ATOMIC-FORCE MICROSCOPIC OBSERVATION OF L OCAL SUPRAMOLECULAR STRUCTURE IN PHOSPHATIDIC-ACID LANGMUIR-BLODGETT-FILMS

The Langmuir-Blodgett bilayer films of phosphatidic acid(DPPA) have be en investigated by using atomic force microscopy in both large and nan o-scale. Large scale AFM image shows that the bilayer of DPPA is a pla ne film with some defects which enable us to detect the thickness of b ilayer by a trace of section analysis across the defects structure, Mo lecularly resolved images show that the polar head groups (phosphate g roups) are packed in an ordered hexagonal organization with a long ran ge orientational and positional ordering, Intermolecular hydrogen bond ing interactions between adjacent phosphate groups are first visualize d and local supramolecular structures are first observed in polar regi on of DPPA bilayer. Some phosphate groups in polar region linked with each other through intermolecular hydrogen bonding interaction to form local supramolecular structure with a diameter of 1.5 nm in size.