(216w) Biopolymer Particles for Stabilization of Pickering Foams

At the beginning of the 20th century, Spencer Pickering and Walter Ramsden determined that particles with appropriate wettability can impart greater stability onto foams and emulsions than molecular surfactant stabilizers.^[1,2]Our goal is to synthesize particles from biologically derived materials – lignin and modified cellulose - and to tune synthesis parameters for the generation of particles with improved foam stabilizing attributes. Materials such as cellulose and lignin are sustainable materials which can find application in foods, personal hygiene products, as well as porous materials.

The increased stability imparted onto aqueous foams by the biopolymer particles studied is largely due to their anisotropic shape, which results in jammed particle layers in the lamella of the foam. A hydrophobically modified cellulose, HP-55, is used as a model biopolymer system since it had previously been shown to stabilize foams very well and has also been used as the stabilizing matrix for the creation of magnetically responsive foams.^[3,4]We elucidate the mechanism behind foam stabilization from anisotropic biopolymer particles by studying the morphology of the thin films formed at varying particle concentrations for systems containing HP-55. We are currently evaluating the effect of particle concentration as well the bulk environment on the morphology of HP-55 foam films. When comparing results from the thin film studies to the bulk foam system, we found that a critical concentration of particles is necessary for the formation of a thick particle shell around all the bubbles in the foam to create superstable foams. Another biopolymer of interest is lignin, which can form particles through the same water-based antisolvent method used for the generation of HP-55 particles. Lignin is the second most abundant biopolymer found in nature with many potential uses as a stabilizer, encapsulation agent, and as a component in composite materials. We used Kraft lignin to generate particles for the stabilization of biodegradable, environmentally-friendly foams. We characterized the effect of a water-based antisolvent precipitation on the surface charge and structure of KL particles. This process was found to increase the effective volume of the KL particles by ~30 times, suggesting that reforming enhances the ability of the particles to sterically stabilize foams and emulsions.

References: [1] Pickering, S. U., J. Chem. Soc. 1907, 91, 2001-2021; [2] Ramsden, W., Proc. R. Soc. London 1903, 72, 156-164; [3] Wege, H. A. et al., Langmuir 2008, 24, 9245-9253; [4] Lam, S. et al., J. Am. Chem. Soc. 2011, 133, 13856–13859.