Sequence-specific polymers are proving to be a powerful approach to assembly and manipulation of matter on the nanometer scale. This has been most impressive in the case of DNA, and progress has been made toward templating inorganic nanoparticles using DNA nanostructures. One obstacle to this progress is that inorganic nanomaterials are often incompatible with DNA assembly conditions, which involve aqueous solutions high in either or both monovalent and divalent salt. Synthetic oligopeptide ligands have been shown by others to improve nanoparticle stability in high concentrations of monovalent salt. Ligands that are peptoids, or sequence-specific N-functional glycine oligomers, allow precise and flexible control over the arrangement of binding groups, steric spacers, charge, and other functionality. We have synthesized short peptoids that can prevent the aggregation of gold nanoparticles in high-salt environments including divalent salt, and allow coadsorption of a single DNA molecule. This degree of precision and versatility is likely to prove essential in bottom-up assembly of nanostructures and in biomedical applications of nanomaterials.