关键词: AFM dual responsive ellipsometry hydrogels surface defects

Mesh : Oxidation-Reduction Surface Properties Nanogels / chemistry Hydrogels / chemistry Temperature Polyethylene Glycols / chemistry Particle Size Polyethyleneimine / chemistry Microscopy, Atomic Force

来  源:   DOI:10.1002/marc.202400049

Abstract:
Hydrogels are usually depicted as a homogenous polymer block with a distinct surface. While defects in the polymer structure are looked into frequently, structural irregularities on the hydrogel surface are often neglected. In this work, thin hydrogel layers of ≈100 nm thickness (nanogels) are synthesized and characterized for their structural irregularities, as they represent the surface of macrogels. The nanogels contain a main-chain responsiveness (thermo responsive) and a responsiveness in the cross-linking points (redox responsive). By combining data from ellipsometry using box-model and two-segment-model analysis, as well as atomic force microscopy, a more defined model of the nanogel surface can be developed. Starting with a more densely cross-linked network at the silica wafer surface, the density of cross-linking gradually decreases toward the hydrogel-solvent interface. Thermo-responsive behavior of the main chain affects the entire network equally as all chain segments change solubility. Cross-linker-based redox-responsiveness, on the other hand, is only governed by the inner, more cross-linked layers of the network. Such dual responsive nanogels hence allow for developing a more detailed model of a hydrogel surface from free radical polymerization. It provides a better understanding of structural defects in hydrogels and how they are affected by responsive functionalities.
摘要:
水凝胶通常被描述为具有不同表面的均质聚合物嵌段。虽然经常研究聚合物结构中的缺陷,水凝胶表面的结构不规则性通常被忽略。在这项工作中,约100纳米厚度的薄的水凝胶层(纳米凝胶)已被合成并表征其结构不规则性,因为它们代表了大分子凝胶的表面。纳米凝胶包含主链响应性(热响应性)和交联点的响应性(氧化还原响应性)。在使用盒模型和两段模型分析组合椭圆光度法的数据时,以及原子力显微镜,可以开发更明确的纳米凝胶表面模型。从二氧化硅晶片表面更密集的交联网络开始,交联密度朝着水凝胶-溶剂界面逐渐降低。主链的热响应行为同等地影响整个网络,因为所有链段改变溶解度。基于交联剂的氧化还原反应性,另一方面,只受内心支配,网络的更多交叉链接层。因此,这种双响应性纳米凝胶允许开发来自自由基聚合的水凝胶表面的更详细的模型。它可以更好地理解水凝胶中的结构缺陷以及它们如何受到响应功能的影响。本文受版权保护。保留所有权利。
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