Surface-Grafted Polymer and Copolymer Assemblies with Gradient in Molecular Weight and Composition
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Date
2005-12-29
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Abstract
The chief goal of this Ph.D. dissertation was to develop methodologies facilitating the formation of assemblies comprising grafted polymers on surfaces with gradually varying length (or, alternatively, molecular weight). Our additional goals accomplished include expansion of these methodologies to incorporate multiple monomer systems and block copolymer assemblies. Lastly we demonstrate the utility of these gradient assemblies to study some complex phenomena of scientific interest. Surface-grafted polymer gradients represent important tools in the combinatorial study of tethered polymer layers. This approach can lead to rapid screening of properties and development of new or more efficient technologies involving tethered polymer films. The areas/technologies of interest are cited throughout the work and span organic electronic materials, responsive surfaces, nonfouling coatings, drug delivery applications, and manipulation of matter on 'small scales' leading to developments in nanotechnology.
In Chapter 3, I describe procedures, methods, and several evolutions of a gradient chamber designed to create homopolymer gradient assemblies. Chapter 3 also includes studies using polymer gradients to understand polymer surface growth kinetics and an introduction to the concept of orthogonal gradient samples. I include, as supplemental information, my studies involving Atom Transfer Radical Polymerization (ATRP) simulations using a step time based Fortran program.
Chapter 4 introduces the concept of block-copolymer gradients and describes my progress and major accomplishments in achieving my goal of formation of tethered copolymer gradient assemblies. I also discuss several studies involving these tethered copolymers. I use a combinatorial approach to create 'step' multiblocks on one sample surface in order to study the efficiency and characteristics of growth of these multiblock layers. I describe how I was able to produce surface-grafted diblock copolymer gradients and how I was able to chemically modify these layers. A major portion of Chapter 4 is devoted to describing a study in which a tethered diblock copolymer gradient was subjected to two selective-solvent exposure procedures designed to collapse the top and bottom blocks, respectively. I was able to study, combinatorially, the formation of and characteristics of micellar and bicontinuous structures formed via these solvent exposure techniques. Clear AFM images, ellipsometric thickness, and wettability measurements made on this sample reveal a possible relationship between surface morphology and the rearrangement of the diblock surface. I also introduce a triangular triblock triple gradient, which I successfully created. Such gradients will yield a wealth of information when applied to the study of tethered triblock copolymers.
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Keywords
copolymer, polymer brush, gradient, ATRP
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Degree
PhD
Discipline
Chemical Engineering
