POROGENS IN THE PREPARATION OF MICROPOROUS HYDROGELS BASED ON POLY(ETHYLENE OXIDES)

To enable the synthesis of hydrogels containing microporosity, a famil y of pore generating additives (porogens) were synthesized from poly(e thylene glycols) (PEGs) with different molecular weights using naphthy l acetic acid. The products formed were characterized by UV-vis, diffe rential scanning calorimetry and solution nuclear magnetic resonance t echniques. Subsequently, poly(ethylene oxide)urethane hydrogels were s ynthesized incorporating the above mentioned PEG porogens to modify th e structure of the hydrogel. These highly water soluble PEG porogens w ere inert and extracted out in water. The hydrogels obtained exhibited significant increase in the equilibrium water uptake. This was attrib uted to the formation of a microporous structure in the hydrogel. It w as also evidenced by the observed increase in the diffusion coefficien ts of the drugs proxyphylline and vitamin B-12 through this hydrogel. The proportional increase was greater for the higher molecular weight vitamin B-12 than for the proxyphylline. These results may be useful i n developing porous hydrogels for controlled release technology.