Amphiphilic polymers facilitated solid-phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry for direct extraction and analysis of zearalenone and zearalanone in corn juice samples

In this work, amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions are demonstrated to be capable of direct extracting zearalenone and zearalanone in samples consisting of an oil-water emulsion system. Under optimal conditions, the maximum adsorption capacities for zearalenone and zearalanone are 17.27 and 13.26 mg/g. The adsorption is mainly attributed to π-π interaction, hydrophobic interaction, and hydrogen-bonding interaction for zearalenone and zearalanone. The adsorption isotherms reveal that the adsorption of zearalenone and zearalanone on amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions follows Freundlich model with multilayer and heterogeneous adsorption due to the presence of multiple kinds of adsorption sites. The relative recoveries of the spiked zearalenone and zearalanone in corn juice samples range from 85% to 93% with relative standard deviations lower than 3.52%. The results manifest the high efficiency of amphiphilic polymers synthesized from carboxylated carbon nanotubes stabilized high internal phase emulsions for the adsorption and separation of analytes in the oil-water emulsion system. This study provides a new perspective on adsorbent engineering for the adsorption application in heterogeneous media.     

Recent advances in controlled/living radical polymerization in emulsion and dispersion

Effective ways to conduct controlled/living radical polymerization (CRP) in emulsion systems are necessary for commercial latex production without significant modification of current industrial facilities. Conducting CRP in emulsion media is more complicated and more challenging than its application in homogeneous bulk. These challenges come from the intrinsic kinetics of emulsion polymerization. They include mass transport, slow chain growth mechanism, and exit of short radicals from polymeric particles. This review describes the recent developments of CRP in heterogeneous dispersion, including miniemulsion, microemulsion, dispersion, and especially emulsion. Various approaches for conducting emulsion CRP are detailed, including controlled seeded emulsion polymerization, nanoprecipitation, use of short oligomers as macroinitiators for in situ block copolymerization, and RAFT‐mediated self‐assembly. In addition many remaining challenges of the current methods barring wide spread industrial application of emulsion CRP are also suggested. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6983–7001, 2008     

Study on novel hydrogels based on thermosensitive PNIPAAm with pH sensitive PDMAEMA grafts

A series of novel hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm) with pendant poly(N-(2-(dimethylamino) ethyl)-methacrylamide) (PDMAEMA) grafts were designed and synthesized. The influence of the pendant PDMAEMA grafts on the properties of the resulted hydrogels was examined in terms of morphology observed by scanning electron microscopy (SEM), thermal property characterized by differential scanning calorimetry (DSC) and shrinking/swelling kinetics upon external temperature changes. In comparison with the conventional PNIPAAm hydrogels, resulting hydrogels presented favorable pH sensitivity as well as improved thermosensitive properties, including enlarged water containing capability at room temperature and faster shrinking/swelling rate upon heating. In addition, fish DNA, used as a model drug, was loaded into the hydrogels, and the controlled release behavior of the drug-loaded hydrogels at different temperatures (22 and 37 °C) was further studied.     

Effects of hectorite content on the temperature-sensitivity of PNIPAM microgels

A new method, adopting inorganic clay (synthetic hectorite) as a physical cross-linker, was used to prepare poly(N-isopropylacrylamide) (PNIPAM) microgels via surfactant-free emulsion polymerization. The effect of hectorite content on the temperature-sensitivity of PNIPAM microgels was investigated by means of DLS, UV/Vis and DSC. It was found that, in the absence of surfactant, with increasing hectorite content, the particle size tends to decrease to 300 nm at room temperature, while increases as weight ratio (WR) of hectorite and N-isopropylacrylamide (NIPAM) exceeds 21%. Furthermore, with increasing WR from 7% to 21%, the volume phase transition temperature of PNIPAM microgels has little shift, while decreases slightly when WR increases up to 28%.     

Synthesis and characterization of polyaniline‐multiwalled carbon nanotube nanocomposites in the presence of sodium dodecyl sulfate

Polyaniline‐carboxylic acid functionalized multi‐walled carbon nanotube (PAni/c‐MWNT) nanocomposites were prepared in sodium dodecyl sulfate (SDS) emulsion. First, the c‐MWNTs were dispersed in SDS emulsion then the aniline was polymerized by the addition of ammonium persulfate in the absence of any added acid. SDS forms the functionalized counterion in the resulting nanocomposites. The content of c‐MWNTs in the nanocomposites varied from 0 to 20 wt%. A uniform coating of PAni was observed on the c‐MWNTs by field‐emission scanning electron microscopy (FESEM). The PAni/c‐MWNT nanocomposites have been characterized by different spectroscopic methods such as UV‐Visible, FT‐Raman, and FT‐IR. The UV‐Visible spectra of the PAni/c‐MWNT nanocomposites exhibited an additional band at around 460 nm, which implies the induced doping of the MWNTs by the carboxyl group. The FT‐IR spectra of the PAni/c‐MWNT nanocomposites showed an inverse intensity ratio of the bands at 1562 and 1480 cm^?1 as compared to that of pure PAni, which reveals that the PAni in the nanocomposites is richer in quinoid units than the pure PAni. The increase in the thermal stability of conductivity of the nanocomposites was due to the network structure of nanotubes and the charge transfer between the quinoid rings of the PAni and the c‐MWNTs. Copyright © 2008 John Wiley & Sons, Ltd.     

Physicochemical behavior of oil-in-water emulsions: influence of milk protein mixtures, glycerol ester mixtures and fat characteristics

Different emulsions based on two protein mixtures (skim milk powder (SMP) and functional dairy proteins (FDP)), two mono-di-glyceride mixtures (MDG) (saturated and partially unsaturated), three fats (hydrogenated and refined coconut oils and refined palm oil) were studied to investigate the interactions occurring between the oil phase, low molecular weight emulsifiers and proteins. Immediately following the emulsification process, high diameters of fat globules were obtained in FDP-based systems, relevant of an aggregation phenomenon. At this stage, the fat globule size characteristics were dependent on the emulsifier and fat types present in the formulation. In contrast, SMP-based emulsions were characterized by low proportions of aggregated particles regardless the formulations. Ageing (24 h at 4 °C) promoted disaggregation in FDP formulations, while SMP emulsions were well stabilized. Just after the homogenization step, less proteins were required to stabilize the globule interface in FDP systems as compared to SMP ones. Only with SMP, the amount of protein load at the fat globule surface was influenced by the oil nature and/or by the emulsifier type. A competitive adsorption of caseins, over whey proteins, was demonstrated in the case of FDP. The ageing period promoted a displacement of the proteins adsorbed at the oil droplet interface, suggesting a disruption of the interfacial protein interactions. This disruption was more marked with SMP than with FDP and, in both cases, was more or less influenced by the emulsifier and oil phase natures. The variations of the viscosity and rheological parameters (elastic and viscous moduli) were not dependent on one specific component of the formulation.     

Preparation of hollow PPy (HPPy) microspheres via template methods with characterization of properties

Template-synthesis method was one of the important methods for the preparation of hollow microspheres. In present work, polystyrene (PS) microspheres were initially synthesized and effects of reaction conditions on the particle size and distribution of PS microspheres were studied. Then sulfonated PS (SPS) microspheres and spherical core (PS) /shell (polypyrrole, PPy) were synthesized by sulfonated and template method respectively. The method was that pyrrole (Py) on the surface of SPS microspheres were polymerized. Then PS (core)-PPy (shell) microspheres by dissolving PS inner core in N, N-Dimethylformamide (DMF), and hollow polypyrrole (HPPy) microspheres were obtained (Figure 1). Thereafter, HPPy microspheres were characterized by fourier transform infrared spectroscopy, X-ray diffraction, particle size analyzer, scanning electron microscope, thermal gravimetric analysis and KDY-4 four-probe resistance meter. The results showed that the size range of PS microspheres were 200～300 nm. HPPy microspheres have been successfully synthesized with good electrical conductivity and excellent thermal stability.     

Stability analysis of environmentally benign green emulsion liquid membrane

A new stable green emulsion liquid membrane (GELM) was formulated by selecting the environmentally benign vegetable oils. The rice bran oil (RBO) based GELM has shown better stability in comparison to that obtained from other oils. GELM was prepared using 10?mL RBO, 0.25 [M] NaOH concentration, 2 (v/v, %) surfactant concentration, 0.4 (v/v) phase ratio, 2000?rpm emulsification speed, and 20?min emulsification time. Under these optimum conditions, GELM has been found to be stable for 120?±?2?min (no significant phase change) and has shown complete phase separation after 4 hours. Therefore, RBO as a green solvent has high potential to be applied in several ELM process applications.     

Ethanol-in-oil emulsion (E/O) stabilized by polyglycerol polyricinoleate: A potential delivery system for ethanolic extract

This study evaluated how variations in polyglycerol polyricinoleate (PGPR) concentration and ethanol dispersed phase content affect the stability of ethanol-in-oil (E/O) emulsions. Results indicate that the stable 10?wt% E/O emulsions can be produced using 2?wt% PGPR. Increasing the ethanol dispersed phased content at constant PGPR concentration caused instability in emulsion. These emulsions remained stable to droplet flocculation and coalescence in the presence of Centella asiatica ethanol extract. PGPR does not greatly decrease the interfacial tension of the ethanol–oil interface. However, it adsorbed at the interface and stabilized the ethanol droplets in the emulsion via steric mechanism.