Highly crystalline and dispersible zirconia nanoparticles, ex situ synthesized from a solvothermal reaction of zirconium(IV) isopropoxide isopropanol complex in benzyl alcohol, were functionalized with 3-(trimethoxysilyl)propyl methacrylate and blended with UV-curable urethane-acrylate formulations to fabricate poly(urethane-acrylate)/zirconia (PUA/ZrO2) nanocomposite coatings. A critical ZrO2 concentration of 20 wt% was observed for the evolutions of both the structure and properties of the nanocomposites as a function of ZrO2 content. Below the critical concentration, completely transparent nanocomposite film was obtained and the nanocomposites exhibited increasing final carbon-carbon double bond conversion, refractive index, hardness, elastic modulus, and thermal stability as ZrO2 content increased. However, serious agglomeration of ZrO2 nanoparticles occurred at 25 wt% of ZrO2, which decreased final conversion, transparency and hardness, and thermal stability of the nanocomposite film. These results clearly reveal that the performance of UV-curable anocomposites is strongly dependent on the dispersion of nanoparticles.

Poly(methyl methacrylate)/zirconia (PMMA/ZrO2) nanocomposites with ZrO2 content as high as 15 wt% were prepared by modifying non-aqueous synthesized ZrO2 nanoparticles with methacryloxypropyltrimethoxysilane (MPS) in tetrahydrofuran, dispersing MPS-functionalized ZrO2 nanoparticles in MMA and following in situ bulk polymerization with controlled pre-polymerization time. The MPS-functionalized ZrO2 nanoparticles showed an efficient crosslinking role in the polymerization, leading to a complete gel of PMMA at 5 wt% of ZrO2 content. Homogeneous dispersion of the ZrO2 nanoparticles at primary particle size level was observed in all nanocomposites, which results in good clarity of the obtained nanocomposites. Hardness tests (pendulum hardness tests and indentation tests) and antiscratch tests (abrasion tests and nano scratch tests) were employed to probe the surface mechanical properties of the nanocomposites. The properties of nanocomposites as a function of ZrO2 content, revealing from various characterization techniques, are not consistent and discussed in detail. At low ZrO2 content, the mechanical properties are enhanced by the formed crosslinking structure. However, remarkable improvements of hardness and scratch resistance of PMMA were achieved when 15 wt% of ZrO2 content was embedded.

In this paper, a series of colloidal polymers with various Tg, composition, and sphere size were synthesized by surfactant-free emulsion polymerization and dispersion polymerization methods and then blended with colloidal silica particles to obtain polymer/silica nanocomposite latexes. When these nanocomposite latexes were forced dry at high temperature (e.g., 110℃) for 2h, a three-dimensional ordered porous structure was directly obtained. Neither complex processes nor removal of any templates like in a templating method is needed. These ordered pores should form from the top surface and then propagate layer by layer from the top surface to substrate.

Zirconia (ZrO2) nanocrystals, synthesized from zirconium(IV) isopropoxide isopropanol complex and benzyl alcohol, were dispersed and functionalized in organic solvents using three kinds of bifunctional silane coupling agents (SCAs), 3-glycidoxypropyltrimethoxysilane (GPTMS), 3-aminopropyltriethoxysilane (APTES), and 3-isocyanatopropyltriethoxysilane (IPTES). Completely transparent ZrO2 dispersions were achieved in tetrahydrofuran (THF) with all three SCAs, in pyridine and toluene with APTES and IPTES, and in N,N-dimethylformamide with IPTES. Dynamic laser scattering (DLS) measurements and high-resolution transmission electron microscopical (HRTEM) observation indicated that the ZrO2 nanocrystals are dispersed on a primary particle size level. Fourier transform infrared spectroscopy, solid-state 13C-and 29Si NMR spectroscopy, and thermogravimetric analysis demonstrated that all three SCAs are chemically attached to the surface of the ZrO2 nanoparticles, however, in different bonding modes. Except for GPTMS/ ZrO2/THF dispersion and IPTES/ZrO2/pyridine dispersion, all other transparent dispersions have poor long-term stability. The increasing polarity, due to high amount of APTES attached and high hydrolysis and condensation degree of the bonded APTES, and the aggregation, due to interparticle coupling via the bonded triethoxysilyl group, are the causes of the poor long-term stability for the ZrO2 dispersions with APTES and IPTES, respectively. Nevertheless, the APTES-functionalized ZrO2 precipitates can be deagglomerated in water to get a stable and transparent aqueous ZrO2 dispersion via addition of a little hydrochloric acid.

The colloidal silica particles were first modified with methyltriethoxylsilane and methacryloxypropyltrimethoxysilane, respectively, then embedded into acrylic based polyurethane using blending method or in situ method. The effects of the silane couple agent type, modified silica content and preparation method on the redispersibility of silica particles and mechanical properties of polyurethane coats were investigated using 29Si NMR, TGA, FT-IR, particle size analyzer, SEM, DMA and Instron machine. It was found that different silane couple agent and preparation method had obvious influences on the redispersibility and mechanical properties. © 2006 Elsevier B.V. All rights reserved.