Conformational statistics and molecular modeling on polybenzoxazine

A Rotational Isomeric State (RIS) model has been developed from the conformational study on a model dimer as a variables of the stereochemistry and the torsional sequence of C-O bond. Chain dimension in terms of the characteristic ratio was calculated for two ideal cases. From the RIS Monte Carlo chains whose end-to-end distances are near the average value, five independent static bulk structures were obtained by employing the cubic periodic boundary conditions at bulk density of 1.1 g/cm{dollar}sp3{dollar} and the MD and energy minimization. The solubility parameter was predicted to be 8.29 (cal/cm{dollar}sp3)sp{lcub}1/2{rcub}{dollar} with the standard deviation of 0.71. The bulk structure was analyzed using the pair correlation function, hydrogen bonding structure, and the orientational order parameter of the phenyl rings. Free volumes were studied as a function of probe radius, and the size distribution and shape were evaluated.; The diffusion of water and oxygen molecules in the PBO matrix was studied at 295 K and 450 K. The predicted diffusion coefficients are remarkably close, given their considerable size difference. The chain mobility at two different temperatures was studied from torsional auto-correlation function. The interaction of the diffusant molecules and the atoms on PBO matrix are studied from the pair correlation function. The hydrogen bonding of water and the hydroxyl groups in PBO is evident in the pair correlation function. The averaged hydrogen bonding fraction and hydrogen bonding life time were studied using hydrogen bonding auto-correlation function. In hydrogen bonding auto-correlation function, the life time of hydrogen bond between water and PBO is much shorter then the average residence time of cavity, therefore the hydrogen bond does not remarkably retard the diffusion of water in PBO matrix. The association of water is also observed at two temperatures.; Thin film of thickness {dollar}sim{dollar}28 A was constructed in vacuum from the bulk amorphous PBO after extending one edge (the Z-axis) of the cubic cell enough so that atoms can not interact with periodic images in that direction. The density profile, orientational order profile, composition distribution of polar and nonpolar atoms with respect to the distance from the center of mass plane of film were studied. The density drops rapidly at a distance of {dollar}sim{dollar}7 A from the free surface and the chain ends locations are {dollar}sim{dollar}5 A from the surface. Polar atoms are rich near the interior of film with local fluctuation. Non-polar atoms are randomly distributed from the center of film through the surface. The fraction of hydrogen bonds in thin film were higher than that in the bulk state. The energetics between the film and bulk structure were studied, and the surface tension were calculated by ignoring the entropy change between the bulk structure and thin film. The predicted surface tension is 46.1 {dollar}pm{dollar} 5.9 dyne/cm.