SUMMARY: Two new diamino monomers based on 3,39,4,49-biphenyltetracarboxylic dianhydride (BPDA) were synthesized and used in a low temperature polyamide polycondensation. High molecular weight homopoly(amide-imide)s and copoly(amide-imide)s were synthesized via in-situ silylation and investigated with respect to their solution, thermal, and film forming properties. All polymers are soluble in strong acids and most in amide type solvents. Inherent viscosities up to 7.4 dl/g in N-methyl-2-pyrrolidone (NMP)/LiCl were achieved. A methyl substitution in ortho-position to the imide group resulted in polymers possessing improved solubility and good thermal stability up to 500 8 C. Isotropic films can be prepared from solution.

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New liquid crystalline diacrylates and tetra-acrylates containing four to six aromatic rings were synthesized and characterized, and their mesophase behaviour was investigated. They are designed to be used in combination with chiral molecules to form cholesteric mesophases which can be crosslinked by photopolymerization. The acrylates presented exhibit broad mesophase ranges since mesogenic moieties longer than three are employed. Most diacrylates show no isotropization, due to premature thermal polymerization above 180ß C. Additionally, liquid crystalline dipropionates were synthesized as reference compounds which cannot be crosslinked, and selected examples of these exhibit isotropization temperatures as high as 238ß C prior to thermal degradation. Substituents at the mesogenic moiety have a great in uence on the mesophase characteristics. Bulky substituents such as the tert-butyl group, induce a nematic mesophase, whereas compounds with small substituents (e.g. OCH 3 ) or unsubstituted molecules also exhibit smectic phases. Tetra-acrylates with unsubstituted and substituted mesogenic units feature nematic mesophases only as a result of the additional spacers attached. Here isotropization was observed without polymerization at temperatures around 120-160ß C.