硼硅树脂和粘弹性硅橡胶：网络液体和网络固体
Borosilicones and viscoelastic silicone rubbers: network liquids and network solids
摘要：
硼硅氧烷（例如，人们已经知道了70年，但他们的奇特行为仍然无法解释。在这项工作中，实验和理论表明，它们是网络液体-动态大分子，在短时间尺度上表现出弹性，但在较长的时间尺度上表现出流动。每个硼硅是由三官能硼交联连接的硅聚合物链的巨大共价网络。在任何时刻，硼硅树脂都是高度交联的弹性材料。然而，由于硼交联是暂时的，因此网络随时间而演变，并且硼硅表现出液体行为。一个简单的硼硅简化了一个经典的瞬态网络模型，并表现为一个简单的（洛奇）弹性流体。其测得的模量和粘度符合瞬态网络模型和麦克斯韦粘弹性模型预测：弹簧串联阻尼器，包括观察到的指数松弛过程。然而，当硼硅包括永久交联时，它不再表现为简单的弹性流体。其测量的模量和粘度符合分数麦克斯韦粘弹性模型预测的那些：弹簧与弹簧罐串联，包括观察到的慢于指数的松弛过程。超过凝胶化阈值，硼硅变成粘弹性硅橡胶（VSR）。在跨越材料的永久网络耦合到也跨越材料的临时网络的情况下，VSR是网络固体上的网络液体背负。分数齐纳粘弹性模型：一个平行于分数麦克斯韦模型的弹性弹簧，准确地预测了VSR的测量模量。硼交联的暂时性是由于交换反应。因为临时交联的平均寿命是硼硅树脂唯一重要的时间尺度，所以它表现出热流变简单性。
英文摘要：
Borosilicones (e.g., Silly Putty) have been known for 70 years, but their peculiar behaviors have remain unexplained. In this work, experiment and theory are used to show that they are network liquids---dynamic macromolecules that appear elastic on short timescales but exhibit flow on longer timescales. Each borosilicone is a vast covalent network of silicone polymer chains joined by trifunctional boron crosslinks. At any instant, the borosilicone is a highly-crosslinked elastic material. Because the boron crosslinks are temporary, however, the network evolves with time and the borosilicone exhibits liquid behavior. A simple borosilicone exemplifies a classic transient network model and behaves as a simple (Lodge) elastic fluid. Its measured moduli and viscosities fit those predicted by the transient network model and the Maxwell viscoelastic model: a spring in series with a dashpot, including the observed exponential relaxation processes. When a borosilicone includes permanent crosslinks, however, it no longer behaves as a simple elastic fluid. Its measured moduli and viscosities fit those predicted by the Fractional Maxwell viscoelastic model: a spring in series with a the spring-pot, including the observed slower-than-exponential relaxation processes. Beyond the gelation threshold, a borosilicone becomes a viscoelastic silicone rubber (VSR). With a permanent network that spans the material coupled to a temporary network that also spans the material, the VSR is a network liquid piggybacking on a network solid. The Fractional Zener viscoelastic model: an elastic spring in parallel to the Fractional Maxwell model, accurately predicts the measured moduli of VSRs. The temporary nature of boron crosslinks is due to exchange reactions. Because the mean lifetime of temporary crosslinks is a borosilicone's only significant timescale, it exhibits thermo-rheological simplicity.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
