Photochromic Properties Of Naphthopyran In Polymer

First: Photochromic polymeric thin films were prepared by dopingnaphthodipyran derivate containing two pyran cycles into polymeric matrixes.Polyvinylpyrrolidone (PVP), styrene-butadiene-styrene (SBS) triblock copolymer,and polymethyl methacrylate (PMMA) at different concentrations were selected asthe polymer matrixes. All of the thin films showed normal photochromism. Thekinetics of the photochromism/decoloration in the thin films was quantified byfitting biexponential equations to their photochromic decay curves after UVirradiation. The results showed that the fastest decoration process was in SBS, andthe slowest one was in PVP. The DSC results indicated that Tg of polymericmatrixes have no obvious effect of the decoration rate of naphthodipyran. Thedecreasing order of the kinetic constant of the decoloration of nahpthodipyran wasconsistent with increasing polarity of polymer matrixes as SBS<PMMA <PVP.Second: Thermoplastic elastomers of styrene-butadiene-styrene (SBS) triblockcopolymers containing grafts of naphthopyran side-china polymer were prepared bypolymerization of naphthopyran acrylate monomer in solutions with dissolved SBSin tetrahydrofuran solution. Stretching thin film at room temperature obviously affectthe fading rate k1of the naphthopyran. The linker length between photochromicnaphthopyran moiety and the acrylate unit in monomer also affects the fading rate k1of the naphthopyran in SBS elastomers. This study presents an example of tuning thephotochromic properties of naphthopyran via two approaches, i.e. polymer structureand stretching of films.