Mechanochromism and Strain‐Induced Crystallization in Thiol‐yne‐Derived Stereoelastomers
Mechanochromism and Strain‐Induced Crystallization in Thiol‐yne‐Derived Stereoelastomers
复制标题
硫醇-炔-衍生立体弹性体中的力致变色现象和应变诱导结晶
DOI：
10.1002/adma.202302163
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发表时间：
2023
影响因子：
29.4
通讯作者：
Becker, Matthew L.
中科院分区：
文献类型：
--
作者：
Ritter, Virginia C.;McDonald, Samantha M.;Dobrynin, Andrey V.;Craig, Stephen L.;Becker, Matthew L.
大多数弹性体在张力下发生应变诱导结晶（SIC）;由于施加的应变将单个链刚性地保持在固定位置，它们沿应变场沿着导致从应变硬化（SH）转变为SIC。类似程度的拉伸与必要的张力，以加速机械耦合，共价化学反应的mechanores在过度拉伸的链，提高SIC的宏观响应和mechanores激活的分子响应之间的相互作用的可能性。在此，报道了用二丙炔酸酯衍生的螺吡喃（SP）机械载体（0.25-0.38摩尔%）共价掺杂的硫醇-炔衍生的立体弹性体。含SP的膜的材料性质与未掺杂的对照一致，表明SP是聚合物的机械状态的报告者。单轴拉伸试验揭示了机械致变色和SIC之间的相关性，这是应变率依赖性的。当机械致变色膜被缓慢拉伸到机械基团活化的点时，即使在去除施加的应力之后，共价束缚的机械基团仍然被捕获在力活化状态中。机械力回复动力学与施加的应变速率相关，导致高度可调的脱色率。由于这些聚合物不是共价交联的，它们可以通过熔融压制成新的薄膜来回收，从而增加了它们在应变传感、形态传感和形状记忆应用中的潜在范围。
Most elastomers undergo strain‐induced crystallization (SIC) under tension; as individual chains are held rigidly in a fixed position by an applied strain, their alignment along the strain field results in a shift from strain‐hardening (SH) to SIC. A similar degree of stretching is associated with the tension necessary to accelerate mechanically coupled, covalent chemical responses of mechanophores in overstretched chains, raising the possibility of an interplay between the macroscopic response of SIC and the molecular response of mechanophore activation. Here, thiol‐yne‐derived stereoelastomers doped covalently with a dipropiolate‐derivatized spiropyran (SP) mechanophore (0.25–0.38 mol%) are reported. The material properties of SP‐containing films are consistent with undoped controls, indicating that the SP is a reporter of the mechanical state of the polymer. Uniaxial tensile tests reveal correlations between mechanochromism and SIC, which are strain‐rate‐dependent. When mechanochromic films are stretched slowly to the point of mechanophore activation, the covalently tethered mechanophore remains trapped in a force‐activated state, even after the applied stress is removed. Mechanophore reversion kinetics correlate with the applied strain rate, resulting in highly tunable decoloration rates. Because these polymers are not covalently crosslinked, they are recyclable by melt‐pressing into new films, increasing their potential range of strain‐sensing, morphology‐sensing, and shape‐memory applications.