Nanostructure of Cationic Polymer Brush at the Air/Water Interface

¹ Department of Polymer Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan
² Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
³ Osaka Organic Chemical Industry, 1-7-2 Hon-cho, Nihonbashi, Chuo-ku, Tokyo 103-0023

^* To whom correspondence should be addressed. matsuoka@star.polym.kyoto-u.ac.jp

Abstract

Cationic amphiphilic diblock copolymers were synthesized by RAFT polymerization and the nanostructure of their monolayers was investigated by π-A isotherm and X-ray reflectivity. Carpet layer (dense hydrophilic block layer) formation under the hydrophobic layer was confirmed and a “brush” layer was found beneath the carpet layer. However, the thickness of brush layer was much thinner than that of the fully-stretched chain length. The critical salt concentration was found to be 0.01 M NaCl, which is much lower than that of the previous strongly anionic brush. These differences were probably caused by the low effective charge on the brush chains due to the hydrophobic nature of the quarternized ammonium cation.