Spiropyran linked to methyl cellulose (SP-MC) is prepared by the treatment of methyl cellulose with 1'-( 2-~arboxyethyl)-3',3'dimethyl-6-nitrospiro [ 2H-benzopyran-2,2'-indoline] as a photofunctional material and photoregulation of some of its properties under irradiation with UV light are investigated. The spiropyran moiety in SP-MC is shown to undergo reversible isomerization from the spiropyran form to the merocyanine form under irradiation with UV light of 1 = 300-400 nm and from the merocyanine form to the spiropyran form under subsequent irradiation with visible light of A > 550 nm, both in solution and in film, although repeated cycles of the alternate irradiation with UV and visible light resulted in considerable fatigue of the spiropyran moieties over up to 20 cycles. The solubility of SP-MC in benzene and the contact angle of the SP-MC film with water are reversibly regulated under alternate irradiations with UV and visible light. A benzene solution of the SP-MC yielded turbidity under irradiation with UV light and the turbidity disappeared under subsequent irradiation with visible light. The contact angle of the SP-MC film with water decreased under irradiation with UV light and then increased under subsequent irradiation with visible light, the reversible change in contact angle is shown to result from the isomerization of the spiropyran moiety in SP-MC.

Photoregulation of properties of polymers containing photochromic moieties has been the subject of many investigations. We have investigated cellulose derivatives containing photochromic moieties. 1 -6 In the previous study, we prepared the photochromic spiropyran moietycontaining methyl cellulose (SP-MC) and the spiropyran moiety in SP-MC was confirmed to be isomerized reversibly under alternating irradiation with UV and visible light, both in solution and in film. 6 Furthermore, the solubility of SP-MC in benzene and the contact angle of the SP-MC film with water were reversibly regulated under alternating irradiation with UV and visible light. However, repeated cycles of the alternating irradiation with UV and visible light resulted in considerable fatigue of the spiropyran moieties over up to 20 cycles. In the present experiment, a spironaphthoxazine (SO) moiety containing methyl cellulose (SO-MC) was prepared and the reversible changes in the properties of the SO-MC under irradiation with UV light and subsequently with visible light, as well as the isomerization behavior of the SO moiety in the derivatives, were examined; the spironaphthoxazine was reported to be isomerized from the colorless closed ring form to the colored open ring form under irradiation with UV light (Scheme I) and to have much greater durability than spiropyran moiety for the repeated irradiations with UV and visible light. 7 -8 OX- UV ~N