Reversible Shape-Color Synchronous Dual-Response Flexible Poly(vinyl chloride)-Based Composite Film via Star-Shaped Diacetylene-Modified Poly(ε-caprolactone)

Shape-color dual-responsive polymers triggered by thermal stimuli have garnered significant attention due to their potential to impart a variety of functionalities within a single material. Nevertheless, developing a nontoxic and durable color-shape dual-responsive polymer system through a cost-effective and feasible strategy remained a challenge. In this study, a star-shaped poly(ε-caprolactone) modified by diacetylene (s-DA-PCL31) was synthesized and blended with poly(vinyl chloride) (PVC) via solution casting followed by in situ photopolymerization, resulting in a nontoxic, reversible shape-color dual-responsive flexible PVC-based composite film. The s-PDA-PCL31@PVC composite film exhibited enhanced mechanical properties, including an elongation at break of approximately 447.1% and toughness of 67.1 MJ/m3, which were ∼94 and ∼60 times greater than those of pure PVC, respectively. Furthermore, the composite film demonstrated excellent durability, with only ∼10.1% volatility and ∼2.0% degree of migration. The PVC-based composite film also displayed shape-memory properties, which can be attributed to the formation of stable physical cross-links through hydrogen bonding interactions and chain entanglements. Due to the feasible conformational transition of PDA enabled by the star-shaped PCL with symmetrical chains, the composite film exhibited reversible thermochromism, with an obvious color transition from blue–purple–red–purple–blue with a temperature cycle from 25–80–120–80–25 °C. More importantly, by fine-tuning the appropriate shape transfer temperature (Ttr), the composite exhibited both shape recovery and color change in response to thermal stimuli within a temperature range of 0 to 80 °C. This dual-responsive smart material demonstrated great potential for a variety of applications, including camouflage, anti-counterfeiting, and temperature monitoring.