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1.8. Catalyst. The catalyst is the most important component of ATRP because it determines the equilibrium constant between the active and dormant species. This equilibrium determines the polymerization rate and an equilibrium constant too small may inhibit or slow the polymerization while an equilibrium constant too large leads to a high distribution of chain lengths. [19] There are several requirements for the metal catalyst: 1. there needs to be two accessible oxidation states that are separated by one electron 2. the metal center needs to have a reasonable affinity for halogens 3. the coordination sphere of the metal needs to be expandable when its oxidized so to be able to accommodate the halogen 4. a strong ligand complexation. The most studied catalysts are those that polymerizations involving copper, which has shown the most versatility, showing successful polymerizations regardless of the monomer. 1.9. Solvent. Toluene,1,4-dioxane, xylene, anisole, DMSO 1.10. Poly(N-isopropylacrylamide). Poly(N-isopropylacrylamide) (variously abbreviated PNIPA, PNIPAAm, PNIPAA or PNIPAm) is a temperature-responsive polymer that was first synthesized in the 1950s. [20] It forms a three-dimensional hydrogel when crosslinked with N,N’-methylene-bis-acrylamide (MBAm) or N,N’-cystamine-bis-acrylamide (CBAm). When heated in water above 33°C, it undergoes a reversible lower critical solution temperature phase transition from a swollen hydrated state to a shrunken dehydrated state, losing about 90% of its mass. In dilute solution, it undergoes a corresponding coil-to-globule transition at similar conditions) [21] . Since PNIPAm expels its liquid contents at a temperature 18
near that of the human body, PNIPAm has been investigated by many researchers for possible applications in controlled drug delivery. [22-24] 1.11. Aim of the Experiment. The surface initiated ATRP of NIPA onto a silicon wafer and Au-deposited mica has been reported, but in many cases, the authors do not give molecular weight and polydispersity data. 25- 32 Judging by our additional examinations, many cases of surface-initiated ATRP of NIPA on a flattened surface such as silicon, the thickness of the grafted PNIPA membranes cannot be well- controlled according to the living polymerization system. Moreover, the densities of the grafted PNIPA membranes are in diluted or semi-diluted regions, and as a result, the intermolecular interaction between grafted polymers is not significant due to the poor choice of the polymerization systems. But Well defined polymer brushes are used for making materials with surfaces that have been designed on the nanoscale. Well controlled PNIPA is also used for cell sheet engineering (figure 1-5). For the preparation of cell sheets, the surface must be hydrophobic around the cultivation temperature, i.e., 37 o C, and hydrophilic below the LCST. As a result, the cell sheets cultured at 37 o C that are useful for tissue engineering are safely isolated from the membranes below the LCST. So aim of this study is to synthesis PNIPA grafted membrane on silicon surface by ATRP and precisely controlled their chain length and graft density, examination of the effect of chain-length and graft density on the surface characteristics, check the change of the wettability at hydration state in the polymer and finally check the stimuli responsive behavior of PNIPA grafted membrane on silicon surface. ATRP is attractive because it can provide good control over predictable polymer molecular weight, PDI and end groups as long as the conditions are suitable. 19
Page 1 and 2: Facile Approach to Synthesize Stimu
Page 3 and 4: Acknowlwdgement This dissertation w
Page 5 and 6: Chapter 1. Table of Contents 1-1. I
Page 7 and 8: 4.2.2.4.General Procedure for Synth
Page 9 and 10: Chapter 1 General Introduction 9
Page 11 and 12: The growth in industrial applicatio
Page 13 and 14: 1.3. Grafting methods. Most of thes
Page 15 and 16: 1.5. Components of ATRP. There are
Page 17: Figure 1-4:Mechanism of the Atomic
Page 21 and 22: References and notes. 1. Plastiquar
Page 23 and 24: Chapter 2 Characteristics of High-D
Page 25 and 26: 2.1. INTRODUCTION. Atom transfer ra
Page 27 and 28: . Cl Si H + OH 9 + 10-undecen-1-ol
Page 29 and 30: Figure 2-3 (b): NMR spectrum of Pro
Page 31 and 32: Figure 2-4: Schematic procedure for
Page 33 and 34: 3000 2000 Wavenumber/cm -1 1000 Fig
Page 35 and 36: Figure 2-7: (a) First order kinetic
Page 37 and 38: free polymers. We performed polymer
Page 39 and 40: Figure 2-9: Contact angles of air b
Page 41 and 42: 2.4. CONCLUSION. A detailed explana
Page 43 and 44: Chapter 3 Dominant influence of the
Page 45 and 46: 3.1. Introduction. Temperature resp
Page 47 and 48: and FT-IR analyses, were used as re
Page 49 and 50: azide Figure 3-2: FT-IR spectra of
Page 51 and 52: Figure 3-3: 1 H NMR spectrum of aci
Page 53 and 54: 3.3. Results and discussion. ATRP t
Page 55 and 56: temperature. 28 Electro-negativity
Page 57 and 58: Contact Angle (degree) 141 138 135
Page 59 and 60: Figure 3-7 shows equilibrium contac
Page 61 and 62: References and Notes. (1) S.A. Prok
Page 63 and 64: Chapter 4 Precise Synthesis and Phy
Page 65 and 66: 4.1. Introduction. Stimuli-sensitiv
Page 67 and 68: 4.2. Experimental Section. 4.2.1. M
Page 69 and 70:
hr and at room temperature for 12 h
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chromatography with hexane/ethyl ac
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4.2.2.4.General Procedure for Synth
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Figure 4-4. Schematic illustration
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Figure 4-5. FT-IR spectra of dried
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are necessary to achieve maximum bo
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Figure 4-1-1: XPS data of (a) C 1S
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The successful deposition of CPU-dM
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where f i is the area fraction of c
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The ATRP in this condition provides
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Figure 4-1-5: AFM image of densely
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Figure 4-1-8. Graft density of PNIP
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Figure 4-1-7. Plots of Ld/Lc,w vers
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Figure 4-1-9. Thickness of high den
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Figure 4-7. a) FT-IR spectra and b)
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Figure 4-1-10 (c): Area ratio for t
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Area ratio 0.4 0.35 0.3 0.25 0.2 0.
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(a) Figure 4-1-11 . Contact angle o
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(c) Figure 4-1-11. Contact angle of
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The temperature dependence for the
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4.4 Conclusions. High-density therm
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(16) Osada, Y.; Gong, J. P. Prog. P
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2006, 22 (9), 4259-4266. L Macromol
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(76) The Young equation, cos θ = (
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Abstract. High-density polymer brus
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previously grafted chain prevents l
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5.3.1. Synthesis procedure of the A
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5.4.1. Fourier Transform Infrared S
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5.5. Result and discussion. Scheme
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graft density (chain/nm 2 ) 0.8 0.6
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Thickness (nm) 50 40 30 20 10 0 0 1
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a nm 1μm b nm 1μm Figure 5-5. The
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5.6. Conclusion. ATRP of PNIPA in D
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(17) Huang, E.; Rockford, L.; Russe
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Publications. 1. Suzuki H., Huda M.
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