Analysis of Multilayer Structure of Amphiphilic Di-block Copolymer by X-ray Reflectivity

The structure of Langmuir-Blodgett (LB) membranes of liquid crystal amphiphilic di-block copolymer, poly(ethylene oxide)-b-poly{11-[4-(4-butylphenylazo) phenoxy]-undecyl methacrylate, (PEO-b-PMA(Az)) was investigated by X-ray reflectivity (XR). XR results indicated that the structure of LB membranes below 6 layers was formed by the head to head type bilayer structure consisting of the extended hydrophilic PEO and the compressed hydrophobic PMA(Az) layers. In the case of 10 layers, the another type of bilayers consisting of the interdigitate PMA(Az) structure corresponding to the smectic C phase in the bulk state and the collapsed PEO layer were lapped on the bilayer structure of 6 layers. The structural transition from the head to head type bilayer to the interdigitate bilayer occurred around 6 to 10 layers.