Melt-state polymer chain dimensions as a function of temperature

Ramanan Krishnamoorti, William W. Graessley, Achim Zirkel, Dieter Richter, Nikolaos Hadjichristidis, Lewis J. Fetters*, David J. Lohse

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

The unperturbed chain dimensions (〈R20/M) of cis/trans-1,4-polyisoprene, a near-atactic poly(methyl methacrylate), and atactic polyolefins were measured as a function of temperature in the melt state via small-angle neutron scattering (SANS). The polyolefinic materials were derived from polydienes or polystyrene via hydrogenation or deuteration and represent structures not encountered commercially. The parent polymers were prepared via lithium-based anionic polymerizations in cyclohexane with, in some cases, a polymer microstructure modifier present. The polyolefins retained the near-monodisperse molecular weight distributions exhibited by the precursor materials. The melt SANS-based chain dimension data allowed the evaluation of the temperature coefficients [dln 〈R20/dT(κ)] for these polymers. The evaluated polymers obeyed the packing length (p)-based expressions of the plateau modulus, GNo = kT/nt2p3 (MPa), and the entanglement molecular weight, Me = ρNant2p3 (g mol-1), where nt denotes the number (∼21) of entanglement strands in a cube with the dimensions of the reptation tube diameter (dt) and Ρ is the chain density. The product nt2p3 is the displaced volume (Ve) of an entanglement that is also expressible as pdt2 or kT/GNo.

Original languageEnglish (US)
Pages (from-to)1768-1776
Number of pages9
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume40
Issue number16
DOIs
StatePublished - Aug 15 2002

Keywords

  • Entanglement molecular weights
  • Neutron scattering
  • Packing length
  • Plateau moduli
  • Rheology
  • Unperturbed chain dimensions

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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