Ling He

Xi'an Jiaotong University, Ch’ang-an, Shaanxi, China

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Publications (18)50.38 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Two copolymer/SiO2 hybrids are prepared by growing SiO2 on the template of well -structured diblock copolymer PMMA-b-PMPS using a "grafting-to" approach. PMMA-b-PMPS is obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate (PMMA) and 3-(trimethoxysilyl)propyl methacrylate (PMPS) using a brominated initiator end group termed 1H,1H,2H,2H-heptadecafluoro (F-Br) and a conventional initiator of ethyl 2-bromoisobutyrate (EBiB), respectively. The "grafting-to" approach is controlled at HCl for 24h by hydrolysis and condensation of Si(OCH3)3 groups in PMPS with tetraethyl orthosilicate (TEOS) to gain both hybrids of F-PMMA-b-PMPS/SiO2 (by F-Br initiator) and E-PMMA-b-PMPS/SiO2 (by EBIB initiator). Comparatively, a little amount of fluorine content provided by F-Br is able to tighten the size of self-assembled micelles, to improve wettability and the viscoelasticity of F-PMMA-b-PMPS film due to F-Br migrating onto the film surface. Therefore, the surface of F-PMMA-b-PMPS film is sufficiently hydrophobic (99° and Δf=2941Hz) than E-PMMA-b-PMPS film (94°and Δf=4820Hz), and the viscoelasticity of the adsorbed layer for F-PMMA-b-PMPS (ΔD/Δf=-0.112) film is much harder than E-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.071). On the other hand, the cross-linked silica in PMMA-b-PMPS/SiO2 could also increase water contact angels of films (100-107°) and decrease the water absorption (Δf=704-798Hz). The influence on the viscoelasticity of the adsorbed layer by the fluorine group is much more obvious than the cross-linked silica, therefore F-PMMA-b-PMPS/SiO2 (ΔD/Δf=-0.347) and F-PMMA-b-PMPS (ΔD/Δf=-0.112) films have harder adsorbed layer than E-PMMA-b-PMPS/SiO2 (-0.071) and F-PMMA-b-PMPS films (-0.042). However, compared with a slightly improvement in thermo stability by F-Br, the cross-linked silica in PMMA-b-PMPS/SiO2 performs significantly improving thermal decomposition temperature at 300°C and 350°C.
    Journal of Colloid and Interface Science 07/2014; 433C:133-140. · 3.17 Impact Factor
  • Aizhao Pan, Ling He
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    ABSTRACT: Novel organic/inorganic hybrid for coating material is prepared by the pentablock copolymer PDMS-b-(PMMA-b-PMPS)2 (PMMDMM) and SiO2 nanoparticles. PMMDMM is obtained via atom transfer radical polymerization (ATRP) by using polydimethylsiloxane (PDMS) as bifunctional macroinitiator. Poly 3-(trimethoxysilyl)propyl methacrylate (PMPS) is designed as the end block for facilitating the chemical bond of triethoxysilane (Si(OCH3)3) groups with SiO2 nanoparticles produced by tetraethyl orthosilicate (TEOS), and poly (methyl methacrylate) (PMMA) is designed as the middle block for improving the solubility and the film-forming ability of copolymer. The homogeneous dispersion of SiO2 nanoparticles in the pentablock copolymer matrix enables PMMDMM/SiO2 to self-assemble into 210nm SiO2 core/PMMDMM shell elliptic or spherical micelles in tetrahydrofuran (THF) solution. This self-assembled aggregate could provide the film surface with uniform distribution of SiO2 nanoparticles, obvious hydrophobicity (101-102° water contact angles), lower surface free energy (22.3-21.8nN/m) and lower viscoelasticity. SiO2 involved into the copolymer matrix could increase the nanostructures roughness. When TEOS is controlled as 20wt.%, the hybrid performs higher glass transition temperature (Tg=113°C) and excellent thermostability (520°C) than PMMDMM (Tg=87°C, 295°C) due to the introduction of SiO2 nanoparticles. These excellent properties promise PMMDMM/SiO2 hybrid as the candidate for coating material.
    Journal of Colloid and Interface Science 01/2014; 414C:1-8. · 3.17 Impact Factor
  • Aizhao Pan, Ling He
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    ABSTRACT: Two novel core–shell pentablock copolymer/silica hybrids are prepared for coating applications, PDMM core/silica shell (PDMM@SiO2) and silica core/PDMM shell (SiO2@PDMM), by pentablock copolymer and 20% TEOS. The effect of different core–shell structure on the film hydrophobicity, water absorption, viscoelasticity, Tg, storage modulus and adhesion to the substrate is discussed.
    Materials Chemistry and Physics. 01/2014; 147(s 1–2):5–10.
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    ABSTRACT: An effective method for characterizing Chinese lacquer as binding medium in historical artwork has been developed by on-line methylation pyrolysis-gas chromatography–mass spectrometry (pyrolysis GC–MS). The characteristic pyrolytic components of Chinese lacquer were identified in artificially aged pure and pigmented lacquer. Methylation of urushiol (mainly composed of catechol derivatives) was performed by adding tetramethyl ammonium hydroxide to convert phenolic hydroxyl groups into methylated derivatives to improve the resolution of catechol derivatives and urushiol monomers. The mechanism of formation of small molecular components was proposed, and the influence of different mineral pigments (azurite, malachite, ochre, and cinnabar) on the determination of characteristic components was discussed. Aliphatic hydrocarbon components, benzene derivatives, catechol derivatives, and urushiol monomers were proposed as characteristic pyrolytic components. In addition to 3-pentadecene-catechol, 3-pentadecane-catechol, and 3-heptadecene-catechol, 3-pentadecene-phenol was also identified as an urushiol monomer in Chinese lacquer. Four pigments slightly reduced the detection of aliphatic hydrocarbon components, but were unconspicuous for the detection of benzene derivatives. Azurite, malachite, and cinnabar decreased the measurement of urushiol monomers, but ochre significantly increased their relative abundance. The established on-line methylation pyrolysis GC–MS procedure and summarized data were successfully applied to the identification of samples collected from Terra-Cotta Warriors and Horses of Qin Dynasty (221–207 BC), Han Yang Mausoleum of Han Dynasty (206 BC–24 AD), and Dazu Grotto of Tang Dynasty (618–907 AD).
    Analytical Letters 01/2014; 47(15). · 0.97 Impact Factor
  • Progress in Organic Coatings 01/2014; · 2.30 Impact Factor
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    ABSTRACT: The reactive rate and surface wettability of three pentablock copolymers PDMS-b-(PMMA-b-PR)2 (R = 3FMA, 12FMA, and MPS) obtained via ATRP for coatings are discussed. Poly(dimethylsiloxane) (PDMS) is used as difunctional macroinitiator, poly(methyl methacrylate) (PMMA) as the middle block, while poly(trifluoroethyl methacrylate) (P3FMA), poly(dodecafluoroheptyl methacrylate) (P12FMA) and poly(3-(trimethoxysilyl)propyl methacrylate) (PMPS) as the end block, respectively. Their reactive rates obtained by gas chromatography (GC) analysis indicate that 3FMA gains 8.053 × 10−5 s−1 reactive rate and 75% conversion, higher than 12FMA (4.417 × 10−5 s−1, 35%), but MPS has 1.9389 × 10−4 s−1 reactive rate and 96% conversion. The wettability of pentablock copolymer films is characterized by water contact angles (WCA) and hexadecane contact angles (HCA). The PDMS-b-(PMMA-b-P12FMA)2 film behaves much higher advancing and receding WAC (120° and 116°) and HCA (60° and 56°) than PDMS-b-(PMMA-b-P3FMA)2 film (110° and 106° for WAC, 38° and 32° for HAC) because of its fluorine-rich surface (20.9 wt % F). However, PDMS-b-(PMMA-b-PMPS)2 film obtains 8° hysteretic contact angle in WAC (114°–106°) and HAC (32°–24°) due to its higher surface roughness (138 nm). Therefore, the fluorine-rich and higher roughness surface could produce the lower water and oil wettability, but silicon-rich surface will produce lower water wettability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40209.
    Journal of Applied Polymer Science 11/2013; · 1.40 Impact Factor
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    ABSTRACT: Two poly(4-vinylpyridine)-b-polystyrene diblock copolymer/silica core-shell nanoparticles (P4VP-b-PS/SiO2 NPs) are developed in this work. Confirmed by DLS analysis and TEM observation, one comprises a SiO2 core surrounded by a P4VP-b-PS shell and the other comprises a P4VP-b-PS core surrounded by a SiO2 shell, which is facilely prepared by the in situ hydrolysis of tetraethyl orthosilicate (TEOS) using cationic P4VP-b-PS micelles obtained in a THF-H2C2O4 (aq, 0.1 mol L(-1)) mixture and a DMF-H2C2O4 (aq, 0.01 mol L(-1)) mixture as template, respectively. The SCA, CAH, SA and SEM measurements reveal that one-step deposition of P4VP-b-PS/SiO2 NPs with SiO2 cores formed at a high level of TEOS creates a superhydrophobic surface with an SCA of 160°, a CAH of 2° and an SA of around 4° originating from the formation of a typical micro-nanoscale binary structure (MNBS). For the NPs with SiO2 cores formed at a low level of TEOS, the superhydrophobicity with a SCA of 151°, CAH of 3° and SA of around 5° can be induced by the transition of the surface microstructure from an uneven and discontinuous MNBS, created by a one-step deposition process, to the coexistence of MNBS and a nanoscale structure (NS) after annealing with toluene for 30 min. In contrast, one-step deposition of P4VP-b-PS/SiO2 NPs with P4VP-b-PS cores and SiO2 shells usually results in the inhomogeneous precipitation of SiO2 from bulk P4VP-b-PS along with the production of micro-cracks, with which is impossible to achieve surface superhydrophobicity.
    Physical Chemistry Chemical Physics 05/2013; · 3.83 Impact Factor
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    ABSTRACT: The novel inorganic/organic core-shell SiO/P(MMA/BA/3FMA) nanocomposite for coating application is synthesized in this paper by seed emulsion polymerization, in which the inorganic phase is composed of nano-SiO modified by vinyl-trimethoxysilane (VMS) or γ-methacryloxy propyl trimethoxylsilane (MPMS), and the organic phase is made of terpolymer by 2,2,2-trifluoroethyl methacrylate (3FMA), methyl methacrylate (MMA), and n-butyl acrylate (BA). The chemical structure of SiO/P(MMA/BA/3FMA) is characterized by FTIR. The effect of surfactant polyvinylpyrrolidone (PVP), sodium dodecyl sulfate (SDS)/octyl phenyl polyoxyethylene ether (TX-10), sodium dodecyl benzene sulfonate (SDBS)/TX-10 and sodium hexametaphosphate (SHMP) on the grafting ratio (GR) of VMS and MPMS, the dispersion of nano-SiO particles and the film properties of SiO/P(MMA/BA/3FMA) are investigated by TGA, DLS, TEM, SEM, and XPS. The morphology variation and the particle size distributions of SiO/P(MMA/BA/3FMA) with the content of surfactant and P(MMA/BA/3FMA) are characterized. It is found that MPMS is more effective than VMS in improving GR and the dispersion of nano-SiO particles. The surfactants are favor of gaining the higher GR in the multilayer grafted nano-SiO, especially SDS/TX-10 for 17.6% GR. The morphology of SiO/P(MMA/BA/3FMA) is controlled by the amount of SDS/TX-10 and P(MMA/BA/3FMA) as the core-shell particles, the stacked pomegranate seed with multicore and the multicore-single shell structure when w(MMA)/w(BA)/w(3FMA)=1.3/1/1. Among the different surfactants, SDBS/TX-10 and PVP could give the monodispersing nano-SiO in the terpolymer matrix of the films, but SDS/TX-10 and SDBS/TX-10 could perform the fluorine-rich surface.
    Journal of Colloid and Interface Science 04/2013; 396:129-37. · 3.17 Impact Factor
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    ABSTRACT: The core-shell polysiloxane/fluoroacrylate copolymer latexes p(D4/D4V)/p(BA/MMA/FA) are prepared for coating materials. P(D4/D4V) core is synthesized by ring-opening polymerization of octamethylcyclotetrasiloxane (Si4O4(CH3)8, D4) and tetravinyltetramethylcyclotetrasiloxane (Si4O4(CH3)4(C2H3)4, D4V). P(BA/MMA/FA) shell is obtained by semi-continuous seed emulsion copolymerization of methylmethylacrylate (MMA), butylacrylate (BA) and fluorinated acrylate (FA) via. Four different FA are used in this paper: hexafluorobutyl acrylate (6FA), trifluoroethyl methacrylate (3FMA), hexafluorobutyl methacrylate (6FMA) and dodecafluoroheptyl methacrylate (12FMA). The as-prepared latexes are characterized by Fourier transforms infrared (FT-IR) spectroscopy and 1H NMR measurement. The typical core-shell structure is proved by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The effect of different shells on the core-shell particles and the surface properties of films are characterized by TEM, dynamic light scattering (DLS), scanning electron microscope coupled with the energy dispersive spectrometry (SEM-EDX), static contact angles (SCA) for surface free energy, and quartz crystal microbalance with dissipation (QCM-D) monitoring for surface water absorption. With the increase of fluoridated side chain in the shell, the individual core-shell particles as 70-90 nm are obtained. The surface free energy for p(D4/D4V)/p(BA/MMA/12FMA) film (19 mN/m) is much lower than other three films (28-29 mN/m). During the film formation, the self-aggregation of–CF3 groups onto the film surface for lower surface free energy and the polysiloxane groups onto the substrate for better adhesion. Therefore, p(D4/D4V)/p(BA/MMA/12FMA) film is much more homogeneous, less wettability and less water absorption.
    Journal of Fluorine Chemistry 01/2013; · 1.94 Impact Factor
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    ABSTRACT: The gilding and painting techniques for the clay-based polychromic sculptures in Jizo Hall of Chongqing Temple, Shanxi Province of China, are analyzed by complementary techniques of microscopy, environmental scanning electron microscopy (ESEM), energy dispersive X-ray mapping (EDX), micro Raman spectroscopy (μ-RS), and Fourier transform infrared spectrum (FTIR) with a reasonable sequence. 7 gilded samples and 6 pigmented samples are collected from Jizo Hall. For the 7 gilded polychromic samples, drying oil-based, Chinese lacquer-based and glue-based “Jin Jiao” techniques are identified respectively according to their different adhesive layers used for jointing gold leaf to the preparation layer. But the presence of a copper foil top surface, as well as the inner layers with crocoites (PbCrO4) and modern red pigment in one alleged gilded polychromic sample indicate a later restoration work. Among them, two gold layers have been identified in 4 samples due to the regilded work in history. For 6 pigmented samples, painting layer is generally applied on a white preparation layer made of kaolinite or the mixture of kaolinite and gypsum. Atacamite, cinnabar, minium, yellow ochre and gypsum of are identified as the main pigments, and the protein-based material is confirmed as the binding medium for red pigments. This research not only reveals the Chinese traditional gilding and painting techniques employed in polychromic sculptures of Jizo Hall, but also demonstrates the advantages and limitations of each analytical technique for identifying polychromic samples, and the necessity of complementary analytical techniques approach.
    Microchemical Journal 01/2013; · 2.88 Impact Factor
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    ABSTRACT: Diblock fluoroacrylate copolymers poly(methyl methacrylate) (PMMA)-b-poly(dodecafluoroheptyl methacrylate) (PMMA-b-PDFHM) for coating materials are synthesized via atom transfer radical polymerization (ATRP) by two different initiators, a brominated initiator end group terminated by 1H,1H,2H,2H-heptadecafluoro (F–Br) and the conventional initiator ethyl 2-bromoisobutyrate (EBiB). The copolymer structures are characterized by 1H NMR, 19F NMR and GPC analyses. The influence of the two initiators on the self-assembly behavior and the surface properties of PMMA-b-PDFHM films are explored. Because of the divergent solubility of the segments in chloroform (CHCl3), tetrahydrofuran (THF) and trifluorotoluene (TFT) solutions, the self-assembly of PMMA-b-PDFHM in CHCl3, THF and TFT was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Accordingly, the properties of PMMA-b-PDFHM films cast from CHCl3, THF and TFT solutions were compared for their surface wettability, surface free energy, surface elemental composition, surface morphology and roughness, and surface water adsorption, through analysis of static contact angle (SCA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and quartz crystal microbalance with dissipation (QCM-D). It is found that the copolymers F-PMMA-b-PDFHM using F–Br initiator and E-PMMA-b-PDFHM using EBIB initiator, reveal both unimers (7–9 nm) and micelles (220–360 nm) in THF and CHCl3 solutions, which are recognized by TEM as dichroic half-spherical or core–shell particles, but occur mainly as unimers (5–9 nm) in TFT solution, which is favorable for obtaining films with low surface free energies. F-PMMA-b-PDFHM films show lower surface free energy (17.1–17.7 mN m−1) than E-PMMA-b-PDFHM films (17.9–22.9 mN m−1) in each solvent. The surface morphology and roughness determined are strongly controlled by the cast solutions. F-PMMA-b-PDFHM films exhibit a low wettability and high stable surface due to a well-ordered fluorocarbon surface provided by both PDFHM and F–Br groups, and therefore can be developed into a high-performance coating material.
    Journal of Materials Chemistry 10/2012; 22(43):23078-23090. · 5.97 Impact Factor
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    ABSTRACT: This paper presents a multi-analytical study of the polychromy in the Guangyuan Thousand-Buddha Grotto. Samples taken from 15 locations in No. 512 and No. 689 caves are prepared as cross-sections for the analysis by optical microscopy (OM) and scanning electron microscopy coupled with backscattered electron imaging (SEM-BSE). The cross section analysis indicates that some paintings were repainted in the past. The chemical composition of each painting layer is obtained by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX). The main pigments for 15 samples including green, red, blue, white and black paint layers, are identified by the combination of polarized light microscopy (PLM), Fourier Transform infrared spectrum (FT-IR), Raman spectroscopy (RS) and X-ray diffraction (XRD) analysis. The integrated analytical results reveal that the green pigments are malachite and atacamite; the red color is attributed to minium, hematite and cinnabar; the blue pigments are lazurite and organic blue materials; the white color is ascribed to anglesite and gypsum; and the black surface of polychrome is the accumulation of longtime smudging by folk burning incense in the devotional practice or the soot deposition resulting from burning bonfires in the caves. Some arsenic-containing pigment is detected in the green samples. This case study also demonstrates the advantages and the limitations of every analytical technique for the pigment identification, confirming the necessity of the integrated analytical techniques approach. The present results are not only useful to assist in the authenticity of the used pigment materials and history of the polychromic in the past, but also aimed at guiding the conservation scientists in taking into account materials and methods utilized in the past.
    Journal of Archaeological Science 06/2012; 39(6):1809–1820. · 1.89 Impact Factor
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    ABSTRACT: The geometric, electronic structure, and thermodynamic stability of large gadolinium-containing endohedral metallofullerenes, Gd(2)@C(98), have been systematically investigated by comprehensive density functional theory calculations combined with statistical mechanics treatments. The Gd(2)@C(2)(230924)-C(98) structure, which satisfies the isolated-pentagon rule (IPR), is determined to possess the lowest energy followed with some stable non-IPR isomers. In order to clarify the relative stabilities at elevated temperatures, entropy contributions are taken into account on the basis of the Gibbs energy at the B3LYP level for the first time. Interestingly, a novel non-IPR Gd(2)@C(1)(168785)-C(98) isomer which has one pair of pentagon adjacency is more thermodynamically stable than the lowest energy IPR species within a wide temperature interval related to fullerene formation. Therefore, the Gd(2)@C(1)(168785)-C(98) is predicted to be the most proper isomer obtained experimentally, which is the largest non-IPR carbon cage found so far. Our findings demonstrate that interaction between metals and carbon cages could stabilize the fused pentagons effectively, and thus, the non-IPR isomers should not be ignored in some cases of endohedral metallofullerenes. The IR features of Gd(2)@C(98) are simulated to assist its future experimental characterization.
    Inorganic Chemistry 02/2012; 51(4):2039-45. · 4.59 Impact Factor
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    ABSTRACT: The surfaces of films cast from core-shell fluorosilicone acrylate copolymer (BA/MMA/DFHM and BA/MMA/DFHM/MPTMS/D(4)) latexes and linear pentablock fluorosilicone acrylate copolymer (PDMS-b-(PMMA-b-PDFHM)(2)) solutions are intensively investigated and compared by XPS, DCA, AFM, and QCM-D measurements. It is found that the molecular structures and in-solution aggregate structures of these well-defined copolymers have a dramatic influence on the surface structure formation, surface wetting, and adsorption behavior. The PDMS-b-(PMMA-b-PDFHM)(2) film cast from chloroform solution with high concentration of low-density unimers is able to perform as strong surface self-segregation of fluorine-containing groups as core-shell copolymer latex films. The BA/MMA/DFHM/MPTMS/D(4) in the core-shell latex particles exhibits the less pronounced surface self-segregation of silicon-containing groups than PDMS-b-(PMMA-b-PDFHM)(2) due to the occurrence of cross-linking reactions between polysiloxane chains. Indeed, such reactions induce the formation of silica network within the film material, which immobilizes tightly the fluorinated groups on the film surface and thus endows the film with higher surface structural stability for water compared to PDMS-b-(PMMA-b-PDFHM)(2) film with similar surface fluorine concentration and even higher silicon concentration. Still, the PDMS-b-(PMMA-b-PDFHM)(2) film definitely demonstrates higher advancing and receding contact angles for water than BA/MMA/DFHM/MPTMS/D(4) latex film in the case of synergism between surface enrichment of fluorine and silicon.
    Journal of Colloid and Interface Science 12/2011; 369(1):435-41. · 3.17 Impact Factor
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    ABSTRACT: With a combined methodology of quantum chemistry and statistical mechanics, two Yb@C76 isomers are disclosed to possess novel fullerene structures which contain one pair of adjacent pentagons and are related by a single Stone–Wales transformation.
    Journal of Materials Chemistry 08/2011; 21(33):12206-12209. · 5.97 Impact Factor
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    ABSTRACT: A series of linear fluorosilicone pentablock copolymers consisting of poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA) and poly(dodecafluoroheptyl methacrylate) (PDFHM), named as PDMS-b-(PMMA-b-PDFHM)2, have been synthesized by ATRP and their thermal properties, self-assembly behavior in different solutions and surface features of films have been systematically investigated. TGA measurements reflect that the thermal stability of PDMS-b-(PMMA-b-PDFHM)2 is enhanced by the middle-block PDMS. TEM observation and DLS analysis reveal that PDMS-b-(PMMA-b-PDFHM)2 is able to self-assemble into unimers in both chloroform and dioxane solutions, and spherical micelles with a core–corona structure in chloroform, oblate spheroidal micelles with a multilayer core–corona structure in dioxane. The diameters of micelles in the dioxane solution are larger, while the concentrations of unimers in the chloroform solution are higher. SCA, QCM-D and XPS measurements have confirmed that the unimers play a dominant role in governing the surface properties of PDMS-b-(PMMA-b-PDFHM)2 films. In the case of PDMS-b-(PMMA-b-PDFHM)2 with a PMMA/PDMS weight ratio of 10:1 and 20%wt of DFHM content, the film cast from chloroform solution has a lower surface free energy of 16.8 mN m−1, lower adsorbed amounts of 8.6 × 104 ng cm−2 for water and 6.6 × 104 ng cm−2 for hexadecane, and higher surface stability. Such excellent thermal and surface properties demonstrate that this novel pentablock copolymerPDMS-b-(PMMA-b-PDFHM)2 is a promising candidate as a coating material.
    Journal of Materials Chemistry 04/2011; 21(19):6934-6943. · 5.97 Impact Factor
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    ABSTRACT: The archeological round bronze coins, nominated as Wu Zhou and regarded as the first issued effective money in the Han Dynasty of China, have been systematically investigated to disclose their chemical composition, nature of the patina and corrosion features on the coin surface by optical microscopy (OM), X-ray diffraction (X-RD), and scanning electron microscopy (SEM) equipped with backscattered electron (BSE) detector and energy dispersive spectrometry (EDS) techniques. It is revealed morphologically that there are some rough surface cracks, pits, and multicolor patina on the surface of the coins. We prove that the coins are made from bronze material of Cu–Sn–Pb–Sb alloy with contents of 84.8–85.4wt.% Cu, 3.3–6.1wt.% Sn, 4.7–6.4wt.% Pb and 2.6–2.9wt.% Sb, and covered by two corrosion layers, 25–35μm for the upper-layer and 20–25μm for the sub-layer. High chloride content has been detected at the interface between the sub-layer and body of the coins. The lead-rich and tin-rich areas in the coin samples indicate the poor metal compatibility during minting in some locations of the coins. The main compositions of patina are ascertained to be Cu2(OH)3Cl, Cu3(CO3)2(OH)2, Cu2(OH)2CO3, and Pb3O4, and the proposed corrosion mechanism is discussed.
    Microchemical Journal - MICROCHEM J. 01/2011; 99(2):203-212.
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    ABSTRACT: In this work the well-defined fluorinated acrylic copolymer latex and solution were prepared by the radical initiated seed emulsion polymerization and solution polymerization, respectively, using the same monomers of dodecafluoroheptyl methacrylate (DFHM), butyl acrylate (BA) and methyl methylacrylate (MMA). The copolymer latex BA/MMA/DFHM was designed as core–shell structure and the copolymer solution poly(BA–MMA–DFHM) was structured with low molecular weight. The chemical and morphology structures as well as the film properties obtained from latex and solution were analyzed and compared by spectroscopic techniques (FT-IR and NMR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscopy coupled with energy-dispersive X-ray detector (SEM–EDX) and static contact angles (CAs) instrument. Moreover, the BA/MMA/DFHM latex and poly(BA–MMA–DFHM) solution (with 29wt% of DFHM) were applied onto two kinds of sandstone samples by capillary absorption, and their preliminary protecting efficiency was evaluated. It is demonstrated that the comprehensive performances of BA/MMA/DFHM latex films were quite comparable to those of poly(BA–MMA–DFHM) solution cast films, the latter exhibited a better protective performance.
    Progress in Organic Coatings - PROG ORG COATING. 01/2010; 69(4):352-358.