A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of...A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES.The effects ofγ-methacryloxypropyltrimethoxysilane(KH-570)content and co-solvent on the properties of PAES films were investigated.Dynamic laser scattering(DLS)data indicate that the average diameter of PAES(96 nm)is slightly larger than that of PAE(89 nm).Transmission electron microscopy (TEM)photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles.The crosslinking degree data and Fourier transform infrared(FT-IR)spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation.Atomic force microscope(AFM)photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES.Thermogravimetric analysis(TGA)curves demonstrate that the PAES films display much better thermal stability than PAE.展开更多
N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of etha...N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the 'free-volume' contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture.展开更多
The sol-gel transition temperature of methylcellulose （MC） solution in the presence of sodium dodecyl sulfate （SDS） as well as the mixtures of SDS and β-cyclodextrin （β-CD） was mea- sured, and the effect of th...The sol-gel transition temperature of methylcellulose （MC） solution in the presence of sodium dodecyl sulfate （SDS） as well as the mixtures of SDS and β-cyclodextrin （β-CD） was mea- sured, and the effect of the two competing interactions, the hydrophobic interaction between SDS and MC and the inclusion interaction between SDS and β-CD, upon the sol-gel transition of MC solution was studied. It has been found that the inclusion interaction between SDS and β-CD is much greater than the hydrophobic interaction between SDS and MC. As a result, in the coexistence of SDS and β-CD, the sol-gel transition temperature of MC solution keeps the same value, independent of the concentration of SDS in solution on con- dition that the concentration of SDS is less than β-CD. Our experimental results not only suggest that the effect of SDS upon the sol-gel transition of MC solution can be screened by β-CD completely but also indicate the inclusion ratio of SDS to β-CD can be determined quantitatively by using rheological measurement. The inclusion ratio of SDS to β-CD is 1：1, which is in good agreement with the inclusion ratio of SDS to β-CD in the presence of poly（vincyl pyrrolidone） determined by the viscosity measurement but is critically different from the inclusion ratio of SDS to β-CD in the presence of the oppositely charged polyelec-trolyte by using the rheological measurement, mainly due to the reason that the mechanism of the interaction between SDS and MC is critically different from the mechanism of the interaction between SDS and the oppositely charged polyelectrolyte.展开更多
Mesoporous silica materials were synthesized via a sol-gel method employing a room temperature ionic liquid （1-butyl-3-methylimidazolium tetrafiuoroborate, [bmim][BF4]） as a new solvent medium and further modified w...Mesoporous silica materials were synthesized via a sol-gel method employing a room temperature ionic liquid （1-butyl-3-methylimidazolium tetrafiuoroborate, [bmim][BF4]） as a new solvent medium and further modified with surfactant （hexadecyl-trimethyl-ammonium bromide, CTAB） as a pore templating material. The synthesized samples were characterized by the transmission electron microscopy, X-ray diffraction, and N2 adsorption-desorption techniques. The results indicated that the mesoporous silica synthesized by using [bmim][BF4] and CTAB as mixed templates showed better mesostructural order and smaller pore size, compared with mesoporous silica materials synthesized by using single [bmim][BF4] as template under the same conditions. This indicates that the presence of surfactant can affect the microstructures of silica prepared by＇the present synthesis method.展开更多
基金Supported by the Program for New Century Excellent Talents in University（NCET-08-0204） National Natural Science Foundation of China（20976060） the Scientific Research Foundation for the Returned Overseas Chinese Scholars State Edu-cation Ministry （China）
文摘A novel polymer/SiO2 hybrid emulsion(PAES)was prepared by directly mixing colloidal silica with polyacrylate emulsion(PAE)modified by a saline coupling agent.The sol-gel-derived thin films were obtained by addition of co-solvents into the PAES.The effects ofγ-methacryloxypropyltrimethoxysilane(KH-570)content and co-solvent on the properties of PAES films were investigated.Dynamic laser scattering(DLS)data indicate that the average diameter of PAES(96 nm)is slightly larger than that of PAE(89 nm).Transmission electron microscopy (TEM)photo discloses that colloidal silica particles are dispersed uniformly around polyacrylate particles and some of the colloidal silica particles are adsorbed on the surface of PAE particles.The crosslinking degree data and Fourier transform infrared(FT-IR)spectra confirm that the chemical structure of the PAES is changed to form Si-O-Si-polymer crosslinking networks during the film formation.Atomic force microscope(AFM)photos show the solvent induced sol-gel process of colloidal silica and the Si-based polymer distribution on the film surface of the dried PAES.Thermogravimetric analysis(TGA)curves demonstrate that the PAES films display much better thermal stability than PAE.
基金Supported by the Science and Tchnology Ministry of Fujian(No.2001Z046)and the Education Commission of Fujian(No.K2001004).
文摘N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the 'free-volume' contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture.
文摘The sol-gel transition temperature of methylcellulose （MC） solution in the presence of sodium dodecyl sulfate （SDS） as well as the mixtures of SDS and β-cyclodextrin （β-CD） was mea- sured, and the effect of the two competing interactions, the hydrophobic interaction between SDS and MC and the inclusion interaction between SDS and β-CD, upon the sol-gel transition of MC solution was studied. It has been found that the inclusion interaction between SDS and β-CD is much greater than the hydrophobic interaction between SDS and MC. As a result, in the coexistence of SDS and β-CD, the sol-gel transition temperature of MC solution keeps the same value, independent of the concentration of SDS in solution on con- dition that the concentration of SDS is less than β-CD. Our experimental results not only suggest that the effect of SDS upon the sol-gel transition of MC solution can be screened by β-CD completely but also indicate the inclusion ratio of SDS to β-CD can be determined quantitatively by using rheological measurement. The inclusion ratio of SDS to β-CD is 1：1, which is in good agreement with the inclusion ratio of SDS to β-CD in the presence of poly（vincyl pyrrolidone） determined by the viscosity measurement but is critically different from the inclusion ratio of SDS to β-CD in the presence of the oppositely charged polyelec-trolyte by using the rheological measurement, mainly due to the reason that the mechanism of the interaction between SDS and MC is critically different from the mechanism of the interaction between SDS and the oppositely charged polyelectrolyte.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.50564006）, the Natural Science Foundation From Science and Technology Committee of Yunnan （No.2005E0042）, and the Specialized Research Foundation for the Doctoral Program of Higher Education of China （No.20070674001）. We also thank Academician Si-shen Xie, Institute of Physics of Chinese Academy Sciences for helping with an SEM facility.
文摘Mesoporous silica materials were synthesized via a sol-gel method employing a room temperature ionic liquid （1-butyl-3-methylimidazolium tetrafiuoroborate, [bmim][BF4]） as a new solvent medium and further modified with surfactant （hexadecyl-trimethyl-ammonium bromide, CTAB） as a pore templating material. The synthesized samples were characterized by the transmission electron microscopy, X-ray diffraction, and N2 adsorption-desorption techniques. The results indicated that the mesoporous silica synthesized by using [bmim][BF4] and CTAB as mixed templates showed better mesostructural order and smaller pore size, compared with mesoporous silica materials synthesized by using single [bmim][BF4] as template under the same conditions. This indicates that the presence of surfactant can affect the microstructures of silica prepared by＇the present synthesis method.
