Department of Biomedical, Biological and Chemical Engineering, University of Missouri, Columbia, MO 65211, USA.
Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA.
J Colloid Interface Sci. 2020 Apr 15;566:304-315. doi: 10.1016/j.jcis.2020.01.080. Epub 2020 Jan 24.
This paper investigates the self-assembly behavior of a new amphiphilic block copolymer, PPEGMA-PPC-PPEGMA, in dilute aqueous solution and at the air-water interface. In PPEGMA-PPC-PPEGMA, the hydrophilic PEG moieties exist as side chains attached to the PMA backbone. Because of this unique non-linear architecture, the morphological and conformational properties of self-assembled PPEGMA-PPC-PPEGMA polymers are expected to be different from those of conventional linear PEG-based polymer surfactants.
For this study, three PPEGMA-PPC-PPEGMA samples having an identical PPC molecular weight (5.6 kDa) and different PPEGMA molecular weights (7.2, 2.8 and 2.1 kDa on either side) (named "G7C6G7", "G3C5G3", and "G2C6G2", respectively) were synthesized. The micellar self-assembly behaviors of these materials were investigated by cryo-TEM, rheology, DLS, and visual observation. Langmuir monolayers of these materials were characterized by surface mechanical testing.
PPEGMA-PPC-PPEGMA micelles were found to have a spherical geometry, irrespective of copolymer composition. Interestingly, G2C6G2 and G3C6G3 micelles formed weakly-bound clusters, whereas G7C6G7 micelles predominantly existed as isolated micelles. Detailed analysis suggests that this unexpected trend in micelle morphology originates from the fact that the PPEGMA blocks are only partially hydrated at aqueous interfaces. Detailed features of the surface pressure-area isotherms obtained from Langmuir PPEG-PPC-PPEGMA monolayers further supported this notion.
本文研究了一种新型两亲嵌段共聚物 PPEGMA-PPC-PPEGMA 在稀水溶液中和空气-水界面中的自组装行为。在 PPEGMA-PPC-PPEGMA 中，亲水性 PEG 链段作为侧基连接在 PMA 主链上。由于这种独特的非线性结构，自组装的 PPEGMA-PPC-PPEGMA 聚合物的形态和构象特性预计将与传统的基于 PEG 的聚合物表面活性剂不同。
在这项研究中，合成了三种具有相同 PPC 分子量（5.6 kDa）但 PPEGMA 分子量不同（两侧分别为 7.2、2.8 和 2.1 kDa）的 PPEGMA-PPC-PPEGMA 样品（分别命名为“G7C6G7”、“G3C5G3”和“G2C6G2”）。通过冷冻透射电子显微镜、流变学、DLS 和肉眼观察研究了这些材料的胶束自组装行为。通过表面力学测试对这些材料的 Langmuir 单层进行了表征。
发现 PPEGMA-PPC-PPEGMA 胶束具有球形几何形状，与共聚物组成无关。有趣的是，G2C6G2 和 G3C6G3 胶束形成弱结合的簇，而 G7C6G7 胶束主要以孤立胶束的形式存在。详细分析表明，这种胶束形态的意外趋势源于 PPEGMA 嵌段在水界面处仅部分水合的事实。从 Langmuir PPEG-PPC-PPEGMA 单层获得的表面压-面积等温线的详细特征进一步支持了这一观点。
