Di Wu,Ying-Mei Leng,Cheng-Jie Fan,Zhi-Yuan Xu,Lu Li,Ling-Ying Shi,Ke-Ke Yang,Yu-Zhong Wang
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.
Chuan-Ying Cheng,Hui Xie,Zhi-yuan Xu,Lu Li,Mei-Na Jiang,Li Tang,Ke-Ke Yang,Yu-Zhong Wang
4D printing, as a booming additive manufacturing technology of smart material, provides a new opportunity for the development of shape memory polymers (SMPs). Meanwhile, the diversity of SMPs structure calls for flexible and well-adapted printing technology. Fused deposition modelling (FDM) is one of the most versatile and cost-effective methods owing to the simplicity of the technique and broad compatibility with a wide variety of materials, but it fails to deal with the fabrication of shape memory networks that possess excellent structural stability as well as shape memory effect (SME). Aiming to personalized or patient-adaptable treatment devices, in this work, we demonstrate a UV-assisted FDM 4D printing strategy to fabricate elbow protector models based on shape memory copolyester networks. First, the linear unsaturated copolyesters were synthesized, amongst, poly(lactic acid) was chosen as hard segment providing the material a good mechanical performance and printability, the poly(ε-caprolactone) with strong crystallizability was employed as switching segment, and a functional coupling agent contained double bonds was used to join the two segments and as the same time. This copolyester can be easily processed into filament, and the in-situ formation of photo-crosslinking network during the UV-assisted FDM printing not only enhances the bonding strength of each layer, but also may guarantee the obtained objects a good shape memory property. Three models with distinctly Chinese characteristics were printed to demonstrate excellent SME. Then, the elbow protectors both in personalized and patient-adaptable treatment strategies were developed, which indicates a great potential in robust applications.
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