MICROPOROUS, RESPONSIVE HYDROXYPROPYL CELLULOSE GELS - 1 - SYNTHESIS AND MICROSTRUCTURE

An effective technique for the synthesis of microporous gels is develo ped along with correlations between synthesis conditions and microstru cture. Such gels have substantially different properties than their no nporous analogues. Microporous hydroxypropyl cellulose (HPC) gels were prepared by heating aqueous HPC solutions above their lower critical solution temperatures (LCST's) while cross-linking the polymer with di vinyl sulfone. The effective porosity of the gel increased from 23 to 76% by decreasing HPC concentration from 22.6 to 9 wt%, as anticipated from the system phase diagram. The pore size range decreased from 0.5 -9.0 to 0.05-0.2 mu m by increasing reaction time before phase separat ion from 1.5 to 25 min, demonstrating that cross-linking in the homoge neous state limits the extent of phase separation possible. Gel morpho logy changed from open-celled to closed-celled by decreasing reaction time in the phase-separated state, which limits cross-linking in the p olymer-rich phase.