Bundlemers-peptide nanoparticles for hierarchical material assembly

Bundlemers are a series of computationally designed peptides that form monodisperse cylindrical particles through aqueous self-assembly into antiparallel homotetrameric coiled coils. The robust coiled-coil-forming motif has extremely tunable surface chemistry while still remaining a monodisperse particle. Using this tunability, we have used bundlemers as macromonomers to create stiff and extremely high aspect ratio supramolecular polymers through covalent chemistry between the neighboring bundlemer ends. The rigid rods (persistence length > 10 microns) exhibit a cross section of 2 nm with controllable length of up to microns. Through computational design, the net charge of the rods can be controlled in order to manipulate solution behavior. The rigid rods show a characteristic shear thinning rheological behavior and, when highly charged at low salt, produce gels due to repulsive electrostatic interactions. With salt screening, the charged rod particles form nematic liquid crystal phases. A combination of rheology, x-ray scattering, and microscopy measurements was used for solution characterization. Processing of the rod suspensions into fibers will also be discussed.