title: Stable Aqueous Foams from Cellulose Nanocrystals and Methyl Cellulose.
abstract: The addition of cellulose nanocrystals (CNC) greatly enhanced the properties of methylcellulose (MC) stabilized aqueous foams. CNC addition decreased air bubble size, initial foam densities and drainage rates. Mixtures of 2 wt % CNC + 0.5 wt % MC gave the lowest density foams. This composition sits near the onset of nematic phase formation and also near the overlap concentration of methylcellulose. More than 94% of the added CNC particles remained in the foam phase, not leaving with the draining water. We propose that the nanoscale CNC particles bind to the larger MC coils both in solution and with MC at the air/water interface, forming weak gels that stabilize air bubbles. Wet CNC-MC foams were sufficiently robust to withstand high temperature (70 °C for 6 h) polymerization of water-soluble monomers giving macroporous CNC composite hydrogels based on acrylamide (AM), 2-hydroxyethyl methacrylate (HEMA), or polyethylene glycol diacrylate (PEGDA). At high temperatures, the MC was present as a fibrillar gel phase reinforced by CNC particles, explaining the very high foam stability. Finally, our CNC-MC foams are based on commercially available forms of CNC and MC, already approved for many applications. This is a "shovel-ready" technology.
authors.affiliation: Department of Chemical Engineering, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Department of Chemical Engineering, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Xu
authors.affiliation: Department of Chemical Engineering, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
authors.forename: Emily D
authors.initials: ED
authors.lastname: Cranston
authors.affiliation: Department of Chemical Engineering, McMaster University , 1280 Main Street West, Hamilton, Ontario L8S 4L7, Canada.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Pelton
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry*; D008747:Methylcellulose / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D058105:Polymerization; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D005782:Gels; D020100:Hydrogels; D014867:Water; D002482:Cellulose; D008747:Methylcellulose