The Study On Preparation,characterization And Application Of Functional Polysilsesquioxane Microspheres

Polysilsesquioxane(PSQ)microspheres are a new type of material that hybridizes at the molecular level,which are widely used in plastics,fiber,coating,flame retardant materials,cosmetics,water treatment,optical and biomedical fields.At present,the preparation and application of functional PSQ microspheres are not only research hotspot in the field of materials,but also attract the attention of many industrial fields.In this thesis,the preparation,characterization and application of functional PSQ microspheres were studied.The main work was as follows:Firstly,an improved one-step hydrolysis condensation method was used to successfully prepared polymethylsilsesquioxane(PMSQ)microspheres and thiol functionalized polysilsesquioxane(PSQ-SH)microspheres with controllable particle size.And no organic solvents and surfactants were used in the preparation process.The structure,morphology and properties of PMSQ and PSQ-SH microspheres were tested by a series of characterization methods.The results indicated that the particle size and morphology of PSQ microspheres could be effectively controlled by changing the reaction conditions such as the ratio of oil to water,the amount of ammonia and temperature.In addition,the formation process of PSQ microspheres mainly included the steps of self-hydrolysis of organic trimethoxysilane,homogeneous nucleation and nuclear growth.Both PMSQ and PSQ-SH microspheres consisted of partial cage structures,ladder-like structures and network structures.And the spacing of the silsesquioxane molecular of PSQ-SH microspheres was larger than that of PMSQ microspheres.Furthermore,PMSQ and PSQ-SH microspheres had good thermal stability and hydrophobicity,mean while,heat resistance and hydrophobic properties of PSQ-SH microspheres were decreased with the increase of the amount of mercaptopropyltrimethoxysiloxane(MPTMS).Secondly,PSQ-SH microspheres were used as adsorbents,the adsorption properties of PSQ-SH mircospheres for silver ions were systematically studied by static adsorption method.PSQ-SH microspheres showed excellent adsorption capacity for silver ions: the maximum adsorption capacity of PSQ-SH microspheres for silver ions was 750.21 mg/g when the temperature was 25 ? and the initial concentration of silver ions was 0.025 mol/L.The adsorption of silver ions by PSQ-SH microspheres was more consistent with Langmuir isothermal adsorption model,indicating that the adsorption was mainly monomolecular layer adsorption.In addition,the adsorption kinetics was more suitable for the pseudo-second order kinetic model.The adsorption thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic,which meant that the raise of temperature was favorable for the adsorption of silver ions by PSQ-SH microspheres.Moreover,the process of adsorption of silver ions by PSQ-SH microspheres not only had the chemical ion exchange,but also had the occurrence of chemical oxidation reduction.Most of all,PSQ-SH microspheres showed good regeneration and reuse performance in the experiment of adsorption-desorption cycles,and good adsorption selectivity for silver ions in competitive adsorption systems,such as Ag+~ Cu2+,Ag+~ Zn2+and Ag+~ Cd2+.Finally,the antibacterial property of nano-Ag-loaded PSQ-SH(Ag/PSQ-SH)composite microspheres which were prepared by simple in situ reduction by using PSQ-SH microspheres as carrier was investigated,meanwhile,no additional reducing agent and stabilizer were needed in the preparation process.The formation of Ag/PSQ-SH composite microspheres was mainly carried out by three processes,including thiol deprotonation,electrophilic attack and silver nanoparticles growth.The morphology of Ag/PSQ-SH composite microspheres could be effectively controlled by changing the reaction conditions such as the reaction time,the concentration of silver ammonia solution and the pH of the system.Gram-negative bacteria Escherichia coli(E.coli)and Gram-positive bacteria Staphylococcus aureus(S.au)were used as the main model bacteria strains.The inhibition zone,minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of Ag/PSQ-SH composite microspheres were used as antibacterial agents to examine the antibacterial activity of these model bacteria.Furthermore,the results indicated that Ag/PSQ-SH composite microspheres had excellent antibacterial activity against E.col and S.au,and the antibacterial activity was improved by increasing of silver nanoparticles loading.