Cornellà Aleix Costa, Furia Francesca, Van Assche Guy, Brancart Joost
Physical Chemistry and Polymer Science (FYSC), Sustainable Materials Engineering (SUME), Vrije Universiteit Brussel, (VUB), Pleinlaan 2, Brussels, 1050, Belgium.
Adv Mater. 2024 Nov;36(46):e2407663. doi: 10.1002/adma.202407663. Epub 2024 Sep 27.
Dynamic polymer networks offer a promising solution to key challenges in polymers such as recyclability, processability, and damage repair. However, the trade-off between combining facile processability, fast self-healing, and high creep resistance remains a major obstacle to implementation. To overcome this, two very distinct dynamic covalent chemistries, Diels-Alder and transesterification, is combined in a single network. The resulting dual dynamic networks offer an unprecedented set of properties and control over the relaxation times. The system decouples the relaxation dynamics of the network from the spatial motifs, and the tuning of the ratio between chemistries enables to control of the relaxation dynamics over six orders of magnitude. Taking advantage of this control, the composition and rheological behavior is optimized to drastically improve the resolution for extrusion-based additive manufacturing of dynamic covalent networks. Additionally, two well-defined and separated stress relaxation peaks are observed at compositions close to 50% of each dynamic chemistry, accentuating the double character of the system's relaxation dynamics. This atypical situation, enables to preparation of self-healing materials with negligible creep, and with shape-memory properties solely leveraging the two distinct relaxation dynamics, instead of the glass transition temperature or the melting point.
动态聚合物网络为解决聚合物领域的关键挑战提供了一种很有前景的解决方案，比如可回收性、可加工性和损伤修复。然而，要同时兼顾简便的可加工性、快速的自我修复能力和高抗蠕变性，仍然是实施过程中的一个主要障碍。为了克服这一问题，两种截然不同的动态共价化学——狄尔斯-阿尔德反应和酯交换反应——被结合在一个单一网络中。由此产生的双动态网络展现出了前所未有的一系列特性，并能对弛豫时间进行控制。该系统将网络的弛豫动力学与空间基序解耦，通过调整化学组成之间的比例，可以在六个数量级范围内控制弛豫动力学。利用这种控制能力，对组成和流变行为进行了优化，以大幅提高基于挤出的动态共价网络增材制造的分辨率。此外，在每种动态化学组成接近50%时，观察到了两个明确且分离的应力松弛峰，突出了该系统弛豫动力学的双重特性。这种非典型情况使得制备出具有可忽略不计蠕变的自我修复材料成为可能，并且仅利用两种不同的弛豫动力学，而非玻璃化转变温度或熔点，就具备了形状记忆特性。
