Date of Award

Summer 6-2014

Embargo Period

8-31-2017

Degree Type

Dissertation (CMU Access Only)

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Krzysztof Matyjaszewski

Abstract

This thesis describes the design and use of nanofillers (NFs) synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP). The history of polymer/inorganic (hybrid) nanocomposites (NCs), the development and fundamentals of SI-ATRP are discussed in the introductory chapter. Chapters II and III present the major challenges in SI-ATRP, including the surface confinement effect that influences the polymerization kinetics and unavoidable termination reactions that limit the molecular weight of polymers tethered on surfaces. Chapter II discusses the experiments that demonstrate the surface confinement effects which were found to be a minor contributor to controlled chain growth in normal SI-ATRP, with one exception, when one attempts to polymerize sterically bulky and hydrophilic monomers. Chapter III discusses ways to suppress termination reactions that contribute to molecular weight limitations by carrying out the reactions under high-pressure, high-dilution, or/and at high-temperature. In addition to extend the fundamental understanding and improvements of SI-ATRP, Chapters IV and V discuss the use of NFs to create novel nanostructured functional materials. Chapter IV focuses on the preparation of traditional filler-matrix composites. Mechanically and thermally stable films with silica nanoparticle (SiO2) filler loadings up to 70 wt% were achieved by introducing enthalpy interactions to improve the dispersibility of SiO2 in a selected matrix. Chapter V presents approaches that allow preparation of a procesesable self-assembled film of hybrid NCs that do not require blending with a host matrix. This class of material was created by NF self-assembly and interparticle brush entanglement which provided uniform NF dispersion in a monolayer film with zero aggregation, as observed by transmission electron microscopy. Chapter VI, VII, and VIII further expands the scope of materials designed in Chapter IV and V. Chapter VI specifically studies the structure-properties relationship of the particle-brush composites and the confirmation that controls the polymer conformation and interface strength which are the keys for various enhanced properties. Chapter VII discusses the effects of thermal self-initiation of styrene (S) on the properties of particle-brush materials. Chapter VIII discusses the use of particle-brush hybrid particles to synthesize porous nanocarbons.

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