| Abstrakt: |
The synthesis and application of helical polyaniline derivatives PANIs have attracted much interest. However, most of these syntheses have been carried out in organic solutions. In our previous reports, helical PANIs were successfully realized in aqueous solution. Because helical architecture in the backbones of PANIs is an induced rather than the natural arrangement, it is significant to study the change in helicity in aqueous solution, especially opposition or reversion. One excesshanded helicity was induced in poly2methoxyaniline PMOA by electrochemical polymerization of 2methoxyaniline at pH 2.5 in the presence of protonated βcyclodextrin sulfate CDS−H. When 0.04 mol L−1NaCl was added to the reaction solution, the PMOA backbone took on an opposite excess of onehanded helicity, which was confirmed by induced circular dichroism. Such a result originates from the dynamic switch between electrostatic and hydrogenbonding interactions. The helixinducing process in PMOA depends on the interaction between PMOA and chiral CDS. Due to the competition of NaCl−with PMOACDS−, the electrostatic interaction between PMOA and CDS is limited or weakened. Thus, the slightly preferred interaction between them switches from electrostatic to hydrogen bonding. Simultaneously, the interaction positions and distance are changed. The changed steric hindrance induces PMOA into adopting an opposite excesshanded helicity. Copyright © 2010 Society of Chemical Industry [ABSTRACT FROM AUTHOR] |
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