热固性塑料因其优点如高稳定性和耐化学性而众所周知。然而,开发具有可降解性和可回收性的可持续热固性塑料面临着几个主要挑战,包括协调服务期间所需的特性与使用寿命结束时所需的回收和再处理特性,建立大规模合成的有效方法,并与当前的制造工艺保持一致。这里提出了一种通用策略,用于在温和条件下利用具有双因素控制的可逆性的动态前体进行热固性塑料的按需降解和回收。具体来说,动态三嗪交联剂通过动态亲核芳族取代(SNAr)引入到用于聚氨酯(PU)合成的前体多元醇中。除去催化剂和醇后,SNAr的可逆性被停用,允许使用标准的PU聚合技术,如注塑成型,铸造,和泡沫。所得的氰尿酸酯交联的PU保持了传统交联PU的高稳定性和多样化的机械性能,然而,通过在特定但温和的条件下激活SNAr的可逆性,提供易于按需解聚的优点,酒精,温和的热量。设想这种方法,涉及预先安装双因素控制的动态交联剂,可广泛应用于目前的热固性塑料制造工艺,引入增强的可持续性。
Thermosets are well known for their advantages such as high stability and chemical resistance. However, developing sustainable thermosets with degradability and recyclability faces several principal challenges, including reconciling the desired characteristics during service with the recycling and reprocessing properties required at the end of life, establishing efficient methods for large-scale synthesis, and aligning with current manufacturing process. Here a general strategy is presented for the on-demand degradation and recycling of thermosets under mild conditions utilizing dynamic precursors with dual-factor-controlled reversibility. Specifically, dynamic triazine crosslinkers are introduced through dynamic nucleophilic aromatic substitution (SNAr) into the precursor polyols used in polyurethane (PU) synthesis. Upon removal of the catalyst and alcohol, the reversibility of SNAr is deactivated, allowing for the use of standard PU polymerization techniques such as injection molding, casting, and foaming. The resulting cyanurate-crosslinked PUs maintain high stability and diverse mechanical properties of traditional crosslinked PUs, yet offer the advantage of easy on-demand depolymerization for recycling by activating the reversibility of SNAr under specific but mild conditions-a combination of base, alcohol, and mild heat. It is envisioned that this approach, involving the pre-installation of dual-factor-controlled dynamic crosslinkers, can be broadly applied to current thermosetting plastic manufacturing processes, introducing enhanced sustainability.