Temperature-sensitive shape memory polyamide elastomers with tunable segments: achieving excellent performances and application prospects

Abstract

Thermoplastic polyamide elastomers (TPAEs) possess remarkable characteristics such as high-temperature tolerance, superior mechanical properties, and the shape memory effect (SME). The current study develops a type of TPAE with SME by fabricating the long carbon chain polyamide (PA512) and polyethylene glycol (PEG) through a two-step melt polycondensation process. The properties of TPAEs were investigated by varying the PA512 prepolymer’s molecular weight and the amount of PEG. During synthesizing TPAEs with SME, the crucial balance of COOH and OH groups was skillfully achieved by introducing biobased butanediol (BDO). The chemical structure of TPAEs is confirmed by FTIR and ¹H NMR tests. By meticulously engineering the PA512 molecular weight and refining the PEG domain content, TPAEs are fabricated to elongate at a break of 592.4% at room temperature while maintaining a tensile strength of 23.1 MPa. TPAEs, which have two distinct melting temperatures, exhibit microphase separation between the PEG and PA512 domains. This phenomenon is further corroborated by the scanning electron microscope (SEM) test. Additionally, TPAEs exhibit the SME, which can fix a temporary shape when heated, twisted, and cooled, and then recover to its original shape upon reheating, with TPAE230 demonstrating the most outstanding shape memory effect, achieving an average shape fixity ratio of 91.2% and a shape recovery ratio of 94.4%. This behavior is attributed to the fixing force provided by the PEG domains and the entropy elasticity of the physically cross-linked PA512 domains. The findings indicate that TPAEs exhibit enhanced SME in response to temperature changes. Leveraging this property, developing a temperature-sensitive device holds promise for breakthroughs in elastic temperature sensing applications.