The packing of azobenzene dye moieties and mesogens in polysiloxane copolymers and its impact on the opto-dielectric effect

Abstract

Broadband dielectric spectroscopy (10 Õ 2 ± 10 5 Hz) is used to study the opto-dielectric e ect in statistical polysiloxane copolymers with side groups containing chiral mesogenic units and others containing azobenzene moieties. Below 64ß C, the unexposed copolymer is ferroelectric. UV-exposure induces a photoisomerization of the azobenzene to the cis-con® guration, and the phase transition, ferroelectric/non-ferroelectric (S * C/SA ), is shifted to lower temperatures. In the temperature interval between the phase transition temperatures ferroelectric/nonferroelectric of the exposed and unexposed samples, an opto-dielectric e ect is observed. The e ciency of this opto-dielectric switching depends on the packing of the chromophore within the smectic layers.

Synthesis and characterization of novel ferroelectric liquid crystals and copolymers containing biphenyl azobenzene and / or phenyl biphenyl carboxylate mesogenic groups

“…This investigation, due to the possibility of their use in Ps photo-modulation e ect has been observed in polydisplays and optoelectronic devices [1]. Fast switching meric ferroelectric liquid crystals by Zentel et al [3,4] between two stable orientations in the SmC* phase is who demonstrated that trans-cis isomerization of an the key for the interest in this subject. In a signi® cant azobenzene side chain shifts the P s vs. temperature curve paper, Ikeda et al [2] showed that ferroelectric switchtowards lower temperatures, which can induce an order± ing can be photochemically induced using a photodisorder transition in a certain temperature range that isomerizable compound based on azobenzene.…”

New Siloxane‐Organic Polyesters with Azobenzene Side Chains. Synthesis, Thermotropic Behavior and Surface Properties

“…For example, the azo content in side-chain siloxane copolymers and terpolymers influences their phase behavior, [10] or optodielectric switching. [11] The role of the siloxane spacer in side-chain azobenzene liquid-crystalline (LC) polymers Summary: New siloxane-organic polyesters, bearing azotype units in the side chain, were synthesized by direct solution polycondensation at room temperature, starting from 2,2 0 -[4-[(4-nitrophenyl)azo]phenyl]iminobisethanol (Disperse Red 19) and different siloxane diacids, using dicyclohexylcarbodiimide as an activator and 4-(N,N-dimethylamino)pyridinium-p-toluenesulfonate as the catalyst. The structure of the obtained polyesters was confirmed by 1 H and 13 C NMR as well as IR spectroscopy.…”

Photoswitchable Polysiloxane Self-Assembled Monolayer

“…[7,8] Attractive properties have been reported for azo-containing siloxane polymers and co-polymers. For example, the azo content of side-chain siloxane copolymers and terpolymers was found to influence their phase behavior [9] and optodielectric switching [10] . The role of the siloxane spacer in side-chain azobenzene liquid-crystalline (LC) polymers was studied in applications in holographic grating [11,12] and the dipolar alignment of nonlinear optical (NLO) materials.…”