Photosensitivity and grating development in trans-4-stilbenemethanol-doped poly(methyl methacrylate) materials

Abstract This paper reports the photosensitivity of poly(methyl methacrylate) (PMMA) and its copolymer doped with trans -4-stilbenemethanol. UV irradiation of the doped-PMMA at 325 nm induced the trans - to cis -isomerization of the dopant. This process was confirmed by 1 H NMR spectra of trans -4-stilbenemethanol in CDCL 3 solvent before and after irradiation. The isomerization can be initiated by the irradiation with an intensity of 0.62 mW/cm 2 . Photo-induced refractive index change of −0.0024 was obtained when a PMMA copolymer film doped with 5.1 wt% dopant was exposed to 325 nm light. Lorentz–Lorenz equation was used to estimate the refractive index of a trans -4-stilbenemethanol–PMMA composite and a trans -4-stilbenemethanol–PMMA copolymer composite from the mole refraction and van der Waals volume of each component. A slight elevation of molecular packing coefficient ( K ) for PMMA and its copolymer containing the dopant implies a denser aggregation as compared to the polymer without the dopant. Long period gratings were created in doped-PMMA films and doped-PMMA copolymer fibers using amplitude mask technique. Gratings were confirmed by microscopic observation and diffraction patterns.