01941nas a2200145 4500008004100000245012600041210006900167260000800236300001600244490000700260520136000267100002501627700001701652856012601669 2012 eng d00aTwin liquid crystals and segmented thermotropic polyesters containing azobenzene?effect of spacer length on LC properties0 aTwin liquid crystals and segmented thermotropic polyesters conta cJUL a2770–27850 v503 a

We report systematic studies on a homologous series of twin liquid crystalline (LC) molecules based on phenyl and naphthyl azobenzene (PnP and NpnNp) as well as segmented copolyesters based on them. The twin series had the structure azobenzene–oligooxyethylene–azobenzene, where the ethyleneoxy length was varied from 2 to 6 units. The LC properties of the twin series depended on the chemical structure of the azochromophore and also the length of the central oligooxyethylene segment. The PnP series exhibited smectic LC properties for n > three oligooxyethylene units. Conversely, NpnNp series exhibited spherulitic phases only for the shortest member –Np2Np. One non-LC short spacer twin (P2P) and one LC long spacer twin (P6P) were incorporated as part of a main chain polyester composed of fully aliphatic segments of sebacate and di or tetraethylene glycol (DEG/TEG) units by melt polycondensation. Non-LC P2P formed LC polymers even at low (5 mol %) incorporation in DEG-based copolymers, whereas the LC-P6P could do so only at 30 mol % incorporation. The LC properties of the twin molecules as well as copolymers were studied using differential scanning calorimetry, polarized light microscopy (PLM) along with variable temperature wide angle X-ray diffraction. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

1 aNardele, Chinmay, G.1 aAsha, S., K. uhttps://library.ncl.res.in/content/twin-liquid-crystals-and-segmented-thermotropic-polyesters-containing-azobenzeneeffect01852nas a2200157 4500008004100000022001400041245008800055210006900143260007100212300001400283490000800297520122200305100002501527700001701552856012501569 2014 eng d a1520-610600aPhotoresponsive smectic liquid crystalline multipods and hyperbranched azo polymers0 aPhotoresponsive smectic liquid crystalline multipods and hyperbr a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB a1670-16840 v1183 a

Liquid crystalline azobenzene containing triped and tetraped monomers were designed and synthesized and further used as B-3 and B-4 type monomers to form hyperbranched polymers with tetraethylene glycol as the A(2) type comonomer. The mesophase characteristics of the multiarm-star mesogens and hyperbranched polymers were analyzed using various instrumentation techniques like differential scanning calorimetry (DSC), polarized light microscopy (PLM) and variable temperature XRD. The multipod monomers as well as hyperbranched polymers exhibited thermotropic smectic liquid crystalline characteristics with a tendency toward higher ordered smectic LC phases with increased branching. The hyperbranched polymers exhibited lamellar organization even in the as-solvent precipitated powder sample indicating higher extent of nanosegregation. Their potential application as fast switching photochromic materials was highlighted by carrying out isothermal photo-switching experiments in the LC state. Reversible isothermal smectic-isotropic phase transition could be achieved by UV irradiation in <1 s in the multipod monomers, while it required >2 s UV irradiation in the case of the hyperbranched polymers.

1 aNardele, Chinmay, G.1 aAsha, S., K. uhttps://library.ncl.res.in/content/photoresponsive-smectic-liquid-crystalline-multipods-and-hyperbranched-azo-polymers-002117nas a2200217 4500008004100000022001400041245008500055210006900140260006700209300001200276490000700288520132500295653001701620653002101637653003801658100002501696700002401721700001801745700001701763856011901780 2015 eng d a0887-624X00aIonic conductivity probed in main chain liquid crystalline azobenzene polyesters0 aIonic conductivity probed in main chain liquid crystalline azobe a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcMAR a629-6410 v533 a

Three main chain thermotropic liquid crystalline (LC) azobenzene polymers were synthesized using the azobenzene twin molecule (P4P) having the structure Phenylazobenzene-tetraethyleneglycol-Phenylazobenzene as the AA monomer and diols like diethylene glycol, tetraethylene glycol (TEG), and hexaethylene glycol as the BB comonomer. Terminal C(O)OMe units on P4P facilitated transesterification with diols to form polyesters. All polymers exhibited stable smectic mesophases. One of the polymers, Poly(P4PTEG) was chosen to prepare composite polymer electrolytes with LiCF3SO3 and ionic conductivity was measured by ac impedance spectroscopy. The polymer/0.3 Li salt complex exhibited a maximum ionic conductivity in the range of 10(-5) S cm(-1) at room temperature (25 degrees C), which increased to 10(-4) S cm(-1) above 65 degrees C. The temperature dependence of ionic conductivity was compared with the phase transitions occurring in the sample and it was observed that the glass transition had a higher influence on the ionic conductivity compared to the ordered LC phase. Reversible ionic conductivity switching was observed upon irradiation of the polymer/0.3 Li salt complex with alternate UV and visible irradiation. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 629-641

10aazo polymers10aglass transition10aliquid-crystalline polymers (LCP)1 aNardele, Chinmay, G.1 aDhavale, Vishal, M.1 aSreekumar, K.1 aAsha, S., K. uhttps://library.ncl.res.in/content/ionic-conductivity-probed-main-chain-liquid-crystalline-azobenzene-polyesters-0