Abstract：
Many stimuli-responsive materials harness the reversible association of supramolecular binding motifs to enable advanced functionalities such as self-healing, switchable adhesion, or mechanical adaptation. Despite extensive research into the structure-property relationships of these materials, direct correlations between molecular-level changes in supramolecular binding and macroscopic material behaviors have mostly remained elusive. Here, we show that this challenge can be overcome with supramolecular binding motifs featuring integrated binding indicators. We demonstrate this using a novel motif that combines a hydrogen-bonding ureido-4-pyrimidinone (UPy) with two strategically placed pyrene fluorophores. Dimerization of this motif promotes pyrene excimer formation, facilitating the straightforward optical quantification of supramolecular assembly under various conditions. We exploit the new motif as a supramolecular cross-linker in poly(methyl acrylate)s to probe the extent of (dis)assembly as a function of cross-linker content, processing history, and applied stimuli. We demonstrate that the stimuli-induced dissociation of hydrogen-bonding linkages strongly depends on the initial cross-link density, which also dictates whether the force-induced dissociation in polymer films correlates with the applied stress or strain. Thus, beyond introducing a robust tool for the in situ study of dynamic (dis)assembly mechanisms in supramolecular systems, our findings provide new insights into the mechanoresponsive behavior of such materials.
摘要：
许多刺激响应材料利用超分子结合基序的可逆关联来实现高级功能，如自我修复，可切换的附着力，或机械适应。尽管对这些材料的结构-性质关系进行了广泛的研究，超分子结合的分子水平变化与宏观材料行为之间的直接相关性大多仍然难以捉摸。这里,我们表明，这一挑战可以克服超分子结合基序具有整合的结合指标。我们使用一种新颖的基序来证明这一点，该基序将氢键键合的脲基-4-嘧啶酮（UPy）与两个战略性放置的芘荧光团相结合。该基序的二聚化促进芘准分子的形成，促进在各种条件下超分子组装的直接光学定量。我们利用新基序作为聚（丙烯酸甲酯）中的超分子交联剂，以探测（dis）组装的程度随交联剂含量的变化，处理历史，和施加刺激。我们证明了刺激诱导的超分子连接的解离强烈取决于初始交联密度，这也决定了聚合物膜中力诱导的解离是否与施加的应力或应变相关。因此，除了为超分子系统中的动态（DIS）组装机制的原位研究引入强大的工具外，我们的发现为此类材料的机械响应行为提供了新的见解。
