Title

Influence of electrostatic interactions on the morphology of ionomeric polymers and blends

Date of Award

2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Robert B. Moore

Advisor Department

Polymers and High Performance Materials

Abstract

The overall goal of this research project was to examine the influence of ionic interactions in a variety of polymeric systems, including: (1) ionomer blends, (2) oriented ionomers, (3) ionomeric sheet polarizers and (4) dye-doped ionomer films. It has been shown that the nature of the Nafion counterion has a strong effect on the blend compatibility and morphology in polymer blends with poly(vinylidene fluoride) (PVDF). Blends of Na + -form Nafion with PVDF were shown to be highly phase-separated due to the strong electrostatic interactions within the ionic aggregates. A greater degree of blend compatibility in the TBA+ -form Nafion/PVDF blend also caused a change in the crystal morphology of the PVDF blend component from the α form to the β or γ crystal forms. The reason for this change in the crystalline structure of PVDF was attributed to a decrease in the crystallization rate of the PVDF component in blends with the TBA + -form Nafion ionomer relative to the Na+ -form Nafion blends. The second area of study in this research project involved the orientation and relaxation characteristics of uniaxially drawn, alkylammonium neutralized Nafion membranes. SAXS analysis showed that when these samples were drawn, an anisotropic scattering pattern developed, suggesting that the orientation process caused an increase in the spatial correlations of the ionic domains in the direction perpendicular to the draw direction. The temperature at which these samples relaxed corresponded to the temperature of the cluster Tg's observed from the DMA analysis. The effect of ionic moieties on the incorporation and orientation of a dichroic dye in a polyethylene ionomer was also examined for potential use as thin film, sheet polarizers. An increase in the orientation of the dye molecules in the ionomer was attributed to the greater degree of interaction between the polar dye and the ionic functional groups along the backbone which effectively binds the dye molecules to the ionomer chain through a tethering effect. The last area of this research project involved the incorporation of azo dyes into several poly(methyl methacrylate-co-methacrylic acid) copolymers with a variety of comonomer contents for potential applications as optical storage devices. It was shown that as the amount of methacrylic acid was increased in the copolymer, the rate of trans [arrow right] cis isomerization was slightly decreased. (Abstract shortened by UMI.)