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 methyacrylate)-block-polydimethylsiloxane (PMMA-b-PDMS) copolymers with various compositions were synthesized with PDMS-containing macroazoinitiator (MAI), which was first prepared by a facile onestep method in our lab. Results from the characterizations of X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed that the copolymer films took on a gradient of composition and more PDMS segments enriched at the film surfaces, which then resulted in the low surface free energy and little microphase separation at the film surfaces. By contrast, transmission electron microscopy (TEM) analysis demonstrated that distinct microphase separation occurred in bulk. Slight crosslinking of the block copolymers led to much steady morphology and more distinct microphase separation, in particularly for copolymers with low content of PDMS. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104:3356-3366, 2007

Waterborne adhesives are extremely environment-friendly but unfortunately deficient in mechanical properties. In this article, nanosilica, stemming from tetraethyl orthosilicate (TEOS), silica sol, and/or fumed silica powder, was employed to reinforce the waterborne silylated polyether adhesives. Effects of TEOS content, silica sol content, and the type and content of fumed silica on the shear strength of the adhesive were investigated using a scanning electronic microscope and an electronic instron tester and the strengthening mechanisms of different silica source were discussed. All the shear strengths of silylated polyether adhesives first increased and then decreased as TEOS content, silica sol content or fumed silica content increased. Colloidal silica particles was less efficient than fumed silica particles for reinforcing the polyether adhesive but can increase the shear strength of hydrophobic fumed silica embedded adhesive. Comparing the adhesives with the hydrophilic fumed silica (HS-5) or the extremely hydrophobic fumed silica (TS-720), the adhesive with moderate hydrophobic fumed silica (TS-610) had the highest shear strength. The maximal shear strength of 2.5 MPa was achieved when TEOS, silica sol, and fumed silica were combined. It seemed that TEOS, silica sol, and fumed silica played crosslinking (with polyether chain), dispersing (for fumed silica), and reinforcing roles on waterborne adhesive, respectively. This reinforcing mechanism opened a new way to fabricate waterborne adhesives (or coatings) with high performances.

The photopolymerization kinetics of poly(urethane-acrylate)/zirconia (PUA/ZrO2) nanocomposite coatings were monitored on-line and in-real-time with microdielectrometry (DEA) in terms of logarithmic ion viscosity (log). For comparison, real-time infrared spectroscopy (RTIR) was also employed to determine the evolution of C=C bond conversion (C) with irradiation time (t). Coupling log-t curves with C-t curves indicates that the relationship between log and C for all the coatings with different formulations (i.e. the type of photoinitiator, ZrO2 content) and curing condition (i.e. irradiation intensity) can be correlated to one linear equation at conversion less than ∼85%. Moreover, DEA monitoring was longer time to reach polymerization equilibrium than RTIR for those cases with high limited conversion, suggesting that the former is more sensitive to C=C bond conversion than RTIR at high conversion stage (C>∼85%). DEA monitoring on the photopolymerization kinetics of PUA/ZrO2 coatings as a function of various parameters further demonstrates that DEA results are reliable and reasonable to conventional radical photopolymerization. It is believed that DEA technique will be useful not only on the optimization of curing condition but also for the formulation of UV-curable coatings.

Europium(III) (Eu3þ)-doped polyurethane films were prepared by mixing Eu-methacrylic acid complex (Eu(MA)3) with aliphatic polyurethane oligomer and subsequently curing under UV irradiation. Transmission electron microscopy photos and the appearance of the resulting hybrid films showed that phase separation occurred only at an Eu(MA)3 content above 20 wt.-%. Fluorescence spectra indicated that the fluorescence of Eu3þ was barely influenced by the polyurethane matrix and its intensity increased with an Eu(MA)3 content in the range of approximately 0 to 10 wt.-%. An obvious applied external-field-dependent magnetization (M) of polyurethane/Eu(MA)3 films, namely, an increasingMat low field and a decreasingMat high field, was observed at room temperature from the hysteresis loops, which was influenced by both the Eu(MA)3 content and the ultrasonication imposed on the coatings before curing. It seems that ultrasonication leads to a thermodynamically-unstable structure of Eu3þ in hybrid films, which can be fixed by UV curing but gradually rearranges to its original form during the thermal-curing process, and enhances the diamagnetic part of the hybrid film. Thus, the magnetic property of Eu3þ-doped polyurethane film at room temperature can be adjusted by simply changing the preparation method and the Eu(MA)3 content instead of the type of Eu3þ-organic complex.