Effect on the Thermo?Gelation Process of the Degree and Molar Substitution of HPMC Polymer Hydrogels

Hydroxypropyl methylcellulose (HPMC) is a polymer made of cellulose backbone with etherified methoxy and hydroxypropyl substitutions that undergoes reversible inverse thermo-gelation upon heating. The follows two-step mechanism: first, phase separation occurs, then fibrils, formed in the polymer-rich phase, entangle to form three-dimensional gel network. This work aims at understanding influence degree (DS) molar substitution (MS) on process. DS number methyl groups, MS content per anhydroglucose unit. process here rheologically investigated for two HPMC samples, which have similar molecular weight but different DS: thermal ramps are coupled time sweep tests selected temperatures frequency experiments. Results show an important effect not only transition (beginning separation, beginning gelation) also kinetics phases