GROUP-CONTRIBUTION TO MOLAR REFRACTION AND REFRACTIVE-INDEX OF CONJUGATED POLYMERS

The functional group contribution to molar refraction and refractive i ndex of pi-conjugated polymers has been evaluated from the available r efractive index dispersion data for 33 conjugated polymers. The Lorent z-Lorenz molar refraction (R(LL)) of 24 functional groups commonly fou nd in conjugated polymers was determined and tabulated at selected wav elengths between 700 and 2500 nm to provide a basis for the computatio nal prediction of the refractive index of conjugated polymers. A signi ficant improvement on the accuracy of semiempirical prediction of the refractive index of conjugated polymers was achieved by using the new R(LL) data (0.9% average error) compared to previous literature molar refraction data (14.8% average error). The new molar refraction data a ccounted well for the effects of optical dispersion, pi-electron deloc alization, and molecular structure on the refractive index of conjugat ed polymers. The wavelength dependent refractive indices of several we ll-known conjugated polymers, trans-polyacetylene, poly(p-phenylene), poly(p-phenylenevinylene), poly(2,5-dimethoxy-p-phenylenevinylene), po lythiophene, and poly(2,5-thiophenediylvinylene), were predicted from the new molar refraction data.