TY - JOUR
T1 - Heterogeneous drying and nonmonotonic contact angle dynamics in concentrated film-forming latex drops
AU - Kumar, Subhalakshmi
AU - Katz, Joshua S.
AU - Schroeder, Charles M.
N1 - Funding Information:
This work was supported by the The Dow Chemical Company through the University Partnership Initiative Program, Grant No. 226772AA. We thank John Halligan for synthesizing the latex particles. We are grateful to Jim Bohling, Ant Van Dyk, Lin Wang, and Keith Harris for useful discussions and the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign for instrumentation.
Publisher Copyright:
© 2017 American Physical Society.
PY - 2017/11
Y1 - 2017/11
N2 - The dynamic drying process is studied in spatially heterogeneous film-forming latex suspensions across a wide range of dispersion concentrations using optical imaging techniques. Systematic changes in latex suspension concentration are found to affect lateral drying heterogeneity and surface topology. A nonmonotonic decay in contact angle is observed at the edges of drying droplets by continuously monitoring evaporation dynamics, which is quantitatively characterized by the peak strain and peak formation time. An analytical model is developed to explain the nonmonotonic contact-angle decay by considering a transient dilational stress imposed on a viscoelastic solid model for the particle network. Importantly, the latex concentration dependence of this phenomenon provides evidence for a smooth transition from fluid-line pinning to fluid-line recession behavior during drying, leading to ringlike to volcanolike deposition patterns, respectively. Using experimental data for drying heterogeneity, we quantitatively explore the influence of Marangoni flow and capillary pressure on drying behavior. Moreover, our results show that latex concentration and particle packing can also be strategically used to reduce contact-line friction, thereby affecting fluid-line recession. Taken together, these results show that studying latex suspensions in seemingly simple droplet geometries provides insight into the emergent spatially heterogeneous viscoelastic properties during film formation.
AB - The dynamic drying process is studied in spatially heterogeneous film-forming latex suspensions across a wide range of dispersion concentrations using optical imaging techniques. Systematic changes in latex suspension concentration are found to affect lateral drying heterogeneity and surface topology. A nonmonotonic decay in contact angle is observed at the edges of drying droplets by continuously monitoring evaporation dynamics, which is quantitatively characterized by the peak strain and peak formation time. An analytical model is developed to explain the nonmonotonic contact-angle decay by considering a transient dilational stress imposed on a viscoelastic solid model for the particle network. Importantly, the latex concentration dependence of this phenomenon provides evidence for a smooth transition from fluid-line pinning to fluid-line recession behavior during drying, leading to ringlike to volcanolike deposition patterns, respectively. Using experimental data for drying heterogeneity, we quantitatively explore the influence of Marangoni flow and capillary pressure on drying behavior. Moreover, our results show that latex concentration and particle packing can also be strategically used to reduce contact-line friction, thereby affecting fluid-line recession. Taken together, these results show that studying latex suspensions in seemingly simple droplet geometries provides insight into the emergent spatially heterogeneous viscoelastic properties during film formation.
UR - http://www.scopus.com/inward/record.url?scp=85038425486&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85038425486&partnerID=8YFLogxK
U2 - 10.1103/PhysRevFluids.2.114304
DO - 10.1103/PhysRevFluids.2.114304
M3 - Article
AN - SCOPUS:85038425486
SN - 2469-990X
VL - 2
JO - Physical Review Fluids
JF - Physical Review Fluids
IS - 11
M1 - 114304
ER -