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

该项目扩展了我们之前在树状大分子上的工作，以研究在有限浓度的溶液中中性和带电树状大分子的性质。对于模拟，我们将使用一个高度优化的键波动模型（BFM）。与分离的树状大分子相比，对树状大分子浓度效应的理论认识仍然不完整，实验结果部分存在争议，并且对包括柔性间隔剂影响在内的大范围参数的系统计算研究仍然缺失。在项目的第一部分中，我们在非热溶剂条件下进行了从稀释到浓缩状态的各种代和间隔长度的中性树状大分子溶液的模拟。这使我们能够研究单个树状大分子的构象性质作为浓度的函数，并以高统计质量详细研究尺寸变化和相互渗透效应。特别是长柔性间隔剂的作用，它通过间隔剂链重叠的开始设定了第二个特征浓度制度，将被研究。我们将开发缩放和平均场型模型来合理化模拟结果。在这个项目的第二部分，我们研究带电树突状分子的解决方案，在明确的反离子的存在。通过加入盐离子，我们特别想研究有限浓度下盐价对树状聚电解质构象性质的影响，以及它们在高价反离子介导的络合作用下的自组织。我们的研究结果有望与软物质物理学和生物学应用相关。

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.