Constrained spreading of a molecular brush

1. Dye droplet mica Nano film spread mica d h Film spread L Engineered Molecular FluidicsNSF NIRT Grant 0609087PIs: S.S. Sheiko1, K. Matyjaszewski2, M. Rubinstein1, O. Velev31University of North Carolina at Chapel Hill, 2Carnegie Mellon University, 3North Carolina State University Concept and methodology Constrained spreading of a molecular brush Katya Zhulina and Gregory Randall constrained As alternative to (a) closed-channel systems, we study (b) open structures, where monolayer masses, residing on a substrate, are moved and configured by an external force. m > NS1/2 – un-stretched molecule (same as spreading of linear chain) N NS < m < NS1/2 – stretched backbone, un-stretched side chains m (NS)1/3 < m < NS – stretched backbone and side chains d unconstrained L S-1/4 < m < (NS)1/3 – fully stretched backbone and H ~ S-1/2 m < S-1/4 – saturated lower layer and appearance of the cap Fbb/(mkT) Tension energy per backbone monomer NS7/4 NS/m3 Free energy per side chain @ constant volume HhL=Nb3 (NS/m)1/2/m 1 1/(NS) NS/m2 1/N spreading disjoining backbone stretching side chain stretching • Advantages • smaller volume and direct accessibility • dynamically configurable flow control • rapid heat exchange • substrate-mediated mixing, orientation, and shape of macromolecules m S-1/4 (NS)1/3 NS NS1/2 Molecular conformation within 2-D asymmetric mixtures Andrey Dobrynin and Frank Sun RA NB=322 NB=11 Molecular visualization: - size, shape, and ordering, - diffusion, mixing, and reactions NB=24 NB=1766 NB=102 NB=8813 Phys. Rev. Lett.99, 137801 (2007) Flow-induced molecular fractionation Electric field manipulation of thin films Jairus Kleinert, Sejong Kim Mike Barrett, Frank Sun, and David Shirvaniants Thin wetting film spreading by electro-osmosis Reservoir Flow Film heterogeneous substrates = 5.7 x 104μm2/ V·sec μeof : standard electroosmotic mobility ε : permittivity ~ (80)·(8.85 × 10-12 F/m) ζ : zeta potential of mica ~ - 80 mV η : viscosity ~ 9x10-4 Pa·sec Manipulating of molecular fluorophore in a thin film Time