Synthesis and characterization of semi-crystalline poly(decamethylene terephthalamide) thermosets

We have explored the synthesis of semi-crystalline polyamide (PA) thermosets via a reactive PA oligomer precursor route. Poly(decamethylene terephthalamide) (PA 10T) oligomers with a target M_n of 1 K and 3 K g·mol⁻¹ were synthesized via solution polymerization and end-capped with reactive phenylethynyl (PE) groups. The reactive oligomers could be cured in a stepwise manner using successive high temperature treatment steps. Depending on the concentration of PE end-groups, the degree of crystallinity of the final thermosets can be controlled and depressed by 60% for the crosslinked 3 K precursor and completely eliminated for the crosslinked 1 K precursor. From the calculated molecular weight between crosslinks, we estimated that 35–41% of the PE end-groups form crosslinking functionalities and the remainder of the PE end-groups contribute to chain extension. All thermoset films are stable up to ∼400 °C in DMTA experiments due to network formation, effectively increase the maximum use temperature of PA 10T by 100 °C.