College Park, Maryland      June 6 - 10 , 2004

MP19: Structure and dynamics of Inorganic nanoparticles templated by soft copolymer cubic structures

D.C. Pozzo, L.M. Walker (Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh PA)

The design of nanometer scale inorganic-organic composites is one of the most exiting areas of material science and engineering. Particular attention is given to structured materials whose order arises at the molecular level but persists over macroscopic length scales. This is driven by the potential that these new materials have in the development of optics, electronics, catalysts, biotechnology devices and in manufacturing materials. Theoretical approaches demonstrate the phase richness of nanoparticles embedded in amphiphilic copolymer mesophases, but there is a lack of systematic experimental studies that characterize the influence of inorganic fillers on the 3D organized structures. We are utilizing water-soluble triblock copolymers (PEO-PPO-PEO) to provide thermoreversible micellar-cubic templates with typical dimensions of tens of nanometers. Using rheology and small-angle neutron scattering (SANS), we characterize the influence of the addition of inorganic nanoparticles (of similar dimensions to the block copolymer micelles) on the macroscopic sample properties and on the local structure. Using contrast matching techniques we demonstrate that the template approach is feasible as reasonable quantities of hydrophilic inorganic nanoparticles are incorporated into the block copolymer mesosphere without destroying the structure. It is also found that the cubic structure is transmitted to the silica particles and that the level of templating is dependent on a number of variables. We quantify the results by studying the influence of relative concentration, relative dimensions and surface chemistry of the inorganic particles. Additionally, using dynamic light scattering (DLS) and contrast-matched neutron spin echo (NSE) experiments we individually study the complex motions of the various components that make up the composite materials. Furthermore the ability to alter these structures using a variety of external parameters including shear and temperature make these materials of considerable interest as processable templates for inorganic-organic nanocomposites.

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