The Preparation of Functional Surfaces

• Main Author: Dirlam, Philip Thomas
• Format: Others
• Published: DigitalCommons@CalPoly 2011
• Subjects: Surface Energy; Nanoparticles; Organic Photovoltaics; Materials Chemistry; Organic Chemistry; Polymer Chemistry
• Online Access: https://digitalcommons.calpoly.edu/theses/588; https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1620&context=theses

Diels-Alder chemistry was utilized to manipulate the surface energy of glass substrates in reversible manner. Glass slides and capillaries were functionalized with hydrophobic dieneophiles resulting in a non-wetting surface. A retro Diels-Alder reaction facilitated by the thermal treatment of the surface’s function to cleave the hydrophobic dieneophile and resulted in the fabrication of a hydrophilic surface. Contact angle (CA) measurements were used as preliminary measurements for monitoring the changes in surface energy exhibited during the initial hydrophobic state (CA - 70±3°), after attachment of the dieneophile creating a hydrophobic state (CA - 101±9°) followed by reestablishment of the hydrophilic state (CA - 70±6°) upon cleavage of the Diels-Alder adduct. The treatments developed on flat glass surfaces were transferred to glass capillaries, with effective treatment confirmed by fluid column measurements. Effective flow gating was developed in the capillaries via patterning of the surface with hydrophilic/hydrophobic regions. Finally, attempts to create self-pressurizing capillaries were unsuccessful due to pronounced contact angle hysteresis for the hydrophobic surface treatment. Indium-tin oxide (ITO) substrates were functionalized with successive surface intiated atom transfer radical polymerization (SI-ATRP) and electropolymerization. A novel hybrid styrenic/thiophene monomer (ProDOT-Sty) was synthesized and employed in the polymerization events. This unique monomer and combination of polymerization methods allowed for the templation of electropolymerized poly(3,4-alkyleneoxythiophene) brushes by first creating a poly(styrene) backbone via SI-ATRP. An ITO electrode functionalized with poly(ProDOT-Sty) brushes grafted from the ITO surface via SI-ATRP was analyzed via cyclic voltammetry which clearly indicated the electropolymerization event beginning at approximately +0.7 V vs Fc/Fc+. Photo patterning of the phosphonic acid ATRP initiator immobilized on the ITO surface was undertaken in order to create a surface that would limit growth of the polymer species to a patterned area for facile film brush thickness characterization via atomic force microscopy (AFM) at a later time. This was accomplished via lithography with ultraviolet radiation (UV) and was confirmed via scanning electron microscopy (SEM). A nanohetero structure composed of platinum tipped cadmium selenide seeded, cadium sulfide nanorods (CdSe@CdS-Pt NRs). CdSe quantum dots (QDs) with variable sizes were prepared by adjusting reaction temperatures and times. CdS nanorods were then grown utilizing the CdSe QDs as seeds. Various lengths of the CdSe@CdS NRs were produced that ranged from ~25 nm to ~135 nm. Investigation of the influence of the various synthetic conditions of the nanorod synthesis led to the conclusion that the ratio of CdSe seeds to Cd and S precursors could be manipulated in order to influence the length to which the nanorods grew. Pt tips were attached to an end of the CdSe@CdS nanorods as photocatalytic hydrogen production sites. TEM was utilized to characterize the different types of nanoparticles at each stage of assembly.