Impregnation of Poly(methyl methacrylate) with Carbamazepine in Supercritical Carbon Dioxide: Molecular Dynamics Simulation
Fully atomistic molecular dynamics simulations are employed to study impregnation of the poly(methyl methacrylate) (PMMA) matrix with carbamazepine (CBZ) in supercritical carbon dioxide. The simulation box consists of 108 macromolecules of the polymer sample with the polymerization degree of 100, 57 molecules of CBZ, and 242,522 CO2 molecules. The simulation is performed at 333 K and 20 MPa. It is found that by the end of the simulation, the CBZ uptake reaches 1.09 wt % and 50 molecules are sorbed by PMMA. The main type of interaction between PMMA and CBZ is hydrogen bonding between the carbonyl oxygen of PMMA and the hydrogen atoms of the CBZ NH2-group. At the polymer surface, CBZ exists not only in the molecular form, as inside the polymer and in the bulk solution, but also in the form of dimers and trimers. The energy of formation of the hydrogen-bonded complexes is estimated within ab initio calculations.