Department of Chemical and Biomolecular Engineering, 911 Partners Way, Engineering Building 1, Box 7905, North Carolina State University, Raleigh, NC, 27695-7905, United States.
Department of Chemical and Biomolecular Engineering, 911 Partners Way, Engineering Building 1, Box 7905, North Carolina State University, Raleigh, NC, 27695-7905, United States.
Colloids Surf B Biointerfaces. 2021 May;201:111595. doi: 10.1016/j.colsurfb.2021.111595. Epub 2021 Feb 3.
Water swellable crosslinked polymers are widely used in oil-in-water emulsions for the healthcare and cosmetic industries due to their thickening properties. In this study, we investigate the rheological and lubrication behavior of a microgel-forming polymer, a lightly-crosslinked hydrophobically modified polyacrylic acid (HMPAA), in an aqueous medium and in an emulsion. Hydrogenated phosphatidylcholine, a class of phospholipids, is used as a surfactant in the emulsions composed of different oil content. Rheological behavior is probed both in the linear and non-linear regimes using small strain amplitude and large amplitude oscillatory shear (LAOS) experiments, respectively. We observe all systems to exhibit gel-like behavior with the elastic modulus (G') dominating and being frequency independent. Lissajous-Bowditch plots and nonlinear parameters obtained under large deformation show that the emulsions can resist greater deformations with smaller increase in the viscous dissipation when compared to a HMPAA gel. For tribology experiments, friction curves in a range of entrainment speeds are examined using substrates to mimic the skin surface (PDMS and Bioskin®). The role of polymer hydrophobicity on the different substrates are also explored by comparing the behavior of HMPAA to that of its hydrophilic analog, a polyacrylic acid highly crosslinked. We find the friction coefficient to be dependent on the hydrophobicity of the substrate and the polymer as well as the substrate roughness. These results taken together provide insights in the formulation of skincare products with efficient lubrication properties for different skin characteristics.
水膨胀交联聚合物由于其增稠性能而广泛用于医疗保健和化妆品行业的水包油乳液中。在这项研究中，我们研究了一种微凝胶形成聚合物，轻度交联的疏水改性聚丙烯酸（HMPAA）在水介质和乳液中的流变和润滑行为。氢化磷脂是一类磷脂，用作不同含油乳液中的表面活性剂。使用小应变幅度和大振幅振荡剪切（LAOS）实验分别在线性和非线性范围内探测流变行为。我们观察到所有系统都表现出凝胶状行为，弹性模量（G'）占主导地位且与频率无关。大变形下获得的 Lissajous-Bowditch 图和非线性参数表明，与 HMPAA 凝胶相比，乳液可以抵抗更大的变形，而粘性耗散的增加较小。对于摩擦学实验，使用模拟皮肤表面的基底（PDMS 和 Bioskin®）检查了在一系列夹带速度范围内的摩擦曲线。通过比较 HMPAA 与其亲水类似物（高度交联的聚丙烯酸）的行为，还探索了聚合物疏水性对不同基底的作用。我们发现摩擦系数取决于基底和聚合物的疏水性以及基底粗糙度。这些结果一起为具有不同皮肤特性的高效润滑性能的护肤产品的配方提供了深入的了解。
