Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
Adv Mater. 2023 Nov;35(46):e2305824. doi: 10.1002/adma.202305824. Epub 2023 Oct 15.
Polymer topology, which plays a principal role in the rheology of polymeric fluids, and non-equilibrium materials, which exhibit time-varying rheological properties, are topics of intense investigation. Here, composites of circular DNA and dextran are pushed out-of-equilibrium via enzymatic digestion of DNA rings to linear fragments. These time-resolved rheology measurements reveal discrete state-switching, with composites undergoing abrupt transitions between dissipative and elastic-like states. The gating time and lifetime of the elastic-like states, and the magnitude and sharpness of the transitions, are surprisingly decorrelated from digestion rates and non-monotonically depend on the DNA fraction. These results are modeled using sigmoidal two-state functions to show that bulk state-switching can arise from continuous molecular-level activity due to the necessity for cooperative percolation of entanglements to support macroscopic stresses. This platform, coupling the tunability of topological composites with the power of enzymatic reactions, may be leveraged for diverse material applications from wound-healing to self-repairing infrastructure.
聚合物拓扑结构在聚合物流变学和非平衡材料流变学性质随时间变化中起着主要作用，这是目前研究的热点。在这里，通过酶消化 DNA 环将环状 DNA 和葡聚糖的复合物推出平衡状态，形成线性片段。这些时间分辨流变学测量揭示了离散的状态切换，复合物在耗散和弹性样状态之间发生突然转变。弹性样状态的门控时间和寿命，以及转变的幅度和锐度与消化速率无关，并且与 DNA 分数呈非单调关系。这些结果使用 sigmoidal 双态函数进行建模，表明由于需要缠结的协同渗透来支撑宏观应力，因此由于连续的分子水平活性可能导致整体状态切换。这种平台结合了拓扑复合材料的可调性和酶反应的能力，可能会在从伤口愈合到自我修复基础设施等各种材料应用中得到利用。
