Geng Peng, Zore Ashish, Van De Mark Michael R
Department of Chemistry, Missouri S&T Coatings Institute, Missouri University of Science and Technology, Rolla, MO 65409, USA.
Polymers (Basel). 2020 Nov 21;12(11):2752. doi: 10.3390/polym12112752.
Studies of the evaporation of aqueous nanoparticle solutions have been limited due to lack of homogeneity of the solution, difficulties in obtaining reproducible samples and stability of substrates, as well as the effect of other volatile components or contaminants such as surfactants. Colloidal unimolecular polymer (CUP) is a spheroidal nanoparticle with charged hydrophilic groups on the surface, and the particle size ranges from 3 to 9 nm. The large amount of surface water on the CUP surface provides the opportunity to evaluate the evaporation of surface water, which may contribute to the investigation the factors that affect the evaporation rate in solutions of ultra-small particles, like protein, micelle, colloidal, etc. Six CUP systems were evaluated by thermogravimetric analysis (TGA) with respect to time and solids content. The evaporation rate of water was initially enhanced due to the deformation of the air-water interface at low to moderate concentration due to particle charge repulsive forces. At higher concentrations, above 20%, surface charge condensation and increasing viscosity began to dominate. At higher concentration where the CUP reached the gel point the rate of diffusion controlled the evaporation. The final drying point was the loss of three waters of hydration for each carboxylate on the CUP surface.
由于溶液缺乏均匀性、难以获得可重复的样品和稳定的基底，以及其他挥发性成分或污染物（如表面活性剂）的影响，水性纳米颗粒溶液的蒸发研究受到了限制。胶体单分子聚合物（CUP）是一种表面带有带电亲水基团的球形纳米颗粒，粒径范围为3至9纳米。CUP表面大量的表面水为评估表面水的蒸发提供了机会，这可能有助于研究影响超小颗粒（如蛋白质、胶束、胶体等）溶液蒸发速率的因素。通过热重分析（TGA）对六个CUP系统的时间和固体含量进行了评估。在低至中等浓度下，由于颗粒电荷排斥力导致气-水界面变形，水的蒸发速率最初会提高。在较高浓度（高于20%）时，表面电荷凝聚和粘度增加开始起主导作用。在CUP达到凝胶点的较高浓度下，扩散速率控制着蒸发。最终干燥点是CUP表面每个羧酸盐失去三个水合水。
