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Urea–formaldehyde resin is widely used as shell materials for microencapsulation of pesticide byin situpolymerization. A series of acetochlor microcapsules were prepared with different formaldehyde to urea molar ratios in this research. Fourier transform infrared spectroscopic analysis suggests that there hardly exists any chemical interactions between shell materials and the acetochlor core materials, and the structure of urea–formaldehyde pre-polymers and shell materials are significantly different when the ratios of formaldehyde to urea increases. The pre-polymer becomes more hydroxymethylated with higher molar ratios, and hydrogen bonds in shell materials interact stronger as well, thus the ratios of formaldehyde to urea affect encapsulation efficiency by hydrogen bonding interactions, which determines the cross-link degree of the shell materials of the prepared microcapsules. [ABSTRACT FROM PUBLISHER]

Abstract In this paper, alkyl groups with different lengths are introduced to the two-dimensional spindle-type chromophores as the steric isolators to improve the poling efficiency and long term stability of the poled polymers for second-order nonlinear optical materials. The structure and thermal properties of alkyl functionalized chromophores are characterized by the 1H NMR, FT-IR, UV–Vis, DSC, TGA et al. The chromophores with different alkyl groups present extremely similar maximum absorbance wavelength (480 nm), which means they have very similar first-order hyperpolarizability. Guest-host polymer doped with chromophores has been prepared. Those materials display different glass transition temperatures and good thermal stability. According to the electro-optic coefficients studies and poling efficiency results, chromophores with longer alkyl side chain groups exhibit better poling efficiency and larger electro-optic coefficients. Especially for the chromophores with octyl group, the poling efficiency increases up to 3 times compared to the reference chromophore 2-(3-{2,5-Phenylmethanol-4-[4-(dimethylamino)styryl]-styryl-5,5-dimethylcyclohex-2-enylidene)malononitrile (STC), while the corresponding electro-optic coefficient of the poled polymers increases up to 4 times, indicating a significant effect of the isolate groups on improving the poling efficiency. Highlights • We synthesized a series of two-dimensional spindle-like chromophores with different length of alkyl groups. • Two-dimensional spindle-like chromophores had good thermal stabilities and met the requirements of the poling process. • Chromophores with longer alkyl groups and linear alkyl group had better long-term stability, poling efficiency and larger electro-optic coefficient. • Poling efficiency of chromophores with octyl group increased up to 3 times and electro-optic coefficient of poled polymers increased up to 4 times compared to STC. [ABSTRACT FROM AUTHOR]

Superhydrophobic coatings were successfully fabricated by photo-crosslinked polyurethane (PU) and organic fluoro group-functionalized SiO 2 nanoparticles (F-SiO 2 NPs), and were introduced for preventing microleakage in a dental composite restoration. The F-SiO 2 NPs possessed low surface energy and the PU can not only improve the mechanical stability but also promote F-SiO 2 NPs to form multiscale structure, which could facilitate the properties of the as-prepared superhydrophobic coating by synergetic effect. The morphology and properties of the resulted superhydrophobic coatings with different PU/F-SiO 2 ratios were studied using 1 H NMR spectrum, fourier transform infrared spectra, scanning electron microscopy, atomic force microscopy and UV–vis spectrophotometry. The results showed that the superhydrophobic coatings with low PU/F-SiO 2 ratio (1:3) possessed excellent hierarchical papillae structure with trapped air pockets, high contact angle (160.1°), low sliding angle (< 1°) and good transparency. Additionally, MTT experiments results certified the prominent cell viability and biocompatibility for clinical application. Based on its fantastically superhydrophobic property, the as-prepared superhydrophobic coatings effectively prevented water permeation in resin composite restoration evaluation. This research may provide an effective method to solve the problem of microleakage and will efficiently increase the success rate of dental composite restorations. [ABSTRACT FROM AUTHOR]