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

Rok publikacji: 2017
Wydawca:  Soft Matter, 2017,13, 4047-4056
Zobacz publikację
M. Chintapalli, K. Timachova, K. R. Olson, M. Banaszak, J. L. Thelen, S. J. Mecham, J. M. DeSimone, N. P. Balsara
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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