Abstract: Novel pH-sensitive polyglycerol hydrogels were designed and synthesized through the reaction of epichlorohydrin (ECH) with L-lactic acid (LLA) in the presence of sodium hydroxide (NaOH), and cetyltrimethylammonium bromide (CTAB) as a phase transfer catalyst (PTC) at room temperature, followed by hydrolysis, polymerization and cross-linking reactions. The resultant gel was characterized by carbon nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy, and it was found that incorporated LLA was bound to polyglycerol network as a pendant acidic substituent by the hydroxyl group of LLA (PGL gel). The PGL hydrogels with different LLA contents and equilibrium swelling ratios were prepared by changing the feed ratios of materials. The results determined by chemical titration showed that under the applied conditions the efficiency of introducing the carboxyl group into polyglycerol network was ca. 86% and the amount of LLA in the hydrogel reached to ca. 17 wt%. The swelling behavior of the hydrogels in different mediums was investigated, and the results showed that the hydrogels are pH-, and ionic strength-responsive. The hydrogels also have the reversible swelling/deswelling properties and exhibites modulated release of drug in response to the environment pH.

Key words: polyglycerol, L-lactic acid, hydrogels, pH-sensitive