Interfacial colloidal crystallization via tunable hydrogel depletants

Gregory E. Fernandes, Daniel J. Beltran-Villegas, Michael A. Bevan

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

We demonstrate an approach using temperature-dependent hydrogel depletants to thermoreversibly tune colloidal attraction and interfacial colloidal crystallization. Total internal reflection and video microscopy are used to measure temperature-dependent depletion potentials between ∼2 μm silica colloids and surfaces as mediated by ∼0.2 μm poly-N-isopropylacrylamide (PNIPAM) hydrogel particles. Measured depletion potentials are modeled using the Asakura-Oosawa theory while treating PNIPAM depletants as swellable hard spheres. Monte Carlo simulations using the measured potentials predict reversible, quasi-2D crystallization and melting at ∼27°C in quantitative agreement with video microscopy images of measured microstructures (i.e., radial distribution functions) over the temperature range of interest (20-29°C). Additional measurements of short-time self-diffusivities display excellent agreement with predicted diffusivities by considering multibody hydrodynamic interactions and using a swellable hard sphere model for the PNIPAM solution viscosity. Our findings demonstrate the ability to quantitatively measure, model, and manipulate kT-scale depletion attraction and phase behavior as a means of formally engineering interfacial colloidal crystallization.

Original languageEnglish
Pages (from-to)10776-10785
Number of pages10
JournalLangmuir
Volume24
Issue number19
DOIs
StatePublished - Oct 7 2008

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