Elastomers are highly valued soft materials finding many applications in the engineering and biomedical fields for their ability to stretch reversibly to large deformations. Yet their maximum extensibility is limited by the occurrence of fracture, which is currently still poorly understood. Because of a lack of experimental evidence, current physical models of elastomer fracture describe the rate and temperature dependence of the fracture energy as being solely due to viscoelastic friction, with chemical bond scission at the crack tip assumed to remain constant. Here, by coupling new fluorogenic mechanochemistry with quantitative confocal microscopy mapping, we are able to quantitatively detect, with high spatial resolution and sensitivity, the scission of covalent bonds as ordinary elastomers fracture at different strain rates and temperatures. Our measurements reveal that, in simple networks, bond scission, far from being restricted to a constant level near the crack plane, can both be delocalized over up to hundreds of micrometers and increase by a factor of 100, depending on the temperature and stretch rate. These observations, permitted by the high fluorescence and stability of the mechanophore, point to an intricate coupling between strain-rate-dependent viscous dissipation and strain-dependent irreversible network scission. These findings paint an entirely novel picture of fracture in soft materials, where energy dissipated by covalent bond scission accounts for a much larger fraction of the total fracture energy than previously believed. Our results pioneer the sensitive, quantitative, and spatially resolved detection of bond scission to assess material damage in a variety of soft materials and their applications.

中文翻译：

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量化弹性体断裂中速率和温度相关的分子损伤

弹性体是极有价值的软质材料，因其可逆拉伸至大变形的能力而在工程和生物医学领域中找到了许多应用。然而，它们的最大可扩展性受到断裂的发生的限制，目前尚不清楚。由于缺乏实验证据，当前弹性体断裂的物理模型将断裂能的速率和温度依赖性描述为仅由于粘弹性摩擦，而裂纹尖端的化学键断裂仍保持恒定。在这里，通过将新的荧光机械化学与定量共聚焦显微镜图谱相结合，我们能够以高空间分辨率和灵敏度定量检测作为普通弹性体在不同应变速率和温度下断裂的共价键的断裂。我们的测量结果表明，在简单的网络中，粘结断裂（不仅限于裂缝平面附近的恒定水平）可以在高达数百微米的范围内离域，并可以增加100倍，具体取决于温度和拉伸速率。这些观察结果，由于机械荧光团的高荧光性和稳定性，表明应变速率相关的粘性耗散与应变依赖的不可逆网络断裂之间存在复杂的耦合。这些发现描绘了软质材料断裂的崭新画面，其中共价键断裂所耗散的能量比以前认为的要大得多。我们的结果开创了敏感，定量，