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构象记忆的基本原理。首先，聚合物必须是杂多聚合物，也就是说，应该有不止一个单体物种，以便某些构象在能量上比其他构象更有利。其次，聚合物必须是缩合的，在这种情况下，由于链连接性和排除体积的相互作用而存在阻碍。第三，必须选择单体的顺序，以使这些挫折最小化。这三个条件允许聚合物在一种特定构象下具有其全局能量最小值，因此可以说是被记忆的。我们研究了上述原理在合成弱交联聚合物凝胶中的实验实现，尽管是在原始水平上。这种凝胶可以记忆其分子构象的一部分，具体地说，就是它的某些单体基团的空间组装。它们可以与特殊的…进行交互更多额外的所谓靶分子，不是连接到凝胶网络，而是每个分子都有几个负电荷。这些带正电荷的少数单体可以与带负电荷的靶分子形成离子络合物。换句话说，它们组装成基团，在这些基团中，它们的相互作用受到目标分子的调节。我们的主要实验策略是比较在靶分子存在或不存在的情况下后交联的凝胶。我们将这些凝胶分别称为印迹凝胶和随机凝胶。我们认为，通过在靶分子存在的情况下进行后交联，我们可以抑制挫折感，从而接近最小挫折感的情况。我们在实验中认识到，凝胶体系中存在并可以最大限度地减少挫折，从而满足了预测的两个关键标准，即能够记忆聚合物的构象。凝胶由一个热敏性主要单体组分和两个次要组分组成。其中一个次要成分带正电，会在溶液中带负电的目标分子周围形成络合物。然后，通过将第二个次要组分交联化，可以将络合物印迹到凝胶中，这将形成除了主要聚合物基质中的那些交联物之外的交联物。当凝胶膨胀和重新收缩时，复合体被破坏和重塑，表明已经实现了记忆。较少

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