Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume 128, Issue 51, Pages 16928-16937Publisher
AMER CHEMICAL SOC
DOI: 10.1021/ja065968v
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Complexes consisting of poly(4-vinylpyridine) and mesogenic wedge-shaped ligands 4'-[3' ',4' ',5' '-tris(dodecyloxy)benzoyloxy]azobenzene-4-sulfonic acid and 4'-[3' ',4' ',5' '-tris(octyloxy)benzoyloxy]azobenzene-4-sulfonic acid have been prepared with different monomer/ligand ratios. Upon protonation of the poly(4-vinylpyridine) chains by the wedge-shaped sulfonic acid molecules a hypsochromic and hyperchromic effect was observed with the pi-pi* transition of the azo-chromophor, allowing us to monitor the neutralization process by means of UV-vis spectroscopy in solution. The changes of the absorption characteristics implied a conformational change of the polymer backbone. In the bulk the interaction between pyridine and sulfonic acid moieties was proved by FT-IR spectroscopy. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurements were used to study the bulk structure of the complexes. The complexes formed a liquid crystalline lamellar phase at low degrees of substitution, while a hexagonal columnar mesophase was observed at degrees of neutralization of 80% and higher.
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