The authors have demonstrated increased light outcoupling from organic light-emitting diodes (OLEDs) based on nanoimprinted amorphous fluoropolymer, poly[perfluoro(4-vinyloxy-l-butene)] (PPFVB). Because PPFVB has a low refractive index and a high transmittance over wide wavelength range, the first-order Bragg diffracted light shows high directionality and decreased waveguide absorption. These characteristics provide an advantage for small- or medium-sized OLEDs, which are mainly viewed from the normal direction.

Liquid crystal phases formed by rigid-rod polymers have been studied extensively in both theoretical and experimental ways. In the initial stage of theoretical approach, it has been shown that a system of long, hard molecules can exhibit an orientationally odered nematic phase if the density is efficiently high. 1 Recently, computer simulation has played an important role in understanding the liquid crystalline behavior of systems composed of hard rod molecules and has given the first indication that the smectic and columnar phases can also be formed by systems of molecules that interact through excluded-volume interaction alone. 2 Prior to this simulation, it was thought that smectic phases could only be exhibited by conventional molecules composed of aromatic mesogen groups and aliphatic tail groups which exhibit mainly attractive interactions. 3 This prompted many further theoretical studies of simple hard-rod systems. 4-6 On the experimental side, lyotropic phases have been extensively studied in biological molecular systems. The columnar and smectic liquid crystals have been reported in lyotropic liquid crystals of synthetic polypeptides, 7 DNA, 8 and the tobacco mosaic virus. 9 These liquid crystal phases observed can be easily differentiated from nematic and cholesteric phases which have so far been well studied for these kinds of rodlike polymers, but the detailed identification and nature of these new phases are still unclear because of the difficulty in managing the lyotropic system.In this study, we treat the polysilanes with chiral side chains that assume a helical rigid-rod conformation with the persistent length of around 85 nm. The rigidity results from severe restriction of main chain's internal rotation by steric hindrance between neighboring side chains. 10,11 Such polymer chain stiffness is closely correlated to the liquid crystallinity in the lyotropic system. Here, we find that these helical polysilanes can form thermotropic liquid crystals (LCs) as well as the lyotropic LCs if the long alkyl side chains are attached to the main chain as a second side group, as reported in a previous study. 12 The ability of thermotropic LC formation is due to the long flexible side chains that act as solvents in the lyotropic system. 13 A typical polysilane that forms a thermotropic liquid crystal is poly[n-decyl-(S)-2-methylbuthylsilane] (PD2MBS) with the following formula:This PD2MBS polymer, having length 1.96 × n Å (n: degree of polymerization) and diameter 15 Å, can be an ideal molecule to use to verify the theoretical predictions of the hard-rod model because the molecules interact mainly through excluded-volume interactions because no significant electrostatic intermolecular attractions are present due to its nonpolar nature. The nonpolar nature is also advantageous for the preparation of a sample with a narrow molecular weight distribution. A simple fractional precipitation method can be used due to the lack of aggregation by the molecules in solution.The results show that the thermotropic phase beha...

The authors have demonstrated defect mode lasing emission from a spin-coated double-layered dye-doped polymeric cholesteric liquid crystal (PCLC) films with a thin rubbed isotropic layer in between. The rubbed layer acts not only as an alignment layer for the second PCLC layer but also as an isotropic defect layer breaking periodicity of PCLC films. All the processes can be achieved in a wet process. Because of the process, the present polymeric solid-state laser is available as a freestanding thin film of only 5.5μm in thickness and an almost limitless large area, which enable one to use it as a disposable laser chip of any shapes.

Observations on the potential fluctuations detected by a small external probe when two energetic plasma jets stream through each other have been described previously. This was attributed to an ion-electron interstreaming instability. Here it is shown that the experimental values for the growth rate and the frequency range of the instability can be explained more accurately by the same theory if the local ion energy distribution is assumed to be different for ions of different energies.