Polyelectrolyte Poly(N‐vinyl‐2‐pyrrolidone‐co‐itaconic acid) hydrogels (P(VP/IA)) with varying compositions were prepared from ternary VP/IA/water mixtures. The effect of external stimuli such as pH of the solution, temperature, substrate concentration of solution, and storage stability on the invertase adsorption capacity of P(VP/IA) hydrogels was investigated. The adsorption capacity of the hydrogels was found to increase from 4.4 to 18.4 mg invertase/g dry gel with increasing amount of IA in the gel system, while P(VP) gel adsorbed only 3.1 mg invertase/g dry gel. Kinetic parameters were calculated as Michaelis‐Menten constant Km = 20.6 mmol L–1 and maximum velocity Vmax = 6.44×10–5 mol dm–3 min–1 for free enzyme and in the range of Km = 26.4–41.1 mmol L–1 and Vmax = 6.35·10–5–6.66·10–5 mol dm–3 min–1, depending on the amount of IA in the hydrogel. Enzyme activities were found to increase from 59.0% to 72.0% with increasing amount of IA in the gel system and retained their activities for one month storage. The enzyme activities, after storage for one month at 4°C, were found to be 21.0% and 59.0–74.0% of the initial activity values for free and adsorbed enzyme, respectively. The optimal pH values for free and adsorbed enzymes were determined as 4.56 and 5.00, respectively. The optimum temperature for free and adsorbed enzymes was 55°C. Adsorption studies have shown that not only the gel composition but also the stimuli, temperature and pH of the solution play an important role on the invertase adsorption capacity of poly(VP/IA) hydrogels.

Poly(N‐vinyl 2‐pyrrolidone‐g‐citric acid) (PVP‐g‐CA) hydrogels with varying compositions were prepared from ternary mixtures of N‐vinyl 2‐pyrrolidone–citric acid–water by using 60Co γ‐rays. The effect of gel composition on the uranyl ions adsorption capacity of PVP‐g‐CA hydrogels was investigated. Uranyl adsorption capacity of these hydrogels were found to be in the range of 18–144 mg [UO 2+2]/g dry gel from the aqueous solution of uranyl nitrate and 22–156 mg [UO 2+2]/g dry gel from the aqueous solution of uranyl acetate, depending on the content of citric acid in the hydrogel, while poly(N‐vinyl 2‐pyrrolidone) hydrogel did not sorb any uranyl ion. The swelling of PVP‐g‐CA hydrogel containing 2.7 mol % CA was observed in water (1620%), in uranyl acetate solution (1450%) and in uranyl nitrate solution (1360%), as compared to 700% swelling of pure PVP hydrogels. The diffusion coefficients were varied from 12.57 up to 4.04 • 10−8 m2 s−1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1037–1043, 2000

ABSTRACT:The ␥-ray-induced copolymerization of vinyl triethoxy silane (VTES) with methyl methacrylate (MMA) was developed to be used in the simultaneous preservation and consolidation of archeological artifacts. A detailed analysis was performed to characterize the copolymerization reaction and conversion. The copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), and elemental analysis techniques. The mol fraction of VTES units in the synthesized copolymers were determined by elemental analysis of silicone pertaining to VTES segments using inductive coupling plasma spectroscopy (ICP). The effect of VTES mol fraction in the initial feed and the irradiation dose (6.5, 8.5, 10.0 kGy) on the yield of copolymerization was investigated. The yield of the copolymerization was found to decrease with increasing the VTES mol fraction in the monomer feed, and to increase with increasing the irradiation dose at each monomer composition. However, using the data obtained from the ICP measurements, the mol fraction of the VTES units in synthesized copolymers was determined to increase with increasing the VTES concentration in the initial monomer feed.