Sustainable thermoplastic elastomers with a transient network

[Display omitted] •Fatty acid-based triblock copolymers with a transient network were synthesized.•Acrylamide, a hydrogen bonding comonomer, was copolymerized into the midblock.•Mechanical properties were significantly improved due to the transient network.•Order-disorder transition temperature decreased, providing enhanced processability.•Negligible impact of acrylamide comonomer on triblock copolymer morphology. Vegetable oils and their fatty acids are convenient sources for polymers due to their wide availability, ease of functionalization, and lack of toxicity; however, the long alkyl chains of the fatty acids have a large impact on the resulting polymer properties. Polymers with bulky constituents, such as the long alkyl side-chains of fatty acid-derived polymers, typically exhibit poor mechanical performance due to lack of entanglements. In this study, hydrogen bonding moieties were incorporated into the fatty acid-based midblock of a thermoplastic elastomeric triblock copolymer as a means to improve its mechanical behavior. Poly(styrene-b-(lauryl acrylate-co-acrylamide)-b-styrene), containing lauryl acrylate (a derivative of lauric acid) and the hydrogen bonding comonomer acrylamide in the midblock, was synthesized via reversible addition-fragmentation chain transfer polymerization. The chemical and physical properties of triblock copolymers of varying composition were explored. Quantitative FTIR analysis confirmed the formation of a transient network, which exhibited a reduction in crosslink density with increasing temperature, beneficial for high temperature melt processing. The triblock copolymers exhibited spherical morphologies lacking long-range order at room temperature, which were unaffected by the presence of acrylamide. Moreover, the order-disorder transition temperature reduced with increasing acrylamide content, due to a reduction in the Flory-Huggins interaction parameter. Importantly, incorporation of acrylamide into the midblock greatly improved both the tensile strength and strain at break. Incorporation of a transient network into the midblock is therefore an effective method of improving the mechanical properties of triblock copolymer-based thermoplastic elastomers containing bulky constituents.