Photoreactive chiral liquid‐crystalline side‐group copolymers containing azobenzene mesogens

Abstract

A series of liquid‐crystalline copolymers 1 with a chiral azobenzene moiety as photoreactive mesogenic unit was prepared. The polymers were fractionated and the mesophase behaviour of the high‐ and low‐molecular weight fractions was examined. The copolymers display smectic A and cholesteric phases. For the cholesteric phases the pitch of the helix was determined, which ranges from 3 to 20 μm. Stable monolayers at the air‐water interface were obtained from two monomers and one of the homopolymers. Multilayer assemblies of the azobenzene‐containing polymers can be used to study photo‐induced order/disorder transitions.

Comb-Shaped Polymers with Mesogenic Side Groups as Electro- and Photooptical Active Media

“…In the case of the acrylic copolymers, the LC phase is formed over a wide range of dye concentration owing to the fact that T g < T cJ for all copolymers. In the methacrylic copolymers the values of glass transition temperatures are higher [34] than their hypothetic clearing temperatures and the mesophase is not realized. A further increase of azobenzene monomeric units in methacrylic copolymers results in changing the relation between T g and T cI (T cI becomes higher than T g) and the mesophase is formed.…”

“…A further increase of azobenzene monomeric units in methacrylic copolymers results in changing the relation between T g and T cI (T cI becomes higher than T g) and the mesophase is formed. In general, it is necessary to note that the azobenzene fragments are well "built" into the LC phase of copolymers and owing to their mesogenic rod-like shape do not disturb the LC structure of the initial matrix [33][34][35]. The high values of the order parameters S of such copolymers show strong evidence for the above-mentioned data.…”

“…The attractive chiral azo dye monomers incorporated in the macromolecules of the acrylic copolymers II are described in [34].…”

Thermotropic comblike polymers with lipobiphenyl side chains: Factors governing nature of mesophases

“…Polymers with carbonitrilebiphenyl mesogens Influence of Temperature and x Å 11 but with different main chains [polyacrylates, 19 polyacrylamides, 5 polymethacrylamThe increase of temperature at about 100ЊC generally involves a transition between two smectic ides (this work), and polystyrylamides 8 ] all exhibit only disordered smectic phases, but the type phases (Table III). The first mesophase is an ordered smectic phase except for R Å CN.…”

Side chain liquid crystalline diethanolamine‐based polyesters with methoxy and/or nitroazobenzene mesogenic moieties

“…Since polymers with photochromic azobenzene moieties in the side chain are promising materials for reversible data storage and nonlinear optical applications, much of the literature deals with the synthesis and properties of this type of polymer. The polymers investigated are mostly based on polyacrylates or polymethacrylates [6][7][8], polysulphones [9], polystyrene [10,11] and polyesters [12][13][14][15]. The SCLC polyesters are particularly interesting as the main chain can be tailored to particular specifications by using different acidic and diol segments, both of which provide the linking unit for the various mesogenic groups.…”