Title page for ETD etd-11172010-062305


Type of Document Dissertation
Author Cureton, LaShonda Tanika
Author's Email Address clashon@vt.edu
URN etd-11172010-062305
Title Modified Poly(arylene ether sulfone) Compositions and their Segmented Block Copolymers
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Turner, S. Richard Committee Chair
Davis, Richey M. Committee Member
Long, Timothy E. Committee Member
McGrath, James E. Committee Member
Moore, Robert B. Committee Member
Keywords
  • random copolymer
  • polydimethylsiloxane
  • poly(arylene ether sulfone)
  • segmented block copolymer
  • microscopy
  • tensile properties
Date of Defense 2010-11-04
Availability unrestricted
Abstract
A series of modified poly(arylene ether sulfone)s (PAES) incorporating hexafluoroisopropylidene units and co-monomers, bisphenol A (BA), 4,4’-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH), were synthesized using a polyetherification synthetic method. These thermoplastic PAES were copolymerized with the elastomer, polydimethylsiloxane (PDMS) to form segmented block copolymers. The segmented block copolymers with diverse PAES structures were studied and investigated for their thermal, tensile, and morphological properties. These multiphase segmented block copolymer materials have the potential to impart useful combinations of optical transparency, thermal stability, and enhanced tensile properties, and enhanced environmentally resistant properties for various high impact, high performance applications.

In Chapter 2, hexafluoroisopropylidene bisphenol PAES (BAF PAES) segmented block copolymers containing various volume fraction of PDMS were synthesized. Analysis of the segmented block copolymer films by atomic force microscopy (AFM) and small angle x-ray scattering (SAXS) show the materials are microphase separated. Further analysis of the BAF PAES segmented block copolymers by transmission electron microscopy (TEM) show an increased morphological order with decreasing PDMS content, with lamellar morphologies formed at higher or near equal PAES and PDMS volume fractions. Comparatively, the morphological properties of the BAF PAES segmented block copolymers are considerably different from the isopropylidene bisphenol PAES (BA PAES) segmented block copolymer of similar PDMS volume percents.

In this document, segmented block copolymers prepared from BA PAES incorporating 4,4’-dihydroxyterphenyl (DHTP) and triptycene-1,4-hydroquinone (TPDH) co-monomers were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR). Films of these materials, prepared from THF solution, were tested for thermal and tensile properties. These materials provide higher thermal stabilities over the BA PAES segmented block copolymers with thermal degradation ranging 380–435 °C under nitrogen at 5%-wt. loss. Similarly, the PAES incorporating co-monomers gave higher Tg (200 °C) than the BA PAES (183 °C) synthesized in our labs. Previously synthesized BA PAES segmented block copolymers showed plastic to elastomeric tensile properties upon increasing addition of PDMS content. These new segmented block copolymers, incorporating co-monomers, provided comparable results with the reported BA PAES segmented block copolymers analogues.

The last research topic discussed in this dissertation covers the preparation of blends from 5% of segmented block copolymer and 95% of Udel®, donated by Solvay Advanced Polymers. The preparation of blends from the segmented block copolymers containing random copolymers led to materials with higher moduli than Udel® as observed by dynamic mechanical analysis (DMA). Tensile measurements performed by Instron also show the blends have high moduli, though no changes in the tensile elongation comparable to Udel®.

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