| dc.description.abstract | In this study, we developed a high refractive index thermoplastic
zirconia/polycarbonate nanocomposite useful in preparing optical components via
injection molding. We have employed our alkaline hydrothermal method to synthesize
cubic zirconia nanoparticles having 5 nm grain size. The surface of these zirconia
nanoparticles was further modified with a carboxylic acid to form a stable dispersion in
a nonpolar solvent. Sulfonated polycarbonate (SPC), produced by the sulfonation
reaction of polycarbonate, was chosen as the coupling agent to make the zirconia
compatible with the polycarbonate (PC) matrix. The carboxylic acid chelated zirconia
nanocrystals formed a stable suspension in dichloromethane. Upon the adding of SPC,
the carboxylic acid ligand was replaced by the SO 3 group of the SPC and the
nanocrystals became transparently dispersible in the solvent. This approach is different
from the use of PEAH as capping agent reported in the literature. The SPC capped
zirconia obtained, after removing the carboxylic acid and solvent, could be cast or hot-
pressed into a transparent piece about 100 µm thick. The maximum zirconia loading
achieved was about 60wt%, leading to an index of 1.67 for the composite.
We used the XRD and Raman spectroscopy to analysis the grain size and crystal
phase of the zirconia nanoparticle, and the DLS to check the particle size distribution
in nonpolar solvents. The Fourier transform infrared (FTIR) spectrometer was
employed to investigate the chemical structure of the nanocomposite. The thermal
stability of nanocomposite was studied by the thermogravimetric analysis and
differential scanning calorimetry. The optical properties of nanocomposite were
investigated by the UV-spectrum and Abbe refractometer.
Our study showed that the degree of sulfonated influences the compatibility
between zirconia and PC. More zirconia nanoparticles must be added to increase the
refractive index of a nanocomposite, which requires a higher degree of sulfonation.
However, excessive sulfonation decreases the thermal stability of the SPC, leading to
yellowing upon thermal treatment during the hot press process. Therefore, there is an
optimal degree of sulfonation that gives a balance between the thermal processability
and refractive index. | en_US |