a Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1, S3-33, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
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Polymeric materials have called our attention to organic device application because of a rich functionalities, flexibility, lightweight, and so on. Among them, p-conjugated polymers are interesting, because they exhibit one-dimensional electron transport, optical anisotropy, and others. However, for utilizing these properties effectively in organic electronics devices, preparation methods that can control the geometrical structure of p-conjugated polymers are needed. The Langmuir-Blodgett technique is one way that can prepare chiral polydiacetylene (PDA) films with a helical structure which show circular-dichroism (CD). Note that precursor TDA films that are deposited onto substrates from a surface of water containing Cu ions must be photopolymerized . Recent our study revealed that the PDA films prepared by the LB technique using precursor TDA films deposited from a pure water surface also show the CD [2,3]. This successful preparation of chiral PDA films, without using Cu ions in the deposition process of TDA, motivated us to use the evaporation method for the preparation, because this success suggested that chiral dopant such as Cu ions is not needed in the preparation process of chiral PDA.
Interestingly, in our previous study [2,4], we could show that chiral PDA films are prepared using vacuum deposited monomer TDA films that are subjected to Circularly polarized light (CPL) irradiation. This result is important in that any chiral materials are not necessary during the polymerization process, though diacetylene monomer is obviously achiral. In other words, the preparation of the chiral p-conjugated polymer from asymmetric materials is possible only by CPL irradiation. Our experimental study shows that the chirality of PDA films depends on the structure of starting monomer film, and it is strongly induced when films are prepared at high substrate temperature . In this presentation, chiral formation mechanism in PDA films is also discussed.
1. X. Huang et al: J. Phys. Chem. B, 109 (2005) pp. 114-119.
2. T. Manaka, H. Kon, Y. Ohshima, G. Zou, and M. Iwamoto: Chem. Lett., (2006) pp. 1028-1029. 3. G.Zou et al: Chem. Phys. Lett. submitted. 4. H. Kohn et al: Jpn. J. Appl. Phys. submitted