Optically active, amphiphilic poly(meta-phenylene ethynylene)s: synthesis, hydrogen-bonding enforced helix stability, and direct AFM observation of their helical structures. | LitMetric
Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Japan.
Published: May 2012
AI Article Synopsis
Article Abstract
Optically active, amphiphilic poly(meta-phenylene ethynylene)s (PPEa) bearing L- or D-alanine-derived oligo(ethylene glycol) side chains connected to the backbone via amide linkages were prepared by microwave-assisted polycondensation. PPEa's exhibited an intense Cotton effect in the π-conjugated main-chain chromophore regions in various polar and nonpolar organic solvents due to a predominantly one-handed helical conformation stabilized by an intramolecular hydrogen-bonding network between the amide groups of the pendants. The stable helical structure was retained in the bulk and led to supramolecular column formation from stacked helices in oriented polymer films as evidenced by X-ray diffraction. Atomic force microscopy was used to directly visualize the helical structures of the polymers in two-dimensional crystalline layers with molecular resolution, and, for the first time, their absolute helical senses could unambiguously be determined.
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