Langmuir, Vol.13, No.19, 5120-5124, 1997
Structure and Photoisomerization of the Z-Type Langmuir-Blodgett-Films of a New Series of Azo-Containing Chiral Copolymers
Three copolymers, Al, A2, and A3, poly{2-hydroxyethyl methacrylate}(1-x)-co-{6-[4-((((((S)-2-methylbutyl)-oxy)carbonyl)phenyl)azo)phenoxy]hexyl methacrylate}(x) with x = 0,25, 0.50, and 0.75, respectively, were successfully deposited as Z-type Langmuir-Blodgett (LB) films. The isobar curves and the compression-expansion isotherms of the three copolymers on water show that the polymer monolayers have good quality, Polarized W-vis and IR spectroscopic measurements reveal that the LB films of Al, A2, and A3 on substrates are organized with the long aids of azobenzene moiety preferentially along the film normal, and the LB films of Al have additional in-plane orientation. The LB films of A1, A2, and A3 are all capable of trans-to-cis and cis-to-trans photoisomerizations. Photoinduced liquid crystal alignment alteration from the homeotropic mode to planar mode is achieved with the Z-type films of A1. It is concluded that the LB films of Al have the right occupied molecular area for photoinduced liquid crystal alignment regulation.
Keywords:PHOTOCHROMIC MOLECULAR FILMS;REVERSIBLE ALIGNMENT CHANGE;NEMATIC LIQUID-CRYSTALS;COMMAND SURFACES;AZOBENZENE;MONOLAYERS;POLYMERS;SPECTROSCOPY;ORIENTATION;MULTILAYERS