| Abstract
| - Some novel properties of organized molecular films of 10,12-tricosadiynoic acid (TDA), which were modulatedby transition metal ions, were investigated. It was found that metal ions such as Cu2+, Zn2+, Ni2+, Cd2+, andAg+ in the subphase can greatly affect the monolayer formation of TDA and the properties of the subsequentlydeposited Langmuir−Blodgett (LB) films, particularly in the case of Ag+, Zn2+, and Cu2+ ions. TDA LBfilm from the subphase containing Ag+ ion could not be photopolymerized. It was suggested that both thestrong chelating property to the carboxylate and the easy reduction of Ag+ in the film disrupted the topochemicalsequence of TDA and resulted in no polymerization in the film. Zinc ion coordinated TDA film could bephotopolymerized into a blue polydiacetylene (PDA) film, which showed a reversible thermochromism betweenblue and purple color upon thermal stimulation. Fourier transform infrared spectra revealed the difference ofthe Zn2+-PDA film from those of the other ions, and the mechanism of the thermochromism was discussed.Copper ion coordinated TDA film could only be photopolymerized to a red PDA film, which showedsupramolecular chirality although TDA itself was achiral. Atomic force microscopic measurements revealedthe nanofiber structure in the Cu2+-PDA film. The supramolecular chirality of the Cu2+-PDA film was suggestedto be due to the arrangement of the polymer backbone in a helical sense. Furthermore, it was found that thechiral assemblies from the achiral TDA molecules were very stable and the chirality could be kept even uponheating or treating with alkaline solution. While many synthetic efforts have been devoted to thefunctionalization of PDA films, we provided a simple method of modulating the organization and function ofPDA films through metal ions.
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