Defense Date


Document Type


Degree Name

Doctor of Philosophy



First Advisor

Maryanne M. Collinson, Ph.D.


Multicomponent synthetic chemical gradients containing amine (NH2) and carboxylic acid (COOH) groups have been prepared on the silanol (Si-OH) containing a base-layer substrate by the controlled-rate infusion (CRI) method. The spatial variation of weakly acidic COOH and basic NH2 functional groups on weakly acidic Si-OH surface was created in such a way that the two antagonist groups at high concentrations were in close proximity (aligned gradient) and were separated (opposed gradient). The difference in concentration of different components (acid, base, or silanol) along the length of aligned or opposed resulted in significantly different physicochemical properties (e.g., wettability and surface charge). X-ray photoelectron spectroscopy (XPS) data show that the degrees of protonation of NH2 groups are different in the aligned and the opposed gradient. The thickness measurements of the multicomponent aligned and opposed gradients revealed that ~2-3 monolayers of COOH were deposited on ~2-3 monolayers of NH2 in aligned and opposed fashion. The contact angle (CA) analysis revealed that the wetting behavior of the pH buffer 2 and 8 are opposite on the opposed gradient compared to the aligned gradient. Finally, the zeta potential (ζ) measurements showed that the isoelectric point (IEP) gradually increases from the bottom to the top of the aligned gradient, and the trend of IEP is reversed in the opposed gradient.


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