Thermodynamics of Highly Interacting Blend PCHMA/dPS by TOF-SANS


Sharratt, William N ORCID: 0000-0003-2148-8423, Aoki, Yutaka, Pont, Sebastian, Seddon, Dale, Dewhurst, Charles, Porcar, Lionel, Clarke, Nigel and Cabral, Joao T (2023) Thermodynamics of Highly Interacting Blend PCHMA/dPS by TOF-SANS. MACROMOLECULES, 56 (14). pp. 5619-5627.

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Abstract

We investigate the thermodynamics of a highly interacting blend of poly(cyclohexyl methacrylate)/deuterated poly(styrene) (PCHMA/dPS) with small-angle neutron scattering (SANS). This system is experimentally challenging due to the proximity of the blend phase boundary (>200 °C) and degradation temperatures. To achieve the large wavenumber <i>q</i>-range and flux required for kinetic experiments, we employ a SANS diffractometer in time-of-flight (TOF) mode at a reactor source and ancillary microscopy, calorimetry, and thermal gravimetric analysis. Isothermal SANS data are well described by random-phase approximation (RPA), yielding the second derivative of the free energy of mixing (<i>G</i>″), the effective interaction (χ̅) parameter, and extrapolated spinodal temperatures. Instead of the Cahn-Hilliard-Cook (CHC) framework, temperature (<i>T</i>)-jump experiments within the one-phase region are found to be well described by the RPA at all temperatures away from the glass transition temperature, providing effectively near-equilibrium results. We employ CHC theory to estimate the blend mobility and <i>G</i>″(<i>T</i>) conditions where such an approximation holds. TOF-SANS is then used to precisely resolve <i>G</i>″(<i>T</i>) and χ̅(<i>T</i>) during <i>T</i>-jumps in intervals of a few seconds and overall timescales of a few minutes. PCHMA/dPS emerges as a highly interacting partially miscible blend, with a steep dependence of <i>G</i>″(<i>T</i>) [mol/cm<sup>3</sup>] = -0.00228 + 1.1821/<i>T</i> [K], which we benchmark against previously reported highly interacting lower critical solution temperature (LCST) polymer blends.

Item Type: Article
Divisions: Faculty of Science and Engineering > School of Engineering
Depositing User: Symplectic Admin
Date Deposited: 25 Jul 2023 11:24
Last Modified: 01 Aug 2023 21:45
DOI: 10.1021/acs.macromol.3c00511
Open Access URL: https://pubs.acs.org/doi/10.1021/acs.macromol.3c00...
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3171886
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