序列诱导同组成共聚物的缩放定律
Scaling Law for Sequence-Induced Demixing of Compositionally Identical Copolymers
AI总结：
研究揭示了同组成共聚物因序列差异导致相分离的缩放规律，提出新的理论模型并通过模拟验证。
摘要：
聚合物不同组成的临界不相容性与链长成反比。例如，长度为N的A和B均聚物混合物在χ_AB^cr=2/N时发生相分离。但若混合组分的差异更为微妙呢？我们证明，即使AB共聚物具有相同的组成——等量的A和B单体——但不同的初级序列仍可能发生相分离。不相容性源于不同链中单体的位相关系差异。计算高斯波动修正对自由能的影响，发现来自序列差异的临界不相容性遵循一种独特的但普遍的链长缩放规律，χ_AB^cr~1/√N。该幂律适用于常规序列和统计共聚物。推导出块交替链混合物的闭合表达式。新的理论缩放通过粗粒模拟得到验证，为生物分子凝聚物的多相共存提供了重要见解。
英文摘要：
The critical incompatibility of polymers with different compositions scales inversely with their length. For instance, a mixture of A and B homopolymers of length $N$ segregates at $χ_{AB}^{cr} = 2/N$. But what if the difference between the blend components is subtler? We demonstrate that a mixture of AB copolymers with identical composition -- equal amounts of A and B monomers -- but different primary sequences can still phase separate. Incompatibility arises from distinct positional correlations between monomers of different chains. Calculating the Gaussian fluctuation correction to the free energy reveals that critical incompatibility from sequence differences follows a distinct yet universal scaling with chain length, $χ_{AB}^{cr} \sim 1 / \sqrt{N}$. This power law holds for both regular-sequence and statistical copolymers. A closed-form expression is derived for blends of block-alternating chains. The new theoretical scaling is confirmed by coarse-grained simulations, offering important insights into multiphase coexistence in biomolecular condensates.
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