Shape Memory Polyurethane Composite With Fast Response to Near-Infrared Light Based on Tannic Acid-Iron and Dynamic Phenol-Carbamate Network.

Intelligent materials derived from green and renewable bio-based materials garner widespread attention recently. Herein, shape memory polyurethane composite (PUTA/Fe) with fast response to near-infrared (NIR) light is successfully prepared by introducing Fe3+ into the tannic acid-based polyurethane (PUTA) matrix through coordination between Fe3+ and tannic acid. The results show that the excellent NIR light response ability is due to the even distribution of Fe3+ filler with good photo-thermal conversion ability. With the increase of Fe3+ content, the NIR light response shape recovery rate of PUTA/Fe composite films is significantly improved, and the shape recovery time is reduced from over 60 s to 40 s. In addition, the mechanical properties of PUTA/Fe composite film are also improved. Importantly, owing to the dynamic phenol-carbamate network within the polymer matrix, the PUTA/Fe composite film can reshape its permanent shape through topological rearrangement and show its good NIR light response shape memory performance. Therefore, PUTA/Fe composites with high content of bio-based material (TA content of 15.1-19.4%) demonstrate the shape memory characteristics of fast response to NIR light; so, it will have great potential in the application of new intelligent materials including efficient and environmentally friendly smart photothermal responder.

Construction of layered double hydroxide-modified silica integrated multilayer shell phase change capsule with flame retardancy and highly efficient thermoregulation performance.

Current energy problems have driven the development of thermal storage technology based on phase change materials (PCMs). However, the leakage and flammability of organic PCMs appeared as troublesome agendas that deserve attention. In this article, the strategy of constructing phase change capsules with paraffin wax (PW) core and multilayer shell was proposed aiming to address the above issues. For the integrated multi-layer shell, silica (SiO2) acts as initial layer to encapsulate the PW core, and then tannic acid (TA) was creatively taken to bridge the subsequent flame retardant layered double hydroxides (LDH) layer on the surface of the silica shell, and polyvinyl alcohol (PVA) layer was further introduced to improve the compatibility of phase change capsules with polymer matrix. Characterization of chemical structure and morphology confirmed that phase change capsules with LDH modified silica multilayer shell (M-EPCMs) was successfully prepared. The results indicated that M-EPCMs, particularly the representative M-EPCM-5, possessed outstanding thermal stability, excellent leak proofness, good thermal regulation performance as well as long-term cycling stability. Importantly, M-EPCM-5 with the thickest LDH layer can self-extinguish when exposed to fire, and especially can keep the integrity of its shell without breakage after being heated at high temperature. Furthermore, the silicone rubber foam (SRF) composite containing M-EPCM-5 can reach UL-94V-1 level, indicating the flame retardancy of SRF matrix was improved significantly. The possible flame retardant mechanism revels that LDH can not only accelerate the formation of dense ceramic protective layer in condensed phase, but also release non-combustible gases (H2O, CO2) in gas phase, thus improving the fire retardancy of M-EPCMs. Therefore, the construction strategy proposed in this article represents a powerful means to improve flame retardancy and prevent leakage of phase change capsules at the same time, which will greatly expand the application scope of PCMs.