Development in electrical and optical properties of organic materials by 3-D structural control using dendrimer as a command molecule.

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Drimers are well defined highly branched, three-dimensional compounds with a large number of reactive end groups. Moreover, these reactive end groups easily react with many reagents to give dendrimers with various functionalities on the surface. Thus, they are receiving interest as new polymeric materials whose properties should differ significantly from those of linear polymers. Generally, dendrimers are amorphous due to highly branched molecules. Introduction of liquid crystalline derivatives to their terminal groups gives them liquid crystalline nature. The liquid crystalline dendrimers can be aligned by applying external field such as magnetic or electric fields. We have synthesized poly (propyleneimine) dendrimers (1st, 2nd, and 3rd generation) having peripheral azobenzene and phenylnaphthalene derivatives, and examined the phase transition behavior, liquid crystalline structure, photoisomerization and carrier transport property. The azobenzene deindrimers exhibite smectic A (SmA) … More phase, and the SmA/isotropic phase transition temperature increases with increasing generation. Cis-trans photoisomerization was observed in the chloroform solution and film at room temperature under UV and visible light irradiation. During the cis-trans photoisomerization, a homeotropic alignment was formed in the film. In addition, the photoinduced surface relief could be formed on the films by irradiating visible light. Therefore, the diffraction grating can be made by surface relief and molecular alignment using azobenzene dendrimers The dendrimers having peripherally phenylnaphthalene derivatives exhibited smectic liquid Crystalline nature at room temperature. The phase transition, structures, and carrier transport property of the dendrimers have been examined. They exhibited the carrier mobility of 10^<-3>cm^<2>/Vs at room temperature (SmEphase). The values are equivalent to that of the low-molecular liquid-crystalline phenylnaphthalene derivatives. Thus, the dendrimer backbone can avoid crystallizing and exhibit high carrier transportation at room temperature. Moreover, the phenylnaphthalene dendrimers also form a homeotropic structure on the substrate. The homeotropic alignment seems to be better for the construction of vertical type transistor. Less