Photoresponsive Ferroelectric Liquid‐Crystalline Polymers

Abstract

The photoresponse of ferroelectric smectic side‐chain liquid‐crystalline (LC) polymers containing a photoisomerizable azobenzene derivative as a covalently linked photochromic side group is investigated. By static measurements in different photostationary states, the effect of trans–cis isomerization on the material's phase‐transition temperatures and its ferroelectric properties (spontaneous electric polarization PS and director tilt angle θ) are analyzed. It turns out that the Curie temperature (transition SC* to SA) can be reversibly shifted by up to 17 °C. The molecular mechanism of this “photoferroelectric effect” is studied in detail using time‐resolved measurements of the dye's optical absorbance, the director tilt angle, and the spontaneous polarization, which show a direct response of the ferroelectric parameters to the molecular isomerization. The kinetics of the thermal reisomerization of the azo dye in the LC matrix are evaluated. A comparison to the reisomerization reaction in isotropic solution (toluene) reveals a faster thermal relaxation of the dye in the LC phase.

Mesomorphic Sugar‐Coated Polydiacetylene Polymers

“…[1][2][3][4] PDA polymers exhibit characteristic thermochromatic properties, as a result these polymers are utilized in a number of biological, interfacial, and materials applications. [4][5][6][7][8][9][10][11][12][13][14][15] Inducing anisotropy in PDAs would result in a liquid crystalline (LC) behavior, [16][17][18] as illustrated through functionalizing the polymers with moieties such as aromatic dicarboxylic acids, [13,18,19] biphenyl esters, [20,21] cyanostilbene, [22] and azobenzene. [23] Incorporation of amphiphilicity in a molecule is a fruitful route to enable mesomorphic behavior.…”

New ferroelectric liquid crystals for high‐performance optical devices

“…Ferroelectric liquid crystals (FLCs) were discovered in 1975 by Meyer et al (1) and since then both the physics as well as the technology of FLCs have been extensively developed (2)(3)(4)(5)(6)(7)(8). Significant interest has been aroused in the chiral smectic C (SmC*) phases owing to their fast electro-optical response, which is useful in many applications.…”

Photoinduced cooperative reorientation in polymer blend films with hydrogen-bonded mesogenic side groups

“…Passive optical devices such as birefringent films and polarization holographic gratings have been fabricated using these molecular reoriented films [3][4][5]. Furthermore, cooperative photoinduced molecular orientation allows to introduce the functionality of the reoriented films by tuning the comonomers with non-photoreactive mesogenic side groups [6][7][8][9][10][11][12][13][14][15][16][17].…”

“…In these copolymers, comonomers consisted of photoreactive and non-photoreactive mesogenic side groups, were randomly polymerized to induce an effective cooperative orientation [6][7][8][9][10][11][12][13][14][15][16][17]. If polymer blends of photoreactive and nonphotoreactive homopolymers reveal a similar photoinduced molecular reorientation, adjusting the blend ratio can be used to easily control the functionality of the reoriented films, without having to synthesize random copolymers.…”