Development of Molecular Memory System Using Hydrogen Bonding-Based Dynamic Controlled Recognition Process

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The synthesis of helical polymers with controlled helix-sense has aroused considerable interest in polymer chemistry. In this study, we developed a series of helical polymers whose helicity could be induced upon complexation with small chiral molecules. We also investigated the mechanism of the helicity induction and the memory of helical chirality by means of IR, UV, and CD spectroscopies.We found that a similar, but unusual memory of the helical chirality is also possible for poly (4-carboxyphenyl isocyanide). In this case, the macromolecular helicity induced on the polymer could be "memorized" without any achiral amines. Most of the poly(phenylacetylenes) prepared were soluble in water and exhibited ICDS with free amino acids through electrostatic interactions in water. Particularly, poly(phenylacetylene)s bearing the phosphonate residues were highly sensitive to the chirality of a variety of biomolecules including amino acids and peptides. A poly(phenylacetylene) bearing an achiral oligoglycine residue could form a one-handed helix with chiral oligopeptides such as an alanine trimer through hydrogen-bonding interaction in water. Another dynamic helical poly(phenlacetylene) with the bulky crown ether as the pendant responded to an extremely small enantiomeric imbalance in amino acids (less than 0.005% enantiomeric excess of alanine for example) and exhibits ICDs with a strong positive non-linear effect. An optically active. C_<60>-based helical poly(phenyl-acetylene) was also prepared by the copolymerization of an achiral fullerene monomer with an optically active phenylacetylene, where the achiral C_<60> pendants arrange in a helical array with a predominant screw-sense along the polymer backbone, thus exhibiting an ICD in the fullerene chromophore region. These methodologies described above are useful for constructing a novel helical polymer with the desired pendant in a one-handed helical array.