Papers by Author: Ping Guan

Abstract: A simple and effective approach was proposed to synthesize uniform surface imprinted polymer microspheres via surface-initiated iniferter polymerization. The chloromethyl groups were firstly introduced onto the surface of the polystyrene microspheres by a one-step dispersion polymerization. After that the photosensitive iniferter groups were modified by the reaction of the polystyrene microspheres surface-bound chloromethyl groups with N, N-diethyldithiocarbamate sodium. The grafting step was then carried out in a stirred solution of polystyrene microspheres containing surface-initiated iniferter in the presence of template molecules (glutathione, GSH), functional and cross-linking monomers. The synthesized surface imprinted polymer (GSH-MIP) microspheres were characterized using SEM and FT-IR. The GSH-MIP microspheres were spherical in shape, and showed homogeneous polymer layer and high encapsulation efficiency. The rebinding properties of GSH for GSH-MIP was evaluated by carrying out batch rebinding tests, the obtained GSH-MIP shows faster mass transfer and higher binding amounts rate toward template than non-imprinted polymer (NIP).

Abstract: Novel Bi-Functional Magnetical Chiral Ionic Liquids (MCILs) Derived from Imidazolium and Pyridinium Were Synthesized via Simply Two Step Reactions. Optically Active Ionic Liquids Have an Asymmetric Carbon Atom Linked to the Positively Charged Imidazole Ring or Pyridine Ring, while the Magnetical Anion Contains Tetrachloroferrate (FeCl₄^-), their Properties of Chirality and Magnetism Were Characterized. the Structure of MCILs Would Promise a New Class of Bi-Functional Ionic Liquids.

Abstract: The low-temperature reversible thermochromic microcapsules was prepared by interfacial polymerization, which an aqueous phase containing CoCl₂ was used as the internal water phase (W₁), cyclohexane was used as the oil phase (O), polyvinyl alcohol was used as the external water phase (W₂) to form the uniform W₁/O/W₂ multiple emulsion. The structures of microcapsules were investigated using infrared spectrum (IR), electron microscopy (SEM) and polarization microscope. The properties of microcapsules, such as thermochromism and solvent resistance were also investigated. The results presented that the particle size of capsules was uniform, their walls were transparency, and the microcapsules were provided with excellent sensitivity to heat, reversibility and solvent resistance.

Abstract: Erythromycin molecularly imprinted polymeric microspheres（EM-MIPMs) which have good shape and well-distributed size were prepared by suspension polymerization in aqueous phase, using EM as a template and methacrylic acid (MAA) as a functional monomer. The size of MIPMs is about 50.17 μm characterized by laser particle size analyzer and polarizing microscope. The interaction between the template and monomer, and selective binding performance were investigated by ultraviolet spectrum analysis, equilibrium binding experiments and Scatchard analysis. The results show tha t hydrogen bonding may contribute to the interaction between EM and MAA, EM-MIPMs demonstrated much higher adsorption capacity compared with the NMIPMs. It has also been found that there are two kinds of binding sites in EM-MIPMs and only one kind in NMIPMs.

Abstract: Three different chiral ionic liquids, chloride (R)-(+)-β-(1-methyl-imidazole)–propio-nate, (R)-(+)-β-(1-methyl-imidazole)-propionate terafluoroborate and hexafluorophosphate, weresuccessfully synthesized via the nucleophilic substitution reaction and the anion metathesis reaction, with (S)-(-)-2-chloro-propionic acid as the chiral source. Structures of the chiral io-nic liquids have been characterized by the infrared spectroscopy, nuclear magnetic resonancespectroscopy and quantum chemical structure optimization method. These new ionic materia-ls can be used as building blocks for the synthesis of ionic liquids.

Abstract: Erythromycin molecularly imprinted membranes (EM-MIMs) were prepared by wet phase inversion from imprinted polymers which were prepared by MAA as functional monomer, AN as membrane monomer and EDMA as crosslinker in the presence of erythromycin as template. The influences of the proportion of EM and MAA, cross-linking use level, different initiators and use level as well as extraction time on the imprinted sites and specific separation of EM-MIMs for EM were investigated. The results show that EM-MIMs were provided with more imprinted sites and more excellent separation properties for EM when adding MAA 0.0461mol, EM 0.724mmol, AIBN and (NH4)2S2O8 each 0.12g as initiators, and the mole ratio of EDMA and MAA at 5:1. The extraction of templates was carried out by using absolute ethyl alcohol as eluant and ultrasonic oscillating for 40min.

Abstract: Polysulfone (PSf) membranes were prepared by the wet-phase-inversion using 1-hexadecyl-3-methylimidazolium thiocyanate [C16mim][SCN] as an new additive. Scanning electron microscope was utilized to visualize cross-sections of the membranes to gain more better understanding the influence of [C16mim][SCN] on the pore-forming. Moreover, Membrane-forming mechanism using ionic liquid as a pore-former was also discussed. The results showed that ionic liquid [C16mim][SCN] had restrained the demixing of the casting solutions and has the ability of the pore-forming, higher than those of its analogues of PEG400. With increase of concentration of ionic liquid [C16mim][SCN] in casting solutions, the structures of the membranes changed from asymmetric finger pores to the spongy-finger-macrovoid structure of the pores. Compared with PEG400 as a pore-former,[C16mim][SCN] has the pore-forming ability to the membrane at lower concentration of [C16mim][SCN] in the casting solution. Especially, at the 4:76 ratio of [C16mim][SCN]/NMP, the prepared membrane has the asymmetric finger-pores structure, with the 2~6μm pores close to surface layer and the 10~24μm pore for its sublayer. Its retention rate of PEG10000 and solution flux are 97.1% and 48.7 L• h-1• m-2. Meanwhile, ionic liquid can be a plasticizer, according the thermal properties of the membranes.

Abstract: The halide-activated pack cementation method was utilized to deposit silicide coatings on a multicomponent Nb-Ti-Si based alloy. The siliconized temperature was 1150 °C and the holding time was 10h. Both the specimens with siliconized coatings and without coatings were oxidized at 1250°C for 5, 10, 20, 50 and 100h respectively. The coating possessed a double layer structure with the composition of (Nb,X)Si2 (X represents Ti, Cr and Hf), and the outer layer was denser. The major structure in the outer layer was composed of columnar crystals perpendicular to the interface between the coating and the substrate, and that in the inner layer was mainly composed of equiaxed crystals. A transitional layer about 5μm thick was found between the coating and the substrate. After oxidation at 1250°C, the major constituents in the scale were SiO2 and TiO2 and the mole ratio of these two phases was about 2:1. The thickness of the (Nb,X)Si2 layer decreased and that of transitional layer increased as the oxidation time prolonged. The siliconized coating exhibited excellent oxidation-resistance at 1250°C within 50 hours.

Abstract: The microstructure and mechanical properties including room temperature fracture toughness Kq, tensile strengthσb and elongationδ at 1250°C of the Nb based alloy directionally solidified in an electron beam floating zone melting (EBFZM) furnace have been evaluated. The microstructure is primarily composed of Nb solid solution (Nbss), α-(Nb)5Si3 and (Nb)3Si phases. After directional solidification with the moving rate of electron beam gun R being respectively 2.4, 4.8 and 7.2 mm/min, the primary Nbss dendrites, Nbss + (Nb)5Si3/(Nb)3Si eutectic colonies (lamellar or rod-like) and divorced Nb silicide plates align along the longitudinal axes of the specimens. When R = 2.4 mm/min, the best directional microstructure is obtained. Directional solidification has significantly improved theσb at 1250°C and Kq. The maximumσb occurs for the specimens with R = 2.4 mm/min and is about 85.0 MPa, meanwhile, the Kq is about 19.4 MPam1/2.

Abstract: The directionally solidified specimens of Nb-13.52 Si-22.60 Ti–6.88 Hf–2.54 Cr–2.24 Al alloy were prepared in an electron beam floating zone melting furnace at the withdrawing rate of 0.1, 0.3, 0.6, 1.0, 2.4 and 6.0 mm/min. All the primary Nb solid solution (Nbss) columns, Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies and divorced (Nb)3Si/(Nb)5Si3 plates or chains align well along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the microstructure is gradually refined, and the amount of Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies increases. Both the room temperature ultimate tensile strength σb and fracture toughness KQ are improved for the directionally solidified specimens. The tensile fracture occurs in a cleavage way.