Doctoral Dissertations

Date of Award

5-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Mark D. Dadmun

Committee Members

Gerd J. Duscher, Michael J. Sepaniak, Bin Zhao

Abstract

This dissertation presents work that expands our understanding of the relationship between structure, conformation, and topology and the properties and dynamics of polymeric materials. These studies focus on novel soft polystyrene and poly (butyl acrylate) nanoparticles and the polyradical poly (2,2,6,6-tetramethylpeperidinyloxy-4-yl methacrylate) (PTMA). Small angle neutron scattering characterizes the structural features of these polymeric materials. These studies provide integral insight that may be used to improve the performance of functional polymers by elucidating a molecular structure:property relationship.The first two projects of this dissertation examined the correlation of synthetic conditions to the structural characteristics of soft nanoparticles. The precise structure of the soft nanoparticles can be tailored by utilizing monomer-starved semi batch nanoemulsion polymerizations. The results correlate synthetic conditions to the individual soft nanoparticle size, internal structure, and overall topology. The correlation between the size and morphology of soft nanoparticles and solvent quality was also emphasized. This research provides a pathway to investigate the effect of nanoscale structural features of the nanoparticle on their individual properties and those of nanocomposites that contain these soft nanoparticles.The dynamics of all-polymer polystyrene nanocomposites through in-situ neutron scattering were also investigated. The addition of soft nanoparticles slowed the diffusion of the matrix polymer chains when the nanoparticles were larger than the polymer and had no significant effect when the nanoparticles were of similar size to the linear polymer. When the soft nanoparticles were smaller than the polymer chains, the nanoparticles enhanced the overall polymer diffusion.Finally, the effect of radical concentration on the conformation of PTMA was examined. In this study, the radical concentration was determined to influence the reorientation of polymer chains in order to increase the amount of radical interactions between neighboring chains. However, when the radical concentration was low, the oxidation of the stable radical groups results in a greater structural reorganization. This structure reorientation knowledge may be utilized to optimize redox active radical polymers for organic radical battery device applications.

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