Block Compositions and Microstructure-Macroproperty Regulation of Biobased Long Carbon-Chain Polyamide Elastomers

Long carbon-chain polyamide elastomers (LCPAEs), an emerging class of high-performance elastomers, have garnered widespread interest due to their excellent flexibility, exceptional low/high temperature resistance, and favorable physical and mechanical properties. In this work, we systematically investigated the influence of block compositions (relative content and molecular chain length of hard segment (HS) and soft segments (SS)) on the microstructural and macroscopic properties of the LCPAEs with gradient HS contents (ca. 20-70 wt.%) by various characterization techniques. The results show that increasing HS content generally leads to better crystallization ability, higher thermal stability, greater mechanical strength (reduced ductility), more pronounced microphase separation morphology, and varied shape memory effect. These findings highlight the feasibility of tailoring LCPAEs' chemical structures and properties through modulating the relative content of HS and SS precisely. More importantly, the quantitative correlations between the block compositions and mechanical properties of LCPAEs were established via using the average distance between adjacent HS domains (L) and the average constrained molecular weight between physical cross-linking junctions ( ${\overline{M}}_C$ ) as the bridge (the correlation coefficients R² of both L and ${\overline{M}}_C$ with tensile strength are greater than 0.99), which helps to guide the precise structural design and property directional control of high-performance LCPAEs.