Semi-interpenetrating Polymer Network Superporous Hydrogels Based on Poly(3-Sulfopropyl Acrylate, Potassium Salt) and Poly(Vinyl Alcohol): Synthesis and Characterization

Semi-interpenetrating polymer network (semi-IPN) superporous hydrogels (SPHs) based on poly(3-sulfopropyl acrylate, potassium salt) (PSPA) and linear polymers were synthesized using poly(ethylene glycol) diacrylate (PEGDA) or N,N′-methylenebisacrylamide (BIS) as a crosslinker. The swelling ratio of SPHs was determined by measuring the weight of absorbed water; and the mechanical strength of swollen SPHs was evaluated using texture analyzer. Taguchi orthogonal experimental design [L₉(3⁴)] was used to evaluate the influence of four factors, consisting of the ratios of 3-sulfopropyl acrylate (SPA) to PEGDA, to initiator, and to acrylic acid (AAc), and acidification of PSPA-SPHs, with each containing three levels on the swelling ratio and mechanical strength of semi-IPN PSPA-SPHs. Analysis of variance (ANOVA) of the experimental design results was carried out using a SAS program. The structure of SPHs was examined using a scanning electron microscope (SEM). Among the polymers evaluated, poly(vinyl alcohol) (PVA) was the best linear polymer to improve the mechanical strength of swollen SPHs. ANOVA indicated that the ratio of SPA to PEGDA and to an initiator, as well as acidification had significant effects on the swelling ratios of PSPA-SPHs. The ratio of SPA to AAc and acidification had significant effects on the mechanical strength, which deceased with increased swelling ratio and time. The optimized semi-IPN PSPA-SPH containing 5% w/w PVA had a swelling ratio 20 times greater within minutes and then up to 40 times. The mechanical strength was over 200 g/cm² for a fully swollen gel in a pH 1.2 HCl medium. The optimal PSPA-SPH has swelling and mechanical properties suitable for development of gastro retentive drug delivery systems.