Deformation of Poly(amido amine) Dendrimers at Surfaces

The adsorption of dendrimers, or repetitively branched polymers, onto charged surfaces plays an important role in many applications, such as increasing the energy density in supercapacitors. Experimental evidence indicates that dendrimers flatten at these interfaces. In order to better understand the deformation of dendrimers at surfaces, molecular simulations of poly(amido amine) (PAMAM) dendrimers at graphite/water interfaces with and without applied electric fields have been performed to examine the degree of flattening, as well as the dependence on the protonation state of the dendrimer, dendrimer generation, concentration of charge, and electric field strength. The rapid increase in size with increasing generation quickly leads to very computationally demanding simulations. To overcome this difficulty, we have used a coarse-grain model, which decreases the computational cost by reducing the number of degrees of freedom. We have validated this model against a more realistic, but also more expensive, united-atom representation.