Jiang Naisheng, Yu Tianyi, Zhang Meng, Barrett Bailee N, Sun Haofeng, Wang Jun, Luo Ying, Sternhagen Garrett L, Xuan Sunting, Yuan Guangcui, Kelley Elizabeth G, Qian Shuo, Bonnesen Peter V, Hong Kunlun, Li Dongcui, Zhang Donghui
Key Laboratory of Advanced Materials and Devices for Post-Moore Chips, Ministry of Education, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Macromolecules. 2024 Jun 28;57(14):6449-6464. doi: 10.1021/acs.macromol.4c00162. eCollection 2024 Jul 23.
We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(-allyl glycine)--poly(-methyl glycine)--poly(-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, AMD triblock terpolypeptoids self-assemble into core-corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature ( ), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At ≳ , the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as AMD and AMD, elongated nonspherical micelles with a crystalline D core were observed at < . Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as AMD, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.
我们使用小角中子散射（SANS）结合对比匹配技术，以及X射线散射和低温透射电子显微镜（cryo-TEM）技术，研究了热可逆三嵌段类多肽水凝胶，即聚（烯丙基甘氨酸）-聚（甲基甘氨酸）-聚（癸基甘氨酸）（AMD）的温度依赖性结构演变。在室温下，AMD三嵌段类多肽在水溶液中自组装成核-壳型球形胶束。加热至临界凝胶化温度（ ）以上时，SANS分析表明形成了一种双隔室水凝胶网络，该网络由脱水的A嵌段和疏水的D嵌段组成的不同胶束核心构成。在 ≳ 时，A嵌段的温度依赖性脱水进一步导致A和D域的逐渐重排，在较高温度下形成有序的胶束网络。对于具有较长D嵌段或较短A嵌段的AMD聚合物，如AMD和AMD，在 < 时观察到具有结晶D核的细长非球形胶束。尽管这些增大的结晶胶束在加热时仍会经历急剧的溶胶-凝胶转变，但较高的链聚集数导致胶束在初始阶段立即缔合成有序聚集体，随后随着温度进一步升高，空间有序性被破坏。另一方面，对于具有较长A嵌段的AMD，如AMD，由于A域的结晶，也观察到了纤维状结构。这也影响了双隔室网络的组装途径。我们的研究结果强调了初始胶束形态对AMD水凝胶在溶胶-凝胶转变过程中结构演变的关键影响，为合理设计具有纳米级可调网络结构的热响应水凝胶提供了有价值的见解。
