Monte Carlo Study Of The Phase And Morphology Of Amphiphilic Diblock Copolymer Brushes

In this thesis, we have investigated the effect of several factors (such as grafting density, interaction energies between different components and the chain length et al.) on the phase morphology of amphiphilic diblock copolymer brushes by means of Monte Carlo simulation, and obtained following results:1. Effect of grafting density on the phase morphology of amphiphilic diblock copolymer brush: the simulation results showed that with an increase in grafting density, the morphological transition from sphere to ripple and then to layer structure occurred. Moreover, the regions of monomer density distribution, end density distribution and the average height of copolymer brush increased when increasing grafting density.2. Effects of different interaction energies on the phase morphology of amphiphilic diblock copolymer brush: the simulation results indicated that changing the interaction energy between A and B (EAB), the interaction energy between A and solvent (EAC) and the interaction energy between B and the surface (EBD) had less effect on the morphologies (i.e. perforated layer) formed in each system. The average height of copolymer brush was slightly increased with increasing EAB. However, when increasing EBC, the number of holes in the perforated layer was increased and the sizes of the holes were decreased. Moreover, the region of monomer density distribution and the average height of copolymer brush were increased at first and then decreased with increasing EBC. Meanwhile, the region of end density distribution shifted to lower value of Z at first and then to higher value of Z. The peak values of these two distributions were both increased and then decrease when EBC were increased. When EBC=0.2, the interplays among EAB, EBD, EBC are balanced, as a result, the region of end distribution are the smallest, while in this case the height of brush are the lowest.3. Effect of chain length and chain length ratio of A and B blocks on the phase morphology of amphiphilic diblock copolymer brush: when the chain length was increased, the morphological transition from sphere to layer was observed; the peak of monomer density distribution turns to be smoother, and the region of density distribution was increased; the region of end density distribution was increased, while its peak value was decreased. When the chain length ratio of A and B blocks was increased, the morphological transition from layer to ripple and then to hexagonal packed spheres was observed; meanwhile, the regions of monomer density distribution and end density distribution were both increased; the peak value of monomer distribution was increased at first and then decrease, and the peak value of end distribution shifted to larger Z value, and the average height of copolymer brush was increased.4. Effect of polydispersity on the phase morphology of amphiphilic diblock copolymer brush: the simulation results indicated that there are three layers in the polydispersity copolymer brush. The peak of monomer density distribution shifted to higher Z value for the chains with the length of 20, while it shifted to lower Z value for the chains with the length of 36 with an increase in PDI. The average height of copolymer brushes decreased with an increase in PDI for the chains with the length of 20 and 36, while its value almost unchanged with an increase in PDI for the chains with the length of 4.