Directing polymer self-assembly through noncovalent interactions is a powerful way to control the structure and function of nanoengineered materials. Dynamic hydrogen bonds are particularly useful for materials with structures that change over time or in response to specific stimuli. In the present work, we use the supramolecular association of urea moieties to manipulate the morphology, thermal response, and mechanical properties of soft polymeric hydrogels. Urea-terminated poly(isopropyl glycidyl ether)-b-poly(ethylene oxide)-b-poly(isopropyl glycidyl ether) ABA triblock copolymers were synthesized using controlled, anionic ring-opening polymerization and subsequent chain-end functionalization. Triblock copolymers with hydroxy end-groups were incapable of hydrogelation, while polymers terminated with meta-bis-urea motifs formed robust gels at room temperature. Rheometric analysis of the bulk gels, variable-temperature infrared spectroscopy (VT-IR), differential scanning calorimetry (DSC), and small-angle X-ray scattering (SAXS) confirmed the formation of structured hydrogels via association of the meta-bis-urea end-groups. Monourea end-groups did not result in the same regular structure as the meta-bis-urea. In future, the reported hydrogels could be useful for elastomeric, shape-morphing 3D-printed constructs, or as biomimetic scaffolds with precisely tailored porosity and mechanical properties.

中文翻译：

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自组装ABA三嵌段共聚物的粘性末端：尿素在刺激响应性水凝胶中的作用†

通过非共价相互作用指导聚合物自组装是控制纳米工程材料的结构和功能的有效方法。动态氢键对于结构随时间或响应特定刺激而变化的材料特别有用。在目前的工作中，我们使用尿素部分的超分子缔合来操纵软聚合物水凝胶的形态，热响应和机械性能。脲封端的聚（异丙基缩水甘油醚）-b-聚（环氧乙烷）-b使用受控的阴离子开环聚合反应和随后的链端官能化反应合成了聚-异丙基缩水甘油醚ABA三嵌段共聚物。具有羟基端基的三嵌段共聚物不能水凝胶化，而以间-双-脲基序终止的聚合物在室温下形成坚固的凝胶。本体凝胶的流变分析，可变温度红外光谱（VT-IR），差示扫描量热法（DSC）和小角X射线散射（SAXS）证实了通过间-双-缔合形成结构化水凝胶尿素端基。Monourea末端基团与meta末端没有相同的规则结构-双脲。将来，报道的水凝胶可用于弹性体，形状变形的3D打印构造，或具有精确定制的孔隙率和机械性能的仿生支架。