Rheological Characterization of the Gel Point: A New Interpretation

René Muller, Eric Gérard, Pascal Dugand, Paul Rempp*, Yves Gnanou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

135 Scopus citations

Abstract

Winter and Chambon have recently shown that the gel point can be precisely identified in a crosslinking process from rheological measurements on the reaction medium. The cross-linking reaction of poly(ethylene oxide) (PEO), carrying at both chain ends hydroxyl functions, with various pluriisocyanates was chosen to check the validity of this new method. The experimental setup included Fourier transform infrared (FTIR) spectroscopy to follow the conversion of the isocyanate functions with time and a rheometer to investigate the mechanical response of the reaction medium to oscillatory solicitations at various stages of the reaction. In stoichiometric systems at a given conversion, the storage modulus G′ and the loss modulus G″ become congruent and proportional to ω1/2 over the entire frequency range. Simultaneously, the extent of reaction reaches the critical value pc predicted by branching theory. This excellent agreement substantiates Winter’s method and confirms its validity. This investigation has been extended to nonstoichiometric systems. When the end-standing hydroxyl functions of PEO are in excess, the rheological behavior observed at the gel point is quite different, and it was attempted to account for the phenomena observed.

Original languageEnglish (US)
Pages (from-to)1321-1326
Number of pages6
JournalMacromolecules
Volume24
Issue number6
DOIs
StatePublished - Nov 1 1991
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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