The behaviour and photoresponses of some indolinospiropyrans in monomolecular films

Surface pressure-area isotherms of two spiropyrans were determined under different conditions of illumination. It was found that the photomerocyanine forms produced stable films whilst this was not always the case with the spiro forms. Photomerocyanine monolayers were stabilized by the polar aqueous subphases and photoinduced ring-opening could be effected on the water surface by U. V. irradiation.The ring-closing reaction, however, was inhibited in monolayers.Photomechanical responses occurred as a consequence of the spiropyran photomerocyanine reaction and these were catalysed on acidic subphases. Factors influencing the magnitude of such responses were assessed.Photoregulation of surface tension at the air-water interface was inferred from measurements on stearic acid monolayers spread on photochromic subphases.