Photo-thermal dual curing of polysilane/diarylfluorene blends-fabrication of films with high and tunable refractive indices-

Abstract

We have developed the crosslinked films of diphenyl-or dinaphthylfluorene having acryl units with polymethylphenylsilane in the presence of a photoradical initiator upon irradiation at 405 nm with thermal treatments at around 100oC. The photopolymerization of the acrylates effectively enhanced by the photo-thermal dual curing technique. Polysilane moieties were incorporated into the film by the termination reaction between the acrylate radicals and Si radicals generated by the slight photo-decomposition of the Si-Si bonds. We have successfully fabricated the films with high refractive indices (nD: 1.62) and the refractive index values were tunable by irradiation at 254 nm by the effective decomposition of the Si-Si bonds of the polysilanes. The reaction mechanism is discussed based on real-time FT-IR measurements. The prepared films have a high thermal stability (temperature for 5% weight loss, Td5: 300oC).