核壳型乳液聚合研究进展

综述了近年来核/壳结构聚合物乳液的聚合工艺、性能及核/壳结构的表征方法进行,讨论了影响核/壳结构聚合物乳胶粒子形态的各种因素。     

水性聚氨酯/丙烯酸酯复合乳液的合成及其性能研究

通过自由基乳液聚合,合成具有核壳结构的水性聚氨酯/丙烯酸酯复合乳液(PUA)。用IR、DSC和TEM对产物结构进行了表征,证明水性聚氨酯(PU)与丙烯酸酯单体在实验条件下发生了共聚反应;考察了PVA乳液及其胶膜耐热性和耐溶剂性。结果表明具有核壳结构的PUA乳液的各项性能均比水性聚氨酯有明显提高。     

Enzyme catalyzed durable and authentic oriental lacquer: a natural microgel-printable coating by polysaccharide–glycoprotein–phenolic lipid complexes

The chemistry and technology of oriental lacquer, proof of long-term durability by a laboratory test, and morphological features of the closely packed shell (polysaccharides–glycoproteins)–core (polymerized urushiol) microgel particles, which are chiefly responsible for degradation due to efflorescence outdoors, are described. The dimerization mechanism of urushiol was demonstrated by separation of over 20 urushiol dimer derivatives. Physiological dimerization of urushiol in the lacquer is very much influenced by the humidity in drying, and the interaction of semiquinone radicals with metal ions, hydrophilic polysaccharides and amphipathic glycoproteins contained in the lacquer. A mechanism for renewable oriental lacquer is proposed, involving harmony of technology and nature within the lacquer tree plantations in south-east Asia. A brief review of studies of lacquer chemistry and synthetic coatings is given.     

Application of silica-containing nano-composite emulsion to wall paint: A new environmentally safe paint of high performance

A new emulsion-type paint was prepared by utilizing a nano-composite emulsion (NCE), which contained nano-size particles (ca. 60 nm in diameter) consisting of silica (inorganic core, ca. 30 nm in diameter) and polyacrylate (organic shell), and evaluated as wall paint. By applying NCE for the wall paint, about 35 wt.% of the organic content in the paint could be reduced in comparison with the commodity emulsion-type paint, which is highly effective to save the petroleum resources. The basic properties of the white NCE paint film on gloss, surface hardness, adhesion, and solvent resistance were evaluated and compared with those of acrylic emulsion-type paints as well as those of silica-containing paints which were prepared simply by blending the acrylic emulsion with silica sol. The NCE paint was especially excellent in solvent resistance. Then the practical tests were performed to evaluate its appropriateness as wall paint, which clarified the excellent antipollution property and the high flame resistance of the NCE paint.     

Thermal/pH-sensitive core-shell copolymer latex and its potential for targeting drug carrier application

In this work, the synthesis, properties of a thermal/pH-sensitive core-shell copolymer latex were studied and its potential application as a targeting drug carrier was also investigated, where the crosslinked copolymer of N-isopropylacrylamide (NIPAAm) and chitosan was synthesized by soapless dispersion polymerization as the core, and the copolymer of methacrylic acid (MAA) and methyl methacrylate (MMA) was prepared as the shell. The weight ratio of chitosan/NIPAAm and the concentration of crosslinking agent in feed had been changed to investigate their effects on the particle size, reaction rate, zeta potential, surface functional groups, and specific surface area of latex particles. The swelling and thermo-sensitive behavior of the film made from these core-shell latexes were also studied under different pH values of buffer solution. The model drug (caffeine) could be loaded inside the copolymer particles and protected from releasing through the transport process effectively. And the thermo-responsive property of these copolymer particles significantly enhanced the protein conjugation that showed the potential of the latex being applied on the targeting drug carrier.     

Microstructure and ablation performance of HfC/PyC core-shell structure nanowire-reinforced Hf1-xZrxC coating

To improve the ablation performance of C/C composites, HfC/PyC core-shell structure nanowire (HfCnw/PyC)-reinforced Hf_1-xZr_xC coating was prepared via three-step chemical vapor deposition (CVD) method. Effects of HfCnw/PyC and PyC layer thickness on the microstructure, residual stress and ablation performance of Hf_1-xZr_xC coating were studied. HfCnw/PyC-reinforced coatings exhibited equiaxial crystal structure. After incorporating HfCnw/PyC, ablation property of Hf_1-xZr_xC coating was enhanced because of the skeleton role of HfO₂ nanowires. PyC possessed low coefficient of thermal expansion (CTE) and high heat conductivity, but poor ablation performance. Hence, with the increase in thickness of PyC layer, ablation property of the coating first increased and then decreased. HfCnw/PyC-reinforced Hf_1-xZr_xC coating with PyC layer thickness of about 50 nm exhibited the best ablation property.     

Coating nanodiamonds with biocompatible shells for applications in biology and medicine

Use of nanodiamonds (NDs) as nontoxic nanoparticles for biological imaging, sensing, and drug delivery is expanding rapidly. The interest in NDs is triggered by their unique combination of optical properties. ND can accommodate nitrogen-vacancy color centers which provide stable fluorescence without photobleaching or photoblinking and their electronic structure is very sensitive to magnetic and electric fields. The limited options to control ND properties during synthesis or by direct surface functionalization leave room to be improved upon by employing surface coatings engineered precisely for a particular application. The major disadvantages of unmodified NDs are their limited colloidal stability and tendency to non-specifically adsorb biomolecules. This review aims to summarize recent advances in coating NDs (namely with silica and polymer shells), which addresses these disadvantages and enables the use of NDs in biological applications such as targeting of specific cells, drug delivery, and biological imaging.     

Nickel layer deposition on SiC nanoparticles by simple electroless plating and its dielectric behaviors

Surface modification of the silicon carbide nanoparticles (SiC_P) by electroless nickel plating was performed. The XRD, TEM and XPS results showed that a nanoscale agglomerative nickel layer was coated on the SiC_P. Dielectric permittivities of the original SiC_P and nickel-coated SiC_P were measured respectively in the GHz frequency range from 8 to 12 GHz. The real part and dielectric loss tangent of the nickel-coated SiC_P were significantly enhanced. The origin of the enhancement was discussed in theory, and also explained by discussing practical influence factors.     

Fabrication of nanoscaled silica layer on the surfaces of submicron SiO2-Ag core-shell spheres

A two-step silica deposition process, including prefunctionalization with poly(vinylpyrrolidone) and the following silica deposition, has been used to fabricate silica layer on the surface of nanoscaled silver shell. The influencing parameters of silica coating process were optimized to prevent the precoated silver nanoparticles from desquamating from silica spheres, finally to obtain mono-dispersed silica spheres with silver and silica multilayer films. The resulted silica layer was dense and uniform, its thickness was controllable in the range of 20–50 nm. Such coated silica layer can provide improved thermal stability of the SiO₂-Ag core-shell structural spheres.     

AuNRs@ZIF-8的制备及其表面增强拉曼散射光谱研究

表面增强拉曼光谱(Surface enhanced Raman spectroscopy, SERS)是一种分子光谱,具有快速、高灵敏和指纹识别的特性,在分析化学、生物医学等领域有着重要的应用。然而,在溶液样品中一些检测分子很难被SERS基底所吸附,导致分子拉曼信号增强困难。为此,本文提出了一种ZIF-8材料包覆金纳米棒(AuNRs)的核壳结构(AuNRs@ZIF-8)来实现拉曼信号增强,既可利用金纳米颗粒的表面等离激元增强特性,又可利用ZIF-8这种多孔MOFs材料的吸附性能,从而实现溶液样品的高灵敏拉曼检测。我们首先采用晶种法制备了均一性良好的AuNRs,然后对其进行聚乙烯吡咯烷酮(PVP)修饰,最后加入金属有机框架ZIF-8前驱体,得到AuNRs@ZIF-8核壳纳米结构。该结构对罗丹明(R6G)的SERS检测灵敏度很高,检测限可低至10⁻⁹ mol/L,并且线性关系和均一性均良好。此外,我们通过测试该结构吸收R6G前后的UV-Vis吸收光谱进一步证实了核壳纳米结构的生成和对目标分子的有效吸附。