Date of Award

Winter 2020

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

First Advisor

Andrew Peters

Abstract

Polymer-nanoparticle hybrids are nanomaterials in which the unique properties of the nanosized structures can be precisely tuned by choosing an appropriate combination of the polymer and the nanoparticle. However, nanoparticle dispersion in a polymer is challenging due to the aggregation tendency of nanoparticles. To improve nanoparticle dispersion and control the location of nanoparticles in block copolymer assemblies, the nanoparticle surface is modified with surface ligands compatible with the block copolymer. In this thesis, hydroxyl-terminated poly(styrene-b-methyl methacrylate) (PS-b-PMMA) was utilized to functionalize the nanoparticle surface, covalently anchoring the hydroxylterminated end of the polymer onto the silicon dioxide nanoparticles. The silicon dioxide nanoparticles were functionalized for their assembly into a microphase separated block copolymer, poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and the nanoparticles were directed within the block copolymer domains. The block copolymer was prepared on silicon substrates chemically modified by hydrogen fluoride (HF) passivation. Functionalized silicon dioxide nanoparticles were characterized by thermogravimetric analysis (TGA), while the location of the nanoparticles was determined by field emission scanning electron microscopy (FE-SEM).

The polymer nanocomposite nanostructure formed is known to depend sensitively on the interactions between the nanoparticles and the block copolymer. In order to verify the importance of functionalizing the nanoparticle surface with polymer ligands, particles that have not undergone any functionalization were incorporated in the block copolymer and we compared the level of dispersion and the sizes of the aggregates formed. The effect of the position of the hydroxyl-terminated end of the block copolymer was studied using block copolymer with the hydroxyl-terminated end attached to the PS block and copolymer with the hydroxyl-terminated end attached to the PMMA block. This thesis also describes the influence of particle loading fraction on the size and volume of aggregates formed, and the effect on the block copolymer morphology.

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