Surface plasmon resonance investigation of a copolymer containing spiroxazine.

Spiroxazines are a class of photochromic compounds whose molecular structures are alterable upon exposure to UV/visible light. The typical reaction of spiroxazines is the conversion between the non-polar ring-closure form and polar ring-open form. In this work, copolymer of 1,6-heptadiyne derivatives containing a spiroxazine was used as photochromic material. Precise photochromic properties of the copolymer's thin-film were evaluated through measuring dielectric constant, optical constant and thickness by surface plasmon resonance (SPR) with multi-solvent approach. The change in structure under UV-light irradiation is accompanied by increase of dielectric constant. However, dielectric constant and UV-induced thickness change of the photochromic polymer thin-film are independent of film thickness.