Doctoral Dissertations

Burak Metin

Keywords and Phrases

Poly(methyl acrylate) (PMA)

Abstract

"The effect of molecular mass on the segmental dynamics in poly(methyl acrylate) (PMA) was probed using solid-state deuterium NMR and modulated DSC (MDSC) through the glass-transition region. A heterogeneity in segmental dynamics for bulk PMA was observed for the lower molecular-mass samples through the glass-transition region. The heterogeneity was ascribed to the effect of chain ends which are more mobile than the chain middles. The lower molecular-mass samples had a higher fraction of chain ends and consequently were more mobile. The effect of molecular mass on the dynamics was also studied when PMA samples were adsorbed on silica surface. An increase in the glass-transition temperature (Tg) for the adsorbed samples, as compared to bulk, was observed due to surface-imposed restrictions. However, a molecular-mass region, in our case observed through the use of a 77 kDalton sample, was identified where the segmental mobility was the slowest on the surface. For PMA with molecular masses larger and smaller than in this region, the segments, on average, were less rigid on silica surface. The results on a strongly adsorbing silica surface were compared with those on a weakly adsorbing one. A weak molecular-mass dependence was found on the weakly adsorbing silica surface. The segmental dynamics was also probed for the chain ends of PMA polymers of similar Tg's. The higher mobility of the chain ends was apparent in the NMR spectra. With increased molecular mass, the mobility of the chain ends became more like the rest of the chains. All the NMR line shapes were fit to a series of simulated line shapes based on a jump model. The model, based on a program called MXQET, was designed for the jumps to occur on the vertices of a truncated icosahedron (soccer-ball shape). Correlation times extracted from the simulations were also found to be reasonable measures of the segmental dynamics"--Abstract, page iv.

Advisor(s)

Blum, Frank D.

Committee Member(s)

Chusuei, Charles C.
Collier, Harvest L.
Rosen, Stephen L.
Switzer, Jay A., 1950-

Department(s)

Chemistry

Degree Name

Ph. D. in Chemistry

Sponsor(s)

National Science Foundation (U.S.)
University of Missouri--Rolla

Comments

Financial support provided by the National Science Foundation Grant DMR-0412320

Publisher

University of Missouri--Rolla

Publication Date

Spring 2006

Journal article titles appearing in thesis/dissertation

  • Molecular mass and dynamics of poly(methyl acrylate) in the glass-transition region
  • Segmental dynamics in poly(methyl acrylate) on silica: molecular-mass effects
  • Segmental dynamics in poly(methyl acrylate) on strongly and weakly adsorbing silica surfaces
  • Segmental mobility of chain ends in poly(methyl acrylate)

Pagination

xii, 146 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2006 Burak Metin, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type

text

Language

English

Subject Headings

DeuteriumGlass transition temperatureNuclear magnetic resonanceSilicates

Thesis Number

T 9048

Print OCLC #

85793634

Electronic OCLC #

905905649

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