Controlling and characterising the deposits from polymer droplets containing microparticles and salt

Msambwa, Y., Shackleford, A.S.D., Ouali, F.F. ORCID: 0000-0002-6530-6786 and Fairhurst, D.J. ORCID: 0000-0001-5311-0762, 2016. Controlling and characterising the deposits from polymer droplets containing microparticles and salt. The European Physical Journal E, 39 (2), p. 21. ISSN 1292-8941

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It is very well known that as suspension droplets evaporate, a pinned contact line leads to strong outwards capillary flow resulting in a robust coffee ring-stain at the periphery of the droplet. Conversely tall pillars are deposited in the centre of the droplet when aqueous droplets of poly(ethylene oxide) evaporate following a boot-strapping process in which the contact line undergoes fast receding, driven by polymer precipitation. Here we map out the phase behaviour of a combined particle-polymer system, illustrating a range of final deposit shapes, from ring-stain to flat deposit to pillar. Deposit topologies are measured using profile images and stylus profilometery, and characterised using the skewness of the profile as a simple analytic method for quantifying the shapes: pillars produce positive skew, flat deposits have zero skew and ring-stains have a negative value. We also demonstrate that pillar formation can be disrupted using potassium sulphate salt solutions, which change the water from a good solvent to a thetapoint solvent, consequently reducing the size of the polymer coils. This inhibits polymer crystallisation, interfering with the bootstrap process and ultimately preventing pillars from forming. Again, the deposit shapes are quantified using the skew parameter.

Item Type: Journal article
Publication Title: The European Physical Journal E
Creators: Msambwa, Y., Shackleford, A.S.D., Ouali, F.F. and Fairhurst, D.J.
Publisher: Springer International Publishing AG
Date: February 2016
Volume: 39
Number: 2
ISSN: 1292-8941
Divisions: Schools > School of Science and Technology
Record created by: Jill Tomkinson
Date Added: 15 Mar 2016 11:08
Last Modified: 29 Sep 2021 08:11

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