Frustrations in Polymer Conformation in Gels and their Minimization through Molecular Imprinting

聚合物统计力学的最新发展阐明了大分子记忆构象的基本原理。首先，聚合物必须是异聚物，也就是说，应该有不止一种单体，这样一些构象在能量上比其他构象更有利。其次，聚合物必须冷凝，在这种情况下，由于链连通性和排除体积的相互作用，存在挫折。第三，必须选择单体的顺序，以尽量减少这些挫折。这三个条件允许聚合物在一个特定的构象上具有其总能量最小值，因此可以说是记忆的。我们研究了上述原理的实验实现，尽管在原始水平上，在弱交联聚合物凝胶的合成中。凝胶可以记忆其分子构象的一部分，特别是某些单体群的空间组合。它们可以与更多额外的所谓目标分子相互作用，这些分子没有连接到凝胶网络上，但每个分子都带有几个负电荷。这些带正电的少数单体可以与带负电的靶分子形成离子配合物。换句话说，它们聚集成一组，它们的相互作用是由目标分子介导的。我们的主要实验策略是比较在存在或不存在目标分子的情况下进行后交联的凝胶。我们把这两种凝胶分别称为印记凝胶和随机凝胶。我们认为，通过在目标分子存在的情况下进行后交联，我们抑制了挫折，从而接近最小的挫折情况。我们通过实验实现了一种凝胶体系，其中挫折存在并且可以最小化，从而满足预测的两个关键标准，以实现聚合物构象的记忆。该凝胶由一种热敏性的主要单体组分和两种次要组分组成。一种带正电的小组分将在溶液中带负电的靶分子周围形成络合物。通过交联第二次要组分，可以将配合物印迹到凝胶中，该次要组分将形成除主要聚合物基质中的交联外的交联。复合物在凝胶的膨胀和收缩中被破坏和重组，表明记忆已经实现。少

The recent development of the statistical mechanics of polymers has clarified the principles underlying the memory of conformation by macromolecules. First, the polymer must be a heteropolymer, i.e., there should be more than one monomer species, so that some conformations are energetically more favorable than others. Second, the polymer must be condensed, in which case frustrations exist due to the interplay of chain connectivity and excluded volume. Third, the sequence of monomers must be selected as to minimize these frustrations. These three conditions allow the polymer to have its global energy minimum at one particular conformation, which thus can be said to be memorized. We investigated an experimental implementation of the above principles, albeit at a primitive level, in the synthesis of a weakly cross-linked polymer gel. The gel can memorize a part of its molecular conformation-specifically, spatial assemblies of certain groups of its monomers. they can interact with special … More additional so-called target molecules, not connected to the gel network, but having several negative charges each. These positively charged minority monomers can form ionic complexes with the negatively charged target molecules. In other words, they assemble into groups in which their interaction is mediated by the target molecules. Our major experimental strategy is to compare gelswhich are post-cross-linked in the presence or in the absence of target molecules. We call these gels imprinted and random, respectively. We argue that, by doing post-crosslinking in the presence of target molecules, we suppress frustrations and thus approach the minimal frustration situation. We experimentally realized that a gel system in which frustrations exist and can be minimized, thus meeting two crucial criteria predicted to enable memory of conformations in polymers. The gels consist of a thermosensitive major monomer component and two minor components. One minor component is positively charged and will form complexes around negatively charged target molecules placed in solution. The complexes can be imprinted into the gel by then cross-linking the second minor component, which will form cross-links additional to those in the major polymer matrix. The complexes are destroyed and reformed upon swelling and reshrinking of the gels, showing that memorization has been achieved. Less