MECHANICAL PROPERTIES OF HPMC/CATIONIC SURFACTANTS BASED HYDROGELS AND CRYOGELS

The combination of polysaccharides and surfactants in the concentrated
regime offers a unique opportunity to adjust rheological properties, which
in turn influences the stiffness of the resulting cryogels. This study focuses
on the rheological behavior of aqueous systems using hydroxypropyl
methylcellulose (HPMC) at 30 g/L, a cellulose ether, in conjunction with
cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium
chloride (CTAC), or cetylpyridinium chloride (CPC) at 20 x 10 -3 mol/L.
Oscillatory and rotational rheology analyses, performed at temperatures
ranging from – 5 o C to + 50 o C, indicated a maximum associated with the
crystallization of CTAB, and a minimum attributed to crystallization of the
water/HPMC/CTAB system (Fig. 1). Due to the crystallization of CTAB
upon cooling, the resulting cryogels were fragile. The resulting HPMC,
CPC/HPMC, and CTAC/HPMC cryogels presented compression modulus
values of 195 kPa, 291 kPa, and 339 kPa, respectively, indicating a direct
correlation with the G’ values (not shown) of the precursor hydrogels.