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Author ORCID Identifier
Campus-Only Access for Five (5) Years
Doctor of Philosophy (PhD)
Polymer Science and Engineering
Year Degree Awarded
Month Degree Awarded
Thomas P. Russell
Polymer and Organic Materials | Polymer Science
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.
Yu, Duk Man, "SOLID-STATE TRANSFORMATIONS OF BLOCK COPOLYMERS: SIGNIFICANTLY INCREASING Χ AND IMPARTING FUNCTIONALITY" (2019). Doctoral Dissertations. 1785.
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