Molecular Dynamics Simulation And Experimental Study Of SiO 2 /crosslinking Polyacrylamide Core-shell Microspheres

Nano/micro inorganic-organic composite microsphere with SiO₂ inorganic nanoparticles as the core and the polyacrylamide?PAM?as the shell is a new kind of composite material,which combines the rigidity and plugging strength of inorganic particles and elasticity,ductility,swelling deformation capacity of the polymer.And the composite material can be applied at some fields,such as pharmaceuticals industry,biological industry,daily chemical industry,oil field industry,et al.The depth of the research about the inorganic-organic composite microsphere through traditional experiment methods is very limited,because the structure of the microsphere is very complicated.Molecular dynamics?MD?simulation can get important information about the structure and properties of the composite microsphere at the molecular level from the microscopic view by using computers to simulate the structure and behavior of moleculars with atomic-level models.In order to get more comprehensive understanding of the composite microsphere,the MD simulation performed by Materials Studio software and relevant experiments are applied to make the following research:Building the models of the SiO₂/crosslinked PAM composite microsphere with a core-shell structure,the structure and properties of the core-shell microsphere at vacuum,in aqueous solution,in inorganic salt aqueous solution and the interaction mechanism of the core-shell micro sphere and quartz surfaces have been studied.The interaction energis between the inorganic phase and the organic phase,the mean square displacements?MSD?of the polymer chains and the mechanical properties of the core-shell microsphere have been calculated when the PAM is whether or not crosslinked and the temperature changes.The results show that as the temperature increases,the interaction between the inorganic phase and the organic phase initially enhances then weakens,the mobility of the polymer chains becomes strong and the mechanical properties of the microsphere do not change according to a monotonous regularity.When the polyacrylamide is crosslinked,the interaction between the inorganic phase and the organic phase become enhanced,the mobility of the polymer chains is restricted,and the mechanical properties of the microsphere become enhanced.The results of the thermogravimetric analysis show that when the PAM is crosslinked the thermal stability of the core-shell microsphere becomes strong.The experiment results are consistent with the simulation results;the interaction energis,MSD,the fractional free volume?FFV?of waters and the microsphere,the radial distribution functions?RDF?of special atoms and the radius of gyration?Rg?of the microsphere have been calculated.Results show that the microsphere swells in aqueous solution,the swelling properties of the microsphere initially enhances then weakens with the increasing the number of the crosslinker and the size of the microsphere initially increases then decreases with the increasing hydration temperature.When the temperature is 330 K,the Rg of the microsphere is the greatest.The results of the size distribution by the Wide Angle Laser Light Scattering Instrument in experiment show that when the temperature is 57 ?,the size of the microsphere is greatest.The experiment results have verified the simulation results;the interaction energis,RDF,MSD,FFV of the components in inorganic salt aqueous solution and the Rg of the microsphere have been calculated.Results show that the Rg of the microsphere in aqueous solutions of potassium chloride is greatest.In the experiment,the size of the microsphere in aqueous solutions of potassium chloride is greatest.The experiment results are corresponding to the simulation results;the interaction energis,RDF,MSD,concentration profile of the components and the Rg of the microsphere of the systems with the microsphere and quartz surface have been calculated.The results find that the interaction between the microsphere and quartz?0 0 1?surface is the strongest.The water molecules would influence the morphology of the microsphere on quartz?0 0 1?surface.The interaction between the microsphere and quartz?00 1?surface at formation temperature is stronger than that between the microsphere and quartz?0 0 1?surface at room temperature in water environment.