Macromolecular dynamics in extensional flows: 2. The evolution of molecular strain

S. P. Carrington, J. P. Tatham, J. A. Odell, A. E. Sáez

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The opposed jets apparatus has been used to investigate the dynamics of the coil-stretch transition of polymer solutions in an idealized stagnation point extensional flow field. Flow simulations generated fluid strain profiles for different geometries. Assuming a molecular uncoiling model, true birefringence profiles have been converted to molecular strains for closely monodisperse, high molecular weight aPS under θ-conditions. This has enabled macromolecular deformation to be followed as a function of position and residence time. Non-linear hydrodynamic friction FENE dumb-bell simulations give qualitative agreement. Initially, molecular uncoiling is non-affine, consistent with changing hydrodynamic screening on extension. Deformation in a good solvent is more affine. Results are compared with PEO/water to investigate the effect of molecular parameters. The effective extensional viscosity has been ascertained by correction for the area of high molecular extension. The increase in extensional viscosity due to molecular stretching is substantial, of the order of the number of equivalent flexible units in the chain.

Original languageEnglish (US)
Pages (from-to)4595-4607
Number of pages13
JournalPolymer
Volume38
Issue number18
DOIs
StatePublished - Jan 1 1997
Externally publishedYes

Keywords

  • Extensional flow
  • Molecular stretching
  • Polymer solutions

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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