Synthesis of polyamide-imides with different monomer sequence and effect on transparency and thermal properties

Abstract

Two novel series of polyamide-imides (PAIs) with different monomer sequence were prepared by two synthesis methods. First series of alternate polyamide-imides PAIs-2(a-e) were synthesized from polycondensation of diimide-diacids 1a-1c monomers with various aromatic diamines. Using the direct polycondensation of trimelletic acid chloride (TMAC) with aromatic diamines, second series of polyamide-imides PAIs-3(a-c) were prepared. The effect of monomer sequence on transparency and thermal properties of polymers is investigated. The transmittance at 550 nm (T550) from the ultraviolet–visible (UV–vis) spectra of the PAIs was found in the range of 74–87%, greatly affected by the monomer sequence in the polymer repeating units. PAI-3a from TMAC exhibited high transparency of 87% and low coefficient of thermal expansion (CTE) of 25 ppm/°C. All copolymers demonstrated good organosolubility and mechanical properties with initial moduli of 3.4–4.9 GPa, tensile strengths of 96–129 MPa and elongations at break of 3.0–5.2%. The glass transition temperatures (Tg) and 10% weight loss temperatures (T10%) of PAIs in nitrogen were in the range of 291–330 °C and 489–501 °C, respectively.