Date of Award

5-2008

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Advisor

William J. DeSisto

Second Committee Member

Douglas Ruthven

Third Committee Member

Carl P. Tripp

Abstract

This thesis presents the results of a study of synthesis and characterization of novel hybrid organic-inorganic membranes. A macroporous alumina support was dipcoated into a sol containing a silica precursor and micelles. A silica matrix polymerized around micelles consisting of self organized non-ionic block copolymers which serve to template the pores of the silica. Removal of the micelle templates leaves an organized pore structure. Gas permeation experiments show the permeance of He, N2, Ar, CO2, CH4 and C3H8 on the order of magnitude of 10-7mol/m2 ⋅ s ⋅ Pα. The permeance and permporosimetry data show that after three to four consecutive coatings of mesoporous silica the membrane has a median pore radius of 2.7nm with a small percentage of pores larger than 15nm. Once the mesoporous silica membranes were fully characterized, they were functionalized with octadecyldimethylchlorosilane and trimethylchlorosilane resulting in hybrid membranes consisting of an inorganic silica matrix with branches of hydrocarbon chains in the pores. Diffuse reflectance infrared transmission (DRIFT) was used to ensure all of the surface hydroxyls where reacted. A comparison of the permeance of a membrane before and after attachment of the trimethylsilane to the surface shows a small permeance reduction after modification, due to the reduction of free space in the pore. A larger permeance reduction was measured for octadecydimethylsilane attachment to the pore structure. Permeance comparisons of the membranes functionalized with octadecyldimethylsilane show a change to a complete Knudsen regime, indicating a healing of defects, but a stronger dependence on temperature than a typical Knudsen regime membrane.

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