Controlling Phases of Isotropic DNA-grafted Nanoparticle Assembly through Tuning Pair Interactions*

Theoretically, complex isotropic pair potentials can yield complex periodic structures, but due to limited practical methods to engineer pair potentials, experimental realization remains challenging. DNA can direct self-assembly in a tailorable manner by leveraging complementary base pairing and repulsive polymeric effects, presenting a material well-suited to encoding designed pair potentials. We utilize a double-linker approach to DNA-grafted NP assembly; linkers have a non-complementary spacer and a hybridization sequence that is complementary to the linker of a paired particle. Complementary regimes drive attraction causing DNA shells to hybridize at an encoded distance (r_att) prescribed by shell length and location of the hybridization regime. Non-complementary regimes drive particle repulsion, the range of which (r_rep) is prescribed by shell length alone. Computational simulations show that isotropic pair potentials are effectively approximated with the parameter: r_rep/r_att. By fixing either linker length or hybridization regime location and altering the other, we achieve a range of r_rep/r_att values, and we validate, via small-angle x-ray scattering, structural evolution from body-centered cubic to simple cubic crystals to weakly ordered cubic diamond-like networks.