Polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA) blend films were prepared using biaxial stretching. The effects of PMMA content and stretching ratio on the crystallinity and β phase fraction of PVDF in blend films were investigated. The distributions of crystallinity and β phase fraction on variable locations were also studied. The results of FTIR and XRD showed that β phase appeared in PVDF/PMMA blends after extrusion and casting procedures. Although β phase fraction decreased after preheating, there was still an increasing trend during following biaxial stretching. More importantly, the increase in PMMA content improved β phase fraction, and the highest β phase fraction of 93% was achieved at PMMA content of 30 wt% and stretching ratio of 2×2. Besides, the reduction in PMMA content and the increase in stretching ratio improved the crystallinity of PVDF. The mechanical properties of the stretched films were significantly improved by increasing the stretching ratio as well. The uniform stress distribution on different regions of biaxial stretching films contributed to the uniform distribution of β phase fraction and crystallinity of PVDF with the aid of simulation. This work confirmed that biaxial stretching can be a candidate method to prepare PVDF/PMMA blend films with uniform distributions of comparable β phase and crystallinity of PVDF.

Two issues are required to be solved to bring intrinsically self-healing polymer coatings into real applications: remote activation and satisfied practical properties. Here, we used MXene, a newly reported two-dimensional material, to provide an epoxy coating with light-induced self-healing capabilities and we worked to enhance the properties of that coating. The self-healing coatings had a reversible crosslinking network based on the Diels-Alder reaction among maleimide groups from bis(4-maleimidopheny)methane and dangling furan groups in oligomers that were prepared through the condensation polymerization of diglycidylether of bisphenol A and furfurylamine. The results showed that the delaminated MXene flakes were small in size, around 900 nm, and dispersed well in self-healing coatings. The MXene flakes of only 2.80 wt % improved greatly the pencil hardness of the coating hardness from HB to 5H and the polarization resistance from 4.3 to 428.3 MΩ cm⁻². The self-healing behavior, however, was retarded by MXene flakes. Leveling agent acted a key part here to facilitate the gap closure driven by reverse plasticity to compensate for the limitation of macromolecular mobility resulting from the MXene flakes. The self-healing of coatings was achieved in 30 s by thermal treatment at 150 °C. The efficient self-healing was also demonstrated based on the recovery of the anti-corrosion capability. MXene flakes also played an evident photothermal role in generating heat via irradiation of near-infrared light at 808 nm and focused sunlight. The healing can be quickly obtained in 10 s under irradiation of near-infrared light at 808 nm having a power density of 6.28 W cm⁻² or in 10 min under irradiation of focused sunlight having a power density of 4.0 W cm⁻².

Shape‐memory polymers (SMPs) are smart materials that change shape when exposed to stimuli and have various applications in different fields due to their unique properties. Light, as a kind of electromagnetic radiation, plays an important role in understanding the structure‐property relations of SMPs, preparing original shapes, using them as non‐contact stimuli sources, and tuning the optical properties of SMPs. This review provides a comprehensive review of the involvement of light in structure‐preparation‐stimuli‐application of SMPs. The review is divided into four sections. First, applications of optical/spectroscopic approaches that provide information for understanding structure‐property relations in SMPs, especially during programming and recovery. Second, describes how to build SMPs with light, including different photochemical reactions and 3D photocuring technologies. Third, discusses how light is used to trigger the shape change of SMPs through both photochemical and photothermal mechanisms. Last, focuses on how to take advantage of the shape‐memory effect to tune the optical characteristics of polymers, including various structures of SMP color‐changing materials and their synthetic strategies. Future research could focus on developing efficient photothermal fillers, new 3D printing techniques for SMPs, exploring their use in biomedical and wearable devices, and optimizing SMPs for industrial applications.

The thermally-induced self-healing behavior of polymer coatings consists of two steps, i.e., gap closure and crack repair. In addition, the polymer coatings with thermally-induced self-healing capability are expected to show satisfied properties to ensure the application. Here, four epoxy coatings with dense irreversible Network I, dense reversible Network II based on a Diels–Alder (DA) reaction, loose irreversible Network III, as well as partially irreversible and partially reversible Network IV were prepared, respectively. The dense irreversible Network I showed an evident gap closure upon heating, while the crack still existed at the high temperature. The dense reversible Network II presented good self-healing upon direct heating at a high temperature of 150 °C, leading to the quick gap closure in 40 s and subsequent crack disappearance in 80 s. The loose irreversible Network III showed negligible crack variations upon heating, while the partially reversible and partially irreversible Network IV showed quick gap closure as well but only partial crack disappearance. Besides, the coating with the reversible Network II based on the DA reaction not only presented good self-healing capability but also possessed the satisfied mechanical properties and the best electrochemical corrosion property, ensuring its further exploitation and potential practical applications.