(194b) Structure and Properties of Aqueous Methylcellulose Solutions and Gels

Cellulose represents the most abundant polymer across the planet. This polysaccharide can be chemically modified to impart solubility in water resulting in a plethora of commercially important products ranging from construction materials to delivery vehicles for pharmaceuticals. Substitution of a fraction of the hydroxyl groups on the native glucose rings with alkoxy moieties leads to the versatile class of polymeric materials known as cellulose ethers. Methylcellulose is especially important owing to a lower critical solution temperature (LCST) when mixed with water leading to gelation at elevated temperatures at relatively low concentrations. This nontoxic, biodegradable material, generally recognized as safe by the US Food and Drug Administration, finds widespread uses in food applications and other commodity products. Only recently has the mechanism of gelation been elucidated, based on cryogenic transmission electron microscopy (cryo-TEM), small-angle neutron scattering (SANS), and dynamic mechanical spectroscopy (DMS) measurements. This lecture will describe the discovery of a remarkable fibrillar structure that accompanies gelation and the associated temperature dependent viscoelastic properties that make methylcellulose so useful.