Synthesis of highly thermally stable divanillic acid-derived polyamides and their mechanical properties

Divanillic acid (DVA)-based monomers with different side-chains (R = -(CH2)n-1-CH3, n = 1, 4, 8) were synthesized from methyl vanillate. Polycondensation of these monomers with various aromatic diamines yielded a series of aromatic biomass-based polyamides with weight-average molecular weights (Mw) ranging from 50,000 to 110,000 g/mol. Thermogravimetric analysis (TGA) of the polyamides found decomposition temperatures ranging from 378 to 420 degrees C. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed an amorphous structure. The polyamides with methyl or butyl side chains exhibited a glass transition temperature (Tg) of 221-322 degrees C, which indicated high heat resistance and thermal stability, while the Tgs of the polyamides with octyl side chains were about 180 degrees C. The DVA polyamides showed good solubility in common polar organic solvents; their cast films were prepared from dimethylformamide (DMF) solution. Thermo-pressed films of some polyamides were prepared at temperatures over the Tg, revealing maximum tensile strengths of about 63 MPa.

Automated summary

A series of aromatic biomass-based polyamides were synthesized with high molecular weights, excellent heat resistance, and thermal stability. These polyamides showed good solubility in organic solvents and could be used to prepare high-strength cast films.