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Arrested and temporarily arrested states in a protein–polymer mixture studied by USAXS and VSANS

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Abstract

We investigate the transition of the phase separation kinetics from a complete to an arrested liquid–liquid phase separation (LLPS) in mixtures of bovine γ-globulin with polyethylene glycol (PEG). The solutions feature LLPS with upper critical solution temperature phase behavior. At higher PEG concentrations or low temperatures, non-equilibrium, gel-like states are found. The kinetics is followed during off-critical quenches by ultra-small angle X-ray scattering (USAXS) and very-small angle neutron scattering (VSANS). For shallow quenches a kinetics consistent with classical spinodal decomposition is found, with the characteristic length (ξ) growing with time as ξt1/3. For deep quenches, ξ grows only very slowly with a growth exponent smaller than 0.05 during the observation time, indicating an arrested phase separation. For intermediate quench depths, a novel growth kinetics featuring a three-stage coarsening is observed, with an initial classical coarsening, a subsequent slowdown of the growth, and a later resumption of coarsening approaching again ξt1/3. Samples featuring the three-stage coarsening undergo a temporarily arrested state. We hypothesize that, while intermittent coarsening and collapse might contribute to the temporary nature of the arrested state, migration-coalescence of the minority liquid phase through the majority glassy phase may be the main mechanism underlying this kinetics, which is also consistent with earlier simulation results.

Graphical abstract: Arrested and temporarily arrested states in a protein–polymer mixture studied by USAXS and VSANS

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Publication details

The article was received on 19 Jul 2017, accepted on 05 Nov 2017 and first published on 06 Nov 2017


Article type: Paper
DOI: 10.1039/C7SM01434A
Citation: Soft Matter, 2017, Advance Article
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    Arrested and temporarily arrested states in a protein–polymer mixture studied by USAXS and VSANS

    S. Da Vela, C. Exner, R. S. Schäufele, J. Möller, Z. Fu, F. Zhang and F. Schreiber, Soft Matter, 2017, Advance Article , DOI: 10.1039/C7SM01434A

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