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Christy F. Landes Carmen G. Reznik , Nicel Estillore , Rigoberto Advincula ,

R. Rice University Department of Chemistry. L A N D E S R E S E A R C H G R O U P. Switchable Transport in Supported Polyelectrolyte Membranes. Christy F. Landes Carmen G. Reznik , Nicel Estillore , Rigoberto Advincula ,.

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Christy F. Landes Carmen G. Reznik , Nicel Estillore , Rigoberto Advincula ,

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  1. R RiceUniversity Department of Chemistry L A N D E S R E S E A R C H G R O U P Switchable Transport in Supported Polyelectrolyte Membranes Christy F. Landes Carmen G. Reznik, NicelEstillore, RigobertoAdvincula,

  2. Motivation: Tunable Molecular/Charge Transport in Charged and Crowded Environments L A N D E S R E S E A R C H G R O U P Processes may proceed via: Tightly Controlled Single Pathways Degenerate and Competitive Pathways Loosely Controlled Single Pathways Frauenfelder, H.; Sligar, S.G.; Wolynes, P.G. Science 1991, 1598. Wang, Y.; Baskin, J.S.; Xia, T.; Zewail, A. Proc. Natl. Acad. Sci. USA, 2004,18000. Papoian, G. Proc. Natl. Acad. Sci. USA 2008, 14237.

  3. - - - - - - - - - - - - - - - - Our Model Synthetic System The Polymer Brush1,2 Polymer Thin Layer: L A N D E S R E S E A R C H G R O U P Polymer chains end-grafted to a surface • High Density • Ordered Environment Polyelectrolyte Brushes • Charge distributed along the • polymer chain 1Prucker, Rühe,, Macromolecules, 1998, 31, 602-613 2Advincula, et al., Polymer Brushes: Synthesis, Characterization and Applications, Wiley-VCH, 2004

  4. A strong connection has been demonstrated between nanostructure & transport1 L A N D E S R E S E A R C H G R O U P Polymer Brush Thin Films: Tunable and responsive structural properties Modify physical/responsive properties via polymer chemistry: • Internal microstructures • Heterogeneous surface coverage • Electroactive polymers Tunable response: 1Whiting, et al. Nanoletters, 2006, 6, 573-578

  5. Charged Molecule Transport : The Environment Poly(styrene sulfonate) polymer brush L A N D E S R E S E A R C H G R O U P via Surface Initiated Polymerization1 Properties: high density water soluble simple synthesis Probe Molecules: Evaluation of: 1) Translational Transport4 , 2) Rotational Transport5 Rhodamine 6G Bodipy – R6G (base structureof dye shown) Alexa 555 (Alexa 546 shown here) 1Prucker, Rühe, Macromolecules, 1998, 31, 602-613 4Reznik, Landes et al., JPC B, 112, 10890–10897 5Reznik,Estillore, Advincula ,Landes, JPC B, 113,14611–14618

  6. Signal Trajectory Methods and Materials: Experimental Configuration L A N D E S R E S E A R C H G R O U P

  7. Methods and Materials: FCS and SM Polarization Resolved Spectroscopy Polarized Light Splitter APD APD L A N D E S R E S E A R C H G R O U P Elson, Madge , Biopolymers, 1974, 13, 1-27 Aragon, Pecora , JCP, 1976, 64, 1791 Axelrod, Biophys. J, 1979, 78, 557-574 Forkey, et al., Prog. Biophys. Mol. Biol., 2000, 74, 1-35

  8. Heterogeneous Transport L A N D E S R E S E A R C H G R O U P Multiple Regions - Multiple kinds of transport possible Multiple Interactions - -Coulomb -Steric • By what mechanisms does transport occur? • Can modes of transport be selected for?

  9. DATA: Single Molecule Events R6G dye diffusing in water L A N D E S R E S E A R C H G R O U P R6G over PSS brush (pH 7): 300 ms trace, AC decay time 440 ms Signal acquired at 10 us and binned to 1 ms

  10. DATA: Heterogeneous Modes of Transport L A N D E S R E S E A R C H G R O U P • Translation • Adsorption • Highly Oriented States • Strong associations • Non-Oriented States • Weak association • State Switching Reznik, Landes et al., JPC B, 112, 10890–10897 Reznik,Estillore, Advincula ,Landes, JPC B, 113,14611–14618

  11. - - - - - - - - - - - - H+ H+ + + + H+ H+ H+ H+ H+ H+ DATA: Switchable Diffusion L A N D E S R E S E A R C H G R O U P Acidified co-solvent increases diffusion rates in the PSS brush counter ion Electrostatic coupling affects diffusion of the counterion:

  12. DATA: Transport Response to Charged Molecular Species L A N D E S R E S E A R C H G R O U P

  13. Charged Molecular Transport L A N D E S R E S E A R C H G R O U P

  14. Data: MultipleTransport Modes Indicated in FCS L A N D E S R E S E A R C H G R O U P Tcherniak, Reznik, Link, Landes, Analytical Chemistry, 2009, 746-754

  15. Brownian Dynamics Simulation Modeling the Effect of the Electrostatic Field on the AC function: L A N D E S R E S E A R C H G R O U P Potential Field in b) is an order of magnitude stronger than in a) Increased electrostatic coupling leads to a shifted AC function, reflecting slower diffusion Reznik, et al. JPCB, 2008

  16. Additional Investigations: • Extended SM evaluation of orientation as a function of time: • - 3 detectors1 • - advancement of techniques to allow lower time resolution (correlation techniques) • Control of charge transport via electrical switching L A N D E S R E S E A R C H G R O U P • Construct a microelectrode device on a glass coverslip using physical vapor deposition techniques. • Grow polymer brush on the electrode device • Measure diffusion and orientation effects as a function of electric field strength 1Fourkas, Opt. Lett., 2001, 26, 211-213

  17. Conclusions Using SM spectroscopy, combined with FCS, we have observed Complex Transport Mechanismsfor single molecule probes with a variety of charge structures diffusing in association with a strong polyelectrolyte brush: L A N D E S R E S E A R C H G R O U P Modes of transport in Include: - non associated/bulk water diffusion - both strong and weak brush association states: from diffusion near/within the brush system, to restricted diffusion and adsorption - polarization state switching Predominate modes of transport are dependent upon: - Coulomb and steric considerations - dye and solvent charge structure And we have provided – experimental evidence of stimuli responsive switchable transport functionality in the polymer brush

  18. Thanks to: • The Whole Landes Research Group • And • SaumyaKhatua, Wei-Shun Chang, • Alexei Tcherniak, and Dr. Stephan Link L A N D E S R E S E A R C H G R O U P • And for Funding: • The Texas Center for Superconductivity • NIH Molecular Biophysics Training Grant (T32 GM008280), • Keck Center for Interdisciplinary Bioscience Training • Rice University • PRF

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