PNIPAM/锂藻土纳米复合凝胶微球的制备及其弹性力学性能

Preparation and mechanical properties of PNIPAM/Laponite nanocomposite hydrogel microspheres

利用微流控技术,以锂藻土作为交联剂,成功制备得到温度响应型聚(N-异丙基丙烯酰胺)(PNIPAM)与锂藻土的纳米复合凝胶微球,并利用一种简单的微步进单轴压缩装置,分别在25℃和37℃下对具有不同锂藻土含量的PNIPAM/锂藻土纳米复合凝胶微球的弹性力学性能进行系统研究。该微步进单轴压缩装置主要包括三个部分:一个程控进样器用以实现对凝胶微球的微步进压缩,一套配有高分辨率数码相机的侧视光学系统用以记录凝胶微球受压时发生的形变,一台精密电子天平作为力传感器用来记录凝胶微球在特定形变下所受的外力。研究结果表明,纳米复合凝胶微球在25℃和37℃下的形变量H与所受压力F的实验数据与Hertz弹性接触理论方程呈现良好的拟合关系,证明了PNIPAM/锂藻土纳米复合凝胶微球在25℃和37℃下均具有弹性形变行为。同时,随着锂藻土含量的增加,PNIPAM/锂藻土纳米复合凝胶微球的温敏性降低,但其杨氏模量增大。具有相同锂藻土含量的纳米复合凝胶微球,由于温度升高凝胶体积收缩、凝胶结构变得致密,因此在37℃下的杨氏模量大于其在25℃下的杨氏模量。研究结果可为PNIPAM/锂藻土纳米复合凝胶微球的设计与实际应用提供指导。

Temperature-responsive poly(N-isopropylacrylamide)(PNIPAM) nanocomposite hydrogel microspheres are successfully prepared by microfluidic technology using Laponite as crosslinker in this work.A simple micro-step uniaxial compression device is developed to study the elastic properties of PNIPAM/Laponite nanocomposite hydrogel microspheres,which only needs a programmed syringe to achieve the micro-compression deformation and a precision electronic balance to measure the applied force.The images of compression process of a single hydrogel microsphere are captured by a side-view optical system.The results show that PNIPAM/Laponite nanocomposite hydrogel microspheres exhibit elastic deformation at both 25℃ and 37℃,and the obtained force-deformation experimental data fit well with the Hertz Theory.The Laponite content in the nanocomposite hydrogel microspheres significantly affects their mechanical properties and temperature-responsive behaviors.With the increase of Laponite content,the thermo-responsive volume change degree of the nanocomposite hydrogel microspheres decreases.But the Young's modulus of PNIPAM/Laponite nanocomposite hydrogel microspheres increases with the increase of the Laponite content at both 25℃ and 37℃.Furthermore,the Young's modulus of PNIPAM/Laponite nanocomposite hydrogel microspheres at 37℃ is much larger than that at 25℃ due to the thermo-induced volume shrinkage and rigidity increase.The results in this study provide a valuable guidance for designing smart hydrogel microspheres for practical applications.