Effect of Molecular Interactions at Polymer-Mineral Interfaces on Mechanical Response
- PDF / 308,986 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 82 Downloads / 174 Views
Y1.6.1
Effect of Molecular Interactions at Polymer-Mineral Interfaces on Mechanical Response Rahul Bhowmik, Kalpana S Katti and Dinesh R Katti Department of Civil Engineering and Construction, North Dakota State University, Fargo, North Dakota.
ABSTRACT Nanocomposites of polymer and hydroxyapatite are widely used as bone replacement materials. The mechanical responses of these nanocomposites are known to be influenced by molecular interactions at mineral polymer interface. Molecular modeling of these interactions is an area of current interest but force field parameters of such dissimilar molecules are not available for a common force field. Also, parameters for several commonly used force fields are not available in the literature for hydroxyapatite. Recently a unique force field was described in literature that represents the structure of hydroxyapatite reasonably well. Yet the applicability of this force field for studying the interaction between dissimilar materials (such as mineral and polymer) is limited as there is no accurate representation of polymer. CVFF is a commonly used force field for which parameters of many material systems are available. We have obtained the parameters of CVFF for monoclinic hydroxyapatite from the known potential energy function of apatites and from experimentally obtained infrared spectra. Validation of simulations is done by comparison of computationally obtained unit cell parameters, vibrational spectra and different atomic distances with experiments. This study represents molecular modeling of polymermineral interfaces with the known parameters of hydroxyapatite.
INTRODUCTION Hydroxyapatite, Ca10(PO4)6(OH)2 (HAP)-polymer composites are becoming increasingly important as new biomaterials for bone replacement [1]. HAP is the mineral component of structural biological materials such as bones and teeth. The mechanical behavior of the polymerHAP composite can be modified by involving nano-sized HAP crystallites. In these nanocomposite systems, molecular phenomena at interfaces have significant effect on the resulting physical properties of composite [2]. Molecular dynamics simulations can be used to study the interfacial behavior in these composite systems. Molecular dynamics is based on newtonian classical mechanics and uses a potential function, often called forcefield, to calculate the energy of a system. In order to simulate interactions bertween dissimilar molecular entities such as polymer and HAP, it is necessary to define parameters for the interacting molecular entities in a common force field. The force field is often typical to the nature of the molecule. For different atom(s) the parameters of a forcefield are obtained either by different experimental methods or from rigorous ab initio quantum mechanics based calculations. Some of the commonly used forcefields are CFF91 (consistent forcefield) [3,4,5], CVFF (consistent valence forcefield) [7], ESFF (extensible systematic forcefield) [6] etc. Due to the structural complexity of HAP, parameters for this mineral are not
Data Loading...
