Properties of Chemically Cross-Linked Methylcellulose Gels

Abstract

Methylcellulose (MC) is widely used as a rheology modifier because, upon heating in aqueous solutions, MC reversibly self-assembles into ∼7–10 nm radius fibrils that percolate into a network, resulting in physical gelation. Here, we have chemically cross-linked both MC solutions at room temperature and MC physical fibril gels at 80 °C and compared the swelling and shear modulus properties of both materials. To achieve this, hydroxyl moieties on MC (Mw ≈ 150 kDa) were substituted with allyl groups, with a degree of substitution of about one pendant carbon–carbon double bond per nine anhydroglucose repeat units. The allyl groups undergo cross-linking in the presence of a photoinitiator and UV light. Chemically cross-linking MC fibril gels (“xfib-MC”) at 80 °C results in opaque solid materials and locks in the fibril structure, which persists even on cooling back to room temperature. From small-angle X-ray scattering analysis, the fibril radius is larger at room temperature ∼20 nm and decreases to ∼10 nm at ...