Molecular Dynmaics Simulation On Surface Modification Of Poymer Materials

With the development of polymers and modern medicine science, drug controlled release and targeting technologies have received much attention. Polymer drug controlled release systems are drug carriers based on natural or synthetic polymers that can control drug release and targeting. With the fast development of science and technology, smart drug controlled release systems are receiving more and more attention, which can improve the therapeutic efficiency as well as to reduce negative effects. As a result, it is very important to study technologies that can improve the controlled release of drugs. In this work, correlations for the estimation of theθ(lower critical solution temperature, LCST) for polymer solutions were developed, and morphology and wettability of polyethylene surface grafting poly(ethylene oxide) as well as surfactant adsorption on the surface of polymeric micelles in aqueous solution were investigated. The main results obtained are:1．Correlations for the estimation of theθ(lower critical solution temperature, LCST) for Polystyrene, Polyethylene, Polypropylene, Polybutene-1, Polyisobutylene, Polypentene-1, Poly(4-methylpentene-1) and Polydimethylsiloxane solutions were proposed based on the molecular connectivity index. And a general model ofθ(LCST) for polymer solutions was also proposed based on the molecular connectivity index. The correlations give satisfactory estimation of theθ(LCST), with the overall average errors smaller than 3 % and 10 % for the two kinds of models, respectively. Since only connectivity indices were used in the newly proposed correlations, they are general models with better predictive capability.2．Morphology of grafting poly(ethylene oxide) chain and wettability of polyethylene surface were investigated when poly(ethylene oxide) was grafted to polyethylene surface using molecular dynamics simulation with the COMPASS (Condensed-phase Optimized Molecular Potential for Atomistic Simulation Studies) force field. With the increase of the density of the graft chain, morphology of graft chain showed the "mushroom", the "overlapping mushroom" or "brush" respectively. The density of the graft chain had great effects on the wettibillity of the PE. When the number of the graft chain was 8 and 16, the PE surface had better wettability than the pristine PE surface. When the number was 24 and 32, it had little effect on the wettability of the PE surface. When the number of the graft chain was more than 48, it had more effect on the wettabillity of the PE surface. When the number of the graft chain monomer was 10-15, it had the best effect on the PE surface. 3．Dissipative particle dynamics simulation was performed to study surfactant adsorption on the surface of polymeric micelles in aqueous solution. The graft hydrophilic polymer could effectively prevent surfactant from adsorbing on the surface of micelles. If the length of the graft chain was unchanged and the number of the graft chain was between 2 and 5, 0．1667-0．4167 volume fraction of hydrophilic polymer, polymeric micelles could effectively prevent surfactant from adsorbing on their surface. It was effective for polymeric micelles to prevent surfactant from adsorbing on their surface when the length of the graft chain was longer than 4 beads.4．Dissipative particle dynamics simulation was performed to study the morphologies and rheological properties of surfactant adsorption on the surface of amphiphilic polymeric micelles in aqueous solution under various shear rates. Some important information on drug controlled released agent was proposed.