Abstract

The hypersonic sound speed and attenuation in a series of PPO polyurethane gels show a strong crosslink dependence in highly crosslinked samples. The temperature of maximum loss for the α-relaxation is raised from ∼370 K to ∼400 K in a highly crosslinked gel whilst the β-loss maximum is unaffected. This result indicates cooperative motion at the transition with a rearranging unit which appears to involve some 3 or 4 monomer units. The hypersonic properties were also found to depend upon the relative proportions of polymer and solvent in the gel. In the dry network hydrogen bonding between the urethane links and the interposed PPO dominates the dynamics. As the proportion of solvent increases, the effect of this hydrogen bonding is reduced, lowering the relaxation temperatures.

Original languageEnglish (US)
Pages (from-to)1884-1888
Number of pages5
JournalPolymer
Volume23
Issue number13
DOIs
StatePublished - Dec 1982

Keywords

  • Brillouin scattering
  • crosslinking
  • polymer gels
  • relaxation temperatures
  • relaxations
  • solvent concentration

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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