Pillar formation in drying polymer droplets
- Event time: 1:00pm
- Event date: 24th June 2013
- Speaker: David Fairhurst (University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
Unlike the familiar "ring-stain" formed when droplets of spilt coffee are left to dry, liquids containing high molecular weight polymer molecules leave a range of other deposit patterns. We observe that aqueous solutions of the common polymer poly(ethylene oxide) (PEO) can dry to form a tall central pillar via a striking 'bootstrap' growth stage. To investigate this phenomenon, we varied several experimental factors including: atmospheric temperature, humidity and pressure; molecular weight and concentration of the polymer solution; volume and contact angle of the initial droplet. We find a region in parameter-space for which the pillars form, favouring fast drying conditions, high contact angle droplets, high concentration solutions and an intermediate range of molecular weights. We show that the pillar-forming region can be predicting by considering the relative effects of evaporation rate, polymer diffusion and solution viscosity.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..