Topology driven structural transition of dendrimers with a dimensional cross-over

Abstract

This contribution proposes the present day picture of dendrimers as a transition from a non-compact sphere to a dense space filling hyperbolic topology, which contradicts the existing perception of a dendrimer with a dense core and open periphery. The unusual maximum in the generation dependent intrinsic viscosity is analyzed within the framework of the optimized Rouse-Zimm theory with excluded volume interactions between the nearest non-bonded monomers. The position of this maximum represents the onset of this structural transition, which is accompanied by a change in the overall shape, characterized by a cross-over from the Euclidean to non-Euclidean dimensions. This structural transition is a characteristic feature of the topology of dendrimers. The actual available volume is a discontinuous function of generation, rather than a continuous cubic power-law in three dimensions. This implies that the core of dendrimers are dense, while the terminal groups are distributed throughout the core and periphery. Hence, large dendrimers, which are extremely dense objects with highly crowded peripheries exhibit fractal nature with a fractal dimension greater than 3.