The internal morphology of temperature-responsive degradable poly(N-isopropylacrylamide) (PNIPAM) microgels formed via an aqueous self-assembly process based on hydrazide and aldehyde-functionalized PNIPAM oligomers is investigated. A combination of surface force measurements, small angle neutron scattering (SANS), and ultrasmall angle neutron scattering (USANS) was used to demonstrate that the self-assembled microgels have a homogeneously cross-linked internal structure. This result is surprising given the sequential addition process used to fabricate the microgels, which was expected to result in a densely cross-linked shell–diffuse core structure. The homogeneous internal structure identified is also significantly different than conventional microgels prepared via precipitation polymerization, which typically exhibit a diffuse shell–dense core structure. The homogeneous structure is hypothesized to result from the dynamic nature of the hydrazone cross-linking chemistry used to couple with the assembly conditions chosen that promote polymer interdiffusion. The lack of an internal cross-linking gradient within these degradable and monodisperse microgels is expected to facilitate more consistent drug release over time, improved optical properties, and other potential application benefits.

中文翻译：

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具有均匀内部结构的动态交联自组装热响应微凝胶

温度响应性可降解聚（N）的内部形态研究了通过基于酰肼和醛官能化的PNIPAM低聚物的水自组装过程形成的（-异丙基丙烯酰胺）（PNIPAM）微凝胶。表面力测量，小角度中子散射（SANS）和超小角度中子散射（USANS）的组合用于证明自组装微凝胶具有均匀交联的内部结构。考虑到用于制造微凝胶的顺序添加过程，该结果令人惊讶，该过程有望产生致密交联的壳－扩散核结构。鉴定出的均匀内部结构也与通过沉淀聚合制备的传统微凝胶显着不同，传统的微凝胶通常表现出弥散的壳密核结构。假定均质结构是由the交联化学的动态性质所导致的，该hydr化学与所选的促进聚合物相互扩散的组装条件结合使用。这些可降解和单分散的微凝胶中缺乏内部交联梯度，有望促进药物随着时间的推移更加一致地释放，改善的光学性能以及其他潜在的应用优势。