Computer simulations and theoretical description of solution of neutral and charged dendrimers: concentration effects and self-organization processes

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This project extends our previous work on dendrimers to investigate the properties of both neutral and charged dendrimers in solutions at finite concentrations. For the simulations we will use a highly optimized version of the bond fluctuation model (BFM). In comparison to isolated dendrimers the theoretical understanding of concentration effects for dendrimers is still incomplete, experimental results partially controversial, and systematic computational studies over a wide range of parameters including the effect of flexible spacers are still missing. In the first part of the project we carry out simulations of solutions of neutral dendrimers of various generations and spacer lengths under athermal solvent conditions from diluted up to the concentrated state. This allows us to study the conformational properties of individual dendrimers as a function of concentration and to investigate size changes and interpenetration effects in detail and with high statistical quality. In particular the role of long flexible spacers which set a second characteristic concentration regime by the onset of overlap of spacer chains will be investigated. We will develop scaling and mean-field-type models to rationalize the simulation results. In the second part of this project we investigate solutions of charged dendrimer molecules in the presence of explicit counterions. By adding salt ions we want to study in particular the effect of salt valency at finite concentration of dendrimers on conformational properties of dendritic polyelectrolytes and their self-organization due to complexation mediated by higher-valent counterions. Our results are expected to be relevant to soft matter physics and biological applications.