| Abstract: | New polydimethylsiloxane-containing segmented block copolyure-thanes were obtained from aromatic or aliphatic diisocyanates, 1,4-butanediol 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 equation and the corresponding group contributions to the molar refraction and to the molar volume. The results are in good agreement with the experimental values. Also, from the dependence between the specific refractive index increments and the weight fraction of 4,4′-methylene diphenylene diisocyanate units, w d , the ν0 and dν/dw d coefficients have been evaluated and the results are situated between the values reported in literature. |
