Properties of chemically crosslinked methylcellulose gels

Methylcellulose (MC) is used in an impressively wide variety of commercial products due to its ability to reversibly form fibrous networks upon heating. To investigate the effect of crosslinking on these materials, we have prepared two types of gels and compared their thermodynamic and elastic properties. First, crosslinked methylcellulose gels were prepared at room temperature using a thiol-ene click reaction. Allyl methylcellulose was crosslinked with dithiol poly(ethylene glycol) (M = 1500 g/mol) and allowed to swell to equilibrium as a function of temperature and strand length. Upon heating, instead of forming fibrous networks, crosslinked methylcellulose gels experience volume change. By measuring the polymer volume fraction and modulus of gels in equilibrium we identify the thermodynamic parameters that drive the gel volume change using a modified Flory-Rehner theory. Second, crosslinked methylcellulose fiber gels were prepared by crosslinking allyl methylcellulose solutions at 80 °C, after the full conversion of chains to fibrils. The swelling and thermodynamic properties of crosslinked chain gels and crosslinked fiber gels will be compared and discussed.