Surface Adsorption of Dendrimers: Structure, Interactions at Graphene/Water Interface and Applications in Supercapacitors

Abstract

The study of structure and dynamics of geometrically con ned polymers has been an interesting topic of research. In this thesis we speci cally studied the adsorption behavior of a hyper-branched polymer called poly(amidoamine) (PAMAM) dendrimer at a graphene/water interface. We have primarily employed molecular dynamics (MD) simulations for this purpose. In case of PAMAM dendrimers, which are well-known for their drug-delivery applications, understanding the surface behavior is important to understand their interactions with cell-membrane. Because of their highly monodisperse sizes and unique star-like architectures with void-spaces within them, the dendrimers have potential applications in energy storage devices, surface patterning, biomedicine, and nanotechnology. It is crucial to study the surface behavior of dendrimers for investigating these interesting applications. In this thesis we specially address two of the applications of the dendrimers i.e., i) surface wetting and ii) as electrode coating materials and as electrolytes in supercapacitors. Supercapacitors are the new-age energy storage devices based on electric double-layer formation. We believe that the work carried out in this thesis is helpful for the dendrimer's applications in surface wetting and supercapacitors. For instance, from the third chapter we can say that the neutral pH dendrimers must be considered for achieving maximum surface wetting. Similarly, from the binding energy strengths obtained in the fourth chapter, one can decide the typical strengths of the electric elds to be used to desorb the dendrimers during discharge cycles for supercapacitor study. Chapter 5 shows that the presence of a surface is a favorable situation when one needs to prevent dendrimer aggregation, as the interactions are repulsive in nature irrespective of the protonation level of the dendrimer. From the positive results from chapter 6, where we nd an enhancement in the capacitance value in the presence of dendrimer, one can investigate their further applications in supercapacitors.