Synthesis and characterization of thermotropic liquid crystalline polyesters with biphenyl unit in the main chain

Optical Behaviors of Cholesteric Liquid-Crystalline Polyester Composites with Various Chiral Photochromic Dopants

New developments in the field of chiral nematic liquid crystals, such as color displays, are now being widely proposed. This article describes the tunable incident reflection band based on composite materials of low-molecular-weight chiroptical dopants and polymeric networks. These materials have advantages including easily manageable color according to a change in the helical pitch of the cholesteric liquid crystal upon exposure to light. A series of novel chiral dopants of isosorbide derivatives containing photochromic groups and three new main-chain liquid crystalline polyesters were synthesized and identified using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and elemental analyses. The phase-transition temperatures and the liquid-crystal phase determination of the synthesized polymers were estimated using DSC, WAXD, and POM analyses. The influence of the dopant concentrations and the solubility in a liquid crystalline polymer blend were also studied. The reflection band of the cholesteric liquid crystalline composites could be adjusted and tuned with a wide range of color variation across the entire visible region. A real image recording of the chiral photochromic liquid crystalline polymer blend was achieved by exposing it to UV light through a mask.

Synthesis and characterization of certain photocrosslinkable thermotropic liquid crystalline random copolyesters containing arylidene moiety

A new series of 12 thermotropic liquid crystalline and photocrosslinkable random copolyesters were synthesized from terephthalic acid, isophthalic acid and 4,4'-oxybis(benzoic acid) with four different arylidene diols and a common diol 1,2-bis(4-hydroxybenzoyloxy)ethane by direct polycondensation with diphenylchlorophosphate. The resulting polymers had inherent viscosities in the range 1.20–1.74 dl/g. Their structural features were investigated by Fourier transform infrared (FTIR), 1H, and 13C nuclear magnetic resonance (NMR) spectroscopy. The thermal behaviour of the copolyesters was investigated with differential scanning calorimetry and hot stage optical polarized microscopy. Our investigation on the effect of monomer structure on liquid crystalline behaviour shows that the copolymers containing bis(benzylidene)cycloalkanone exhibited higher melting and isotropization temperatures and extended liquid crystalline range. All of the copolymers showed some degree of crystallinity as evidenced by wide-angle X-ray diffraction and scanning electron microscopy. The photocrosslinkability of these polymers was established with UV irradiation/UV spectroscopy and scanning electron microscopy.

Physicochemical performances of indomethacin in cholesteryl cetyl carbonate liquid crystal as a transdermal dosage

A transdermal formulation of indomethacin (IMC) was developed by incorporation into cholesteryl cetyl carbonate (CCC). The liquid crystalline phase properties of the IMC-CCC mixture were detected by polarized light microscopy and differential scanning calorimetry. A low drug loading was obtained (1-5 %) similar to that used in conventional topical IMC in a clinical setting. A controlled release of IMC was found over 12 h. A low amount of IMC in 1 % IMC-CCC permeated the stratum corneum. Further formulation development has been carried out by the addition of lauryl alcohol into 5 % IMC-CCC mixture it was found that the permeation of IMC was significantly improved to 45 % within 24 h.