title: Vesicle--biopolymer gels: networks of surfactant vesicles connected by associating biopolymers.
abstract: The effect of adding an associating biopolymer to surfactant vesicles and micelles is studied using rheology and small-angle neutron scattering (SANS). The associating polymer is obtained by randomly tethering hydrophobic alkyl chains to the backbone of the polysaccharide, chitosan. Adding this polymer to surfactant vesicles results in a gel; that is, the sample transforms from a Newtonian liquid to an elastic solid having frequency-independent dynamic shear moduli. SANS shows that the vesicles remain intact within the gel. The results suggest a gel structure in which the vesicles are connected by polymer chains into a three-dimensional network. Vesicle-polymer binding is expected to occur via the insertion of polymer hydrophobes into the vesicle bilayer. Each vesicle thus acts as a multifunctional junction in the network structure. Significantly, gel formation does not occur with the native chitosan that has no hydrophobes. Moreover, adding the hydrophobically modified chitosan to a viscous sample containing wormlike micelles increases the viscosity further but does not give rise to a gel-like response. Thus, the formation of a robust gel network requires both the presence of hydrophobes on the polymer and vesicles in solution.
authors.affiliation: Department of Chemical Engineering, University of Maryland, College Park, MD 20742-2111, USA.
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: John P
authors.initials: JP
authors.lastname: Gustin
authors.forename: Tianhong
authors.initials: T
authors.lastname: Chen
authors.forename: Gregory F
authors.initials: GF
authors.lastname: Payne
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Raghavan