Solvent extraction of thorium(IV) using W/O microemulsion

The extraction of thorium(IV) was investigated using two types of W/O microemulsion,one of which was formed by a surface-active saponified extractant sodium bis(2-ethylhexyl) phosphate(NaDEHP) and the other was formed by a mixture of an anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate(AOT) and an extractant bis(2-ethylhexyl)phosphoric acid(HDEHP) as the cosurfactant.The extraction capacities of the above two systems were higher than that of the HDEHP extraction system.High concentration of NaNO 3 showed no influence on the extraction in the NaDEHP based W/O microemulsion system,whilst reduced the extractability in the AOT-HDEHP W/O microemulsion system.The mechanism in acidic condition was demonstrated by the log-log plot method.The structure of the aggregations and the water content in the organic phase after extraction were measured by dynamic light scattering and Karl Fischer water titration,respectively.It was found that NaDEHP based W/O microemulsion broke up after extraction,while AOT-HDEHP W/O microemulsion was reserved.     

Fluorescence Quenching of Anthracene by N,N－Diethylaniline and Phenothiazine in Triton X－ 100／n－C10H21OH／H2O Microemulsion

The photo-induced electron transfer reactions of anthracene with N, N-diethylaniline (DEA) and phe-not hiazine(PTZ) occur in the membrane phase of a Triton X-100/n-C10H21OH (1-decanol)/H2O microemul-sion. DEA and PTZ exist in the membrane phase of the microemulsion. Anthracene exists in the oil continu-ous phase of the W/O microemulsion and in the oil core and membrane phase of the O/W microemulsion.     

Surfactant-free oil/water and bicontinuous microemulsion composed of benzene, ethanol and water

<正>Generally,a microemulsion consists of oil,water,surfactant and sometimes cosurfactant.Herein,we report a novel suffactant-free microemulsion(denoted as SFME) composed of benzene,water and ethanol without the amphiphilic molecular structure of traditional surfactant.The phase behavior of the ternary system was investigated,finding that there were a single-phase region and a two-phase region in ternary phase diagram.The electrical conductivity measurement was employed to investigate the microregion of the single-phase region,and a bicontinuous microregion and a benzene-in-water(O/W) microemulsion microregion were identified,which was confirmed by freeze-fracture transmission electron microscopy(FF-TEM) observations.The sizes of the microemulsion droplets are in the range of 20-50 nm.     

青霉素G钾盐对SDS水溶液物理化学性质的影响及其在SDS/n-C5H11OH/H2O体系中的释放

The effects of penicillin potassium salt （PenK） on the solubility, Krafft temperature TK, critical micelle concentration CMC of SDS micelle and the phase behavior of SDS/n-C5H11OH/H2O system were studied. The partial phase diagrams of SDS/PenK/H2O system at different temperatures were determined. The release amounts of PenK in SDS/n-C5H11OH/H2O system and the distribution coefficient of PenK between micelle and water were measured by UV-Vis spectroscopy. The results show that in the presence of PenK, the CMC of SDS was decreased while the TK of SDS was increased and the solubility of SDS in both water and SDS/n-C5H11OH/H2O oil in water （O/W） microemulsion was decreased, but increased in water in oil （W/O） microemulsion. SDS micelles and SDS/n- C5H11OH/H20 O/W microemulsion could accelerate the release rate of PenK. The addition of SDS and water could both increase the release rate of PenK, whereas the presence of n-C5H11OH reduced the release rate of PenK. The above results were related to the electrostatic repulsion between PenK and SDS.     

Directed Self-assembly of Vertical PS-b-PMMA Nanodomains Grown on Multilayered Polyelectrolyte Films

Layer-by-layer polyelectrolyte self-assembly, a common method for preparing high-quality ultra-thin films, was employed to direct the self-assembly behavior of polystyrene-block-poly(methyl methacrylate)(PS-b-PMMA) block copolymer for the first time. Differing from the previous neutral polymer brushes anchored to silicon substrates via chemical modification, polyelectrolyte multilayers(PEMs) were anchored by electrostatic interaction and provided a stable, smooth, and neutral interface. In the present study, PS-b-PMMA was deposited on poly(acrylamide hydrochloride)/poly(acrylic acid)(PAH/PAA) PEMs prepared by layer-by-layer self-assembly to successfully yield vertical nanodomains after thermal annealing. Seven layered PEMs revealed an excellent, smooth surface, with a low roughness of 0.6 nm. The periodic structure with interlamellar spacing of 47 nm was determined by grazing-incidence small-angle X-ray scattering(GISAXS). The morphology of the PS-b-PMMA nanodomains depended on the polyanion-to-polycation concentration ratio, which is related to the interaction between the block copolymer and the substrate. Our results demonstrate that layer-by-layer self-assembly is a helpful method for the phase separation of block polymers and the fabrication of vertical, ordered nanodomains.     

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on in situ Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid)(PLA) and poly(propylene carbonate)(PPC). By virtue of their similar chemical structures, in situ cross-linking reaction initiated by dicumyl peroxide(DCP) between PLA and PPC chains was realized in PLA/PPC blends. Therefore, the compatibility between PLA and PPC was increased, which obviously changed the phase structures and increased the elongation at break of the blends. The compatibilized blends had a recovery performance at 45 °C. Combining the changes of phase structures, the mechanism of the shape memory was discussed. It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.     

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on <Emphasis Type="Italic">in situ</Emphasis> Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC).By virtue of their similar chemical structures,in situ cross-linking reaction initiated by dicumyl peroxide (DCP) between PLA and PPC chains was realized in PLA/PPC blends.Therefore,the compatibility between PLA and PPC was increased,which obviously changed the phase structures and increased the elongation at break of the blends.The compatibilized blends had a recovery performance at 45 ℃.Combining the changes of phase structures,the mechanism of the shape memory was discussed.It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.     

Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) and its effect on the surface wettability of PVDF blend membranes

Polymerizable ionic liquid copolymer P(MMA-co-BVIm-Br) was synthesized by radical polymerization technique, and characterized by Fourier transform infrared spectrometry(FTIR), 1H Nuclear magnetic resonance(1H-NMR) and gel permeation chromatography(GPC). The resulting copolymer was used to prepare poly(vinylidene fluoride)(PVDF) blend membranes via a phase inversion method. The effects of the copolymer on the polymorphism, surface wettability and zeta potential(ζ) of the blend membranes were investigated by ATR-FTIR, contact angle instrument and zeta potential analyzer. Scanning electron microscopy(SEM and SEM-EDS) was also applied to investigate the morphology and the surface element changes of the fabricated membranes. The results indicated that P(MMA-co-BVIm-Br) copolymer existed on the surface of the membrane which made the blend membrane have a positive surface during the experimental p H range. The copolymer was also in favor of the formation of β crystal phase in PVDF membranes. The contact angle experiment indicated that P(MMA-co-BVIm-Br) copolymer could switch the wettability of the blend membranes from hydrophilic to hydrophobic by exchanging Br-anion with PF-6. Compared with pure PVDF membranes, the water flux and water recovery flux of the blend membranes were enhanced obviously. The results from the flux recovery ratio(FR) and total fouling ratio(Rt) all suggested that the blend membranes had good anti-fouling properties.     

SDS/n－C5H11OH/n－C7H16/H2O体系中W/O－BI微乳液界面电性质

In the system of SDS/n-C5H11OH/n-C7H16/H2O with the weight ratio of SDS/n-C5H11OH/H2O system at5.0/47.5/47.5, the upper phase of the system was W/O microemulsion, and the lower phase was the bicontinuous microemulsion. When the n-heptane content was less than 1%, with the increase of the n-heptane content, the capacitance (Co, Cod) in the upper phase (W/O) dropped, the capacitance (CB1, CBld) in the lower phase (BI) raised. At the same time, the W/O-BI inteffacial potential (ΔE), capacitance (Ci), and charge-transfer current (ict) decreased.After the n-heptane content reached 1%, with the increase of the n-heptane content, ΔE, Ci and ict demonstrated no significant change.     

Electrosyntheses and characterization of a fluorescent conducting copolymer of benzanthrone and thiophene

<正>Poly(benzanthrone-co-thiophene),a new conducting copolymer,was successfully prepared by direct anodic oxidation of benzanthrone and thiophene(Th) in a binary solvent system containing boron trifluoride diethyl etherate (BFEE) and acetonitrile(ACN).The as-formed copolymer film electrodeposited with monomer feed ratio of benzanthrone/Th = 1:1 at the applied potential of 1.3 V versus Ag/AgCl exhibited the advantages of both polybenzanthrone and polythiophene,such as active electrochemical behavior,excellent thermal stability,relatively high electrical conductivity and mechanical properties.UV-Vis spectroscopy,~1H-NMR and SEM were used to characterize and investigate the structures and morphologies of the copolymers.Fluorescence spectroscopy studies revealed that the obtained copolymer films show strong emission at about 525 nm.Moreover,the emitting properties of the copolymers could be tuned by changing some parameters during the electropolymerization process,such as monomer feed ratio.     

Electrospinning of cyclodextrin functionalized chitosan/PVA nanofibers as a drug delivery system

A new type of nanofibrous structure from chitosan bearing carboxymethyl-β-cyclodextrin (CS-g-β-CD) as a novel drug delivery system was synthesized by grafting carboxymethyl-β-cyclodextrin (CM β-CD) onto chitosan (CS) in the presence of water soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as the condensing agent and N-hydroxysuccinimide (NHS). Defect free mats containing CS-g-β-CD have been fabricated using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)/CS-g-β-CD blends. The morphology and diameter of the electrospun nanofibers were examined by scanning electron microscopy (SEM). The average fiber diameter was in the range of 130–210 nm. SEM images showed that the morphology and diameter of the nanofibers were mainly affected by weight ratio of the blend at constant applied voltage. The results revealed that increasing CS-g-β-CD content in the blends decreases the average fiber diameter. It was observed that the PVA/CS-g-β-CD nanofibrous mat provided a slower release of the entrapped drug in compare to PVA/CS nanofibrous mat.     

Structure characterizations and protein resistance of chitosan membranes selectively crosslinked by poly(ethylene glycol) dimethacrylate

Chitosan (CS) is a fragile material with a high modulus of elasticity. Improving its flexibility as well as membrane permeability are the key aspects that need to be addressed for using CS as a biomaterial. Poly(ethylene glycol) (PEG) has several unique properties such as protein resistance, low toxicity, immunogenicity, and good solubility in both water and organic solvents. In this study, a vinyl compound was grafted to the C-6 position of CS by protection-grafting-deprotection. The vinyl CS was then crosslinked with PEG dimethacrylate (PEGDMA) selectively at its C-6 position to form CS-g-PEG copolymer membranes. Analyses from spectra of Fourier-transform infrared and nuclear magnetic resonance confirmed the chemical structure of the crosslinking CS-g-PEG copolymer membranes. Thermal and mechanical properties of the prepared CS-g-PEG membranes were measured and well-correlated to their structures. The incorporation of PEGDMA into the CS increased the material’s flexibility and thermal resistance. Finally, the CS-g-PEG membranes were found to have good protein resistance and blood compatibility; therefore, it has potential application as the biomedical material especially for hemodialysis.     

pH-responsive Micelles from a Blend of PEG-<Emphasis Type="Italic">b</Emphasis>-PLA and PLA-<Emphasis Type="Italic">b</Emphasis>-PDPA Block Copolymers: Core Protection Against Enzymatic Degradation

pH-responsive micelles with a biodegradable PLA core and a mixed PEG/PDPA shell were prepared by self-assembly of poly(ethylene glycol)-b-poly(lactic acid) (PEG-b-PLA) and poly(2-(diisopropylamino)ethyl methacrylate)-b-poly(lactic acid) (PDPA-b-PLA). The micellization status with different pH and the enzyme degradation behavior were characterized by ¹H-NMR spectroscopy, dynamic light scattering measurement and zeta potential test. The pH turning point of PDPA block was determined to be in the range of 5.5?7.0. While the pH was above 7.0, the PDPA block collapsed onto the PLA core and could protect the PLA core from invasion of enzyme, as a result, the micelle exhibited a resistance to the enzymatic degradation.     

Electrospinning of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-polylactic acid to produce a fibrillar scaffold

α,β-Poly(N-2-hydroxyethyl)-dl-aspartamide grafted with polylactic acid (PHEA-g-PLA) is a biocompatible and biodegradable amphiphilic copolymer that has been already employed to prepare a drug delivery system.In this study we have prepared for the first time a fibrillar scaffold from PHEA-g-PLA by the electrospinning of a solution of this copolymer in a mixture of N,N-dimethyl formamide (DMF) and acetone (80:20 vol/vol). The average diameter and the morphology of electrospun fibers were detected by scanning electron microscopy.Chemical degradation studies in phosphate buffer solution pH 7.4 have been performed until 15 days in order to obtain a preliminary information about the hydrolytic resistance of the prepared scaffold.     

Fabrication of cationic nanomicelle from chitosan-graft-polycaprolactone as the carrier of 7-ethyl-10-hydroxy-camptothecin

In this research, amphiphilic brush-like polycations were synthesized, and used to fabricate cationic nanomicelle as the carrier of 7-ethyl-10-hydroxy-camptothecin (SN-38), in order to enhance its cellular uptake, solubility and stability in aqueous media. In particular, cationic chitosan-graft-polycaprolactone (CS-g-PCL) copolymers were synthesized with a facile one-pot manner via ring-opening polymerization of ɛ-CL onto the hydroxyl groups of CS by using methanesulfonic acid as solvent and catalyst. The formation of CS-g-PCL nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with narrow size distributions. Their sizes ranged from 47 to 113 nm, and the zeta potentials ranged from 26.7 to 50.8 mV, depending on the grafting content of PCL in CS-g-PCL, suggesting their passive targeting to tumor tissue and endocytosis potential. Water-insoluble antitumor drug, SN-38, was easily encapsulated into CS-g-PCL nanomicelles by lyophilization method. In comparison with bare CS-g-PCL nanomicelles, the corresponding SN-38-loaded nanomicelles showed increased particle sizes and a little reduced zeta potentials. With an increase of grafting PCL content, the drug encapsulation efficiency (EE) and drug loading (DL) of the nanomicelles increased from 64.3 to 84.6% and 6.43 to 8.66%, respectively, whereas their accumulative drug release showed a tendency to decrease due to the enhanced hydrophobic interaction between hydrophobic drug and hydrophobic PCL segments in CS-g-PCL. Also, the CS-g-PCL nanomicelles effectively protected the active lactone ring of SN-38 from hydrolysis under physiological condition, due to the encapsulation of SN-38 into the hydrophobic cores in the nanomicelles. Compared with free SN-38, the SN-38-loaded nanomicelles showed essential decreased cytotoxicity against L929 cell line, and bare CS-g-PCL nanomicelles almost showed non-toxicity. These results suggested the potential utilization of the CS-g-PCL nanomicelles as the carriers of hydrophobic drugs with improving the delivery and release properties.     

“One pot” homogeneous synthesis of thermoplastic cellulose acetate-graft-poly(l-lactide) copolymers from unmodified cellulose

Using native cellulose as the starting material, cellulose acetate-graft-ploy (l-lactide) (CA-g-PLA) copolymers were successfully synthesized by “one-pot” process in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). In this process, cellulose was first reacted with acetic anhydride, yielding cellulose acetate (CA), and then ring opening graft copolymerization of l-lactide was carried out from the residual hydroxyl groups of CA in the same solution using 4-dimethylaminopridine (DMAP) as the catalyst. Both acetyl and ploy (l-lactide) contents in CA-g-PLA copolymers could be well controlled by changing reaction conditions. The structures and thermal properties of CA-g-PLA copolymers were characterized. The glass transition temperature T_g of copolymers decreased with increasing PLA content. Compared to the pure PLA and cellulose-graft-PLA copolymers, the CA-g-PLA copolymers possessed better thermo mechanical properties in a temperature range of 60–130 °C. When the molar substitution of PLA (MS_PLA) was above 1.71, the CA-g-PLA copolymers exhibited thermoplastic behavior and could be processed by conventional thermal processing methods, such as injection molding and melt spinning.     

Chitosan-graft-poly(ϵ-caprolactone)s: An optimized chemical approach leading to a controllable structure and enhanced properties

A novel synthetic approach was developed for the controllable modification of chitosan (CS) with poly(ϵ-caprolactone) (PCL). 6-O-Triphenylmethyl-chitosan (TMCS) was synthesized as a highly soluble intermediate in organic solvents to facilitate an efficient grafting reaction of PCL onto CS in a homogeneous reaction medium. Subsequently, the syntheses of CS-g-PCL copolymers with different degrees of substitution (ds) and various chain lengths of PCL (number-average molecular weight = 1200–11,000) were carried out by a coupling reaction between the carboxylic terminal groups of PCL chains and the amino groups of TMCS. The successful grafting reaction was confirmed by GPC measurements, which indicated that the products were graft copolymers rather than physical blends. The ds, defined as the number of PCL chains per saccharide unit, of the graft copolymers could be adjusted simply by changes in the molar feed ratios of PCL to CS, and graft copolymers with different ds values ranging from 0.28 to 0.49 were synthesized, as calculated by ¹H NMR and elemental analysis. DSC and X-ray measurements showed that the melting temperature and enthalpy of the PCL grafts of these graft copolymers could be adjusted by the ds and the chains length of PCL, respectively. Meanwhile, the CS-g-PCL copolymers exhibited better solubility in various solvents, such as in chloroform for some of the resultant graft copolymers, than the original CS. Finally, nanoparticles of 100–200 nm, having hydrophobic PCL domains and cationic hydrophilic surfaces, were obtained through the self-assembly of the copolymers in selective solvents. These types of graft copolymers have great potential in various applications, such as targeted drug and gene delivery as well as tissue engineering. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2556–2568, 2007     

Preparation of corn stalk-based adsorbents and their specific application in metal ions adsorption

Corn stalk-based adsorbents modified from corn stalk were prepared by Cu(0)-mediated reversible-deactivation radical polymerization (Cu(0)-mediated RDRP). They were applied to remove metal ions and they exhibited good adsorption capacity, especially for Hg(II). Adsorption properties of corn stalk can be enhanced by introducing cyano, amino, amidoxime, and carboxyl groups onto its surface, which results in efficient adsorbents for different metal ions. TGA, SEM, EA, and FTIR analyses were employed to characterize the structures of corn stalk-graft-polyacrylonitrile (CS-g-PAN), corn stalk-graft-polyacrylamide (CS-g-PAM), amidoxime corn stalk-graft-polyacrylonitrile (AO CS-g-PAN) and carboxyl corn stalk-graft-poly(methyl acrylate) (CO CS-g-PMA). The maximum adsorption capacity for Hg(II) was 8.06 mmol g^?1 of AO CS-g-PAN. Kinetics of the Hg(II) adsorption on AO CS-g-PAN was found to follow the pseudo-second-order model and the adsorption isotherms were well fitted with the Freundlich isotherm model.     

Production of nanoparticles of methyl methacrylate and butyl methacrylate copolymers by microemulsion polymerization in the presence of maleic acid terminated poly(N-acetylethylenimine) macromonomers as cosurfactant

In this study, MMA/BMA copolymer nanoparticles were synthesized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SDS) and initiated by potassium persulphate KPS. Maleic acid terminated poly(N-acetylethylenimine) (PNAEI) with two different chain lengths was also included in the recipe, as a cosurfactant and a comonomer. FTIR and ¹H-NMR proved incorporation of the macromonomer in the structure. High polymerization yields were achieved upto 98%. The viscosity average molecular weights of the copolymers were in the range of 2.77-5.50 × 10⁵. The glass transition temperatures of these copolymers were between 50.0 and 63.9 °C. The average diameter of nanoparticles were in range of 40-96 nm. It was possible to produce nanoparticles smaller than 100 nm and with narrower size distributions by using much lower concentrations of SDS by including the macromonomers in the microemulsion polymerization recipe.     

Design,Synthesis and Characterization of A Novel Cationic Polymer Poly(lactic acid-b-L-lysine)

A novel biodegradable block copolymer poly(lactic acid-b-lysine) (PLA-b-PLL) has been synthesized and characterized in this study. This product was synthesized via a five-step reaction: Synthesis of hydroxyl-tailed poly(lactic acid) (PLA) by the ring-opening polymerization (ROP) of D,L-lactide in the presence of stannous octoate (Sn(OCt)₂) as initiator; coupling N-t-butoxycarbonyl-L-phenylalanine to hydroxyl-tailed PLA using dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP); the amino-tailed PLA was obtained through de-protection of the Boc-protective group in trifluoroacetic acid (TFA) solution; and then ring-opening polymerization of N ^ε -(Z)-lysine-N-carboxyanhydride (NCA) using the amino-tailed PLA as macro-initiator; finally removal of the Cbz-protective group of PLA-b-poly(N ^ε -(Z)-L-lysine) (PLA-b-PLL(Z) in a mixed hydrobromic acid/acetic acid solution to give the target copolymer. The characterization of this copolymer and its precursors were performed by ¹H-NMR, FTIR and GPC. The block copolymer PLA-b-PLL, combining the characteristics of an aliphatic polyester and poly(amino acids), could be of potential interest in a variety of medical applications, such as the fields of targeted drug delivery and gene delivery systems.