Liquid-crystalline main-chain polyesters with polystyrene side chains of different length and number per main chain were synthesized using aromatic hydroxyfunctional polystyrene (PS) macromonomers, terephthalic acid derivatives and tert-butylhydroquinone as co-diol. The molecular weight of the polystyrene side chain was varied in the range from 1000 to 20000. The influence of this novel type of substituent on the solubility, thermal behaviour and miscibility with PS as a flexible matrix polymer is discussed. The properties of the new compounds are compared to those of the respective homopolyester. The graft copolyesters are, depending on the characteristics of the polymeric substituent, soluble in common organic solvents and their thermal transition points are lowered compared to the homopolyester. Compared to blends of the homopolyester, the improvement of miscibility of the polymer-substituted rigid rods with PS as an example for a flexible matrix polymer can be valued as a step to molecular reinforcement.

The synthesis of poly(bispheno1-A carbonate)-graft-polystyrene with grafts of definite, predictable, nearly identical length was achieved using the macromonomer technique, i. e., copolycondensation of polystyrene macromonomers, carrying aromatic hydroxyl functions, with bisphenol-A and triphosgene in pyridine/methylene chloride solution. The incorporation of the macromonomer into the polycarbonate backbone was examined both qualitatively and quantitatively. The copolycarbonates show -in the contrast to polystyrene/polycarbonate blends of comparable molecular weights and compositiononly one glass transition temperature, which proved to be dependent on the polystyrene content, following the Fox equation. The title compounds exhibit reduced stress-induced birefringence compared to polycarbonate.