新型3D打印光敏树脂：光-热双固化的多嵌段苯并噁嗪树脂的合成与性能研究

Photosensitive resins with high performance and multifunction become more and more critical in photosensitive resins based 3D printing technology. 3D printed parts were actually built by 2D printing over and over again during the manufacture. This layer-by-layer process leads to defects in mechanical properties on the interfaces between two layers. Therefore, 3D printed materials often exhibit variable strength and mechanical properties depending on the direction in which they were printed. In this project, we will develop a new type of resin, which is benzoxazine with both photo curable and thermally curable groups. This new resin will be used to divide the 3D printing process into two parts, including a shaping process in which the photo curable groups play a part and a strengthening process where thermally curable groups come into play. This design will help to eliminate the mechanical defects on parts during the strengthening process. The resin will be designed with multiblock structure and amphipathicity, so that the cured resin can adsorb water and swell to hydrogel when soaking in aqueous solution. Benefited from this advantage, through adjusting structure parameters of this resin, we will fabricate hydrogel material with high precision and quality using 3D printing technology, to find applications such as in shape memory materials and implant materials. In addition, the proposed resin has good compatibility and strong interaction with graphene nanosheets. It will be further utilized to print graphene nanocomposites parts, aiming to improve parts properties, including mechanical properties, electrical conductivity and thermal conductivity. The implementation of this project will be useful for developing advanced 3D print resin with high quality and multi-functionalization, hence to promote the development of 3D printing technology and applications.

高性能及多功能化是光固化3D打印树脂研究的前沿方向。光固化3D打印技术通过逐层增加材料完成制品的制造，其制品的层间力学强度相比层内要弱，从而形成层间力学缺陷。本项目提出使用光-热双固化功能的苯并噁嗪树脂用于3D打印，旨在将其中的成型与强化过程分开，其中光固化基团用于成型过程，并在期间保留热固化基团，从而促使在后期热固化过程中消除制件层间的力学缺陷。同时，该树脂被设计成多嵌段结构且具有两亲性，发生交联后能够在溶液中溶胀形成凝胶。因此本项目还将通过调节树脂结构参数控制其交联密度，实现高精度和高性能水凝胶的3D打印。另外，利用该树脂与石墨烯纳米片之间良好的相容性及较强的相互作用力，本项目还将进行高性能石墨烯复合材料的3D打印，旨在增强制件的性能，包括力学强度、导电、导热性能等。本项目的实施将为高性能及多功能的新型3D打印树脂的开发提供新的思路，从而推动3D打印技术的进一步发展和应用。

基于光敏树脂的3D打印成型方法具有众多突出的优势。然而在树脂的逐层光固化过程中，由于层间缺乏足够的化学交联，会导致显著的层间力学缺陷，影响制件性能。在本项目的资助下，我们设计并合成了具有光和热双重固化功能的树脂，其中光固化过程用于成型并在期间保留热固化基团，并经过随后的热固化过程用于增强材料性能。具体如下：对含二苄叉丙酮和查尔酮的双酚化合物的合成方法及工艺进行深入研究，实现了该类化合物的高效合成；合成以二苄叉丙酮和查尔酮作为光固化基团的光-热双重固化功能的苯并噁嗪树脂，然后将其作为功能性的表面活性剂用于辅助石墨烯在水相中的超声剥离，在此基础上制备了石墨烯复合薄膜，再利用树脂的光固化性质对石墨烯薄膜进行图案化以及通过双重固化后实现薄膜力学和电学性能的提升；设计并合成了以甲基丙烯酸酯为光固化基团的光-热双重固化功能的苯并噁嗪树脂，并通过优化其合成工艺实现对树脂粘度和光敏性的调控，基于此证实具有热固化基团的光敏树脂在逐层光固化成型后的层间力学缺陷可以得到有效改善。此外，项目负责人还利用合成的光-热双固化树脂作为界面粘附层，用于电极材料在石英晶体微天平芯片上的稳定粘附，实现储能器件充放电过程中离子在电极上吸附和脱出的实时表征。本项目的实施，为解决光敏树脂3D打印制件的层间力学缺陷提供了实验依据，并为光敏树脂的高性能化和多功能化提供了研究思路。