Glassy liquid crystals films

SH Chen, D Katsis, AW Schmid, JC Mastrangelo, T Tsutsui, and TN Blanton, Circularly polarized light generated by photoexcitation of luminophores in glassy liquid-crystal films, Nature, 397 506-508, 1999. 

S. H. Chen, D. Katsis, A. W. Schmid, J. C. Mastrangelo, T. Tsutsui, T. N. Blanton, Circularly Polarized Light Generated by Photoexcitation of Lumino-phores in Glassy Liquid-crystal Films, Nature 1999, 397, 506-508. 

Fig. 6.7 a Molecular structures of the three components for b a 22-pm-thick gradient-pitch glassy liquid crystal film with (27) (28) (29) at 1.00 0.23 0.13 molar ratio through irradiation at 334 nm (140 pW/cm ) and 100 °C for 2 h using circularly polarized incidents for transmission measurement, and c 8-pm-thick constant-pitch films with (27) (28) (29) at 1.00 1.65 0.40 molar ratio through irradiation at 334 mn (70 pW/cm ) and 120 °C for durations as Indicated using unpolarized incidents for transmission measurement. Used with permission [41]... 

Fig. 6.8 Glassy liquid crystal Films A-D defined by wt% of (20) in the (19) (20) mixtures at 100, 95, 51, and 38, respectively, all doped with Exalite 428 at 0.2 wt% for photoexcitation at 370 nm dissymmetry factors for a 14-pm-thick films, and b Film A as a function of film thickness. Used with permission [43]...

H.M.P. Chen, D. Katsis, J.C. Mastrangelo, S.FL Chen, S.D. Jacobs, P.J. Hood, Glassy liquid-crystal films with opposite chirality as high perftmnance optical notch filters. Adv. Mater. 12,... 

S.H. Chen, J.C. Mastrangelo, R.J. Jin, Glassy Liquid-crystal films as broadband polarizers and reflectors via spatially modulated photoracemization. Adv. Mater. 11, 1183-1186 (1999)... 

Glassy Liquid Crystals as Self-Organized Films for Robust Optoelectronic Devices... 

S.K.-H. Wei, S.H. Chen, Spatially resolved lasers using a glassy cholesteric liquid crystal film with lateral pitch gradient. Appl. Phys. Lett. 98, 111112 (2011)... 

The thickness of the membrane phase can be either macroscopic ( thick )—membranes with a thickness greater than micrometres—or microscopic ( thin ), i.e. with thicknesses comparable to molecular dimensions (biological membranes and their models, bilayer lipid films). Thick membranes are crystalline, glassy or liquid, while thin membranes possess the properties of liquid crystals (fluid) or gels (crystalline). 

The macromolecular nature provides an interesting feature of LC polymeric cholesterics, namely the possibility of obtaining monochromic films. Thus for polymeric liquid crystals the helix pitch is practically not altered with temperature below Tg, when a cholesteric phase is frozen in a glassy matrix (Fig. 23a). This implies that fast cooling of polymeric films from a mesomorphic state (shown with arrows) fixes their optical properties, which makes it possible to use them at ordinary temperatures as selective monochromic reflectors. On the other hand, such polymeric films display the extraordinary polarizing properties of cholesterics, i.e. the different absorption... 

In the 1930 s it was shown by E. Vorlander [Trans. Faraday Soc., 29, 907 (1933)] that some liquid crystals could be quick frozen to a metastable brittle glassy state. By working with a polymeric molecule, a synthetic polypeptide called poly-y-benzyl-L-glutamate, we have been able to obtain stable solid films with a liquid crystalline local structure. These films can be obtained in conditions describable as rubbery, leathery, or glassy, as is common for polymer films. The unusual local structure of the molecules in the liquid crystalline phase gives rise to magnetic and optical properties heretofore not obtainable with polymeric systems. 

Similar to the other liquid crystal polymers described in Section 11.16, these materials offer the possibiUty of locking the chiral nematic phase into the glassy state by rapid supercooUng to temperatures below T. This leads to a preservation of the structure and, of course, the reflected color, thereby leading to the formation of stable, lightfast, monochromatic films, when suitable systems are used. 

A. Trajkovska, C. Kim, K.L. Marshall, T.H. Mourey, S.H. Chen, Photoalignment of a nematic liquid crystal fluid and glassy-nematic oligofluorenes on coumarin-containing polymer films. Macromolecules 39, 6983-6989 (2006)... 

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