Center for Functional Nanomaterials Seminar

In the past decade, it has been recognized that polymer brush is a key to enable a wide range of potential surface applications related to bio- and nano-technologies. Several approaches on how to tether chains to substrate have been proposed, for example, physical absorption, chemically grafting chains onto substrates via the “grafting to” or the “grafting from” methods. We developed an approach to precisely control the density of tethered chains of near mono-dispersed molecular weights on polymer single crystal template by crystallization of block copolymers with one crystalline block. For amorphous-crystalline diblock copolymer system, we utilized the thickness of single-crystals grown at different crystallization temperatures in solutions as a probe to monitor changes of entropic surface free energy generated by the tethered chains. Using this strategy we systematically investigated the crossover regime of tethered polymer chains. The idea was further applied to study surface behaviors of tethered diblock copolymers and tailor triblock copolymer single crystal surfaces to achieve unbalanced surface stresses.
Polymer brushes can be used to stabilize colloids. By using Brillouin Light Scattering we investigated the micromechanics and phononic properties of assembly of spherical virus which has an uniform core size of about 140 nm and fibrils about 30 nm long protruding from the core of virus. We found that the virus multilayer is more film-like suggesting strong mechanical coupling of individual viruses probably due to the interlock of the tethered fibrils.
Phonons of individual viruses were identified which is similar to localized modes of PMMA colloids.