Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.
Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.
J Colloid Interface Sci. 2020 May 15;568:264-272. doi: 10.1016/j.jcis.2020.02.057. Epub 2020 Feb 15.
Control over the size and functional group distribution of soft responsive hydrogel particles is essential for applications such as drug delivery, catalysis and chemical sensing. Traditionally, targeted functional group distributions are achieved with semi-batch techniques which require specialized equipment, while the preparation of size-tailored particles typically involves the use of surfactants. Herein, we present a simple and robust surfactant-free method for the modulation of size and carboxylic acid functional group distribution in poly(N-isopropylacrylamide) thermoresponsive microgels, employing reaction pH as the single experimental parameter. The varying distributions of carboxylic acid residues arise due to differences in kinetic reactivity, which are a function of the degree of dissociation of methacrylic acid, and thus of reaction pH. Incorporated charged residues induce a surfactant-like action during the particle nucleation stage, and impact the final particle size. Characterization with dynamic light scattering, and electron microscopy consistently supports the pH-tailored morphology of the microgels. A mathematical model which accounts for particle deformation on the imaging substrate also shows excellent agreement with the experimental results.
控制软响应水凝胶颗粒的大小和官能团分布对于药物输送、催化和化学传感等应用至关重要。传统上，目标官能团分布是通过半分批技术实现的，这需要专用设备，而尺寸可调颗粒的制备通常涉及使用表面活性剂。在此，我们提出了一种简单而强大的无表面活性剂方法，用于调节聚（N-异丙基丙烯酰胺）温敏微凝胶的大小和羧酸官能团分布，使用反应 pH 作为单个实验参数。由于动力学反应性的差异，羧酸残基的分布不同，这是甲丙烯酸离解度的函数，因此也是反应 pH 的函数。掺入的带电残基在颗粒成核阶段产生类似表面活性剂的作用，并影响最终颗粒尺寸。动态光散射和电子显微镜的表征一致支持微凝胶的 pH 定制形态。考虑到在成像衬底上的颗粒变形的数学模型也与实验结果非常吻合。
