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Synthesis, Liquid‐Crystalline Properties, and Photo‐optical Studies of Photoresponsive Oligomeric Mesogens as Dopants in a Chiral Glassy Liquid Crystal
Author(s) -
Akiyama H.,
Mallia V. A.,
Tamaoki N.
Publication year - 2006
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200500176
Subject(s) - dopant , materials science , liquid crystal , oligomer , cholesteric liquid crystal , alkyl , polymerization , reflection (computer programming) , bilayer , crystallography , photochemistry , polymer chemistry , doping , polymer , organic chemistry , optoelectronics , composite material , membrane , chemistry , computer science , programming language , biochemistry
We have prepared photoresponsive oligomers that have molecular weights of ca. 4500, 8000, and 16 000 g mol –1 via the free‐radical polymerization of 4‐[4‐alkylphenylazo]phenoxyalkyl acrylates. All of the oligomers possess bilayer smectic A (SmA) and smectic B (SmB) phases. Increasing the concentration of these oligomeric dopants in a glass‐forming cholesteric liquid crystal causes a dramatic red‐shift in the reflection wavelength. The pitch shifts are very dependent on the alkyl chain lengths and molecular weights of the dopants. The oligomer that contains octyl chains and an octyl spacer, and that has a molecular weight of 4500 g mol –1 exhibits the largest shift in the reflection wavelength. UV exposure has been used to control the cholesteric reflection pitch of the oligomer‐cholesteric glassy liquid‐crystal mixture over the entire visible region of the electromagnetic spectrum and vitrifies the samples by rapid cooling from their cholesteric temperatures to 0 °C. Extremely stable, even at 70 °C, erasable, full‐color images have been created using this host–guest mixture.