IMAGING OF POLYDIACETYLENE ON GRAPHITE BY SCANNING TUNNELING MICROSCOPY

Scanning tunneling microscopy has been applied to obtain atomically resolved images of polydiacetylene on graphite and to observe hydrogen bonding between polymers directly. Polydiacetylenes have a pseudo-one-dimensional conjugated pi-electron system which gives rise to nonlinear optical behaviour of both fundamental and practical significance. Under low surface coverage, the images show a single polymer of CH3(CH2)11-C = C-C = C-(CH2)8-COOH. At high coverage, the image show a well-ordered monolayer of polymers with the nonpolar side groups pointing toward the hydrophobic graphite surface. The spatial electron distribution indicates substantial hydrogen bonding between polymers in the plane containing the polar side groups.