WAVELENGTH SENSITIVITY OF THE PHOTODEGRADATION OF POLY(METHYL METHACRYLATE)

Poly(methyl methacrylate) (PMMA) was photolyzed with monochromatic light of wavelengths 260, 280, 300, 320, 400, and 500 nm in vacuo by the use of the Okazaki Large Spectrograph. UV spectral changes, the quantum yields of main-chain scission (phics), and effects of wavelength were investigated. UV spectral changes around 280 nm were observed with irradiation at 260 nm. The phics has a maximum value in case of irradiation with 300 nm light. It turned out that photodegradation of PMMA took place by irradiation of 260-320 nm light but did not by irradiation with the light longer wavelength than 340 nm. The average values of phics obtained in this work were 0.84 X 10(-4), 1.06 X 10(-4), 4.21 X 10(-4), 1.23 X 10(-4), 0, and 0 for irradiations at 260, 280, 300, 320, 400, and 500 nm, respectively. It was found that the photo-induced side-chain scission initiates the main-chain scission of PMMA by irradiation of 260 and 280 nm light.