Computer simulations of dendrimers with charged terminal groups

Abstract

Static, structural properties of dendrimers with generations ranging from g = 3 up to g = 7 with charged, monovalent terminal groups and neutralizing counterions in an athermal solvent are studied by lattice Monte Carlo simulations using the cooperative motion algorithm as the tossing scheme. The full Coulomb potential and the excluded volume interactions between pairs of ions and beads are taken explicitly into account with the reduced temperature T* as the main, variable parameter. In particular, the influence of variation of the latter on the mean effective charge per end-bead , total mean energy , mean-square radius of gyration , and mean-square centre-to-end-bead distance is analysed and the molecular weight dependences of , are shown. The simulations indicate that condensation of counterions onto the end-beads occurs as T* is lowered. This effect is accompanied by weak, gradual swelling and shrinking of the molecules.

Monte Carlo simulations of a charged dendrimer with explicit counterions and salt ions

“…[16][17][18][19][20][21][22][23] Although inspection of such systems is computationally extremely demanding due to a sharp rise in the number of terminal groups with the dendrimer size, a number of off-lattice and on-lattice simulations have successfully been carried out for salt-free solutions, leading to the conclusion that counterions have a tremendous impact on the structure and conformations of charged den-drimers. [24][25][26][27][28] Despite different models and computational methods used, the obtained results correspond well, and prove that ion condensation onto dendrimers is an effect of generic nature. As for linear chains, condensation occurs with increasing strength of electrostatic couplings and is accompanied by subsequent swelling and shrinking of the molecules.…”

“…Here, the configurations are tossed by a version of the cooperative motion algorithm (CMA) that is generalized to dendrimeric molecules. 28 Originally, this idea was formulated for linear chains, i.e., for pairs of neighboring bond vectors. 65 The CMA is based on a sequence of translations by one lattice site of a virtual point referred to as the searching point (s.p.).…”

The Structure of Dendrimers with Charged Terminal Groups: Monte Carlo Simulations

“…In the Monte Carlo scheme configurations are tossed using the generalized version of the cooperative motion algorithm (CMA) [35]. The tossing scheme used can be outlined in the following way.…”

“…It turns out, however, that this issue must be handled with great care. The question of the role of counterions treated explicitly has only recently been taken up by means of molecular dynamics and lattice Monte Carlo simulations [35,36]. In spite of different models and computational methods used, the overall pictures reported correspond well.…”

Heuristic Monte Carlo method applied to cooperative motion algorithm for binary lattice fluid

“…In the first case, the difference between energy of new and previous states is considered, and in case of heuristic method only the energy of new state is taken into account. The CMA method was used to investigated various polymer system [15][16][17][18][19][20][21][22][23][24][25][26][27] but the comparison of the different criteria of state acceptance (the Metropolis and heuristic approach) were not systematically studied and described in literature. For example, Vilgis and Weyersberg [15] applied CMA with the Metropolis test to analyze phase behavior of symmetric diblock copolymer and their results were favorably compared with random-phase approximation.…”