Technologies for manufacturing molecular assemblies have made rapid progress in the past decade. The Langmuir-Blodgett (LB) technique is one of the most hopeful candidates to assemble organic molecules, because it makes the fabrication of mono-molecular thin films possible. The molecules for LB films must be amphiphilic and are typically low molecular weight long-chained aliphatic acids (fatty acids). This class of LB films are seen as a standard and, consequently, have a long history. On the other hand, when these films are used in the fabrication of new devices, the shortcomings of LB films that arise from their inherent thermal and mechanical instabilities have been pointed out. Polymeric LB films were studied for two main reasons. One of them was to see if mono-molecular layers of polymers were possible and if so what the nature of such polymeric LB films was, and secondly to achieve an improvement of the physical shortcomings of low molecular weight LB films.We have investigated polyimide LB films.['] Polyimides are well known for their high degree of thermal stability and superior electrical properties. Since it is difficult to process polyimides because of their infusibility and insolubility in organic solvents, films are produced from the soluble precursor polymers (polyamic acids). The most interesting characteristic of polyimide LB films is that they do not have long alkyl chains in the structure, which makes them atypical for LB films.The preparation of the polyimide LB films is shown in Scheme 1. Polyamic acids 1 are mixed with long-alkyl amines 4 to introduce hydrophobic alkyl chains in order to form the amphiphilic structure 2. The LB films of the materials (2) are prepared by the usual LB technique, which consists of the preparation of a monolayer at the air-water interface and deposition of this layer onto a substrate. The LB films of 2 are dipped into a mixed solution of acetic anhydride and pyridine to convert the LB films into polyimide 3. Alternatively, the conversion can be achieved by heating the precursor LB films at 300 "C for a short period. The polyimide LB films have excellent thermal stability and solvent resistance as high as commercially available polyimide thick films. I 2 9 Scheme 1We have applied the polyimide LB films to devices such as liquid-crystalline optical cells where they were used as a liquid-crystalline aligning layer,r21 solar battery cells,[31 and photomemory devices working in the photon mode.[41 In the course of our studies concerning the formation of the microstructure of the polyimide LB films, we discovered phase separation behavior in the mixed LB films of two different p~lyimides.~~] The polyamic acids used in the present study are shown in Scheme 1. One of them has an aliphatic structure la, and the other consists of a wholly aromatic structure lb. These two polyamic acids were dissolved in the mixture of N,N-dimethylacetamide (DMAc) and benzene at the various ratios. The same molar amount of long-alkyl amine 4 (relative to the carboxylic function of the mixed...

The influence of cooling conditions on the bending properties and Mode I interlaminar fracture toughness of commingled PET/GF and PA6/GF composites was investigated. The morphology and thermal properties of the composites were studied using scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results show that cooling conditions had no major effect on bending properties, but the fracture toughness (GC) was affected; i.e., fracture toughness of gradual cooling was lower than rapid cooling. The bending properties are not significantly affected by crystallinity, but GC is strongly influenced by the level of crystallinity in the matrix resin.

The photo-active compound (PAC) in positive tone photosensitive polyimide (posi PSPI) was investigated in order to obtain good photo lithographic performance (small development loss and good photosensitivity). When the PAC structure was changed posi PSPI showed different levels of photosensitivity and development loss. The development loss and photosensitivity showed a good correlation. The lower development loss posi PSPI showed lower photosensitivity. From the molecular orbital calculation, the PAC in the lower development loss posi PSPI had a lower dipole moment than that in the larger development loss posi PSPI. In addition, dissolution rate measurement (DRM) results suggest that posi PSPI may have two layers from the point of dissolution. The dissolution rate of the surface layer in posi PSPI was shown to be lower than that of a bottom layer. This suggests that PAC using the lower development loss posi PSPI may exist mainly on its surface. These results are quite important for the design of good posi PSPI.

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We investigated the soft baking condition effect on residual solvent amount, decomposition of photo sensitive diazonaphthoquinone group, photosensitivity, and development loss amount of positive photosensitive polyimide, which composed of partial esterified poly(amic acid) and photosensitive diazonaphthoquinone sulfonate. After soft baking, 10-14% of solvent was remained. Below 120°C baking, the naphthoquinone group was remained more than 90%. More than 40% of the naphthoquinone group was decomposed when 130°C baking. Photosensitivity seems to be determined by development loss of photosensitive polyimide. 120°C for 4min is suitable soft baking condition in this study.