Ultrafine polystyrene(PS) nanofibers were prepared via the simple electrospinning technique.Uniform and smooth PS nanofibers were obtained with adding the organic salt BTEAC into the PS solutions and adjusting the concentration of PS solutions.Without the addition of BTEAC,PS fibers with few beads could be achieved with a PS mass fraction of 20%,and the average diameter of the fibers was 280 nm.The addition of the organic salt BTEAC could lower the critical concentration for the fiber formation and reduce the amount of beads on the fibers.Unltrafine PS fibers without any beads were obtained with a PS mass fraction of 10% and an ionic salt mass fraction of 0.5%.The average diameter of the fiber was successfully reduced to 100 nm.The influence of the salt concentration on the morphology and diameter of the PS fibers was also investigated.The viscosity and surface tension changes were measured with changing the concentration of BTEAC.The results show that the changes were so small that these factors could be ignored.It was suggested that variations of the fiber diameter should be mainly resulted from the changes of conductivity and conformation of the polymer chain as the concentration of BTEAC is varied.
A novel azo compound with ’dumbbell shape’ was synthesized successfully and characterized by MALDI-MS,FTIR,elemental analysis,1H NMR and 13C NMR.UV-Vis spectrum was used to monitor the trans-cis isomerization and theoretical calculations were used to modelize the trans and cis isomers.The trans and cis isomers of the ’dumbbell shape’ azo compound are both stable at room temperature because of the large end group.
Silver nanoparticles were prepared in the channels of mesoporous silica SBA-15 through silver mirror reaction.The results of X-ray diffraction(XRD) and transmission electron microscopy(TEM) reveal that Ag nanoparticles with uniform size about 2-3 nm were dispersed inside the channels of mesoporous SBA-15.UV-Vis absorption spectra indicate the quantum size effect of the Ag nanoparticles.Bacteriological tests were performed in Luria-Bertani(LB) medium on solid agar plates and in liquid systems supplemented with different concentrations of Ag/SBA-15.This nanocomposite was shown to be an effective bactericide against Staphylococcus.
Organic templates of as-synthesized siliceous,MCM-41 and SBA-15 can be effectively removed by oxidation treatment.The highly ordered mesostructures and surface properties of inorganic frameworks were retained after the template being removed.MCM-41 and SBA-15 obtained after oxidation treatment showed larger pores and richer silanol groups compared with those obtained by conventional calcinations at 550 ℃ in air.The removing ratios of templates of MCM-41 and SBA-15 were respectively 88% and 98%.
