Photopolymerization of Zeolite/Polymer-Based Composites: toward 3D and 4D Printing Applications

In recent years, photopolymerization has found wide applications in industry and daily life, especially 3D printing. However, some defective properties of photopolymers limit their development, such as their mechanical properties, density, compressive strength, and functionality. Herein, in this work, we reported the fabrication of composites containing seven different kinds of zeolites used as fillers under mild photopolymerization conditions (LTA-5A was selected as the benchmark zeolite), that is, visible LED light irradiation at room temperature under air. The filler properties affecting the related depth of cure and the enhanced mechanical (the storage modulus increased by 10-fold compared to that of a pure polymer) and functional properties were examined in detail. In addition, the production of 3D patterns was performed through direct laser writing (DLW) as a lithography technique. As a real breakthrough, the 3D printing of zeolite/polymer composites is presented here for the first time with high filler contents (up to 75 wt %) using this stereolithography approach. 4D behavior can be established in the presence of water, that is, the 3D object can change the shape and return to the starting geometry after desiccation. Remarkably, after debinding of the composites by thermal treatment, a high zeolite porosity can be regenerated. Therefore, the 3D printing of zeolites is possible in two steps: (i) photopolymerization of organic/zeolite composites to generate the desired shape, followed by (ii) removal of the organic part by thermal treatment. This work is expected to lead to valuable developments in the field of photopolymerization reactions in highly filled composites (with the filler content exceeding 50 wt %) and thereby expand their potential application for 3D or 4D printing in the fields of, for example, high-performance light-weight materials and adsorption.