DIELECTRIC SPECTROSCOPY INVESTIGATION OF ION-CONTAINING AND INTERMOLECULAR HYDROGEN-BONDED POLYMER SYSTEMS

Open Access
Author:
Atorngitjawat, Pornpen
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 22, 2007
Committee Members:
  • James Patrick Runt, Committee Chair
  • Qing Wang, Committee Member
  • Ronald Hedden, Committee Member
  • Janna Kay Maranas, Committee Member
Keywords:
  • dielectric relaxation spectroscopy
  • ion-containing polymers
  • hydrogen-bonded polymers
  • polymer dynamics
  • sulfonated PS ionomers
  • poly(2-vinylpyridine)-lithium perchlorate mixtures
Abstract:
Ion-containing and intermolecular hydrogen-bonded polymers are used widely in a variety of industrial and commercial applications, from food packaging to battery electrolytes to pharmaceuticals. Yet the dynamics of these polymers, which are both complex and important to the application, are poorly understood. This thesis provides the first systematic study of the dynamics of several ion-containing and intermolecular hydrogen-bonded polymers by broadband dielectric relaxation spectroscopy. The systems under consideration include sulfonated polystyrene (SPS) in acid (SPS-H) and neutralized forms, and mixtures of poly(2-vinylpyridine) (P2VPy) with lithium perchlorate (LiClO4) and low molecular weight phenolic molecules. Dynamic mechanical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering and wide-angle X-ray diffraction were employed in a complementary role. Multiple relaxations were generally observed at high temperatures. For SPS ionomers, the segmental process, Maxwell-Wagner-Sillars interfacial polarization, and electrode polarization were detected. Three relaxations were also found in spectra of SPS-H, attributed to the segmental process, hydrogen bond association/dissociation, and electrode polarization. Three dielectric relaxations above the segmental process were observed for P2VPy - LiClO4 mixtures: ion-mode relaxation, slow hindered segmental relaxation and electrode polarization. However, only electrode polarization was observed above the segmental relaxation for all P2VPy – small phenolic molecule mixtures, except P2VPy + 10 mol % 2,3,3,4,4,5-hexahydroxybenzophenone. This mixture exhibited an additional relaxation due to Maxwell-Wagner–Sillars interfacial polarization, arising from the existence of phase-separated complexes within the P2VPy matrix. Sub-Tg local relaxations were suppressed by ionic intermolecular interactions for SPS ionomers and P2VPy – LiClO4 mixtures. Intermolecular hydrogen bonding also suppressed the local relaxation in P2VPy – small phenolic molecule mixtures by decreasing the mobility of the pyridine-side groups. Both the concentration of small phenolic molecules and the number of hydroxyl groups per molecule played an important role in suppression of the local relaxation, which was significant for all mixtures where the small molecules contained more than one hydroxyl group per molecule.