Fabrication of Polysilane–Silica Hybrid Thin Films with Controlled Refractive Index

Abstract

We have developed the photocrosslinked films of a diphenyl-or dinaphthylfluorene having epoxy and oxetane moieties and polysilanes blends in the presence of a photoacid generator by irradiation at 405 nm. Photo-induced decomposition of the Si-Si bonds of the polysilanes was successfully suppressed during the visible light irradiation. The cationic photocrosslinking properties of the blends were strongly affected by the post-exposure-bake conditions and irradiation dose. Polysilane moieties were incorporated into the film by the termination reaction of the polymerization with the terminal OH groups. We have successfully fabricated films with high refractive indices (nd: 1.70) and the refractive index values were tunable by irradiation at 254 nm due to the decomposition of the Si-Si bonds of the polysilanes.

Change in Surface and Optical Properties of Polysilane-silica Hybrid Thin Films by UV Irradiation.

“…A little change of the film thickness and surface state of the relatively silica-rich hybrid was observed with UV irradiation, while the compositional change seemed to occur due to the photo-degradation of polysilane block. We have already reported that the compositional change affected the refractive index in the polysilane-silica hybrid thin films [5]. Table 2 shows a more detailed result of refractive index change and decrease of film thickness in the polysilane-silica hybrid thin films after UV irradiation.…”

“…The hybrids were produced via sol-gel reaction using poly(methylphenylsilane)/3-methacryloxypropyltriethoxysilane block copolymer [P(MPS-co-MPTES)] and tetraethoxy orthosilicate (Si(OC2H5)4: TEOS) (Scheme 1) [4]. The hybrid thin films were transparent with a wide range of compositions between polysilane and silica, and moreover, it was found that they have certain durability to UV irradiation in comparison with polysilane thin films [5]. The polysilane-silica hybrid thin films exhibited specific properties on photoluminescence and polarization memory [6].…”

Preparation of Porous Titania Thin Films from Polysilane-Titania Hybrid by UV Irradiation.

“…For developing new functionalities of polysilane, we have prepared various polysilane-silica hybrid thin films from sol-gel reaction using metal alkoxides and polysilane-acrylic or polysilane-methacrylic block copolymers [4][5][6][7][8][9][10][11][12]. It has also been found that the polysilane-titania hybrid thin films prepared by the similar manner gave numerous unevenness around 10 -20 nm at a few hundred nm intervals, which mainly consisted of porous titania component, after photolysis of the polysilane segments by UV irradiation [13].…”

Preparation and Applications of a Polysilane-allyl Methacrylate Copolymer

“…Our research group developed photopolymerization of methacrylate to prepare polysilane-methacrylate copolymers using the polysilane itself as a photoradical initiator to retain the polysilane block [6,7]. In particular, we prepared a copolymer bearing an alkoxy group, which could be used to produce a polysilane-inorganic hybrid material through a sol-gel reaction with metal alkoxide [8]. However, the alkoxy group is significantly unstable for long-term storage.…”