Sandwiched film with reversibly switchable transparency through cyclic melting-crystallization

Polymer functional films (PFFs) with switchable transparency have drawn increasing interests recently for their promising applications. Unfortunately, it still remains a challenge to fabricate large-area temperature-driven PFFs by a facile, continuous and environmentally friendly method. Herein, via coextrusion blow film molding, sandwiched polymer functional films (SPFFs) were massively fabricated, whose skin and core layer are respectively low density polyethylene (LDPE) and polyethylene oxide (PEO) phase. Moreover, such SPFFs show wide range of reversibly switchable transparency and rapid response to varied temperatures during cyclic melting crystallization process. In view of this, the as-prepared SPFFs can be used for thermo-photo door in photo catalytic reaction system and serve as smart windows. This work proposes a facile, cost-efficient and environmentally-friendly method for developing low-cost, durable and large-area SPFFs, and first builds the relationship between crystallization performance and functional application in industrial product, providing a new pathway to build the functional architecture based on the concept of polymer structuring processing.

Automated summary

Polymer functional films (PFFs) with switchable transparency have attracted increasing attention recently. However, it has been challenging to fabricate large-area temperature-driven PFFs using a simple, continuous, and environmentally friendly method. In this study, sandwiched polymer functional films (SPFFs) were mass produced using coextrusion blow film molding. The SPFFs consist of a low density polyethylene (LDPE) skin layer and a polyethylene oxide (PEO) core layer. These SPFFs exhibit a wide range of reversibly switchable transparency and rapid response to temperature changes, making them suitable for applications in thermo-photo doors and smart windows. This work presents a facile, cost-effective, and environmentally friendly method for developing low-cost, durable, and large-area SPFFs, and establishes the link between crystallization performance and functional applications in industrial products.