Studies on photolithography and photoreaction of copolymer containing naphthyl in ultrathin nanosheets induced by deep UV irradiation

A novel polymer containing photoactive naphthyl group, poly (N-dodecylmethacrylamine/β-naphtylmethacrylate) (pDDMA-NPMA) was synthesized and its molecular arrangement and photochemical reactions were investigated in ultrathin film. The polymer p (DDMA-NPMA) could self-aggregate into a crystal film at air/water interface and this monolayer could be transferred onto solid supports, giving Y-type uniform Langmuir-Blodgett (L-B) films. Upon deep UV irradiation, photochemical reaction occurred in L-B films, and the irradiated parts could be eliminated as the verified images of optic-microscopy, resulting in a fine positive tone photolithographic patterns with a resolution of 0.75 μm. Changes of molecular chemistry induced by the 248 nm light treatment were investigated by atomic force microscopy, fluorescence, ultraviolet, Flouried transform infrared spectroscopy and gel permeation chromatography (GPC). The results showed that the main route of the photoreaction was dimerization of the naphthylene, and then photodecomposition of not only naphthyl group but also main chains of polymer. In the present paper, several possible mechanisms of photochemical reaction induced by deep UV light were also proposed.