Synthesis of fully divanillic acid-based aromatic polyamides and their thermal and mechanical properties

Fully divanillic acid (DVA)-based aromatic polyamides (R-R′-DVAPAs) having methyl or butyl side chains (R = -(CH2)n-1-CH3; n = 1 or 4) with weight-average molecular weights ranging from 49,000 to 60,000 g mol−1 were synthesized by polycondensation of alkylated DVA-based dicarboxylic acid monomers and diamine monomers. Thermogravimetric analysis of the polyamides found decomposition temperatures at approximately 380 °C and glass transition temperatures of 207 °C–262 °C, depending on the side-chain length, indicating high heat resistance and thermal stability. Differential scanning calorimetry and dynamic mechanical analysis revealed an amorphous structure for the DVAPAs. The DVAPAs showed good solubility in common polar organic solvents, although cast films prepared from dimethylformamide solution were brittle. Thermo-pressed films were prepared at temperatures higher than the glass transition temperature. The film of Bu-Bu′-DVAPA, which has butyl side chains along the fully aromatic main chain, exhibited a maximum tensile strength of approximately 40 MPa. These polyamides are promising as fully bio-based aromatic high-performance plastics.