2017 Volume 30 Issue 2 Pages 247-252
Photolabile crosslinking units can provide drastic changes of many properties of networked polymers. Herein polyurethanes (PUs) networked with photolabile O-carbamoyloxime units were prepared and characterized. The PUs were made of hexamethylene diisocyanate (HDI), polyethylene glycol (PEG), and truxenone trioxime whose absorption band reached 450 nm. The molar ratio of [NCO] in HDI / [OH] in PEG / [OH] in oxime was 1.10 / 0.967 / 0.033 in feed. Obtained PU was an elastic film with 3 mm thickness and 96% of gel fraction. On irradiation with Hg-Xe lamp, the gel fraction slightly decreased. Also, the decrease in viscoelastic parameters was observed when irradiated at 365 nm in a photorheometer, showing slight degradation of networked structure on near UV-irradiation. The ATR spectra of irradiated surface showed the disappearance of a small peak around 1760 cm-1, suggesting the photodegradation of O-carbamoyloxime units proceeded.
