Molecular Simulations Group - publications

Monte Carlo structure factors and selected physical properties of symmetric copolymer melts at low temperatures

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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