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

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.

<em>In Situ</em> Synthesis of Hybrid Inorganic-Polymer Nanocomposites

“…With increasing amount of inorganic content, the refractive index increased for the PDMS-TiO2 hybrid films (Figure 16). The Abbe number decreased with increasing TiO2 content, showing increased dispersion in the visible region of the light spectrum [11]. The hybrid films were flexible and stiff below and above approximately 5 vol.% TiO2, respectively.…”

“…The PDMS chains can also contain silanol end groups (Si-OH), forming hydroxy-terminated PDMS (PDMS-OH). The use of transition metal oxide fillers for PDMS has recently attracted interest due to the improvements in the optical and mechanical properties of the nanocomposites, opening new possibilities for applications in optical devices [11]. The unique flexible and rubbery properties of PDMS, along with its thermal stability, have also made it suitable for application as thermally stable rubbers and hydrophobic coatings [60,62,66].…”

“…This strategy is used in several other works where PDMS hybrids were prepared without chelating agents. The strategy usually involves the use of an alcohol as a solvent -if the same alcohol is a product of hydrolysis of the metal alkoxide, then the reaction equilibrium is shifted to stabilize the alkoxide [11]. Julian et al [68] prepared PDMS-O-M nanocomposites using dimethyldiethoxysilane (DMDES) as the PDMS precursor, and metal alkoxides of Al, Ge, Sn, Ti, Zr, Nb and Ta.…”

“…The hydrolysis of TIP was reduced by mixing with isopropanol, before being mixed with PDMS. This procedure was then adapted by Dalod et al [11] with anhydrous isopropanol instead, and with different viscosities of a PDMS-OH precursor. No chelating agent was used in either of these works.…”

“…can enable a wide range of applications for these nanocomposites. These range from common plastics reinforcement to abrasion resistant coatings [2,4], flame-retardant materials [5,6], catalysis [7,8], memory devices [9], integral capacitors [10], optical devices [11,12], electrical insulation in microelectronics and nanodielectrics [13][14][15], fuel cells [16], etc. The defining feature of nanocomposites is the larger interfacial area of the nanoscale inorganic fillers, in comparison to traditional composites.…”