Guo Yan-Dong, Su Jun-Feng, Mu Ru, Wang Xin-Yu, Zhang Xiao-Long, Xie Xin-Ming, Wang Ying-Yuan, Tan Yi-Qiu
Department of Polymer Material, School of Material Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, China.
School of Civil and Transportation Engineering, Hebei University of Technology, Tianjin 300401, China.
Nanomaterials (Basel). 2019 Apr 10;9(4):587. doi: 10.3390/nano9040587.
Graphene has attracted attention in the material field of functional microcapsules because of its excellent characteristics. The content and state of graphene in shells are critical for the properties of microcapsules, which are greatly affected by the charge adsorption equilibrium. The aim of this work was to investigate the effect of pH value on the microstructure and properties of self-assembly graphene microcapsules in regard to chemical engineering. Microcapsule samples were prepared containing liquid paraffin by a self-assembly polymerization method with graphene/organic hybrid shells. The morphology, average size and shell thickness parameters were investigated for five microcapsule samples fabricated under pH values of 3, 4, 5, 6 and 7. The existence and state of graphene in dry microcapsule samples were analyzed by using methods of scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Fourier Transform Infrared Spectoscopy (FT-IR) and Energy Dispersive Spectrometer (EDS) were applied to analyze the graphene content in shells. These results proved that graphene had existed in shells and the pH values greatly influenced the graphene deposition on shells. It was found that the microcapsule sample fabricated under pH = 5 experienced the largest graphene deposited on shells with the help of macromolecules entanglement and electrostatic adherence. This microcapsules sample had enhanced thermal stability and larger thermal conductivity because of additional graphene in shells. Nanoindentation tests showed this sample had the capability of deforming resistance under pressure coming from the composite structure of graphene/polymer structure. Moreover, more graphene decreased the penetrability of core material out of microcapsule shells.
由于其优异的特性，石墨烯在功能性微胶囊材料领域引起了关注。壳层中石墨烯的含量和状态对微胶囊的性能至关重要，而这又受到电荷吸附平衡的极大影响。本工作的目的是从化学工程角度研究pH值对自组装石墨烯微胶囊微观结构和性能的影响。采用具有石墨烯/有机混合壳层的自组装聚合法制备了含有液体石蜡的微胶囊样品。对在pH值为3、4、5、6和7条件下制备的五个微胶囊样品的形态、平均尺寸和壳层厚度参数进行了研究。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）等方法分析了干燥微胶囊样品中石墨烯的存在情况和状态。利用傅里叶变换红外光谱（FT-IR）和能量色散谱仪（EDS）分析壳层中的石墨烯含量。这些结果证明石墨烯存在于壳层中，且pH值对石墨烯在壳层上的沉积有很大影响。研究发现，在pH = 5条件下制备的微胶囊样品，借助大分子缠结和静电吸附，壳层上沉积的石墨烯最多。由于壳层中额外的石墨烯，该微胶囊样品具有更高的热稳定性和更大的热导率。纳米压痕测试表明，由于石墨烯/聚合物结构的复合结构，该样品在压力下具有抗变形能力。此外，更多的石墨烯降低了核心材料从微胶囊壳层中渗出的渗透性。
