Novel photocrosslinkable liquid-crystalline polymers: poly[bis(benzylidene)] esters

Abstract

A new class of photo-cross-linkable main-chain liquid crystalline polymers (PMCLCPs) containing bis(benzylidene)cycloalkanone groups have been synthesized and studied for their liquid crystalline and photochemical properties. The bis(benzylidene)cycloalkanone group in the chain functions both as a mesogen and as a photoreactive center. All of the polymers exhibit a nematic mesophase. Two kinds of photoreactions, namely, photoisomerization and photo-cross-linking, operate in these polymers. Above T" at the initial stages of irradiation, photoisomerization predominates the cross-linking, which results in the disruption of the chromophore aggregates. Below Tg, because of the restricted mobility of the chains, only cross-linking takes place. Studies on the model compound, bis(benzylidene)cyclopentanone, confirm the above observations and demonstrate further that the cross-linking proceeds by the 2v + 2v cycloaddition reaction of the bis(benzylidene)cycloalkanone moieties. The cross-linking rate decreases with increase in the size of the cycloalkanone ring. Heating the solution cast polymer film results in the ordered aggregation of the chromophores just above T, and also at the crystal to crystal transition temperature, which facilitates the photo-croes-linMng reactions. In the isotropic phase, the random orientation of the chromophores drastically curtails the cross-linking rate.

Liquid crystalline photoactive hyperbranched and linear benzylidene polyester with terminal epoxy and pendant hydroxyl groups

“…This corresponds to formation of cyclobutane ring due to cycloaddition reaction in both polymers. 56 This behavior is also confirmed by studying the change in inherent viscosity at 30 8C (in DMSO) by using Ubbelohde viscometer at a concentration of 0.5 g/dL under UV exposure [ Fig. 4].…”

“…These results support the spectral studies, which are discussed in previous reports on similar class of polymers. 25,26,56 CONCLUSIONS Novel epoxy terminated photoactive linear and hyperbranched liquid crystalline benzylidene polyesters with pendant hydroxyl groups were synthesized by polyad- 1 H NMR spectrum of LECPE in DMSO-d 6 during photolysis (0-120 min). dition reaction of photoactive epoxidised bisbenzylidene cyclopentanone monomer with terephthalic acid and trimesic acid respectively.…”

Synthesis and Studies on Certain Semiconducting Copolyesteramides Containing 2, 5-Pyridine Dicarboxylic Acid and their Photocross linkable Blend Nanofibers

“…[19] Borden et al [20,21] synthesized photo-responsive linear bis(benzylidene) polycarbonates and observed that they were poorly soluble. In 1993, Gangadhara and Kishore [6] prepared polybis (benzylidene) esters from tetragolic acid dichloride and bis(4-hydroxy benzylidene) cyclohexanone and reported improved solubility. The present investigation showed appreciable solubility in polar solvents.…”

“…[1][2][3][4][5] Photocrosslinkable polymers have attracted considerable attention in the research field because of their interesting mechanical, electrical and optical properties. Photocrosslinkable polymers find potential applications in the preparation of photo curable coating, photocrosslinked hydrogels, optical lithographic materials, photo sensitizers, photo resists, photorefractive materials [6 ] and information storage devices. Polymers having photodimerizable groups find applications in immobilization of enzymes [7][8][9][10][11][12][13].…”

Synthesis, Characterization and Photocrosslinkable Studies of Certain Thermotropic Liquid Crystalline Poly(ester-amides)

“…Synthesis of bisbenzylidene cycloalkanone molecule was first reported by Samdahl [1,2]. This photo-active molecule has attracted the attention of macromolecular chemists [3][4][5][6][7]. They were found to be a potential mesogen [8][9][10] and their incorporation in the polymeric backbone has imparted thermotrophic liquid crystalline property to the polymeric materials.…”