| Polyhedral oligomeric silsesquioxane (POSS) material has been described as the next generation of materials; meanwhile, the computer simulation of structures and properties of the hybrid material has become increasingly mature. In this paper, the QMC method (calculation of quantum mechanics) was used to identify the most probably reasonable structure of the MSSO. Molecular dynamics simulation has been employed to investigate the diffusion coefficient of small gas molecular in pure T8-POSS system and organic-inorganic hybrid films. Molecular dynamics simulation was also used to investigate the effects of incorporated AP-POSS particles on diffusion properties of polymer-inorganic hybrid films.The molar mass distribution of MSSO was determined by UV-MALDI-TOF MS. The proposed formulas of their structure were assigned with a generic formula of the POSS. The total energy of the simplified model of MSSO were calculated by QMC. As results of the calculation,all cage structures had the lower total energy than that of the ladder isomers, therefore,the most probably reasonable and optimum structure of the MSSO system was the cage type.Based on the conclusion that the most probably reasonable and optimum structure of the MSSO system was the cage type, the dynamics properties of pure GPMS-T8 POSS(GP) and MPMS-T8 POSS (MP)systems were studied to investigate the diffusion properties of O2 and H2O in the systems. By the analysis of the MSD(mean-square dispalcement) of cagelike T8- POSS, find that in the time scale of molecular dynamics,the displacement of POSS was very small, they all stay about where they started. The angle change of Si-O-Si and the distance change of Si-Si in cagelike T8-POSS were both small,which prove that in the time scale of molecular dynamics the strcture of POSS kept stabe. Molecular dynamics simulation has also been employed to investigate the diffusion coefficient of small gas molecular in organic-inorganic hybrid films. The diffusion coefficients of O2, NO2 and SO2 in f-GST and f-GSTD hybrid films systems were studied. The diffusion coefficient of gas molecule in f-GSTD was obviously lower than that of in f-GST, for the reason that the addition of DGEBA reduces the free volume in f-GSTD systemsFurthermore, the effects of incorporated AP-POSS particles on diffusion properties of polymer-inorganic hybrid films were investigated by molecular dynamics simulation. The interchains distance of the polymer was calculated by x-ray scatte; polymer chain mobility was analyzed by mean-square displacement (MSD); the diffusion behavior of O2 molecule in epoxy films was also studied. It can be found that incorparation of POSS particles into epoxy increase the interchains distance of the polymer and polymer chain mobility. Although there were some significant differences in dimension scale between the simulated model and the system used in the experiments, some important qualitative similarities were well observed. Therefore, molecular dynamics simulation can be used to guide the selection of organic—inorganic hybrid films in anti-corrosion materials. |
