Main chain photoresponsive liquid crystalline polymer synthesized through hydrosilylation

Abstract

Liquid crystalline siloxane azo polymers are synthesized through hydrosilylation reaction between diallyl azo monomer and siloxane.dihydride. The molecular weights of the polymers ranged from 3000 -4000 gmol -1 . The polymers were found to be soluble in chloroform, THF, DMF, DMSO, and DCM respectively. The photoresponsive behavior was studied during exposure of the polymers to UV radiation. The trans-cis photoisomerisation rate constants were also determined. The thermotropic behavior of the polymers was studied by using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The polymers exhibited liquid crystalline texture of nematic droplets in POM images existing at room temperature and extending over broad temperature range up to 155°C. The DSC thermogram also supported the characteristic liquid crystalline transitions.

Main-chain liquid crystalline polymers bearing periodically grafted folding elements

“…12,13 Inclusion of flexible spacers in the polymer backbone, on the other hand, leads to completely different organization of the chains in the mesophase, which is also of a smectic-type; however, the chains typically lay extended perpendicular to the layer plane, with the mesogenic units lying either perpendicular (smectic A) or at an angle (semctic C) to the plane. A variety of flexible spacers, such as polymethylene, [17][18][19][20][21][22][23][24][25][26][27] oligoethylene oxide, [28][29][30][31][32][33] and oligosiloxane segments [34][35][36] have been incorporated within the backbone of the main-chain LCPs; oligosiloxane spacers have been found to reduce the phase transition temperatures most drastically and often lead to the formation of a nematic mesophase with wide temperature stability. In the cases where the pendant substituent is installed on the flexible spacer of the backbone, folding of the chain to exclude the pendant substituent is often seen; [37][38][39][40][41][42][43] this happens especially when a bulky pendant unit, such as a ferrocenyl 38,39 or phenyl unit, [40][41][42][43] is present.…”

Triptycene-Derived Photoresponsive Fluorescent Azo-Polymer as Chemosensor for Picric Acid Detection

“…18 Photochromic properties of azobenzene were also applied in the design of molecular machines, 19 nanodimensional vehicles, 20 molecular scissors, 21 molecular pedals, 22 molecular sunflower, 23 molecular lift, 24 and host–guest recognition. 25 Azo-polymers may have the azobenzene chromophore incorporated either in the side chains 26 or in the polymer main chain. 27…”

“…The potential applications of azo-polymers are, thus, mainly due to their unique ability to photoisomerize, photo-orient, and show refractive effect changes induced by light. , These materials are, therefore, recognized as promising candidates for applications such as optical data storage, , rewritable holograms, reversible photomechanical systems, holographic media for high-capacity data storage, as adsorbents with tunable pore size for CO 2 capture, and light-triggered drug release . Photochromic properties of azobenzene were also applied in the design of molecular machines, nanodimensional vehicles, molecular scissors, molecular pedals, molecular sunflower, molecular lift, and host–guest recognition . Azo-polymers may have the azobenzene chromophore incorporated either in the side chains or in the polymer main chain …”

“…18 Photochromic properties of azobenzene were also applied in the design of molecular machines, 19 nanodimensional vehicles, 20 molecular scissors, 21 molecular pedals, 22 molecular sunflower, 23 molecular lift, 24 and host−guest recognition. 25 Azo-polymers may have the azobenzene chromophore incorporated either in the side chains 26 or in the polymer main chain. 27 Triptycene is the smallest member of a class of aromatic compounds known as "iptycene" in which three or more arene rings are integrated via a bicyclo[2.2.2]octatriene bridgehead unit.…”

A facile synthetic route to novel thermotropic liquid crystalline polymers and characterization of their mesophases

“…Thermotropic liquid crystalline polymers (TLCPs) are high performance engineering materials because of their outstanding physical properties, particularly their high stiffness, strength, excellent dimensional and thermal stability, high chemical resistance, and remarkable barrier properties. [1][2][3][4][5] These superior properties arise from the unique structures of their mesogenic units which induce liquid crystalline phase ordering in the melt. Compared to lyotropic liquid crystalline polymers that form liquid crystalline structures in solution, thermotropic liquid crystalline polymers form liquid crystalline structures upon heating, which means they can be utilized in the fabrication of general thermoplastics with three-dimensional structures by using conventional processing equipment.…”