Partially bio‐based poly(amide imide)s by polycondensation of aromatic diacylhydrazides based on lignin‐derived phenolic acids and aromatic dianhydrides: Synthesis, characterization, and computational studies

Abstract

ABSTRACTTwo new bio‐based diacylhydrazide monomers, namely, 4,4′‐(propane‐1,3‐diylbis(oxy))bis(3‐methoxybenzohydrazide) and 4,4′‐(propane‐1,3‐diylbis(oxy))bis(3,5‐dimethoxybenzohydrazide) were synthesized starting from lignin‐derived phenolic acids, namely, vanillic acid and syringic acid. A series of poly(amide imide)s was synthesized by polycondensation of these diacylhydrazide monomers with commercially available aromatic dianhydrides. Poly(amide imide)s showed inherent viscosity in the range 0.44–0.56 dL g−1 and exhibited good solubility in organic solvents. Poly(amide imide)s could be cast into transparent, flexible, and tough films from their N,N‐dimethylacetamide solutions. Poly(amide imide)s showed 10% weight loss in the temperature range 340–364 °C indicating their good thermal stability. Glass transition temperature (Tg) of poly(amide imides)s were measured by DSC and DMA which were in the range 201–223 °C and 214–248 °C, respectively. The Tg values of poly(amide imide)s were dependent on the number methoxy substituents on aromatic rings of diacylhydrazide monomers. Molecular dynamics simulation studies revealed that chain rigidity is the dominant factor for observed trends in Tg. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3636–3645