Zhang Li, Cao Jun, Yeung Pui Wo Felix, Jiang Hang, Jiang Jianzhong, Liu Wei, Ngai To
The Key Laboratory of Synthetic and Biological Colloids, Ministry of Education & School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China.
Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
J Colloid Interface Sci. 2025 May;685:1173-1183. doi: 10.1016/j.jcis.2025.01.189. Epub 2025 Jan 21.
Poly(N-isopropylacrylamide)-based microgels are soft and deformable colloids, which can swell and shrink in response to external stimuli such as temperature or pH, making them suitable for various industries. Herein, poly(styrene-co-N-isopropylacrylamide) microgels with varying softness were synthesized through the doping of different proportions of styrene into their network structure. Rheological tests revealed that the deformability, surface charge, and wettability of microgels were precisely regulated through adjustments to styrene doping levels. As the molar ratio of styrene increased, the range of the linear viscoelastic region regarding stain did not exhibit a consistent change. The microgel suspensions exhibited a pronounced viscous-like behavior, as indicated by their frequency dependence. Additionally, the concentration or volume fraction of microgels significantly influenced the phase distribution in the phase diagram. At lower concentrations, the microgel suspensions typically underwent a colloidal gel-to-liquid-to-glass transition, with the liquid-like regime expanding as the styrene doping level increased. At higher microgel concentrations, the volume phase transition shifted to a direct colloidal gel-to-glass transition, particularly at high styrene levels. This study also revealed a strong correlation between the power-law viscoelastic exponents and the loss tangent during the entire phase transition, offering valuable insights for structure and rheological properties of poly(N-isopropylacrylamide)-based microgels.
基于聚（N-异丙基丙烯酰胺）的微凝胶是柔软且可变形的胶体，能够响应温度或pH等外部刺激而膨胀和收缩，使其适用于各种行业。在此，通过将不同比例的苯乙烯掺杂到其网络结构中，合成了具有不同柔软度的聚（苯乙烯-共-N-异丙基丙烯酰胺）微凝胶。流变学测试表明，通过调整苯乙烯掺杂水平，可以精确调节微凝胶的可变形性、表面电荷和润湿性。随着苯乙烯摩尔比的增加，关于应变的线性粘弹性区域范围没有呈现出一致的变化。微凝胶悬浮液表现出明显的类似粘性的行为，如其频率依赖性所示。此外，微凝胶的浓度或体积分数显著影响相图中的相分布。在较低浓度下，微凝胶悬浮液通常经历胶体凝胶-液体-玻璃态转变，随着苯乙烯掺杂水平的增加，液态区域扩大。在较高的微凝胶浓度下，体积相变转变为直接的胶体凝胶-玻璃态转变，特别是在高苯乙烯水平下。这项研究还揭示了在整个相变过程中幂律粘弹性指数与损耗角正切之间的强相关性，为基于聚（N-异丙基丙烯酰胺）的微凝胶的结构和流变性质提供了有价值的见解。
