Mesomorphic polyacrylates containing isomeric methyl‐substituted azobenzene mesogens

Abstract

The synthesis and characterization are reported of two new series of structurally isomeric polyacrylates containing the azobenzene moiety spaced away from the backbone by a hexamethylene spacer and substituted in 4-position with linear alkoxy groups (C1-C6, Clo) and with a lateral methyl group in 2'-or 3'-position. Thermal optical and X-ray analyses of the prepared polymer samples, with molecular weight ranging from 50 X lo3 to 35 X lo4 Dalton ( M u / M n = 2-3), provide evidences for the establishment of liquid crystalline behavior in the melt in a fairly broad range of temperature. In any case, quenching from the mesophase allows for the lock-in of the liquid crystalline structure in the glassy state. The presence of the lateral methyl-substituents causes a drop as high as 50-100 K in the stability of the mesophase with respect to the corresponding samples of the methyl-unsubstituted series.A parallel depletion of the smectogenic character is also observed. Typical even-odd effects on the isotropization temperature and relevant thermodynamic parameters have been detected along with the formation of interdigitated smectic structures.

On the simulation of inhomogeneous ESR lineshape of a spin probe in a liquid crystalline polymer

“…The side chain liquid crystalline polymer of the present study is a polymethacrylate (PMA) containing an azobenzene mesogenic unit connected by a hexamethylene spacer to the main chain [30]. It forms a nematic phase between the glass transition temperature (Tg = 294 K) and the nematic isotropic transition temperature (TNI = 353 K).…”

Molecular relaxation in a photosensitive liquid-crystalline polymeric glass former

“…The specific material that we studied is PA4: poly[[4-pentiloxy-3 -methyl-4 -(6-acryloxyexyloxy)]azobenzene] [6]; it shows solid-nematic and nematic-isotropic transitions at 83…”

A calorimetric study of structural relaxation in the glassy state of a liquid-crystal polymer

“…Experimental details The polymer under investigation is a polymethacrylat e containing a (3-methyl-4 0 -pentyloxy) azobenzene mesogenic unit connected at the 4-position by a hexamethylene spacer to the main chain (®gure 1). It was synthesized by following a general procedure given in the literature (Angeloni et al 1991). It forms a nematic mesophase between the glass transition temperature …T gˆ2 92 K) and the nematic± isotropic transition temperature (T NIˆ3 53 K).…”