Page 166 - Photoreactive Organic Thin Films

CHHtAL POLYMERS WITH

PHOTOAFFECTED PHASE

BEHAVtOR FOR OPTICAL DATA

STORAGE

MIKHAIL V. KOZLOVSKY*,*
LEV M. BLINOV*
WOLFGANG HAASE*
* Institute of Physical Chemistry, Darmstadt University of Technology, D-64287, Darmstadt,
Germany
r
Institute of Crystallography, Russian Academy of Sciences 117333, Moscow, Russia

5.1 INTRODUCTION
5.2 AMORPHOUS, OPTICALLY ISOTROPIC MESOPHASE OF
CHIRAL SIDE-CHAIN POLYMERS WITH A HIDDEN LAYER
STRUCTURE—THE "ISOTROPIC SMECTIC" PHASE
5.3 PHOTOINDUCED BIREFRINGENCE IN PHOTOCHROMIC
ISOSM* COPOLYMERS
5.4 HOLOGRAPHIC GRATING RECORDING
5.5 PHOTOINDUCED ALIGNMENT OF LOW MOLAR MASS
LIQUID CRYSTALS
5.6 PHOTOAFFECTED PHASE BEHAVIOR AND THE LCPT
PHOTORECORDING
5.7 CONCLUSIONS

5.1 INTRODUCTION

During the decade of the 1990s, substantial interest has grown in photoad-
dressed polymer materials. These systems are characterized by their capability
of reversible reorientation and/or photochemical transformations under the
action of UV or visible light, followed by corresponding change in such opti-
cal properties as birefringence, transparency, or color. Therefore, they are
widely investigated as optical data storage and photorecording media, coat-
1 2 3
ings for contactless surface controlling, NLO active materials, and so on. ' '
Among these photosensitive polymer materials, foremost are the systems
containing dichroic azobenzene moieties either as low molar mass compo-
nents or as fragments of the macromolecule itself. The key physical process
involved is the repetitive E/Z-isomerization of azobenzene groups, as shown
next.

Photoreactwe Organic Thin Films 145
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