Preparation of highly oriented thin films of organo-LDH(layered double hydroxide) hybrids

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The aim of this study is to develop new synthetic routes to the highly oriented thin films of organic-LDH (layered double hydroxide) hybrids. In the FY 2006, the oriented LDH films with anion-exchangeability were prepared from the starting CO_3^<2->LDH (a) by casting a CO_3^<2->LDH water suspension onto a glass slide, followed by decarbonation in an HC1/NaC1 solution and anion-exchange to C1O_4LDH, and (b) by casting delaminated C1O_4LDH in formamide (FA) onto a glass slide. These C1O_4LDH films formed on glass substrates were further anion-exchanged by p-toluenesulfonate anions (Tos) to produce organic-LDH hybrid films with retention of their orientation and transparency. The direct delamination of TosLDH in FA was also successfully conducted, and a highly-oriented TosLDH hybrid film was obtained by casting the colloidal TosLDH solution on a glass slide. These three procedures offered well-oriented organic-LDH films, and especially, the process involving the delamination treatments gave more dense and transparent films.In the FY 2007, we elaborated the elemental techniques necessary for LDH-film preparation (1) preparation of highly crystalline homogeneous LDH crystals, (2) refinement of decarbonation method, and (3) development of new methods for LDH delamination. As for (1), it became possible to control the size of LDH crystals by controlling the amount of hexamethylenetetramine in the homogeneous preparation method. As for (2), by using acetate buffer/NaC1 mixed solution instead of HC1/NaC1 solution, the decarbonation of LDHs could be conducted in milder conditions, and decarbonation took place in more homogeneous way. As for the nano-sheet preparation, nobel LDH hybrids which delaminate in water were synthesized, and because of the affinity of the LDH colloidal suspensions to the substrates such as glass, the oriented thin films could be obtained more easily. And furthermore, self standing film of the LDH hybrids could be obtained successfully.