Solution and Surface Composition Gradients via Microfluidic Confinement: Fabrication of a Statistical-Copolymer-Brush Composition Gradient


  • Contribution of the National Institute of Standards and Technology. Not subject to copyright in the United States. This work was carried out in the NIST Combinatorial Methods Center (NCMC). More information can be found at D.M.D. acknowledges the NIST/NRC fellowship program for funding and thanks Sharadha Sambasivan of NIST for her help. Equipment and instruments or materials are identified in the paper to adequately specify the experimental details. Such identification does not imply recommendation by NIST, nor does it imply the materials are necessarily the best available for the purpose.


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A stable solution composition gradient is generated inside a microchannel by varying the relative flow rates of two solutions that differ in composition. This solution gradient is used to synthesize a surface-grafted statistical-copolymer-brush composition gradient via surface-initiated atom transfer radical polymerization (ATRP; see schematic). Near-edge absorption fine structure spectroscopy confirms the continuous transition of surface composition from one end of the substrate to the other.