LC polyimides. XXI. Thermotropic poly(amide‐imide)s based on trimellitimides

Polycondensation of α, ω‐bis(‐4‐aminophenoxy) alkanes with trimellitic anhydride chloride (TMA‐Cl) in m‐cresol yielded a new class of poly(amideimide)s. Starting from the same diamine spacers poly(amideimides) with a more regular sequence of amide and imide groups were prepared by another synthetic method. All these poly(amide‐imide)s are semi‐crystalline and melt in the range of 250–300°C. They form a smectic‐A phase over a narrow temperature range and suffer thermal degradation at the isotropization temperature (330–350°C). The smectic‐A phase was characterized by optical microscopy (“batonnet texture”) and by synchrotron radiation measurements conducted at a heating rate of 20°C. Furthermore, it is demonstrated that slight variation of the chemical structure, such as methyl substituents or meta positions in the spacer prevent the formation of a LC phase.