Brownian dynamics simulations of hydrophobic dendrimer adsorption

Abstract

The adsorption of an isolated hydrophobic dendrimer onto a flat surface is studied in this work using Brownian dynamics simulations. The dendrimer is modelled as a freely jointed bead-rod chain. Bead -bead and bead -surface hydrophobic interactions along with excluded-volume interactions are accounted for using a Lennard-Jones potential. Adsorption behaviour is studied as a function of the strength of hydrophobic interactions, dendrimer generation and distribution of hydrophobic groups within the dendrimer. The adsorbed dendrimer adopts a disk-like conformation by compressing in the direction normal to the surface and expanding in the direction parallel to the surface. As the strength of hydrophobicity decreases, the adsorbed dendrimer expands in the normal direction and contracts in the parallel direction. Eventually, at a very low level of hydrophobicity, the dendrimer desorbs and adopts a sphere-like conformation. Bead density profiles show that the adsorbed hydrophobic dendrimer forms a two-layer structure, with one layer corresponding to adsorbed groups, and another layer in free solution, similar to charged dendrimer adsorption. However, unlike charged dendrimer adsorption, all terminal groups can be attached to a surface using a dendrimer having all hydrophobic groups or hydrophobic terminal groups. In the case of a dendrimer having only hydrophobic branching groups, most of the terminal groups can be placed in free solution. Also, an adsorbed hydrophobic dendrimer forms a relatively compact structure unlike the stretched configuration of adsorbed charged dendrimers. The results presented here suggest how to tune the levels of hydrophobicity and charge to tailor dendrimer surface conformations, and may help guide hydrophobic dendrimer design for applications such as drug delivery and surface functionalisation.

Adsorption of Silicon-Containing Dendrimers: Effects of Chemical Composition, Structure, and Generation Number

“…This behavior has qualitatively been predicted by simple models [14]. Furthermore, silicon-containing dendrimers follow the general trends in shape changes predicted theoretically [25] and observed within coarse-grained computer simulations [24,25]. With an increase in the adsorption strength, the dendrimer shape changes less with an increase in generation, an increase in core functionality, or a reduction in spacer length.…”

“…Up to now, computer simulations of the dendrimer adsorption were mainly focused on (i) differences in adsorption depending on which particular atoms are attracted to the surface and on (ii) effects of the nature of attractive interactions, i.e., either Coulomb or hydrophobic [ 23 , 24 ]. In the case of Coulomb attraction, the repulsion between similarly charged monomer units of the adsorbing dendrimer affects considerably its final conformation, making it more stretched, regardless of which particular structural units of the dendrimer are attracted to the surface [ 23 ].…”

“…In the case of Coulomb attraction, the repulsion between similarly charged monomer units of the adsorbing dendrimer affects considerably its final conformation, making it more stretched, regardless of which particular structural units of the dendrimer are attracted to the surface [ 23 ]. In contrast, the hydrophobic mechanism of attraction leads to a denser structure of adsorbed dendrimers [ 24 ]. If both adsorption mechanisms are involved, then the final conformation is closer to that determined by electrostatics [ 24 ].…”

Coarse-grained modelling of urea-adamantyl functionalised poly(propylene imine) dendrimers

“…Other models where the solvent was treated implicitly were made with molecular dynamics [17][18][19] (MD) and Brownian dynamics. [20][21][22][23] One improvement in detail has been including solvent particles. [24][25][26][27][28] Another was using atomistic MD to model specific dendrimers, but still in implicit solvent or actual vacuum.…”

Synthesis, Electrochemical Behaviors and Anion Recognition of A Novel Star-[Polystyrene-b-poly(ferrocenyloxy ethyl acrylate)]6with Hexafunctional Cyclotriphosphazene Core

“…[24][25][26][27][28][29] Ferroene-based star-polymer keeps some properties of dendrimer and hyperbranched polymer and also contains cavities in the surface. Above all, star-polymer with precise structure can be readily prepared by controllable method such as atom transfer radical polymerization (ATRP) [30][31][32][33] .…”