Poly(methacrylamide-co-acrylic acid) hydrogels for gastrointestinal delivery of theophylline. I. Swelling characterization

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作者：
Dubey, Seema [1 ]
Bajpai, S.K. [1 ]
机构：
[1] Polymer Research Laboratory, Department of Chemistry, Government Model Science College (Autonomous), Jabalpur (M.P.), 482001, India
来源：
Journal of Applied Polymer Science | 2006年 / 101卷 / 05期
关键词：
pH sensitive copolymeric hydrogels have been synthesized by free-radical polymerization of methacrylamide and acrylic acid in aqueous medium. The gels were characterized by FTIR spectroscopy; thermogravimetric analysis; and swelling measurements. To determine the suitability of theses hydrogels for gastrointestinal oral delivery of model drug theophylline; their swelling behavior was investigated as a function of pH and various structural parameters such as the average molecular weight between crosslinks; crosslink density; and mesh size were calculated. Likewise initial; average and late time diffusion coefficients were also evaluated in simulating intestinal fluid of pH 6.8 at 37°C. The gel underwent sharp volume phase transition in the vicinity of pH 5.8. The mesh sizes of the hydrogel were between 8.4 and 9.2 Å in the collapsed state (pH range 1-2; SGF) and between 514 and 524 A in the swollen state (pH range 7-8; SIF). The experimental data was found to fit well to Beren-Hopfenberg equation thus suggesting that later part of swelling was chain relaxation controlled. The activation energy; as determined from Arrhenius equation was found to be 13.71 kj mol-1. Likewise; enthalpy of mixing was also evaluated using Gibbs-Helmholtz equation. © 2006 Wiley Periodicals; Inc;
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页码：2995 / 3008
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