-
[show abstract]
[hide abstract]
ABSTRACT: We propose a modified polymer reference interaction site model (PRISM) to describe the interfacial density profiles of polymers in contact with planar and curved solid surfaces. In the theoretical approach, a bridge function derived from density functional method is included. In description of hard-sphere polymer at planar and curved surfaces with an arbitrary external field, the effect of modification has been validated by the available simulation data, except for low density system. When extended to confined real systems, the modified theoretical model also shows an encouraging prospect in description of the interfacial structure and properties.
The Journal of chemical physics 11/2012; 137(18):184901. · 3.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this work, integral equation theory is extended to describe the structures and surface tensions of confined fluids. To improve the accuracy of the equation, a bridge function based on the fundamental measure theory is introduced. The density profiles of the confined Lennard-Jones fluids and water are calculated, which are in good agreement with simulation data. On the basis of these density profiles, the grand potentials are then calculated using the density functional approach, and the corresponding surface tensions are predicted, which reproduce the simulation data well. In particular, the contact angles of water in contact with both hydrophilic and hydrophobic walls are evaluated.
The Journal of Physical Chemistry B 05/2012; 116(22):6514-21. · 3.70 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Poly(2,6-diimidazo [4,5-b:4′5′-e]pyridinylene-1,4(2,5-dihydroxy) phenylene) (PIPD) was synthesized via polycondensation in
phosphorus acid and separated as nano-spheres about 50nm in diameter. When a heterogeneous additive, acid-treated carbon
nanotubes, or calcium carbonate nanoparticles were present during polycondensation, nano-spheres near or larger than 100nm
could be obtained. The morphology of PIPD nano-spheres was observed using transmission and scanning electron microscopy. The
thermal behavior and the relative composition of the nano-spheres were characterized using thermal gravimetric analysis. The
function of the additives was explored in terms of heterogeneous nucleation. The effect of the solvents used for sphere separation
was also considered.
Journal of Nanoparticle Research 04/2012; 12(1):319-325. · 3.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This work involves a theoretical study to investigate the effects of the structure on CO(2) sorption in polymers, where poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), poly(vinyl acetate) (PVAc), poly(ethylene carbonate) (PEC) and poly(propylene carbonate) (PPC) were examined. In the theoretical approach, the multi-site semiflexible chain model and the renormalized technique of electrostatic potentials were incorporated into the polymer reference interaction site model (PRISM). To test the theory, molecular dynamic simulations were performed using the TraPPE-UA force field. The theoretically calculated reduced X-ray scattering intensities and intermolecular correlation functions of these five polymers are found to be in qualitative agreement with the corresponding molecular simulation data. The theory was then employed to investigate the distribution functions between CO(2) and different sites of the polymers with consideration of the Lennard-Jones, potential of mean force, and columbic contributions. Based on the detailed structure characteristics of CO(2) in contact with different groups, the CO(2) coordination molecular numbers were obtained and their sorption intensities analyzed. Finally, the sorption isotherms of CO(2) in these five polymers were calculated. The results for PEO, PPO and PVAc are close to the available experimental curves, and the trend of CO(2) solubility is PPC > PEC > PVAc ~ PPO > PEO.
Physical Chemistry Chemical Physics 12/2011; 13(47):21084-92. · 3.57 Impact Factor
-
Journal of Polymer Science Part A Polymer Chemistry 09/2010; 48(21):4697 - 4703. · 3.92 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A methodology for preparing porous epoxy monolith via chemically induced phase separation was proposed. The starting system was a mixture of an epoxy precursor, diglycidyl ether of bisphenol-A (DGEBA), a curing agent, 4,4′-diaminodiphenylmethane (DDM), and a thermoplastic polymer, polypropylene carbonate (PPC). As DGEBA was cured with DDM, the system became phase-separated having PPC particles dispersed in epoxy matrix. After PPC particles were removed by thermal degradation, a porous structure was obtained. The phase separation mechanism was determined by the initial composition and illustrated by a pseudophase diagram. The pore size increased with increasing the concentration of PPC and raising the curing temperature. The intermediate and final morphologies of the system were studied using optical and scanning electron microscopy, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Journal of Polymer Science Part B Polymer Physics 08/2010; 48(20):2140 - 2147. · 1.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Chain extension of poly(ethylene terephthalate) (PET) with bisphenol-A dicyanate (BADCy) was studied using an internal mixer under reactive blending conditions. The reaction between PET and BADCy was confirmed by Fourier transform infrared (FTIR) and chemical titration. With increasing amount of BADCy introduced, the modified PET gave rise to higher torque during stirred in an internal mixer, higher viscosity (η′), and higher storage modulus (G′). Measurement of intrinsic viscosity showed that BADCy indeed extended the molecular weight of PET. DSC analysis represented that Tm and Tc of the modified PET were shifted to low temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Journal of Applied Polymer Science 04/2010; 117(4):2003 - 2008. · 1.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Porous epoxy monoliths were prepared via a step polymerization in a concentrated emulsion stabilized by non-ionic emulsifiers and colloidal silica. A solution in 4-methyl-2-pentanon was used as the continuous phase, which contained glycidyl amino epoxy monomer (GAE), curing agent, and an emulsifier. An aqueous suspension of colloidal silica was used as the dispersed phase of the concentrated emulsion. After the continuous phase was completely polymerized, the dispersed phase was removed and a porous epoxy was obtained. An optimal HLB value of emulsifier for the GAE concentrated emulsion was determined. In addition, the morphology of the porous epoxy was observed by SEM. The effect of the colloidal silica, the emulsifier, the curing of the epoxy, and the volume fraction of the dispersed phase on the morphology of porous epoxy are systematically discussed.
Journal of Colloid and Interface Science 07/2009; 338(1):145-50. · 3.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Continuous macroscopic aligned polyacrylonitrile (PAN) composite nanofiber sheets embedded with highly aligned PAN-grafted multiwalled carbon nanotubes (MWCNTs) have been prepared by electrospinning followed by hot-stretching. Homogeneous and highly aligned MWCNTs in the polymer matrix were obtained by hot-stretching of the electrospun fibers, which led to a significant enhancement in the mechanical performance of the resulting composite nanofiber sheets. After hot-stretching, the tensile strength and modulus of an electrospun PAN nanofiber sheet (containing 2 wt % grafted MWCNTs) increased by 320.7% and 204.5%, respectively, compared with the values for the pristine PAN terpolymer. In addition we show, for the first time, that a Raman mapping method can be successfully employed to investigate the distribution and alignment of MWCNTs in nanofiber sheets.
03/2009;
-
[show abstract]
[hide abstract]
ABSTRACT: Inverse concentrated emulsions were prepared using aqueous colloidal silica suspension as the hydrophilic dispersed phase and a solution of diglycidyl ether of bisphenol-A (DGEBA), its curing agent polyamide resin, low molecular weight 650, surfactant nonyl phenol polyoxyethylene ether (NPE-4) in 4-methyl-2-pentanon as the continuous phase, which was expected to be used as the precursors of preparation of porous epoxy resins. The stability, i.e., the resistance to phase separation was studied. The effects of various parameters on the stability of the concentrated emulsions were investigated. The colloidal silica can strengthen the steric repulsion in the system and improve the stability. Viscosity of both phases played a major role in the stability. Precuring of the continuous phase provided an increased initial viscosity and enhanced the stability. Lower volume fraction of the dispersed phase can help to maintain stability of the concentrated emulsions. Properly increasing the curing rate, the concentrated emulsions may acquire a high viscosity in a short time, which retarded the phase separation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Journal of Applied Polymer Science 10/2008; 111(2):746 - 752. · 1.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel porous material was designed and prepared in this work. A hydrophobic open-celled porous polystyrene (PS) was first synthesized via a concentrated emulsion polymerization of water in styrene. Subsequently the porous polystyrene was saturated with an aqueous solution of acrylamide (AM) and an initiator, which was subjected to another polymerization and the resulted polyacrylamide (PAM) penetrated in the cells and intercellular pores of the PS matrix. The PAM would change its volume according to the environmental humidity and thus adjusted the permeation of the material. The morphology, pore size distributions, water absorption, and vapor permeation of the materials were investigated.
Journal of Colloid and Interface Science 08/2008; 323(1):120-5. · 3.07 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Step polymerization was introduced into the concentrated emulsion templating method and was illustrated with the preparation of porous epoxy monolith. A solution of diglycidyl ether of bisphenol-A (DGEBA), its curing agent low molecular weight polyamide resin, and surfactant nonyl phenol polyoxyethylene ether in 4-methyl-2-pentanon as a solvent was used as the continuous phase, an aqueous suspension of colloidal silica as the dispersed phase of the concentrated emulsion. After the continuous phase polymerized and the dispersed phase removed, a porous material is obtained. The key point in this work is to find a compromise between the rates of curing and phase separating and thus achieve a kinetic stability of the concentrated emulsion. The effects of loading of colloidal silica, the pre-curing of the epoxy precursors, and the volume fraction of the dispersed phase were systematically investigated.
Journal of Colloid and Interface Science 07/2008; 325(2):453-8. · 3.07 Impact Factor
-
Journal of Polymer Science Part A Polymer Chemistry 06/2008; 46(14):4857 - 4865. · 3.92 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Three bisphenol-A based novolac epoxy resins with different bridging groups: methylene, methine-phenyl and methine-naphthyl, respectively, between bisphenol-A phenyl rings were prepared to study the effect of structure of bridging group on curing and properties of the epoxy resins. The structures of the obtained epoxy resins were characterized using FT-IR and 1H NMR spectra, the molecular weight and polydispersity index were determined using GPC. The effect of bridging groups on the curing kinetics, thermal mechanical properties, thermal stability, and moisture resistance of the synthesized epoxy resins cured with 4,4′-diaminodiphenyl sulphone (DDS) were investigated by dynamic differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, X-ray diffraction and moisture absorption measurement. It was concluded that the methylene-bridged epoxy resin possessed the highest curing reaction reactivity toward DDS and the methine-naphthyl-bridged epoxy network possessed the highest storage modulus, glass transition temperatures, thermal stability, and moisture resistance.Keywords: Bisphenol-A, 1-Naphthaldehyde, Benzaldehyde, Bridging Group
Polymer Journal 04/2007; 39(5):478-487. · 1.26 Impact Factor
-
International Journal of Polymer Analysis and Characterization 07/2006; 11(4):299-315. · 1.41 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A bisphenol A type novolac resin (Bis-ANR) was synthesized from bisphenol A and formaldehyde; the resulting novolac was epoxidized to generate a bisphenol A type novolac epoxy resin (Bis-ANER). The chemical structures of Bis-ANR and Bis-ANER were confirmed by 1H-NMR spectroscopy and IR spectroscopy; the molecular weights and molecular weight distributions were determined by gel permeation chromatography. In addition, the curing process of Bis-ANER with 4,4′-diaminodiphenyl sulfone was studied in both dynamic and isothermal modes with differential scanning calorimetry. The dynamic curing kinetic analysis was evaluated with both the Kissinger and Flynn–Wall–Ozawa methods, and the curing activation energy values were obtained. The isothermal curing reaction exhibited autocatalytic behavior, and the curing kinetics were described with the Kamal kinetics model, which accounted for both the autocatalytic and diffusion-control effects. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 858–868, 2006
Journal of Applied Polymer Science 11/2005; 99(3):858 - 868. · 1.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel polymerization procedure, the concentrated-emulsion graft polymerization of styrene monomer with poly(butyl acrylate) seed, was proposed for the production of a self-compatibility macromolecule alloy. The effects of the butyl acrylate content, sodium dodecyl sulfate concentration, and polymerization temperature on the graft ratio were investigated. Scanning electron microscopy, transmission electron microscopy, and impact strength were used to characterize the microstructure and mechanical performance of the self-compatibility macromolecule alloy. The results showed that increasing the butyl acrylate content, reducing the sodium dodecyl sulfate concentration, and improving the polymerization temperature all favored an increased graft ratio, which resulted in increased impact strength of the self-compatibility macromolecule alloy. Therefore, the concentrated-emulsion polymerization method is particularly suitable for seed-graft polymerization. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2915–2920, 2002; DOI 10.1002/app.10288
Journal of Applied Polymer Science 01/2002; 83(13):2915 - 2920. · 1.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel polyethylene/palygorskite nanocomposite with excellent processability was prepared via in-situ coordination polymerization.
A mixed catalyst of TiCl4/MgCl2/AIR3 was employed. Firstly the Ziegler-Natta catalyst of TiCl4/AlR3 was loaded on the surface of the nanoscale Whiskers of palygorskite to prepare the “macromolecular comb”. Secondly the MgCl2 catalyst was introduced into the reaction system to prepare the ordinary PE molecular chain. The polyethylene/palygorskite
nanocomposites thus obtained possessed excellent mechanical properties.
Polymer Bulletin 01/2002; 49(2):151-158. · 1.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A silica–polymer–carbon nanotube hybrid was prepared in which the nanotubes were encapsulated by poly(3-acrylaminopropylsiloxane) with silica nanospheres on the polymer surface. First, highly reactive poly(acryloyl chloride) (PAC) was grafted onto the nanotubes through the reaction of side acyl chloride groups with hydroxyl groups present on the surface of acid–oxidized nanotubes. Second, reacting 3-aminopropyltriethoxysilane with the grafted PAC through the reaction between amino and acyl chloride groups, siloxane-containing sub-grafts were introduced onto the primary PAC grafts. Third, silica nanospheres were covalently linked to the sub-grafts by condensation to form a nanotube–polymer–silica hybrid. Each intermediate structure was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy (TEM). TEM observation revealed a nanostructure in which the nanotube was encapsulated with a polymer layer bearing silica nanospheres on its surface.
Carbon. 46(13):1670-1677.
