Loescher Sebastian, Liang Chen, Plamont Remi, Breu Josef, Ikkala Olli, Zhang Hang
Department of Applied Physics, Aalto University, P.O. Box 15100, 02150 Espoo, Finland.
Bavarian Polymer Institute and Department of Chemistry, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany.
Soft Matter. 2025 May 21;21(20):4003-4009. doi: 10.1039/d5sm00317b.
Stimuli-responsive hydrogels with thermal phase transitions serve as pivotal components in advancing biomedical and soft robotics applications. In contrast to widely studied LCST-type thermo-responsive hydrogels, UCST-type hydrogels provide reverse thermo-responses. However, conventional UCST-type hydrogels suffer from weak mechanical properties and fixed phase transition kinetics. Here, we present polyzwitterionic UCST-type hydrogels under coplanar nanoconfinement by large aspect ratio hectorite nanosheets. The nanoconfinement significantly enhances the strength and stiffness of the hydrogels. In addition, the nanosheets serve as kinetic barriers for water diffusion. This regulates the swelling and shrinking kinetics of the polyzwitterionic hydrogels and thus allows for tunable phase transitions dependent on the thermal history of the hydrogels. Furthermore, we demonstrate that the incorporation of gold nanoparticles allows precise control of the optical properties of the hydrogel through photothermal means. These findings pave the way for engineering both the mechanical and thermoresponsive properties in polyzwitterionic hydrogels, thus broadening their applications in smart soft materials.
具有热相变的刺激响应水凝胶是推进生物医学和软机器人应用的关键组件。与广泛研究的最低临界溶解温度（LCST）型热响应水凝胶不同，最高临界溶解温度（UCST）型水凝胶具有相反的热响应。然而，传统的UCST型水凝胶存在机械性能较弱和相变动力学固定的问题。在此，我们展示了通过大长宽比的锂蒙脱石纳米片在共面纳米限域下制备的聚两性离子UCST型水凝胶。纳米限域显著提高了水凝胶的强度和刚度。此外，纳米片充当了水扩散的动力学屏障。这调节了聚两性离子水凝胶的溶胀和收缩动力学，从而实现了取决于水凝胶热历史的可调相变。此外，我们证明金纳米颗粒的掺入允许通过光热手段精确控制水凝胶的光学性质。这些发现为设计聚两性离子水凝胶的机械和热响应特性铺平了道路，从而拓宽了它们在智能软材料中的应用。
