Emergent Sequence Biasing in Step-Growth Copolymerization: Influence of Non-Bonded Interactions and Comonomer Reactivities
Emergent Sequence Biasing in Step-Growth Copolymerization: Influence of Non-Bonded Interactions and Comonomer Reactivities
复制标题
逐步增长共聚中出现的序列偏向：非键相互作用和共聚单体反应性的影响
DOI：
10.1021/acs.jpcb.2c04092
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
DuBay, Kateri H.
中科院分区：
文献类型：
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作者：
Nguyen, Nhu Q.;Hamblin, Ryan L.;DuBay, Kateri H.
共聚物的相行为和材料性能本质上取决于它们的初级共聚单体序列。在合成共聚过程中实现对单体序列的精确控制是具有挑战性的，因为序列的确定不仅受反应条件和反应物性质的影响，还受共聚过程本身的统计性质的影响。梅奥-刘易斯反应性比通常用于预测共聚物的组成和序列，并基于静态反应性常数的比率。然而，先前的研究结果表明，在一般的基于溶液的阶梯生长a， b共聚过程中，某些单体对之间相对较弱的非键吸引会导致出现微相分离。由于反应物浓度的非均质性，这种聚合驱动的分离会导致偏离标准动力学，这也会导致所得共聚物序列的显著变化。以前，这些效应是在所有反应途径的活化能相等的系统中观察到的，即在所有单体对组合之间。在这项工作中，我们探讨了单体之间活化能和非键吸引的差异对共聚动力学的综合影响，并检查了在相同的阶梯生长共聚模型中产生的序列。我们的研究结果表明，改变活化能影响动力学和序列的方式，也取决于非键吸引，表明这些影响可能协同工作或相互反对，以偏向形成的序列。在一定条件下，观察到非标准的动力学行为和长程序列偏置，并且随着反应的进行，它们的程度明显变化。这些发现为序列和新生低聚物相行为之间的复杂相互作用提供了见解，突出了在先进序列偏向材料的知情设计中利用涌现相特性的潜力。
The phase behavior and material properties of copolymers are intrinsically dependent on their primary comonomer sequences. Achieving precise control over monomer sequence in synthetic copolymerizations is challenging, as sequence determination is influenced not only by the reaction conditions and the properties of the reactants but also by the statistical nature of the copolymerization process itself. Mayo–Lewis reactivity ratios are often used to predict copolymer composition and sequence and are based on ratios of static reactivity constants. However, prior results have demonstrated that in a generic, solution-based step-growth A,B-copolymerization, relatively weak non-bonded attractions between certain monomer pairs induce emergent microphase separations. Such polymerization-driven separations lead to deviations from standard kinetics due to the emergent heterogeneities in reactant concentrations, which can also cause significant shifts in the resulting copolymer sequences. Previously, these effects were observed in systems where the activation energies were equal for all reaction pathways, that is, between all monomer pair combinations. In this work, we explore the combined effects on copolymerization kinetics of differences in both activation energies and non-bonded attractions between monomers and examine the sequences produced within this same step-growth copolymerization model. Our results indicate that altering activation energies influences the kinetics and sequences in a manner that also depends on the non-bonded attractions, showing that these effects may work in concert or in opposition to one another to bias the sequences formed. Non-standard kinetic behaviors and long-range sequence biasing are observed under certain conditions, and the extent of each clearly shifts as the reaction proceeds. These findings provide insight into the complex interplay between sequence and nascent oligomer phase behavior, highlighting the potential for exploiting emergent phase properties in the informed design of advanced sequence-biased materials.