Role of polymer graft stiffness in electrostatic-driven self-assembly of nanoparticles in solutions

Self-assembly of nanoparticles (NPs) in solution has garnered tremendous attention among researchers because of their electrical, chemical, and optoelectronic properties at the macroscale with potential applications in bio-imaging, bio-medicine, and therapeutics. Control of size, shape, and composition at the nanoscale is important in tuning the material's bulk properties. The grafting of NPs with polymers enables us to tune such bulk material properties at the nano level by controlling their assemblies, especially in solutions. The stiffness of grafts plays a crucial role in tuning the self-assembly of spherical NPs grafted with polyions (PGNs). Many recent studies based on single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) showed the potential applications of such assemblies. In this work, we have performed coarse-grained molecular dynamics (MD) simulations to understand the charge-driven self-assembly of PGNs by varying stiffness of polymer grafts, the grafting density, and graft length. Self-assembly of these PGNs leads to the formation of different structures driven by the rigidity of polyion chains and the electrostatic interactions. A dramatic change in morphological transitions can be achieved, ranging from rings, strings, and percolated structures and ordered to disordered aggregates by tuning the control parameters. The percolated structures form disordered structures upon annealing with potential applications in thermal under filling, neuromorphic devices, and biological systems including drug delivery, and therapeutics.