Synthesis and properties of novel poly(ester-amide-imide)s containing pendant phthalimide substituents

Two series of novel poly(ester-amide-imide)s (PEsAIs) with pendant phthalimide side group were synthesized by copolymerization of phthalimide-hydroquinone bis(trimellitate anhydride) (PI-TAHQ), p-phthaloyl chloride (TPC) and other fluorinated monomers using the two-step method. These PEsAIs had glass transition temperatures (T_gs) in the range of 228 °C–296°C and coefficients of thermal expansion (CTEs) of 18–55 ppm·K⁻¹. These films had good mechanical properties with tensile modulus of 3.7–5.7 GPa, tensile strengths of 92–153 MPa and elongations at break of 2.2%–8.3%. All films displayed good transparency with transmittances at 400 nm (T_400nm) of 43%–79% and transmittances at 850 nm (T_850nm) exceeding 89%, and these PEsAIs were amorphous. Especially, PEsAI-d-60 presented the best comprehensive performance with T_g of 296°C, low CTE of 18 ppm·K⁻¹ and high transmittance (T_400nm of 79%, T_850nm of 91%), which exhibited the potential of this novel poly(ester-amide-imide) containing pendant phthalimide substituent in optical transparent materials.