Self-diffusion of a polystyrene-polyisoprene block copolymer

Mark W. Hamersky, Matthew Tirrell, Timothy P. Lodge

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29 Scopus citations

Abstract

Forced Rayleigh scattering (FRS) has been used to measure the self-diffusion coefficient, D, of a lamellar-forming polystyrene-polyisoprene diblock copolymer (MPS = 1.0 × 104, MPI = 1.3 × 104) as a function of temperature. The measurements traverse the order-disorder transition (ODT), which occurs at 160°C. There is no obvious change in either D or the temperature dependence of D at the ODT, in agreement with measurements on several other systems. Electron microscopy confirms that the sample in the ordered state is quenched, with no long-range orientation of lamellae, and a typical grain size well below 1 μm. In contrast to previous measurements on a similar styrene-isoprene diblock, these FRS signals are well-described by single exponential decays; this may be largely attributed to differences in average grain size. The temperature dependence of D is modeled with several empirical expressions, based on the known monomeric friction factors for pure polystyrene and pure polyisoprene, but without quantitative success. These results underscore the need for a greater understanding of the composition and temperature dependences of local friction in polymer mixtures.

Original languageEnglish (US)
Pages (from-to)2899-2909
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume34
Issue number17
DOIs
StatePublished - Dec 1996

Keywords

  • Block copolymer
  • Diffusion
  • Forced Rayleigh scattering
  • Monomeric friction

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