Antipolyelectrolyte swelling of amphiphilic hydroxypropyl methylcellulose phthalate gels

Hydroxypropyl methylcellulose phthalate (HPMCP) gel was synthesized from the sodium form of HPMCP by radiation-induced crosslinking, followed by converting the phthalate groups on HPMCP to non-ionic forms via ion exchange. The non-ionic H-type gels showed different phase transition behaviors from Na-type gels. Significant antipolyelectrolyte swelling behavior of this amphiphilic gel was observed in various aqueous salt solutions, comparing with the polyelectrolyte swelling behavior of ionic HPMCP gels. After immersed in aqueous salt solution, the morphology of H-type HPMCP gels changed from heterogeneous structure to homogeneous structure. The swelling behavior of the gels in several circumstances with potential applications, for instance, solutions with different temperature and pH, surfactants, and typical drug models, were investigated. H-type HPMCP gels showed similar temperature and pH-stimuli responses to that of Na-type HPMCP gels. Furthermore, H-type HPMCP gels showed different swelling behaviors in cationic surfactant (C12TAB) and anionic surfactant (SDS) solutions. The investigations regarding drug embedment and release of this amphiphilic gel in inorganic salt and BSA solutions revealed that the embedment amount and release ratio were both high due to the improved swelling ability in saline condition of H-type HPMCP gels.