Synthesis, Characterization, and Gas Permeation Properties

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General Introduction cellulose to decipher the impact of polar substituents on the structural characteristics and hence the gas permeation parameters of the polymeric membranes. The attenuated FFV of the polymer matrices has been described to be at the helm of the decrement in the gas diffusion and solubility and consequently the decreased gas permeability of the membranes. However, the increase in CO2 permselectivity was not so evident and has been explicated by the author to be due to the unavailability of the polar groups on the peripheries to interact with CO2. As discussed above, spherical pendants are acknowledged to endow the polymers with enhanced local mobility; therefore a blend of polar and spherical substituents was envisioned to enhance permeability without loss in CO2 permselectivity. The interpolation of moderately polar carbamoyl groups with spherical t-butyl periphery was accomplished to bring in the improved gas permeability which was much more pronounced for the carbamates of cellulose acetate while no significant decrease in CO2 permselectivity of polymer membranes has been ascribed to the retained solubility selectivity. The intricate features of synthetic strategies and mechanistic aspects of cellulosic membranes explored in the present study are anticipated to lead us to new frontiers of potential applications of this renewable energy resource. Outline of the Thesis The present dissertation delineates the synthesis of novel functional cellulose ethers/esters, their characterization and investigation of various properties, and is comprised of five chapters. A variety of functional substituents have been appended to the backbone of different organosoluble cellulosics, i.e., ethyl cellulose, cellulose acetate, and hydroxypropyl cellulose while the core synthetic strategy was to exploit the residual hydroxy protons for the sake of derivatization. The incorporated moieties encompass various silyl, perfluoroacyl, dendryl, carbamoyl, and aminoalkanoyl groups, and the nature of the substituents was revealed to be of considerable significance in determining the solubility and thermal characteristics of 17
General Introduction the derivatized polymers. Moreover, the role of functional appendages on the fabricability of free-standing membranes and in tailoring the gas permeation characteristics has been elucidated in detail. Chapter 1 describes the synthesis of silyl ethers of ethyl cellulose (R = Me3Si, 2a; Et3Si, 2b; Me2-i-PrSi, 2c; Me2-t-BuSi, 2d; Me2-n-OctSi, 2e; Me2PhSi, 2f) and the effect of the incorporation of silyl substituents on the solubility, thermal stability, and gas permeation parameters of the starting polymer/ethyl cellulose. Silylation of ethyl cellulose (DSEt, 2.69) was accomplished with halosilanes of diversified chemical nature (alkyl and aryl) and various chain lengths. The substitution of hydroxy groups with nonpolar bulky silyl moieties accompanied the enhanced solubility in relatively nonpolar solvents without any significant decrease in thermal stability. The gas permeability of all of the silylated derivatives was higher than that of ethyl cellulose and followed a decline with increasing size/bulk of the silyl pendants (2a > 2b ≈ 2c > 2d > 2e > 2f > 1) whereas 2a–c were located above the upper bound for the CO2/N2 gas pair. The enhanced gas permeability was elucidated to ensue from the increment in the gas diffusion coefficients because of the increased FFV of the polymer membranes. H/EtO R OEt R Si = Chapter 2 reveals another contribution in the synthetic arena of novel R O O OEt/H + R R Si Cl R cellulose derivatives demonstrating the quantitative esterification of ethyl cellulose (DSEt, 2.69) with perfluoroalkanoyl 2d substituents of 2e various chain lengths and partial 2f 18 in THF Imidazole, r.t., 24 h R 3Si/EtO 1 n 2 OEt Si Si Si 2a 2b 2c Si Si Si O O OEt/SiR 3 n
Page 1 and 2: Synthesis, Characterization, and Ga
Page 3 and 4: Table of Contents General Introduct
Page 5 and 6: General Introduction cellulose deri
Page 7 and 8: General Introduction biogenetically
Page 9 and 10: General Introduction chemistry offe
Page 11 and 12: General Introduction solution-diffu
Page 13 and 14: General Introduction A simplified t
Page 15 and 16: General Introduction been observed
Page 17 and 18: polymers. 41,46 General Introductio
Page 19: General Introduction Keeping in vie
Page 23 and 24: General Introduction strategy (G1-a
Page 25 and 26: General Introduction In conclusion,
Page 27 and 28: General Introduction 5. (a) Kobayas
Page 29 and 30: General Introduction 15. (a) Goetma
Page 31 and 32: General Introduction American Chemi
Page 33 and 34: General Introduction Macromolecules
Page 35 and 36: Silylation of Ethyl Cellulose Intro
Page 37 and 38: Silylation of Ethyl Cellulose milli
Page 39 and 40: Silylation of Ethyl Cellulose chlor
Page 41 and 42: Silylation of Ethyl Cellulose Resul
Page 43 and 44: Silylation of Ethyl Cellulose Solub
Page 45 and 46: Silylation of Ethyl Cellulose 1.034
Page 47 and 48: Silylation of Ethyl Cellulose poly(
Page 49 and 50: Silylation of Ethyl Cellulose the r
Page 51 and 52: Silylation of Ethyl Cellulose D.; Y
Page 53 and 54: Chapter 2 51 Chapter 2 Synthesis, C
Page 55 and 56: 53 Chapter 2 are few and far betwee
Page 57 and 58: 55 Chapter 2 constant volume/variab
Page 59 and 60: 57 Chapter 2 Membrane Density. Memb
Page 61 and 62: 59 Chapter 2 IR spectrum of 1 (Figu
Page 63 and 64: 61 Chapter 2 1,3-bis(trifluoromethy
Page 65 and 66: 63 Chapter 2 The increase in the po
Page 67 and 68: 65 Chapter 2 other fluorinated poly
Page 69 and 70: 67 Chapter 2 of the gas permeabilit
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69 Chapter 2 Gas Diffusivity and So
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71 Chapter 2 mobility of the perflu
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73 Chapter 2 1325-1329. (b) Hamza,
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Chapter 3 75 Chapter 3 Synthesis an
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77 Chapter 3 cost, and above all ap
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79 Chapter 3 molecular weights (Mn
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81 Chapter 3 1.99-2.07 (m, 2H, (CH3
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83 Chapter 3 25 °C, ppm): 11.9, 13
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85 Chapter 3 38.1, 44.7, 46.8, 47.9
Page 89 and 90:
87 Chapter 3 CH2CH2C(=O)O), 2.50-4.
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89 Chapter 3 1091, 1053, 853, 806,
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91 Chapter 3 dendrons (G1-a-ІІ-G1
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93 Chapter 3 (DMAP) as a base, as s
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Figure 3. FTIR spectra of 1, 2c, an
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97 Chapter 3 (partly soluble) and 3
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99 Chapter 3 increased polarity of
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101 Chapter 3 that of 1, and approx
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103 Chapter 3 derivatization per th
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105 Chapter 3 (2a-c) were in the or
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107 Chapter 3 2709-2719. (b) Schenn
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109 Chapter 3 17. van Krevelen, D.
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Chapter 4 111 Chapter 4 Synthesis,
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113 Chapter 4 Since, no significant
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115 Chapter 4 Materials. Ethyl cell
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DStotal = DSEt + DSCarb (for 1a and
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119 Chapter 4 Figure 2. 1 H NMR spe
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121 Chapter 4 ruling out the possib
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123 Chapter 4 t-butyl moiety. A str
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125 Chapter 4 reported to lead to t
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127 Chapter 4 Table 4. Gas Permeabi
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129 Chapter 4 augmentation in eithe
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131 Chapter 4 indicate the signific
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133 Chapter 4 M.-R. J. Appl. Polym.
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Chapter 5 135 Chapter5 Synthesis an
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137 Chapter5 acid- and peptide-cont
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139 Chapter5 Specific rotations ([
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141 Chapter5 1.66 (brs, 1.1H, NHCH(
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143 Chapter5 as shown in Scheme 1,
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145 Chapter5 in Table 1. The molecu
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147 Chapter5 almost same pattern of
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Conclusions Table 3. Thermal Proper
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151 Chapter5 W.; Jing, X. J. Polym.
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Chapter 5 Synthesis and Properties
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Acknowledgments While submitting th
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Synthesis, Characterization, and Ga
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Synthesis, Characterization, and Gas Permeation Properties

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