4D Printing of a Fully Biobased Shape Memory Copolyester via a UV-Assisted FDM Strategy

The emergence of 4D-printing technology provides a new opportunity for the development of shape memory polymers (SMPs) with sophisticated or individualized architectures in the most material-saving way. Fused deposition modeling (FDM) has been regarded as a feasible and facile printing technology to print thermoplastics, but the low adhesion between interlayers of the obtained objects is an unavoidable problem caused by its printing principle. Fortunately, abundant biobased chemicals with a variety of reactive groups make it easy to design ecofriendly linear SMPs with active sites, which are ready for in situ reactions during FDM printing. Herein, we developed fully biobased shape memory copolyesters (PBSe-co-PBIs) by polycondensation of dimethyl itaconate, dimethyl sebacate, and 1,4-butanediol. The flexible and crystalline PBSe may serve as a molecular switch to ensure the desirable shape memory effect (SME) of the materials, and the PBI moiety with double bonds forming cross-linking points between layers during the printing process under UV irradiation acts as net points for SMPs and enhances interlayer adhesion. The shape memory performance and the enhanced interlayer adhesion of printed materials by this strategy were verified by DMA analysis and tensile tests. Finally, a 4D-printed "Sanxingdui bronze mask" and an overheating protection cover were demonstrated, which indicated a great potential in high-temperature protection devices.