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Download BIO-INSPIRED POLYMER SCAFFOLDS FROM WELL
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Neutron Reflectivity of Stimuli-Responsive Brushes Based on PVDMA Brad Lokitza1, Jamie Messmana, John F. Anknerb and S. Michael Kilbey, IIa,c a) b) C) Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 Department of Chemistry, University of Tennessee, Knoxville, TN 37996 Soft polymeric materials that can be tailored to assemble into well-defined nanostructures offer promising solutions to address challenges in human health and energy sustainability. In promoting the development of useful systems for such applications, neutron scattering methods provide the ability to examine structure-property-function relationships of polymers and interfaces at the nanoscale. Here neutron reflectivity was used to investigate stimuli-responsive polymeric brushes based on the functional monomer, vinyldimethylazlactone. Reversible addition fragmentation chain transfer (RAFT) polymerization was used to synthesize a well-defined block copolymer consisting of poly(glycidyl methacrylate) (PGMA) and poly(vinyl dimethylazlactone) (PVDMA). Functional brush layers were assembled by spin-coating the diblock copolymer (Mn= 43,400 g/mol; PDI = 1.21) onto silicon surfaces from chloroform followed by annealing for 18 hr at 110 °C. The neutron reflectivity profile for the dry layer was well-fit by a model comprised of two distinct polymer layers, indicating that the PGMA block serves as a covalently bound base layer that is anchored to the silicon substrate while the PVDMA block comprises the top layer of the film. Subsequent insitu functionalization of the PVDMA “brush” by nucleophilic reaction with either sodium hydroxide or isopropyl amine leads to the formation of pH or temperature responsive brushes. The nanoscale structure and swelling behavior of these stimuli-responsive interfaces was studied using neutron reflectivity. The results show that base catalyzed hydrolysis creates a weak polyacid brush that responds to changes in pH; and isopropyl amine functionalization creates a thermally-responsive brush that exhibits LCST behavior. These efforts demonstrate the promise of tailored polymeric materials and their assembly, as well as the important role of neutron scattering techniques to advance fundamental science and address technological needs in soft matter science. 1 [email protected]
