This report studied changes in the dynamic fragility (m) of poly(butyl methacrylate) (PBMA) by introducing guest hindered phenols capable of forming two or three intermolecular hydrogen bonds (inter-HBs) per molecule with the host polymer. The small molecules effectively decrease the m value, even if they apparently increase the glass transition temperature (T_g) of mixtures. The reduction in m was confirmed by enthalpy relaxation in two aspects: adding the guest molecule leads to a stronger cooling rate dependence of the limiting fictive temperature together with an apparent increase in aging rate of PBMA hybrids at low concentrations. By varying the molecule size and steric hindrance of the hydroxyl group on the hindered phenols, we clarified that m is primarily governed by the strength of inter-HB interactions, while the T_g value of mixtures depends on a combined effect of additive bulkiness and HB interaction. The anomalous dynamics was further rationalized not only by the HB-induced flexibility balance between side groups and backbone, but also by the reduction of cooperative rearranging sizes and alleviation of long-chain connectivity in such HB-driven hybrids.

中文翻译：

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通过小分子调节丙烯酸聚合物的动态脆性：分子结构的相互作用

该报告通过引入能够与主体聚合物形成两个或三个分子间氢键 (inter-HBs) 的客体受阻酚，研究了聚甲基丙烯酸丁酯 (PBMA)的动态脆性 ( m ) 的变化。小分子有效地降低了m值，即使它们明显增加了混合物的玻璃化转变温度 ( T _g )。米的减少通过两个方面的焓弛豫证实了这一点：添加客体分子导致限制假想温度的更强冷却速率依赖性以及低浓度下 PBMA 杂化物老化速率的明显增加。通过改变受阻酚上羟基的分子大小和空间位阻，我们澄清了m主要受 HB 间相互作用的强度控制，而T _g混合物的价值取决于添加剂的体积和 HB 相互作用的综合影响。异常动力学不仅通过 HB 诱导的侧基和主链之间的灵活性平衡进一步合理化，而且还通过在这种 HB 驱动的杂种中减少协同重排大小和缓解长链连接。