PEO-Silane Amphiphiles to Decrease Biofouling on Silicones
Prof. Melissa A. Grunlan, Department of Biomedical Engineering, Department of Materials Science & Engineering, Texas A&M University, College Station, TX. http://grunlanlab.tamu.edu
Abstract Silicones, particularly silica-reinforced crosslinked polydimethylsiloxane (PDMS), are widely-used for medical, marine and industrial applications. Unfortunately, their extreme hydrophobicity causes poor-antifouling behavior. Although polyethylene oxide (PEO) is known to be exceptionally anti-fouling (e.g. protein resistant), these observations have been largely made when PEO is grafted to a physically stable substrate (e.g. gold and silicon wafer). In this way, migration of the PEO to the water-surface interface, where biological adhesion occurs, is not required. In this work, we sought to enhance the water-driven surface-migration of PEO incorporated into silicones in order to achieve superior anti-fouling behavior. Conventional PEO-silanes consist of a PEO segment separated from the reactive group by a short alkane spacer. In contrast, we prepared PEO-silane amphiphiles with siloxane tethers of varying lengths and as well as variable PEO segment lengths. The resistance of these coatings to proteins, bacteria, whole blood and marine biofoulers are related to PEO-silane structure and concentration.
High power factor, completely organic, nanotube-filled thermoelectric polymer nanocomposites
Jaime GRUNLANa, Choongho YUa, Gregory MORIARTYb
a Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, b Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, e-mail: jgrunlan@tamu.edu, http://nanocomposites.tamu.edu
Low electrical conductivity (s) and thermopower (S) have long excluded polymers from thermoelectric applications. Adding carbon nanotubes produces polymer nanocomposites that exhibit thermoelectric behavior (i.e., generate electricity via a thermal gradient). These nanocomposites exhibit electrical conductivity as high as 200,000 S/m, with a reasonable S (35 – 70 mV/K). This high electrical conductivity is paired with low thermal conductivity (k ~ 0.3 W/m•K). Power factors (PF = S2s) are as high as 500 mW/(m•K2) for these composites, containing carbon nanotubes stabilized by porphines and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), making them competitive with inorganic semiconductors (e.g., lead telluride) in terms of conversion efficiency. These composites are lightweight and relatively flexible when compared with traditional semiconductor thermoelectrics (e.g., bismuth telluride). Very recent work using layer-by-layer assembly will also be described. Sequential layering of PANi, graphene, and double walled carbon nanotubes (DWNT) produces films with increased carrier mobility, originating from strong π-π interactions between PANi and DWNT and the higher electrical conductivity of graphene. In this investigation of the thermoelectric behavior of an LbL-assembled film, the resulting multilayer thin films exhibit a remarkable power factor (PF (S2σ) = 1825 µW m-1 K-2) that exceeds lead telluride and is more than half the value of bulk bismuth telluride. Additionally, these water-based systems can be applied like ink or paint, which should further improve their usefulness in harnessing waste heat from a variety of sources (e.g., exhaust manifolds or the human body). For more information about the Polymer Nanocomposites Lab: http://nanocomposites.tamu.edu.
The Speaker Prof. Melissa Grunlan is currently an Associate Professor of Biomedical Engineering at Texas A&M University. She is also a faculty member of the Department of Materials Science & Engineering. Prof. Grunlan obtained her B.S. in Chemistry and M.S. in Polymers in Coatings from North Dakota State University (Fargo, ND). After spending four years at the H.B. Fuller Company (St. Paul, MN), she received her Ph.D. in Chemistry from the University of Southern California (Los Angeles, CA). Prof. Grunlan joined Texas A&M University as an Assistant Professor in August of 2005 and was promoted to Associate Professor with tenure in September 2011. She is the recipient of the TEES Faculty Fellow Award (2013), the Herbert H. Richardson Faculty Fellow Award (2010-2011), the Association of Former Students Distinguished Achievement Award (2009) and the BP Teaching Excellence Award (2013) from the College of Engineering at TAMU. Prof. Grunlan is the director of the “Silicon-Containing Polymeric Biomaterials Group” http://grunlanlab.tamu.edu |
Grunlan Bio Dr. Jaime Grunlan joined Texas A&M University as an Assistant Professor of Mechanical Engineering in July of 2004, after spending three years at the Avery Research Center in Pasadena, CA as a Senior Research Engineer. He obtained a B.S. in Chemistry from North Dakota State University and a Ph.D. from the University of Minnesota in Materials Science and Engineering. Prof. Grunlan was promoted to Associate Professor in 2010 and then Professor in 2014. His research focuses on thermal and transport properties of nanocomposite materials, especially in the areas of thermoelectric energy generation, gas barrier and fire prevention. He won the NSF CAREER and 3M Untenured Faculty awards in 2007, the Dow 2009 Young Faculty Award, and the 2013 E. D. Brockett Professorship and the 2015 Dean of Engineering Excellence Award for his work in these areas. He has published over 100 journal papers and filed several patents. Dr. Grunlan also holds joint appointments in Chemistry and Materials Science and Engineering. |
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