Construction Of Micro-model About A Novel Composites Resin Incorporated With POSS And Its Atomistic Molecular Simulation

As a novel organic-inorganic nano hybrid composite material, Polyhedral Oligomeric Silsesquioxane (POSS) has been widely used to improve the properties of other materials, experimental research has indicated that the properties of resin composite material could been improved by incorporateing with POSS physically or chemically, however the improvement mechanism has not been studied sufficiently. This paper investgates the structure and properties of improved dental composites resin incoporated with POSS based on the combination of experiment and molecular simulation methods. The results provide some molecular insight about the effect of POSS on the dental composite resin, which could be used to direct the design of a better dental material.Firstly, an improved dental composite resin incorporated with POSS is synthesized by visible light, and several experiment tests are performed to investigate the properties of the composite resin. Compression test showes that mechanical properties of composite resin could be improved remarkably by introducing a little POSS. Differential Scanning Calorimeter (DSC) results indicate that glass transition temperature ( Tg ) is not specially linked to the contents of POSS. The profiles of wide X-ray scattering (WXRS ) indicate that improved composite resin has similar amorphous structure with initial resin.Secondly, an improved method named polymer molecular dynamic (PMD) is proposed to construct polymer network models dynamically. Combined with previous experimental data, three improved composite resin models with different loading of POSS are constructed via this method. Molecular mechanical (MM) simulation is performed on the polymer network models. WXRS of the optimized models are calculated to compare with experimental results, the excellent agreement proves the accuracy of the models and the force field.Then, molecular dynamical (MD) simulation is performed on the polymer network models to evaluate their micro-structures and properties. Volume temperature behavior of the network model is calculated to predict Tg , the results consist with previous experimental ones and the energy changes in the process of temperature rise are analyzed. In addition, radial distribution fuction and mean square displacement of the composite resin models are evaluated to clarify the influence of POSS on composite resin's micro-structure. Finally, constant-strain minimization method is carried out to predict mechanical properties of modified composite resin models. The results are compared with experimental profiles and further indicate that POSS could improve Young's modulus and shear modulus of composite resin.Energy method is performed to interpret the working mechanisms. It is found that POSS could reduce the non-bond energy of composite resin, which is the main reason of improvement. Moreover, electrostatic term palys active effect while Van der Waals term plays negative effect. Besides, we calculated the densities of uncured and cured network polymer models to predict the volume shrinkage, the result behaves similar trend with experimental research. Further analysis indicates that the special volume structure of POSS has great influence on the packing of linear molecular chains. Thus the packing of composite resin moleculars change loose, which leads the reduction of volume shrinkage.