乳液体系中的RAFT可控/活性自由基聚合研究进展

可逆加成-断裂链转移聚合(RAFT)是新近发展起来的可控/活性自由基聚合方法。由于该方法具有适用单体范围广、反应条件温和、可采用多种聚合实施方法等优点,已成为一种有效的分子设计手段。本文总结了近几年文献报道的在乳液和细乳液体系中实施RAFT聚合反应的研究进展,对非均相体系的稳定性、聚合反应过程中的动力学特点、以及聚合产物的分子量及其分布等方面的研究进行了综述。     

Polymer dispersions from catalytic polymerization in aqueous systems

By contrast to traditional free radical emulsion polymerization, catalytic polymerization allows for polymer microstructure control. In terms of polymerizable monomers, both techniques are largely complementary. Since the beginning of this decade, an increasing number of reports on polyolefin, polybutadiene, polyalkenamer, polynorbornene, polyketone, and polyacetylene dispersions prepared by catalytic polymerization in disperse aqueous systems has appeared. This contribution reviews the preparation of these dispersions, their colloidal properties, particle formation mechanisms, particle morphologies, and polymer microstructures.     

细乳液聚合法制备磁性复合微球及其表征

在制备超细Fe3O4 磁性粒子的基础上 ,以 3种低分子量聚合物Disperbyk 1 0 6、Disperbyk 1 0 8和Disperbyk 1 1 1为Fe3O4 微粒在单体相中的分散稳定剂 ,采用细乳液聚合法制备了平均粒径为 3 40nm的PS Fe3O4 磁性复合微球 .详细研究了分散剂种类对细乳液聚合制备磁性复合微球的影响 ,并采用XRD、TGA和TEM等手段对磁性复合微球的形态、结构及磁响应性等进行了表征 .实验结果证明分散剂的选择对磁性复合微球的成功制备起着至关重要的作用 ,兼具酸性和碱性功能基的分散剂Disperbyk 1 0 6具有更好的分散和稳定效果 .TEM结果表明 ,所制备的复合微球具有一些缺陷 ,而缺陷处往往是Fe3O4 磁性粒子聚集的地方     

Colorimetric Chemosensor for Chloramphenicol Based on Colloidal Magnetically Assembled Molecularly Imprinted Photonic Crystals

A novel colorimetric chemosensor with good sensitivity, specificity, and self‐reporting capability for chloramphenicol (CAP ) has been successfully constructed based on colloidal, magnetically assembled photonic crystals coupled with molecular imprinting. The colloidal, magnetically assembled, molecularly imprinted photonic crystals (CMA ‐MIPCs ) were prepared by assembling CAP in magnetic, molecularly imprinted nanohydrogels (MMIHs ) in a magnetic field. The magnetic assembly of photonic crystals and the sensing processes could be completed simultaneously when MMIHs were dispersed in CAP solutions and in a magnetic field, and the response time was less than 1 min. The CAP concentration could be visually determined from the color change of the CMA ‐MIPCs sensor. The diffraction color blue‐shifted from luminous yellow of the blank to purple in a 1.0 mg/mL CAP solution, with a determination limit of 1.0 × 10⁻³ mg/mL. It could provide a new strategy for qualitative or semiquantitative detection of CAP .     

Preparation and study of photoswitchable fluorescence nanoparticles based on spirobenzopyran

The preparation and performance characterization of〈50 nm spirobenzopyran-based photochromic nanocomposites with photoswitchable fluorescence are presented.The nanocomposites were fabricated by means of a modifed miniemulsion polymerization process,in which the hydrophobic spirobenzopyran was covalently attached to the polymer chains and the matched fluorescent dyes were noncovalently embedded in the nanoscale cross-linked polymeric matrix,respectively.The obtained nanocomposites with a high relative fluorescence quantum yield（Q）exhibited superior fluorescent photoswitchable performance due to the effective photo-induced intermolecular energy transfer.The stability of photomerocyanine was also improved.     

Time evolution of the size distribution of nano-sphere droplets in the hexadecane-in-water miniemulsion stabilized by nonionic surfactants

Time evolutions of the droplet size distribution in miniemulsions, which is constituted of water/n-hexadecane/nonionic surfactants, were investigated by using light scattering techniques. A hard-sphere model is applied to characterize the polydispersity of miniemulsion droplets. Measuring the relative scattering intensity as a function of the volume fraction of dispersed phase, the variance of the droplets size distribution, σ², was evaluated. Miniemulsions developed gradually from monodisperse systems (σ²≅0.02) to polydisperse ones (σ²≥0.13) over 12 days after preparation. σ² increased rapidly in the early stage, and ceased to develop at about 6 days after preparation. The z-average hydrodynamic radius of miniemulsion droplets grew with time over the whole time range. The change with time of the total droplet number of miniemulsion is in agreement with that predicted by Smoluchowski's theory for diffusion-controlled coagulation. Although the characteristic coagulation time obtained here was much larger than that estimated by Smoluchowski's theory, the qualitative agreement between the theory and the experimental results obtained here is good. At the earlier stage of the destabilization process of miniemulsions, the growth mechanism of droplets may be explained in terms of a diffusion-controlled coagulation. Received: 1 April 2000 Accepted: 10 August 2000     

Synthesis of styrene–butadiene rubber latex via miniemulsion copolymerization

High-butadiene-level styrene–butadiene rubber latexes up to high solid-contents are synthesized using the miniemulsion process. It is shown that the miniemulsion polymerization approach offers an efficient heterophase route synthesizing styrene–butadiene copolymer latexes with flexible copolymer composition and narrow size distribution of the resulting latex particles. Secondary nucleation was successfully prevented by using a hydrophobic initiator. Due to the nanoreactor situation, even at high conversions, a low crosslinking degree and, therefore, low gel contents are obtained. The microstructure of the polymers obtained in miniemulsion is independent of the synthesis parameters, especially the temperature. The molecular weight can be easily adjusted by the application of transfer agents while the insoluble gel content is substantially reduced. An up-scaling of the procedure is easily possible.     

预聚物复合助稳定剂条件下含氟丙烯酸酯共聚物的细乳液聚合

以甲基丙烯酸三氟乙酯(TFMA)、苯乙烯(St)和丙烯酸丁酯(BA)为共聚单体,在十二烷基硫酸钠(SDS)/磺酸盐型阴离子氟表面活性剂(S100)/辛基苯基聚氧乙烯醚(OP-10)组成的乳化体系中,采用预聚物和十六醇(HDL)共同组成的复合助稳定剂,对细乳液聚合制备St/BA/TFMA三元共聚物的过程进行了研究.通过F...     

非离子乳化剂细乳液聚合制备草莓型PSt/SiO2纳米复合微球

通过细乳液聚合,使用非离子乳化体系辛基酚聚氧乙烯醚(CA-897),在纳米二氧化硅水分散介质中,以1-乙烯基咪唑(1-VID)作为辅助单体制备了苯乙烯为核,纳米二氧化硅为壳的草莓型PSt/SiO2有机-无机复合微球.实验范围内得到的复合微球的平均粒径和最终SiO2含量分别介于140～180 nm和19 wt%-31wt...     

Solid lipid nanoparticles prepared by solvent diffusion method in a nanoreactor system

In this study, water-in-oil (W/O) miniemulsion was used as nanoreactor to prepare solid lipid nanoparticles (SLN) by solvent diffusion method. n-Hexane, Tween 80 and Span 80 were used as the oil phase and surfactant combination for preparation of W/O miniemulsion, respectively. The stable miniemulsion with the particle size of 27.1 ± 7.6 nm was obtained when the composition of water/Tween 80/Span 80/n-hexane was 1 ml/18 mg/200 mg/10 ml. Clobetasol propionate (CP) was used as a model drug. The physicochemical properties of the SLN, such as particle size, zeta potential, surface morphology, drug entrapment efficiency, drug loading capacity and in vitro drug release behaviors were investigated, comparing with those of SLN prepared by conventional aqueoethod. The SLN prepared by the novel method displayed smaller particles size and higher dus solvent diffusion mrug entrapment efficiency than those of SLN prepared by the conventional method. The drug entrapment efficiency decreased with increasing of charged amount of drug, and 15.9% of drug loading was achieved as the charged amount of drug was 20%. The in vitro drug release tests indicated that the drug release rate was faster than that of SLN prepared by the conventional method, and the drug content in SLN did not affect the in vitro drug release profile.