Microgels composed of poly(ethylene imine) and carboxymethoxycoumarin: pH-dependent and photodependent integrity

초록

We developed novel microgels by taking advantage of electrostatic interactions between poly(ethylene imine) (PEI) and carboxymethoxycoumarin (CMC) and hydrophobic interactions among CMCs. CMC was obtained by the hydrolysis of 7-ethoxycarbonyl methoxycoumarin, which was derivatized from 7-hydroxycoumarin. The microgels were prepared by the mixture of PEI solutions (pH 5.0 and 7.5) with CMC solutions of the same pHs so that the molar ratio of PEI to CMC was 1:23. The size of the microgels prepared at pH 7.5 (a few nanometers) was much smaller than that of the microgels prepared at pH 5.0 (a few micrometers); this was possibly due to the more electrostatic interaction of the PEIs and CMCs at higher pH values. The microgels disintegrated when the pH of medium (e.g., pH 7.5) changed to strongly acidic (e.g., pH 3.0) and strongly alkaline (e.g., pH 9.0). Under acidic conditions, PEI hardly interacted with CMC because of the lack of ionization. Under alkaline conditions, the PEI was electrically neutralized, so no electrostatic repulsion developed, and this led to collapsed microgels. In addition, CMCs contained in the microgels were readily photodimerized as much as free CMCs. The microgels developed in this study could be used as drug vehicles that respond to pH changes and photoirradiation. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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