Enhancing the toughness of composites via dynamic thiol–thioester exchange (TTE) at the resin–filler interface
Enhancing the toughness of composites via dynamic thiol–thioester exchange (TTE) at the resin–filler interface
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DOI：
10.1039/d0py00563k
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发表时间：
2020-07
影响因子：
4.6
通讯作者：
Nancy Sowan;Yinan Lu;Kevin J. Kolb;L. Cox;Rong Long;C. Bowman
中科院分区：
文献类型：
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作者：
Nancy Sowan;Yinan Lu;Kevin J. Kolb;L. Cox;Rong Long;C. Bowman
由于力学模量的不匹配，复合材料中组成材料之间的界面是应力集中导致裂纹形核的主要场所。在不改变组成材料性能的情况下，界面应力的松弛是提高复合材料性能的有效手段，具有广泛的吸引力。在此，我们开发了一种新型的自适应界面，在填料-聚合物界面上利用硫-硫酯交换（TTE）。具体来说，在硫酯部分、过量硫醇和碱/亲核催化剂存在的情况下，材料界面上的动态共价键可逆交换。利用这种活性界面有效地减轻了界面应力的有害增长，从而在降低聚合收缩应力和提高韧性方面提高了复合材料的机械性能。在静态基体中激活界面TTE可使聚合应力降低45%，聚合后应力松弛更明显，与不能进行TTE键交换但其他方面相同的对照复合材料相比，韧性大幅提高。数字图像相关分析表明，te活化复合材料具有较高的断裂韧性，主要归因于裂纹尖端应变浓度的降低。
Due to a mismatch in mechanical moduli, the interface between constituent materials in a composite is the primary locus for crack nucleation due to stress concentration. Relaxation of interfacial stresses, without modifying the properties of constituent materials, is a potent means of improving composite performance with broad appeal. Herein, we develop a new type of adaptive interface that utilizes thiol–thioester exchange (TTE) at the filler–polymer interface. Specifically, dynamic covalent bonds sequestered at material interfaces are reversibly exchanged in the presence of thioester moieties, excess thiol and a base/nucleophile catalyst. Employing this active interface effectively mitigates deleterious growth of interfacial stresses, thereby enhancing the composite's mechanical performance in terms of reductions in polymerization shrinkage stress and improvement in toughness. Activating interfacial TTE in an otherwise static matrix resulted in 45% reduction in the polymerization stress, more significant post-polymerization stress relaxation and drastically increased toughness relative to control composites incapable of TTE bond exchange but otherwise identical. In particular, the higher fracture toughness in TTE-activated composites is attributed to the alleviation of crack tip strain concentration, as revealed by digital image correlation.