A pH/temperature and degradable-responsive hydrogel (PSMEA) was prepared from chitosan (CS), N-acryloylglycine methyl ester (NAGME), N-acryloylglycine ethyl ester (NAGEE), acrylic acid (AA), and N-methylenebisacrylamide (NMBA). The swelling properties of PSMEA were systematically investigated at different temperatures, pH, and CS contents. It was found that the PSMEA demonstrated obvious pH and temperature-responsive natures. The caffeine-release behaviors showed that only 42.9% caffeine was released from PSEMA in pH 2.1 phosphate buffer solution (PBS) after 360 min, whereas more than 71.5% caffeine was gradually diffused into pH 7.4 PBS over the same time interval. In addition, the caffeine release was much higher at 37.0°C than that at 14.0°C in PBS medium. The apparent degradability of PSMEA was also observed in the pH 7.4 PBS at 37.0°C through the chemical cleavage of CS. As seen from the results, PSEMA seems to be a potential application in the drug-delivery system controlled by the external pH value and temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

In this study, a novel thermo-sensitive poly(N-acryloylglycinates) was prepared in order to get a potential drug release carrier. The corresponding monomers and the polymers were characterized with Fourier-transform infrared (FTIR) and ¹H NMR. The thermo-sensitivity of the poly(N-acryloylglycinates) was evaluated by measuring their lower critical solution temperatures (LCST) in water, inorganic salt solution, and different pH solutions. The results indicated that poly(N-acryloylglycine methyl ester) (NAGME) and poly(N-acryloylglycine ethyl ester) (NAGEE) exhibit a reversible thermo-sensibility in their aqueous solutions at 61.5 and 12.5°C, respectively. However, no thermo-sensitive behavior of poly(N-acryloylglycine propyl ester) (NAGPE) was found due to its over hydrophobicity. The swelling studies on hydrogels were carried out at different temperatures, in different pH, and inorganic salt solutions. The hydrogels showed a remarkable phase transition at about 35°C with changing temperature. The release rate of caffeine from the thermo-sensitive hydrogel was apparently decreased as the crosslinker content increased and temperature decreased. Seventy five percent caffeine from the polymeric hydrogel with 5% NMBA (N, N-methylenebis(acrylamide)) was released at room temperature within 240 min, whereas 95.4% caffeine diffused into the medium at 37°C. Copyright © 2009 John Wiley & Sons, Ltd.

In this study, a novel pH–temperature-responsive copolymer was first synthesized by the radical copolymerization between HPA (2-hydroxypropyl acrylate and 2-hydroxyisopropyl acrylate) and AMHS (aminoethyl methacrylate hydrochloric salt). The molecular structure of the corresponding copolymer has been confirmed by ¹H-NMR and FTIR. The lower critical solution temperature of the resulting copolymer exhibited a considerable dependence upon the ratio of monomers and pH value in the medium. On the basis of the copolymer, a hydrogel as drug release carrier was prepared via the introduction of a crosslinker, N,N′-methylenebisacrylamide. The swelling behaviors of hydrogel in the different pH value, temperature, and NaCl concentration have indicated that the hydrogel showed a remarkable phase transition at 31.5°C. The swelling ratio was increased with an increasing of pH value, especially in the greater pH values. By the use of caffeine as a model drug, we investigated the caffeine-controlled release from hydrogel systematically as a function of pH value, temperature, and crosslinker content. The caffeine release was sensitive to the temperature. Only 55% caffeine was released from the hydrogel at room temperature, whereas ∼ 92% caffeine diffused into the medium at 37°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The graft copolymerization of sodium acrylate (SA) onto organophilic montmorillonites (OMMT) initiated by redox reaction of potassium diperiodatonickelate (IV) [Ni(IV)] with reactive groups on OMMT substrate was studied in alkaline medium. The grafting parameters have been investigated as a function of the ratio of monomer to OMMT, the concentration of initiator, temperature, and pH value. The structure of the graft copolymer (OMMT-g-PSA) was systematically characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscope (SEM). It was found that [Ni(IV)] belongs to a highly efficient initiator for graft copolymerization of SA onto OMMT via the redox iniation (grafting efficiency > 95%). Furthermore, the experimental results also showed that the graft copolymer gels synthesized under optimal condition exhibited a maximum water absorbency of 1104 g/g in distilled water and 111 g/g in 0.2 wt % NaCl solution, respectively, and its water retention ability is more than 91% after centrifugal separation for 2 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008