THERMOTROPIC LIQUID-CRYSTALLINE AROMATIC-ALIPHATIC POLYIMIDES, .2. EFFECT OF ALIPHATIC SPACER LENGTHS AND POLYMER COMPOSITIONS ON THE LIQUID-CRYSTALLINE PROPERTIES OF POLY(IMIDE-CARBONATE)S

Novel thermotropic liquid-crystalline (LC) aromatic-aliphatic poly(imi de-carbonate)s were prepared by melt polycondensation of N,N'-bis(omeg a-hydroxyalkyl)pyromellitdiimide and/or 6,6'-(4,4'-biphenylylenedioxy) dihexanol with hexamethylene bis(phenylcarbonate). The monomers, dihyd roxyalkyl derivatives of pyromellitdiimide. were obtained by deacetyla tion of the intermediate diacetylated compounds with p-toluenesulfonic acid. The intermediates were synthesized by condensation of pyromelli tic dianhydride (PMDA) with omega-aminoalcohols followed by cyclizatio n with acetic anhydride. Most of the poly(imide-carbonate)s obtained i n high yields have high molecular weights and show very good solubilit ies in organic solvents. The structures of the resulting polymers were confirmed by FT/IR and NMR spectroscopy measurements and elemental an alyses. Thermotropic LC properties of the polymers were evaluated by d ifferential scanning calorimetry (DSC), polarizing microscopy and powd er X-ray analyses. These measurements suggested that only biphenyl uni t-rich copolymers and polymers with shorter spacers next to the imide ring, which favor the orientation of the imide ring and the polymer ch ains, form nematic LC mesophases. The glass transition temperatures (T (g)) and the LC phase transition temperatures tend to decrease with in creasing imide-neighboring aliphatic spacer lengths.