Development of Photochemical Surface Modification Technique

This thesis will investigate two main areas of surface modification research: I. Designing a photoactive monolayer with improved photo-grafting efficiency. II. Fabrication of NP-Films via phthalimide self-assembled monolayer on glass surfaces. Concluding the thesis, I will briefly describe an outreach research project in collaboration with my GK-12 fellowship team. In Chapter One, we will introduce nanotechnology and surface chemistry, with an emphasis on the use of monolayers for photochemical surface modification. The goal of this chapter is also to equip the reader with a comprehensive overview of common surface analytical techniques and a "how-to" analysis guide for thin films. Chapter Two delves into the fundamentals of SAMs and thin films - the behavior and orientation of adsorbates on surfaces, particularly at air-monolayer interfaces. We discuss the importance of studying the orientation of phthalimide-undecyl-thiol molecules on gold surfaces because the photo-reactivity (i.e. accessibility) of phthalimide terminal groups is dependent on its tilt angle, surface exposure, and packing density. One of the interesting observations includes the possibility that low packing density can potentially have higher photo-grafting efficiency. In Chapter Three, we address the challenge of applying nanoparticles to surfaces. We introduce a fairly well known photochemical surface modification technique to fabricate nanoparticle-films. By using a phthalimide self-assembled monolayer on a glass substrate, we photo-grafted organic nanoparticles to the surface and subsequently, produced a patterned NP-film. Using a photomask allows us to have spatial control and selection on NP-grafting. Lastly, Chapter Four is a brief introduction and overview of the outreach project, studying the heavy metal intake of oysters in the New York Harbor. As a GK-12 fellow, I was given the opportunity to start a research project for the high school students and contribute to the New York Harbor Oyster restoration efforts. The research is focused on detecting heavy metal concentrations in oyster tissue and shells

Shedding light on surfaces: using photons to transform and pattern material surfaces

The ultimate goal of surface modification is to quantitatively control surface properties by precise manipulation of surface chemical structure at the molecular level. Advances in the understanding of molecular design principles for soft matter surfaces can be combined with the available arsenal of interesting photochemical reactions to create an exciting paradigm for surface modification: the use of photons to both transform and pattern chemical functionality at soft matter surfaces. The success of the paradigm is predicated on the ability to design and synthesize "photochemical surface delivery vehicles," complex photoactive molecules that form stable surface monolayers and subsequently deliver photoactive moieties to the surface. Shedding light onto these smart, modified surfaces brings about a wide variety of precise photochemical reactions that are preprogrammed within the surface delivery vehicle. Surface chemical patterns are formed by exposure through a mask. Some photochemical surface transformation can be considered as "green" chemistry since only photons are required as reagents. In this review, we provide a brief tutorial on photochemistry fundamentals to illustrate the nature of possible photochemical surface reactions and discuss the principles of design for photochemical surface delivery vehicles. Applications of the paradigm drawn from a variety of fields emphasize the tremendous potential for photochemical surface transformation and patterning on both hard and soft substrates

Brush-First and ROMP-Out with Functional (Macro)monomers: Method Development, Structural Investigations, and Applications of an Expanded Brush-Arm Star Polymer Platform

The efficient synthesis of complex functional polymeric nanomaterials is often challenging. Ru-initiated ring-opening metathesis polymerization (ROMP) of multivalent macromonomers followed by cross-linking to form brush-arm star (BASP) polymers enables access to well-defined nanostructures with diverse functionality. This "brush-first" method leaves active Ru in the BASP microgel core, which could potentially be used in a subsequent "ROMP-out" (RO) step to introduce further modifications to the BASP structure via the addition of (macro)monomers. Here, we study this RO approach in depth. The efficiency of RO is assessed for a variety of BASP compositions using a combination of inductively coupled plasma mass spectrometry and gel permeation chromatography. To demonstrate the modularity of the RO process, arylboronic acid-functionalized BASPs were prepared; uptake of these RO-BASPs into hypersialylated cancer cells was enhanced relative to non-functionalized BASPs as determined by flow cytometry and fluorescence microscopy. In addition, the self-assembly of miktoarm BASPs prepared via brush-first and RO with different macromonomers is demonstrated. The combination of brush-first ROMP with RO provides a simple, modular strategy for access to a wide array of functional nanomaterials.National Institutes of Health (U.S.) (Grant (1R01CA220468–01)Rollins College (Winter Park, Fla.). Dean of the Faculty Office. Critchfield Research Grant (110000–46333)National Institutes of Health (U.S.). Post-doctoral Fellowship (1F32EB0231–01)National Institutes of Health (U.S.). Post-doctoral Fellowship (1F32GM123710–01)National Cancer Institute (U.S.) (Grant P30-CA14051)United States. Department of Energy. Office of Science (Contract DE-AC0206CH11357