Structure and Optical Properties of Titania-PDMS Hybrid Nanocomposites Prepared by In Situ Non-Aqueous Synthesis.

Antoine Dalod,Anders Blichfeld,Mari-Ann Einarsrud,Tor Grande,Ola Grendal,Vedran Furtula,Lars Henriksen,Javier Pérez

doi:10.3390/nano7120460

Abstract

Organic-inorganic hybrid materials are attractive due to the combination of properties from the two distinct types of materials. In this work, transparent titania-polydimethylsiloxane hybrid materials with up to 15.5 vol. % TiO2 content were prepared by an in situ non-aqueous method using titanium (IV) isopropoxide and hydroxy-terminated polydimethylsiloxane as precursors. Spectroscopy (Fourier transform infrared, Raman, Ultraviolet-visible, ellipsometry) and small-angle X-ray scattering analysis allowed to describe in detail the structure and the optical properties of the nanocomposites. Titanium alkoxide was successfully used as a cross-linker and titania-like nanodomains with an average size of approximately 4 nm were shown to form during the process. The resulting hybrid nanocomposites exhibit high transparency and tunable refractive index from 1.42 up to 1.56, depending on the titania content.

Highlights

The progress in organic-inorganic hybrid materials with advanced and multifunctional properties [1,2,3] has led to the development of new materials for various optical applications [4,5,6,7,8,9,10,11]
We extended the sol-gel procedure described by Lu and Mullins [16] by using different PDMS-OH precursors and various titanium(IV) isopropoxide (TIP)/PDMS-OH molar ratios (i.e., 25 cSt, 50 cSt and 750 cSt and 2:1, 5:1, 10:1, 15:1 and 20:1, respectively) to prepare mould-casted and spin-coated Ti-PDMS hybrid materials
The rectangular and circular films of Ti-PDMS-750-20:1 (Figure 1C1) had merged, these samples were substantially more viscous than the PDMS-OH precursor and the film could still be held with a pair of tweezers, indicating that a partial cross-linking had occurred

Summary

Introduction

The progress in organic-inorganic hybrid materials with advanced and multifunctional properties [1,2,3] has led to the development of new materials for various optical applications [4,5,6,7,8,9,10,11]. Ethyl acetoacetate has been used as metal alkoxide modifier to reduce the hydrolysis reaction rate [14,17,20,28] By using this sol-gel method, Yamada et al [14] prepared M-PDMS (M = Al, Ti, Ta) and investigated the effect of the thermal treatment, the PDMS-OH precursor molecular mass and the nature of the metal alkoxide on the mechanical properties. The cross-linking reaction is induced by evaporation of the solvent followed by a curing step By this method, Ti-PDMS films were produced with refractive index (at 600 nm) from 1.45 to 1.67, using TIP/PDMS molar ratios from 5:1 to 20:1, respectively. The materials were solely analysed by infrared spectroscopy and ellipsometry and the nanostructure of the materials was not investigated in detail

Methods

Results

Conclusion