Mechanochromic functionality realized via the force-responsive mechanophores in polymers has great potential for damage sensing and information storage. Mechanophores with the ability to recognize multiple stimuli for tunable chromic characteristics are highly sought after for versatile sensing ability and color programmability. Nevertheless, the majority of mechanophores are based on single-component chromophores with limited sensitivity, or require additional fabrication technology for multi-modal chromism. Here, we report a novel multifunctional mechanophore capable of vividly detectable and tunable mechanochromism in polymers. This synergistic optical coupling relies on strategically fusing rhodamine and spiropyran (Rh-SP), and tethering polymer chains on both subunits. The mechanochromic behaviors of the Rh-SP-linked polymers under sonication and compression are thoroughly evaluated in response to changes in force and the light-controlled relaxation process. Non-sequential ring-opening of the two subunits under force is identified, endowing high-contrast mechanochromism. Light-induced differential ring-closing reactions of the two subunits, together with the acidichromism of the SP moiety, are employed to engineer elastomers with programmable and wide-spectrum colors. Our work presents an effective strategy for highly appreciable and regulable mechanochromic functionality, and also provides new insights into the rupture mechanisms of π-fused mechanophores, as well as how the stimuli history controls stress accumulation in polymers.

中文翻译：

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罗丹明-螺吡喃缀合物在多重刺激下赋予聚合物可调节的机械致变色性


通过聚合物中的力响应力力团实现的力致变色功能在损伤传感和信息存储方面具有巨大的潜力。具有识别多种刺激以实现可调色彩特性的能力的机械载体因其多功能传感能力和颜色可编程性而受到高度追捧。然而，大多数机械基团都是基于灵敏度有限的单组分发色团，或者需要额外的制造技术来实现多模态发色。在这里，我们报告了一种新型多功能机械基团，能够在聚合物中清晰地检测和调节机械致变色性。这种协同光学耦合依赖于策略性地融合罗丹明和螺吡喃（Rh-SP），并将聚合物链束缚在两个亚基上。彻底评估了 Rh-SP 连接聚合物在超声处理和压缩下的力致变色行为，以响应力的变化和光控松弛过程。两个亚基在受力下的非连续开环被鉴定出来，赋予了高对比度的机械致变色性。两个亚基的光诱导微分闭环反应以及 SP 部分的酸变色性被用来设计具有可编程和广谱颜色的弹性体。我们的工作提出了一种有效的策略，可实现高度可感知和可调节的力致变色功能，并且还为π融合力力团的破裂机制以及刺激历史如何控制聚合物中的应力积累提供了新的见解。