Langmuir–Blodgett membrane of amphiphilic di-block copolymer as the quasi-equilibrium state

The Langmuir–Blodgett (LB) membrane of amphiphilic di-block copolymer, PEO40-b-PMA(Az)19, was prepared at 24 mN m−1 of surface pressure in the two-dimensional solid state. The structure of 20 layers LB membrane was analyzed by X-ray diffraction (XRD), total X-ray reflectivity (TR) and grazing incidence X-ray scattering (GISAXS) measurements. The molecular section area of one hydrophobic PMA(Az) molecule obtained by π–A isotherm was 0.31 nm2. The LB membrane thickness was 67.9 nm consisted of the ordered lamellar structure with 3.2 nm spacing from TR and XRD measurements. From azimuthally scattering of GISAXS, two ordered structures with 0.4 and 2.175 nm existed perpendicular to LB surface, the former was corresponded to the distance between azobenzenes with random orientation and the latter was to the compressed PMA(Az)19 domains which oriented normal to the dipping direction.