The fractal dimension (D f) of the clusters formed during the aggregation of colloidal systems reflects correctly the coalescence extent among the particles (Gauer et al., Macromolecules 42:9103, 2009). In this work, we propose to use the fast small-angle light scattering (SALS) technique to determine the D f value during the aggregation. It is found that in the diffusion-limited aggregation regime, the D f value can be correctly determined from both the power law regime of the average structure factor of the clusters and the scaling of the zero angle intensity versus the average radius of gyration. The obtained D f value is equal to that estimated from the technique proposed in the above work, based on dynamic light scattering (DLS). In the reaction-limited aggregation (RLCA) regime, due to contamination of small clusters and primary particles, the power law regime of the average structure factor cannot be properly defined for the D f estimation. However, the scaling of the zero angle intensity versus the average radius of gyration is still well defined, thus allowing one to estimate the D f value, i.e., the coalescence extent. Therefore, when the DLS-based technique cannot be applied in the RLCA regime, one can apply the SALS technique to monitor the coalescence extent. Applicability and reliability of the technique have been assessed by applying it to an acrylate copolymer colloid.

The anodization of high-purity titanium was carried out via a potentiostatic approach in 0.1 mol/L H 2SO 4 solution, with a traditional three-electrode cell, a high-purity titanium plate, a platinum electrode and a saturated Ag/AgCl electrode respectively as the template, the working electrode, the counter electrode and the reference electrode. Then, the effects of anodization potential and oxidation time on the formation and crystallization characteristics of the anodic titanium oxide films were analyzed, and the films were characterized by means of SEM-EDS, Raman spectroscopy and XPS. The results show that there exist anatase-phase TiO 2 nano-crystals in the films prepared via an anodic oxidation at 6 V, 60 min or at 30 V, 10 min, and that high anodization potential and long oxidation time both promote the transformation of intermediate titanium oxides to stable titanium dioxide and accelerate the formation and growth of the anatase-phase nano-crystals, thus resulting in a structural evolution of the anodic titanium oxide films from a short-range ordered structure with few TiO 2 nano-crystals to a long-range one mainly composed of anatase-phase TiO 2.

The title waterborne polyurethane emulsion modified by epoxy resin was prepared using toluene diisocyanate(TDI),polyether(N220),dimethylolpropionic acid(DMPA),epoxy resin and hydroxypropyl acrylate(HPA) as the main materials.Effects of the reaction temperature,the dispersing speed,the degree of neutralization and the content of epoxy resin on the properties of the PU emulsion and the films were studied.The results showed the PU emulsion will show a better property when the dispersing speed,the degree of neutralization and the content of epoxy resin are 4000~5000rpm,90~95% and 4~6%,respectively.The film of waterborne polyurethane modified by epoxy resin is featured by its higher hardness,strong water resistance and mechanical properties.