Facile synthesis of polyamide 6 (PA6)-based thermoplastic elastomers with a well-defined microphase separation structure by melt polymerization

A facile “2-step” melt polymerization method with high efficiency, easy accessibility, little pollution and low cost was proposed to fabricate thermoplastic elastomers (TPAEs) composed of polyamide 6 (PA6) and poly(tetramethylene glycol) (PTMG). To elucidate the thermal properties of these TPAEs measured by differential scanning calorimetry (DSC), a three-phase system was represented: a “pure” PA6 crystalline phase, a phase-separated mesophase (soft phase domains embedded in a PA6 ordered phase matrix) and a mixed phase (PA6 disordered phase + soft segments). The X-ray technology, dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM) results offered further support to the morphological structural interpretation. The soft segment weight fraction in the mixed phase (WSS) was found to be equal to the overall soft segment weight concentration (CSS). The multiple melting transitions (TM and TMMT) occurring in these TPAEs were assigned to the disruption of the “pure” PA6 crystalline phase and the phase-separated mesophase, respectively. Additionally, the prepared TPAEs demonstrated better thermal and mechanical properties than PEBAX®, one of the commercial elastomers, presenting the potential to be widely used in various industrial fields.