Polymer Brushes for Molecular Transport - Paul Braun Research ...

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POLYMER BRUSHES FOR MOLECULAR TRANSPORT BY HUILIN TU B.S., Peking University, 1997 M.S., Peking University, 2000 DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Science and Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2005 Urbana, Illinois
ABSTRACT This thesis studies 2-dimensional transport of a fluorescent molecule, Prodan, in various polymer brushes and self-assembled monolayers (SAMs). Microcontact printing and photolithography combined with surface-initiated atom transfer radical polymerization are the major techniques to construct patterned polymer brushes; extensive surface characterizations, including atomic force microscopy (AFM), ellipsometry, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), X-ray reflectometry (XRR) and etc., are used to confirm chemical identities and physical properties of the polymer brushes; fluorescence recovery after photobleaching (FRAP) is used to determine diffusion coefficients of Prodan. Similar diffusion coefficients of Prodan, ~ 20 µm 2 /s, are found for the SAMs formed by chlorotrimethyl silane (CTS) and silanated poly(ethylene glycol) (PEG). No fluorescence recovery is observed on the octadecyltrichlorosilane (OTS) SAM or on the clean silica surface. Our hypothesis is that Prodan may partially intercalate in CTS and PEG layers whereas Prodan may aggregate on the OTS SAM, and form hydrogen bonds with the silanol groups on the clean silica surface. Patterned poly(N-isopropylacrylamide) (PNIPAAm) brushes were fabricated on silica substrates by surface-initiated atom transfer radical polymerization (ATRP) of N- isopropylacrylamide from a micropatterned initiator. Variable temperature ellipsometry indicated that the lower critical solution temperature (LCST) of the hydrated PNIPAAm brush was broad, occurring over the range of 20-35 °C. FRAP results of Prodan in PNIPAAm layers indicate that bulk translational diffusion is very slow relative to other diffusion mechanisms. iii
Page 1 and 2: POLYMER BRUSHES FOR MOLECULAR TRANS
Page 3: © 2005 by Huilin Tu. All rights re
Page 7 and 8: For my family v
Page 9 and 10: from a vision to concrete plans, an
Page 11 and 12: TABLE OF CONTENTS LIST OF ABBREVIAT
Page 13 and 14: 4.3.6.2 FRAP of Prodan in the patte
Page 15 and 16: CHAPTER 1 INTRODUCTION 1.1 Objectiv
Page 17 and 18: fundamentally different from most o
Page 19 and 20: 1.1.2 General experimental approach
Page 21 and 22: 1.2.1 “Grafting to” approach
Page 23 and 24: mechanism at the later stage, and t
Page 25 and 26: laboratory), sometimes rough,[36] a
Page 27 and 28: (a) (b) Figure 1.4. Schematic repre
Page 29 and 30: 31. S.-J. Ahn, W.-K. Lee, S. Zausch
Page 31 and 32: CHAPTER 2 PRODAN DIFFUSION ON SELF-
Page 33 and 34: tested under continuous flow of nit
Page 35 and 36: coverslips. Water contact angle dat
Page 37 and 38: (a) 0 s 10 s 30 s 120 µm 60 s 120
Page 39 and 40: also sometimes observe bright dots
Page 41 and 42: and the dye, and thus recovery due
Page 43 and 44: 2.5 References 1. C. E. Heitzman, P
Page 45 and 46: formed on gold through microcontact
Page 47 and 48: organic solvents.) for 30 minutes f
Page 49 and 50: Scheme 3.1. SiO2 OH SiO2 O Si 3.2.4
Page 51 and 52: sp 3 hybridized carbon peak confirm
Page 53 and 54: Reflectivity Figure 3.5. X-ray refl
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The AFM images of the patterned PNI
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3.3.7 Fluorescence studies 3.3.7.1
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FRAP images and corresponding fluor
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advancing water contact angles for
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ushes was in the range of 446-450 n
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of interest to inside, and so the e
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observed are rotational diffusion a
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38. D. Hall, J. Torkelson, Macromol
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energy-density battery applications
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4.1.3 Oligoethylene glycol containi
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was used to test the thickness chan
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The samples are sonicated in aceton
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ToF SIMS characterization of POEGA
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0 = f where fp and fH2O are volume
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T gp temperature over solvent glass
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elative humidity), 25% relative hum
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(a) 15s 30s 60s 120s Figure 4.8. FR
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of 2.5 nm (as measured by AFM on a
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4.3.5.2 Diffusion of Prodan in the
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(a) (b) (c) (d) 500 nm 0 25 nm 0 0
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Another possibility is that the nak
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ToF SIMS, and the physical properti
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26. L. Lavielle, in Polymer Surface
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presence of a flat wall, and (4) mo
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ultrasonication. After two centrifu
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silicone solution holder (GRACE Bio
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5.3.3 Temperature-response of the c
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more frequently within its “cage
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From the trajectories presented in
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described by Equation 5.5. And then
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3. D. Rosenbaum, P. C. Zamora, C. F
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XPS and FTIR confirmed the chemical
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developed in this thesis have intri
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