Polymers of carbonic acid, 23. Photoreactive cholesteric polycarbonates based on isosorbide, 4,4′‐dihydroxychalcone and 4,4′‐dihydroxybiphenyl

Numerous copolycarbonates were prepared from 4,4′‐dihydroxychalcone, on the one hand, and methylhydroquinone, 4,4′‐dihydroxybiphenyl or isosorbide (1,4:3,6‐dianhydro‐D‐sorbitol), on the other. Three different polycondensation methods were compared, but polycondensation in an organic solvent using diphosgene as condensing agent proved to be the most satisfactory. The resulting copolycarbonates were characterized by their inherent viscosities, elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR) and 13C NMR spectra, by differential scanning calorimetry (DSC) measurements and by optical microscopy. The 13C NMR spectra proved the formation of almost random sequences in all cases. In contrast to the homopolycarbonate of chalcone which is crystalline and insoluble in inert solvents, all copolycarbonates of chalcone are completely or largely amorphous and soluble. Whereas 4,4′‐dihydroxychalcone itself proved to be nonmesogenic, copolycarbonates containing 4,4′‐dihydroxybiphenyl are thermotropic. Ternary copolycarbonates containing isosorbide as a chiral component are cholesteric and form Grandjean textures upon shearing in the molten state. Ultraviolet (UV) irradiation of thin films resulted in crosslinking.