Qin K Peter, Herzog-Arbeitman Abraham, Zou Weizhong, Chakraborty Saswata, Kristufek Samantha L, Husted Keith E L, Joly Guy D, Craig Stephen L, Olsen Bradley D, Johnson Jeremiah A
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
Department of Chemical, Biological and Materials Engineering, University of South Florida, 4202 E. Fowler Ave, Tampa, FL, 33620, USA.
Adv Mater. 2024 Nov;36(44):e2406600. doi: 10.1002/adma.202406600. Epub 2024 Sep 11.
Thermoset toughness and deconstructability are often opposing features; simultaneously improving both without sacrificing other mechanical properties (e.g., stiffness and tensile strength) is difficult, but, if achieved, could enhance the usage lifetime and end-of-life options for these materials. Here, a strategy that addresses this challenge in the context of photopolymer resins commonly used for 3D printing of glassy, acrylic thermosets is introduced. It is shown that incorporating bis-acrylate "transferinkers," which are cross-linkers capable of undergoing degenerative chain transfer and new strand growth, as additives (5-25 mol%) into homemade or commercially available photopolymer resins leads to photopolymer thermosets with substantially improved tensile toughness and triggered chemical deconstructability with minimal impacts on Young's moduli, tensile strengths, and glass transition temperatures. These properties result from a transferinker-driven topological transition in network structure from the densely cross-linked long, heterogeneous primary strands of traditional photopolymer networks to more uniform, star-like networks with few dangling ends; the latter structure more effectively bear stress yet is also more easily depercolated via solvolysis. Thus, transferinkers represent a simple and effective strategy for improving the mechanical properties of photopolymer thermosets and providing a mechanism for their triggered deconstructability.
热固性材料的韧性和解聚性通常是相互对立的特性；在不牺牲其他机械性能（如刚度和拉伸强度）的情况下同时提高这两者是困难的，但是，如果能够实现，则可以延长这些材料的使用寿命并增加其报废处理的选择。在此，我们介绍一种策略，该策略在常用于玻璃状丙烯酸热固性材料3D打印的光聚合树脂背景下应对这一挑战。结果表明，将双丙烯酸酯“转移交联剂”（一种能够进行退化链转移和新链生长的交联剂）作为添加剂（5-25摩尔%）加入自制或市售的光聚合树脂中，可得到拉伸韧性显著提高且具有触发化学解聚性的光聚合热固性材料，同时对杨氏模量、拉伸强度和玻璃化转变温度的影响最小。这些性能源于转移交联剂驱动的网络结构拓扑转变，从传统光聚合网络中密集交联的长而不均匀的初级链转变为更均匀、几乎没有悬垂端的星形网络；后一种结构能更有效地承受应力，但也更容易通过溶剂解作用发生去渗透。因此，转移交联剂是一种改善光聚合热固性材料机械性能并为其触发解聚提供机制的简单有效策略。
