A fundamental paradigm in polymer physics is that macromolecular conformations in equilibrium can be described by universal scaling laws, being key for structure, dynamics, and function of soft (biological) matter and in the materials sciences. Here we reveal that during diffusion-influenced, nonequilibrium chain-growth polymerization, scaling laws change qualitatively, in particular, the growing polymers exhibit a surprising self-avoiding walk behavior in poor and $\theta$ solvents. Our analysis, based on monomer-resolved, off-lattice reaction-diffusion computer simulations, demonstrates that this phenomenon is a result of (i) nonequilibrium monomer density depletion correlations around the active polymerization site, leading to a locally directed and self-avoiding growth, in conjunction with (ii) chain (Rouse) relaxation times larger than the competing polymerization reaction time. These intrinsic nonequilibrium mechanisms are facilitated by fast and persistent reaction-driven diffusion (“sprints”) of the active site, with analogies to pseudochemotactic active Brownian particles. Our findings have implications for time-controlled structure formation in polymer processing, as in, e.g., reactive self-assembly, photocrosslinking, and three-dimensional printing.

中文翻译：

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通过时间控制溶剂质量：非平衡聚合中的自我避免冲刺

高分子物理学的一个基本范式是平衡中的大分子构象可以通过通用标度定律来描述，这是软（生物）物质和材料科学的结构、动力学和功能的关键。在这里，我们揭示了在受扩散影响的非平衡链增长聚合过程中，缩放规律发生了质的变化，特别是，增长的聚合物在较差的和$\theta$溶剂。我们基于单体解析、非晶格反应扩散计算机模拟的分析表明，这种现象是 (i) 活性聚合位点周围非平衡单体密度消耗相关性的结果，导致局部定向和自回避增长，结合（ii）链（Rouse）弛豫时间大于竞争聚合反应时间。这些内在的非平衡机制是由活性位点的快速和持久的反应驱动扩散（“冲刺”）促进的，类似于假趋化活性布朗粒子。我们的发现对聚合物加工中的时间控制结构形成有影响，例如反应性自组装、光交联和三维印刷。