Abstract
The photochromic behavior of polydiacetylene LB films has been investigated for samples with different secondary treatments. The monomer film is initially converted to the A-type polydiacetylene LB film showing a pronounced red-shifted band and then to the B-type one, depending on the duration time of UV irradiation. Acid vapor treatments, either before or after the initial UV irradiation, show a tendency to hinder the transition from A-type to B-type on the excessive UV irradiation, with the yield of A-type polymer being enhanced. Further, another type of red-shifted band has been found in the case of a successive process; acid vapor treatment→ heat treatment→UV irradiation, which may be dependent on the degree of polymerization. The relation between these results and the yield of polymerization of the films is explained by assuming an order-disorder scheme of the phase transition.