Preparation and characterization of TiO₂ and polymer nanocomposite films with high refractive index

Abstract

Novel nanocomposite films of TiO 2 nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol-A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent-resistance, good thermal stability, and mechanical properties were prepared by incorporating surface-modified TiO 2 nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO 2 nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and longchain alkyl amines. These TiO 2 nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free-standing films were obtained by drying a mixture of TiO 2 nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO 2 nanoparticles of 3-6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO 2 nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO 2 and poly(bisphenol-A and epichlorohydrin) was in the range of 1.58-1.81 at 589 nm, which linearly increased with the content of TiO 2 nanoparticles from 0 to 80 wt %.

Sol–gel derived titania hybrid thin films with high refractive index

“…Yoshida and Prasad [20] and Que and Hu [21] considered that the absorption may result from acetylacetate complex. Nakayama and Hayashi [14] had explained the reason for the color of film. Because the reagents with lone electron pair (oxygen atom in a molecule) would bind the Lewis acid site (Ti + ) onto the surface of the TiO 2 nanoparticle, and a dipole layer was formed toward the inner TiO 2 nanoparticles.…”

“…The most popular one is the introduction of nanoparticles. Metal oxide powders with high refractive index can be dispersed in a certain solvent and added to appropriate polymer matrix [12][13][14]. However, this method often results in agglomeration because of the large specific surface energies of small nanoparticles.…”

Nanoparticles in polymer-matrix composites

“…for TiO 2 , leading to substantial changes of the refractive index (Nussbaumer et al 2003;Guan et al 2006;Nakayama and Hayashi 2007;Zhang et al 2007). But, the authors only measure the transmittance using thin films.…”

“…In this case, the particle size, respectively, agglomerate size, must be smaller than 1/10th of the applied wavelength to avoid Rayleigh scattering, because otherwise the transmittance is degrading. Many research groups work on this area, fabricating mainly TiO 2 /polymer nanocomposites with modified refractive index (Nussbaumer et al 2003;Guan et al 2006;Nakayama and Hayashi 2007). Usually, chemical in-situ methods are used, generating the nanoparticles directly in a sol, with a subsequent polymerization of the sol.…”

Reaktív hibrid nanokompozit felületek antibakteriális hatása

“…Ezzel a módszerrel olyan reaktív felületek hozhatóak létre, melyek felhasználhatóak például a vízkezelésben, szennyvíztisztításban [43,44], illetve a levegőben található különböző káros vegyületek és mikroorganizmusok lebontásában, illetve eliminálásában. A fotokatalizátorokat általában valamilyen polimer alapú rétegben rögzítik, ezáltal olyan hibrid felületek alakíthatók ki, amelyek mechanikailag stabilak és fotokatalitikusan aktívak [45]. Több tanulmány említi a TiO2 nanorészecskék egészségre káros hatását, viszont ha a nanorészecskék különböző polimer rétegben stabilizálva kerülnek alkalmazásra, úgy ez a kockázat is megszűnik [46, [47].…”