Synthesis and properties of semi-crystalline poly(decamethylene terephthalamide) thermosets from reactive side-group copolyamides

We have prepared semi-crystalline polyamide (PA) thermosets using reactive side-group functionalized copolyamides as precursors. Reactive meta- and para-based phenylethynyl diacid chlorides (IPE and TPE) were synthesized and incorporated in poly(decamethylene terephthalamide) (PA 10T) using a low temperature solution polymerization method. The phenylethynyl-based comonomers disrupt crystallization of the final copolyamides and lower the onset of melting. Copolyamides containing 5, 10 and 15 mol% of the reactive comonomer could be cured at 350 °C into freestanding PA thermoset films. All thermoset films are stable up to 400 °C, as confirmed by DMTA, which is the result of network formation. The thermosets exhibit both a crystalline phase and a crosslinked amorphous phase. Depending on the concentration of the side-groups, the degree of crystallinity of the final thermosets can be controlled and suppressed by 52–76% compared to the PA 10T reference polymer. Most notable is the fact that the IPE-15 thermoset film exhibits outstanding stress–strain behavior, i.e. elongation at break (∼17%) and toughness (766 MJ·m⁻³).