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Author ORCID Identifier

https://orcid.org/0000-0003-0682-0870

Document Type

Campus-Only Access for Five (5) Years

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Thomas P. Russell

Subject Categories

Polymer and Organic Materials | Polymer Science

Abstract

To achieve small-scale features in semiconductors, storage devices, or porous membranes, self-assembly of block copolymers (BCPs) have been considered as a promising bottom-up platform, since BCPs offer a tremendous potential to push feature sizes into the single nanometer scale with highly-ordered periodic dot or line patterns. In this dissertation, a high χ−low N system, where χ is the Flory−Huggins segmental interaction parameter and N is the degree of polymerization, was developed for a self-assembled BCP morphology with a sub-10 nm period through an acid-catalyzed hydrolysis of symmetric poly(solketal methacrylate-b-styrene) (PSM-b-PS) copolymers. The acid-catalyzed hydrolysis transforms PSM-b-PS, having two hydrophobic blocks, into poly(glycerol monomethacrylate-b-styrene) (PGM-b-PS), having one hydrophilic and one hydrophobic block. This simple transformation significantly enhances χ such that a phase-mixed PSM-b-PS can be transformed in the solid-state into a microphase separated BCP without the use of any additives. Small-angle X-ray scattering (SAXS) measurements as functions of the degree of polymerization and PSM conversion were performed to examine the lamellar microdomain features. Using a mean-field correlation-hole analysis of the scattering, χ for PSM and PS was determined before and after the conversion of PSM to PGM. With the large increase in χ, even smallest synthesized PGM-b-PS copolymers underwent microphase separation, allowing us to achieve a center-to-center lamellar microdomain spacing of 5.4 nm. We also investigated the two-step chemical transformation of symmetric poly(styrene-b-solketal acrylate) (PS-b-PSA) as another responsive high χ BCP. Through an acid-catalyzed hydrolysis, the PSA block is converted into a poly(glycerol acrylate) (PGA), which subsequently can be hydrolyzed to a poly(acrylic acid) (PAA) block. With this two-step conversion, the responsive PSA block becomes increasingly polar as the reaction proceeds, improving the strength of segmental interactions. As a result, lamellar and cylindrical microdomain spacings of 7.4 nm and 6.9 nm were achieved after conversion to PS-b-PGA and PS-b-PAA, respectively, demonstrating that the size scale of the microdomains was reduced to the sub-10 nm level as well. Consequently, it is evident that PSM-b-PS and PS-b-PSA copolymers have a high potential for advanced nano-patterning as a template with a single nanometer feature size through a simple chemical transformation.

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

Available for download on Tuesday, September 01, 2020

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