Thermoplastic elastomers (TPEs) are widely used in electronics, clothing, adhesives and automotive components due to their high processability and flexibility. ABA triblock copolymers, in which A represents glassy endblocks and B the rubbery midblock, are commercially available TPEs. The most commonly used triblock copolymer TPEs contain glassy polystyrene endblocks and rubbery polydiene midblocks. However, commercial TPEs are derived from petroleum. The manufacturing and disposal of petroleum-derived products have undesired environmental impacts, which promotes development of TPEs from sustainable sources. Vegetable oils and their fatty acid derivatives are attractive alternatives to petroleum due to their abundancy and low cost. Our group has previously reported replacing polydienes in commercial TPEs with sustainable polyacrylates derived from fatty acids. However, 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 the rubbery matrix. To improve the mechanical properties, a transient network was incorporated into the fatty-acid derived midblock through hydrogen bonding. Specifically, triblock copolymers containing polystyrene endblocks and a midblock composed of a random copolymer of poly(lauryl acrylate) (derived from lauric acid) and acrylamide (which undergoes hydrogen bonding) were synthesized. Quantitative FTIR analysis confirmed the formation of a transient network. The polymers exhibits disordered spherical morphologies, desirable for application as TPEs. Rheological measurement revealed the order-disorder transition temperature reduced with increasing acrylamide content, beneficial for high temperature melting process. Importantly, triblock copolymers with hydrogen bonding in the matrix exhibited significantly higher modulus, strain at break, and tensile strength as compared to comparable polymers in the absence of hydrogen bonding.

Improving mechanical properties of fatty acid-derived thermoplastic elastomers by incorporating a transient network

2019 Spring National Meeting

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