Role of the Brush Sizes and Sidechain architecture on Linear Polymer Bottlebrushes: an atomistic simulation.

Bottlebrush polymers (BBPs) are unique and versatile macromolecules used in material science, electronics, battery materials, self-healing, and more. In this paper, using all atom molecular dynamics simulations, we studied the structural and hydration properties of Poly (methyl methacrylate) -g- poly(2-ethyl-2-oxazoline) (PMMA-g-PEtOx) BBP, as well as the BBP supported water properties as a function of backbone monomers (N_BB) and sidechain monomers (N_SC). The radius of gyration follows a scaling of Rg~N_SC^0.38 for smaller grafts and Rg~N_SC^0.5-0.63 for longer grafts. The overall shape (quantified by anisotropy) of the bottlebrush goes from rod to sphere shape with increasing N_SC. Both hydration per sidechain monomer and hydrogen bonds per oxygen and nitrogen decrease with increasing N_SC, with water-oxygen HBs being much higher than water-nitrogen HBs. The BBP-supported water molecules had two ordered domains, one more structured and one less structured, with the former disappearing with an increase in NSC due to the localization of the sidechain in the interior of the BBPs. Finally, despite the highly negative partial charges of the oxygen and nitrogen atoms (of the sidechain monomers), water molecule dipole orientation distributions around these atoms show a neutral environment. Overall, we anticipate that our research will generate a substantial future interest in probing the various widely explored BBPs systems in greater atomic detail.