Dissertation/Thesis Abstract

Synthesis of PDMS-metal oxide hybrid nanocomposites using an in situ sol-gel route
by Lu, Qiaoyu, Ph.D., Michigan Technological University, 2012, 203; 3553363
Abstract (Summary)

Organic-inorganic hybrid nanocomposites are widely studied and applied in broad areas because of their ability to combine the flexibility, low density of the organic materials with the hardness, strength, thermal stability, good optical and electronic properties of the inorganic materials. Polydimethylsiloxane (PDMS) due to its excellent elasticity, transparency, and biocompatibility has been extensively employed as the organic host matrix for nanocomposites. For the inorganic component, titanium dioxide and barium titanate are broadly explored as they possess outstanding physical, optical and electronic properties.

In our experiment, PDMS-TiO2 and PDMS-BaTiO3 hybrid nanocomposites were fabricated based on in-situ sol-gel technique. By changing the amount of metal precursors, transparent and homogeneous PDMS-TiO 2 and PDMS-BaTiO3 hybrid films with various compositions were obtained. Two structural models of these two types of hybrids were stated and verified by the results of characterization.

The structures of the hybrid films were examined by a conjunction of FTIR and FT-Raman. The morphologies of the cross-sectional areas of the films were characterized by FESEM. An Ellipsometer and an automatic capacitance meter were utilized to evaluate the refractive index and dielectric constant of these composites respectively. A simultaneous DSC/TGA instrument was applied to measure the thermal properties. For PDMS-TiO2 hybrids, the higher the ratio of titanium precursor added, the higher the refractive index and the dielectric constant of the composites are. The highest values achieved of refractive index and dielectric constant were 1.74 and 15.5 respectively for sample PDMS-TiO2 (1-6). However, when the ratio of titanium precursor to PDMS was as high as 20 to 1, phase separation occurred as evidenced by SEM images, refractive index and dielectric constant decreased. For PDMS-BaTiO 3 hybrids, with the increase of barium and titanium precursors in the system, the refractive index and dielectric constant of the composites increased. The highest value was attained in sample PDMS-BaTiO3 (1-6) with a refractive index of 1.6 and a dielectric constant of 12.2. However, phase separation appeared in SEM images for sample PDMS-BaTiO3 (1-8), the refractive index and dielectric constant reduced to lower values. Different compositions of PDMS-TiO2 and PDMS-BaTiO3 hybrid films were annealed at 60 °C and 100 °C, the influences on the refractive index, dielectric constant, and thermal properties were investigated.

Indexing (document details)
Advisor: Mullins, Michael E.
Commitee: Caneba, Gerard T., Middlebrook, Christopher T., Rogers, Tony N.
School: Michigan Technological University
Department: Chemical Engineering
School Location: United States -- Michigan
Source: DAI-B 74/06(E), Dissertation Abstracts International
Subjects: Polymer chemistry, Chemical engineering
Keywords: Hybrid, Metal oxides, Nanocomposites, PDMS, Sol-gel
Publication Number: 3553363
ISBN: 978-1-267-92814-6
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