Monte Carlo Simulations of Model Molecular and Polymer Fluids
Three different rigid rod fluids, rigid rods on a cubic lattice, off-lattice spherocylinders with restricted orientational freedom and off-lattice spherocylinders with total orientational freedom have been investigated by Monte Carlo simulations. Comparisons have been made between simulation results and theoretical predictions, such as DiMarzio's theory for rigid rods on a cubic lattice and Scaled Particle Theory (SPT) for spherocylinders with restricted orientational freedom. The study concludes that rigid rods on a cubic lattice show an isotropic-nematic transition only when a modified potential, no close contact allowed for a non-parallel pair of rods, is applied. The spherocylinders with both restricted and total orientational freedom exhibit an isotropic-nematic transition. The imposition of restricted orientational freedom reduces the transition density. The SPT shows good agreement with the simulations for spherocylinders with restricted orientational freedom. The simulations for the spherocylinders with restricted orientational freedom in a slitlike pore have been performed and various slit width dependent properties have been investigated. Polymer liquid crystals modeled as jointed spherocylinders have also been studied using Monte Carlo simulations. From the simulations for binary mixtures of hard spheres and spherocylinders, it has been concluded that these mixtures show positive constant pressure excess free energy and negative constant packing fraction excess free energy due to size effects. The SPT predictions are consistent with the simulations for binary mixtures of hard spheres. The mixing properties two binary mixtures, ethylbenzene -anisol and ethylbenzene-(2,6-dimethyl)anisol, have been investigated using molecular mechanics in Monte Carlo simulations. Comparisons between simulations and experiments have also been made. The experimental data indicate a positive heat of mixing for ethylbenzene-anisol and negative for ethylbenzene-(2,6 -dimethyl)anisol system. The simulations do not predict the heat of mixing very well due to the errors caused by many factors, such as system size effects and nonoptimized force field parameters.
- Pub Date:
- MOLECULAR FLUIDS;
- Engineering: Chemical; Chemistry: Polymer; Physics: Molecular