index increment.