Shear properties for thin films of star and linear polymer melts

Shinji Yamada, Gen Ichi Nakamura, Takayuki Amiya

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Shear properties for the thin film of star polyisoprene (PIP) melt were studied by use of the surface forces apparatus. Results were contrasted with those for films of linear PIP, whose average molecular weights Mw are well above or below the molecular entanglement weight of Me ≈ 6000. Analyses were made from rheological and tribological points of view. When a thin film of star PIP (having 22 arms and an arm molecular weight of around 5000, Mw ≈ 110 000) is compressed under normal load (pressure), the film "solidifies" and reaches a "glasslike" hard-wall state. Shear properties show tribological or "frictional" features, reflecting the glasslike phase. Comparison with the results of linear PIP indicates that star PIP molecules do not produce a chain entanglement effect because the arm chains are too short, although Mw is well above Me. The lack of chain entanglement reduces the viscosity forces and/or steric repulsion of polymers against thickness constraint; the phase of the film transits to a glasslike state and shear properties shift from bulk rheological to thin film tribological behavior. In addition, some tribological features for the star PIP film imply the star molecule's "soft adhesive sphere" contribution to the film properties.

Original languageEnglish
Pages (from-to)1693-1699
Number of pages7
JournalLangmuir
Volume17
Issue number5
DOIs
Publication statusPublished - 2001 Mar 6

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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