PHOTO-RESPONSIVE BEHAVIOR OF A MONOLAYER COMPOSED OF AN AZOBENZENE CONTAINING POLYPEPTIDE IN THE MAIN-CHAIN

A photoresponsive polypeptide, two alpha-helical poly(gamma-methyl L-glutamate)s joined with an azobenzene (MAzoM, Mn = 11000), have been prepared. Monolayers of the polypeptide were formed at air-water interface and the photoresponsive behavior of the monolayer obtained was investigated. A trans to cis photo-isomerization of the azobenzene moiety in the main chain of MAzoM induced by UV light irradiation resulted in a bending structure formation in the main chain of the polypeptide via photo-induced changes in the geometry of the azobenzene chromophore. As a result, the limiting area per molecule of the MAzoM monolayer was decreased. Based on the degree of the decrease in the limiting area per molecule, it was estimated that the bending angle between the two ct-helical rods of MAzoM molecule under UV light irradiation was ca. 140 degrees. The photoresponsive behavior of the MAzoM monolayer was reversible and consisted along with the photoisomerization of azobenzene moiety.