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Thermodynamics of model PaMSAN/dPMMA blend: a combined study by SANS, ellipsometry and locally correlated lattice (LCL) theory

White, Ronald P., Aoki, Yutaka, Higgins, Julia S., Keddie, Joseph L., Lipson, Jane E. G. and Cabral, Joao T. (2020) Thermodynamics of model PaMSAN/dPMMA blend: a combined study by SANS, ellipsometry and locally correlated lattice (LCL) theory Macromolecules.

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We combine experiment and theory to elucidate how small, local, structural changes can impact miscibility in polymer blends. Small-angle neutron scattering (SANS) experiments yield both the phase boundaries and the temperature dependence of the second derivative of the free energy of mixing. We demonstrate here, for the first time, that a fundamental characterization of pure component properties can be achieved through ellipsometry measurements on films of pure polymers (thickness ∼200 nm) to provide key data on the volume (or thickness)–temperature relationships; this development is significant given the scarcity of precise pressure–volume–temperature (PVT) data on pure polymers and blends. The experimental measurements allow us to undertake a detailed thermodynamic analysis of mixing using the locally correlated lattice (LCL) theory, which has been shown to be effective in rationalizing blend miscibility in terms of the pure component properties. We focus here on polymer blends of poly(α-methyl styrene-co-acrylonitrile) (PαMSAN) with deuterated poly(methyl methacrylate) (dPMMA), which differ in the degree of tacticity in the dPMMA component (atactic or syndiotactic), leading to an increase in miscibility for the latter. By combining LCL analysis of pure and mixed systems, we are able to connect tacticity changes to shifts in local nonbonded interactions, in free volume, and in thermal expansion coefficients, which in turn impact the thermodynamic compatibility of the blend components.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
White, Ronald P.
Aoki, Yutaka
Higgins, Julia S.
Keddie, Joseph
Lipson, Jane E. G.
Cabral, Joao T.
Date : 7 August 2020
Funders : National Science Foundation
DOI : 10.1021/acs.macromol.0c00706
Grant Title : National Science Foundation
Copyright Disclaimer : Copyright © 2020 American Chemical Society
Uncontrolled Keywords : Thickness; Thin films; Ellipsometry; Mixtures; Polymers
Additional Information : Embargo OK Metadata OK Awaiting version published in print.
Depositing User : James Marshall
Date Deposited : 24 Jul 2020 09:31
Last Modified : 10 Aug 2020 09:45

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