Molecular Simulations Group - publications

Incipient microphase separation in short chain perfluoropolyether-block-poly(ethylene oxide) copolymers

Chintapalli M.1,2, Timachova K.2,3, Olson K. R.4, Banaszak M.5, Thelen J. L.3,6, Mecham S. J.4, DeSimone J. M.4,7, Balsara N. P.2,3,6
  • 1Department of Materials Science and Engineering, University of California, Berkeley, USA
  • 2Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
  • 3Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California, USA
  • 4Department of Chemistry, University of North Carolina at Chapel Chill, Chapel Chill, North Carolina, USA
  • 5Faculty of Physics and NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, Poznan, Poland
  • 6Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
  • 7Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
Soft Matter, 13, pp.4047-4056, 2017
DOI: 10.1021/acs.macromol.6b02619
Abstract: Incipient microphase separation is observed by wide angle X-ray scattering (WAXS) in short chain multiblock copolymers consisting of perfluoropolyether (PFPE) and poly(ethylene oxide) (PEO) segments. Two PFPE–PEO block copolymers were studied; one with dihydroxyl end groups and one with dimethyl carbonate end groups. Despite having a low degree of polymerization (N ∼ 10), these materials exhibited significant scattering intensity, due to disordered concentration fluctuations between their PFPE-rich and PEO-rich domains. The disordered scattering intensity was fit to a model based on a multicomponent random phase approximation to determine the value of the interaction parameter, χ, and the radius of gyration, Rg. Over the temperature range 30–90 °C, the values of χ were determined to be very large (∼2–2.5), indicating a high degree of immiscibility between the PFPE and PEO blocks. In PFPE–PEO, due to the large electron density contrast between the fluorinated and non-fluorinated block and the high value of χ, disordered scattering was detected at intermediate scattering angles, (q ∼ 2 nm−1) for relatively small polymer chains. Our ability to detect concentration fluctuations was enabled by both a relatively large value of χ and significant scattering contrast.
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