| 초록 |
There has recently been much interest in polyelectrolyte copolymers since they have been shown to have numerous applications as biomimetic or electronic materials. In particular, thin films of these polymers have been used as coatings to control the adhesion of cells or in producing electronic devices. In all these cases the polyelectrolytes were used in solvents or their mixtures under conditions of varying salts or dielectric properties. Most theoretical studies to date have concentrated on the conformation of polyelectrolyte brushes. Since these brushes are very difficult to synthesize, only limited experimental results have been reported. In addition, the films most relevant for practical applications have been random copolymers where even less in known about the conformation in thin films in contact with various solvents. In this work, we conducted a detailed study on the structure of Langmuir monolayers of sulfonated polystyrene with low level of sulfonation (3 ?5 %) at the air/water interface. To get the exact depth profiles, neutron reflectivity was performed. With the 35% charged polymer, the highly stretched brush was observed, while only localized thin layer was observed for the polymers with less than 24% of sulfonation. The brush profile can be numerically simulated by self consistent fields (SCF) theory, and compared to the parabolic profile from neuron reflectivity data, providing basic structural information including (a) how the adsorbed sulfonated PS blocks are submerged into the water subphase when the ionic strength of subphase is modified, (b) whether the associated ions are indeed localized within the films. Part of this work was supported by the Korean Research Foundation. |
