ChBE Seminar Series: Lloyd Robeson
Tuesday, November 13, 2007
11:00 a.m.-12:00 p.m.
Room 2110, Chemical & Nuclear Engineering Bldg.
Professor F. Joseph Schork
Polymer Blends in Emerging Technologies
Presented by Lloyd Robeson
Dr. Robeson is an alumnus (Ph.D. chemical engineering '67) and a member of the Clark School's Innovation Hall of Fame.
Polymer blends offer an important option in solving materials needs for emerging technologies. The ability to combine combinations of existing polymers into new materials offering a diversity of properties allows for a rapid response to solving the property requirements. Often polymer blends can yield a property profile not capable of being achieved by development of new monomer/polymer combinations. This lecture will discuss the relevance of polymer blends in the emerging technology areas of nanotechnology, optoelectronic applications, biotechnology/biomedical applications, fuel cell components, lithium battery membranes, conductive polymers and application of supercritical fluids in polymer processing.
Nanotechnology is particularly relevant to polymer blends and phase separated polymers often achieve separation at nanoscale dimensions. Exfoliated montmorillonite clay has been studied in detail in polymer composites and has recently been noted to be an effective compatibilizer for polymer blends by stabilizing the blend by preventing coalescence of the finely divided structure after shear application. In the area of optoelectronics, polymer blends have been reported in countless examples offering improved properties over the unblended counterparts. Specifically in photovoltaic applications, the combination of donor-acceptor conjugated polymer blends spinodally phase separated allowed for a co-continuous structure desired to allow the transport of holes and electrons yielding electrical current production. A number of examples of blends of electroactive polymers have been noted with synergistic results in quantum efficiency and brightness compared to the unblended constituents. Fuel cell proton exchange membranes employing anionic polymers also has seen an interest in polymer blends as phase separated combinations of low and high ion exchange capacity polymers often yield improved performance versus the unblended counterparts. An upper bound relationship has been noted for proton conductivity versus water sorption. An analysis of phase separated polymers shows that blends can actually yield better fuel cell performance at intermediate blend compositions than the components. In the reemerging biomaterials/biotechnology field, polymer blends have been employed in scaffolds for tissue engineering to optimize the multiplicity of performance variables including cell growth, attachment and adhesion.