中性子反射率測定によるポリマーブラシの水界面構造解析

抄録

This article describes the swelling behavior of polyelectrolyte brushes in aqueous solutions with different salt concentrations analyzed by neutron reflectometry. Densely-grafted polyelectrolyte brushes such as poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMTAC), and poly(3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate) (PDMAPS) were prepared on quartz substrate by "grafting-from" method based on a surface-initiated polymerization technique. Neutron reflectivity at swollen brushes/D₂O interface afforded the neutron scattering length density profiles and the corresponding volume fraction profiles based on a parabolic function to estimate the swollen brush thickness. PMTAC brush was fairly extended from the substrate surface in D₂O, while it shrunk in NaCl/D₂O solution due to the screening of the repulsive interaction between polycations by hydrated salt ions. In contrast, PDMAPS brush in D₂O formed shrunk structure due to strong attractive interaction between sulfobetain groups, while the swollen thickness was drastically increased by addition of salt ions to D₂O. Non-dependency of swollen thickness on NaCl concentration was observed in PMPC brush because of weak electrostatic interaction between phosphorylcholine groups.