화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.104, No.17, 4141-4147, 2000
Modeling the interface region of command surface 1. Structural evaluations of azobenzene/liquid crystal hybrid Langmuir monolayers
Langmuir films composed of mixtures of an amphiphilic polymer containing azobenzene (Az) side chain (6Azn-PVA, II being the spacer length) and a nematic liquid crystal (LC) molecule, 4'-pentyl-4-cyanobiphenyl (5CB), were prepared at the air-water interface in an attempt to construct the interface model of the command surface system which performs the photoswitching of LC alignment. Surface pressure-area isotherms, visualization by Brewster angle microscopy (BAM) and atomic force microscopy (AFM), and UV-visible absorption spectroscopy revealed that the two components are homogeneously mixed at a molecular level without lateral phase separation under proper conditions concerning the way of mixing, the mixing ratio, and the spacer length of the side chain. Upon homogeneous co-spread mixing, both the Az side chain of 6Azn-PVA and the LC molecule were oriented highly perpendicular to the water surface, which was unavailable with the individual component. This orientational induction can be ascribed to a mutual insertion of the two rod-shaped components attained in a cooperative fashion. The above structural features of the hybrid monolayer fulfill important criteria in modeling the interface region of the photoswitchable LC alignment layer. Effects of changes in mixing ratio and the spacer length (n) on the film structure are also described.