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The structures and photoreactions of the Langmuir and LB films of an amphiphilic spiropyran, 1',3'-dihydro-3',3'-dimethyl-6-nitro--1' -octadecyl-8-(docosanoyloxymethyl)spiro[2H-1-benzopyran-2,2'-(2H)-indole] (SP) are investigated. Results indicate that the criteria of the J-aggregation of MC in Lagmuir and LB films are the presence of the bilayer domains and the nucleation sites with the mobility of the molecules large enough for the morphological change necessary for the J-aggregation.

The interaction energy calculation of the thiophene dimmer is presented by using very large basis sets near saturation. The estimation of MP2 and CCSD(T) level interaction energies at the basis set limit are described by using model chemistry.

The Langmuir-Blodgett (LB) films of C60 are designed via a thermal dissociation method. The effect of heat treatments of the LB films is investigated by using UV-visible and infrared absorption spectroscopies.

A reversible morphological transformation of the Langmuir-Blodgett (LB) films of AZ-/PDAA+ on alternate illumination with UV and visible light was observed. This was possibly due to the conformational transformation caused by photoisomerization, followed by thermal relaxation processes. Photoisomerization in LB films leads to substantial changes in the two-dimensional structures in response to the stress imposed by a rise in area per molecule caused by trans-to-cis photoisomerization of azobenzene.

We have fabricated organic field-effect transistors (OFETs) with a highly oriented active layer of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2), which was formed with the help of a photoaligned polyimide film. Photoalignment is an attractive technique for integrating OFETs with aligned active layers on the same substrate, because of its potential capability of two-dimensional alignment patterning. The F8T2 layer formed on the photoaligned polyimide film showed an absorption dichroic ratio greater than 15 after annealing at 285 °C. Top-gate/bottom-contact-type OFETs with a parylene gate insulating layer exhibited an enhanced hole mobility (0.016 cm2 V-1 s-1) along the alignment direction of the F8T2 backbone structure and a suppressed one (0.002 cm2 V-1 s-1) along the perpendicular direction. This result shows that the photoaligned polyimide film is an attractive alignment layer for fabricating and integrating OFETs with aligned active layers. Current-direction-dependent bias stress effect was observed for those OFETs; when the current flowed parallel to the alignment direction of the F8T2 backbone structures, a larger negative threshold voltage shift was observed. This anisotropic bias stress effect was discussed on the basis of a microstructure model of aligned F8T2 films. [ABSTRACT FROM AUTHOR]

Polarized polymer-based light-emitting diodes (PLEDs) have been fabricated by inserting a very thin photoaligned polyimide film into the device structure. The photoaligned polyimide film was used to form a highly oriented layer of light-emitting polymer, poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO). The polyimide contains azobenzene in the backbone structure, allowing us to control the alignment of its backbone structure by optical treatment. Since the photoalignment treatment is scratch-free, the thickness of the photoaligned film can be reduced below 4 nm without decreasing its alignment ability for PFO. Even though polyimide is a good insulator, such a very thin photoaligned film can be inserted into PLED structures. We examined the influence of the thickness of the photoaligned polyimide film and the light-emitting layer on the polarization ratio and the current efficiency of the polarized PLEDs. Using a 2.9 nm-thick polyimide photoalignment layer and a 101 nm-thick PFO light-emitting layer, we have succeeded in fabricating a polarized PLED with a current efficiency of 0.3 cd/A at 150 cd/m2 and polarization ratios of 46 at 434 nm, 27 at 460 nm, and 20 for integrated intensity from 400 to 600 nm. [ABSTRACT FROM AUTHOR]

A backbone aligned thin poly(2,5-dioctyloxy-1,4-phenylenevinylene) (DOPPV) film on substrate is obtained by the fraction-transferred method from a compressed polymer powder block. The results have shown that the DOPPV molecules in friction-transferred film are perfectly arranged three-dimensionally and two neighboring DOPV molecules along the direction of inter-backbones are shifted with respect to one another.

A series of alpha,omega-dicyano end-capped oligothiophenes NC(C4H2S)nCN ranging in length from the dimer to the hexamer (n = 2-6), in the neutral state as pure solids, by means of Fourier transform IR and Fourier transform Raman (FT-Raman) spectroscopes were investigated. The cyclic voltammetry analysis of the compounds in dichloromethane reveals that most of them show two oxidation and two reduction waves, associated with the injection of either positive or negative charges into the pi-conjugated system.

The correlation of the number of thiophene with the structural order and carrier mobility of the films through studies on thin-film transistors based (TFTs) based on alpha-quinquethiophene (5T), alpha-sexithiophene (6T), and alpha-septithiohene (7T) is investigated. The structural order intrinsically in grown films and carrier mobilities extrinsically in their TFTs are affected due to the parity of the number of thiophene units

The effect of keto defects in fluorene units on the performance of organic field-effect transistors (OFETs) is examined on the basis of fluorene end-capped fused bithiophenes (BFTT) and biphenyl end-capped fused bithiophene oligomers(BPTT). A density of trap sites [N(sub t)] of around 2.7 x 10(super 15) cm(super -3) was found for the BPTT film due to the formation of keto defects after 6 h of UV irradiation.

The hysteretic behaviors in the photoresponsivity of a Langmuir film are found for the first time. The hysteretic should be related with the phase transitions that occur in the Langmuir film. The structure change of the Langmuir film of spiropyran (SP) is examined.