Methyl cellulose solutions and gels: fibril formation and gelation properties

Methyl cellulose (MC) is a semiflexible cellulose ether derivative with a wide range of industrial applications, owing to its water solubility at low temperatures and thermoreversible gelation upon heating. The gelation mechanism of aqueous MC solutions has been debated for many years. However, in 2010, gelation was discovered to be concurrent with fibril formation upon heating, whereby the MC polymer chains self-assemble into fibrils with a remarkably consistent mean diameter, largely independent of polymer concentration, molecular weight, and temperature of gelation. This discovery has shed important light on the gelation mechanism, and initiated studies that lead to more intriguing questions about the fibrils themselves. This review emphasizes various developments since the discovery of fibril formation, while highlighting unanswered questions that require further investigation.