Swelling kinetics, mechanical properties, and release characteristics of chitosan-based semi-IPN hydrogels

Two series of pH-sensitive semi-interpenetrating network hydrogels (semi-IPN) based on chitosan (CS) natural polymer and acrylamide (AAm) and/or N-hydroxymethyl acrylamide (HMA) monomers by varying the monomer and CS ratios were synthesized by free radical chain polymerization. 5-Fluorouracil (5-FU), a model anticancer drug, has been added to the feed composition before the polymerization. The characterization of gels indicated that the drug is molecularly dispersed in the polymer matrix. The swelling kinetics of drug-loaded gels have decreased with increased HMA content at 37 degrees C in both distilled water and buffer solutions with a pH of 2.1 or 7.4. Elastic modulus of the gels increased with the increase in HMA content and higher CS concentration enhanced the elastic modulus positively. Moreover, cumulative release percentages of the gels for 5-FU were ca. 10% higher in pH 2.1 than those in pH 7.4 media. It was determined that they can be suitable for the use in both gastric and colon environments. (C) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41886

Synthesis and swelling behavior of poly(2-dimethylaminoethyl methacrylate-co-N-hydroxymethyl acrylamide) hydrogels

Crosslinked poly(2-(N,N-dimethylamino) ethyl methacrylate-co-N-hydroxymethyl acrylamide) poly(DMAEMA-co-NHMAAM) copolymers were synthesized using ammonium persulfate (APS)/N,N,N',N'-tetramethyl ethylenediamine (TEMED) as initiator/accelerator system in the presence of tetraethyleneglycol diacrylate (TEGDA) as crosslinker in water at 60 degrees C. The effects of comonomer composition in the feed, pH of the swelling medium, and the temperature on the equilibrium swelling (ES) values of hydrogels were investigated. While the initial total monomer concentration was kept constant at 0.5 or 1 mol/l, the contents of APS and TEGDA in the feed were 1 mol% of the total monomers. ES values of DMAEMA-NHMAAM gels increased with the increase in DMAEMA content in the feed. Although DMAEMA-NHMAAM hydrogels containing up to 30 mol% were transparent in appearance, the presence of 40% DMAEMA in the copolymer worsened its transparency. ES values of the copolymer gels with high DMAEMA contents increased with both temperature and the pH of swelling medium. Copyright (c) 2006 John Wiley & Sons, Ltd

Noncompetitive Removal of Heavy Metal Ions from Aqueous Solutions by Poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] Hydrogel

Noncompetitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solutions by the copolymer of 2-(acrylamido)-2-methyl-1-propanesulfonic acid with itaconic acid and its homopolymer poly [2-(acrylamido)2-methyl-1-propanesulfonic acid] was investigated. Both poly[2-(acrylamido)-2-methyl-1-propanesulforlic acid] and poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] removed the maximum and same amounts (1.74 mmol Pb2+/g polymer) of Pb2+ ion among the ions investigated in this work. The equilibrium swelling values of poly (2-(acryl amido)-2-methyl-1-propanesulfonic acid] and poly [2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] showed that the swelling of the copolymer is dominated by its completely ionizable constituent 2-(acrylamido)-2-methyl-1-propanesulfonic acid. Although the incorporation of itaconic acid into poly [2-(acrylamido)-2-methyl-1-propane sulfonic acid] did not affect the removal rates of poly [2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] for Pb2+ and Cd2+ ions, it considerably enhanced the removal rates of the copolymer for the Cu2+ ion. The trends in the single-ion sorption of ions on poly [2-(acrylamido)-2-methyl-1-propanesulfonic acid] and poly [2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] followed the orders Pb2+ > Cd2+ > Cu2+ and Pb2+ > Cu2+ > Cd2+ respectively. Noncompetitive adsorption profiles of Pb2+, Cu2+, and Cd2+ ions on both polymers were demonstrated to fit the pseudo-second-order-type kinetics

A novel poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) gel: preparation in the absence/presence of a pore-forming agent and characterization

Poly(N-isopropylacrylamide) (PNIPAM) homopolymer gel and copolymer gels of N-isopropylacrylamide (NIPAM) and N-hydroxymethyl acrylamide (NHMAAM) were prepared in the absence/presence of a pore-forming agents, poly(ethylene glycol) (PEG) (PEG 400 or PEG 2000) using N,N'-methylenebisacrylamide (NMBA) as a crosslinker in aqueous solution at 4 degrees C. The chemical structures and microscopic morphologies of PNIPAM and P(NIPAM-co-NHMAAM) copolymer gels were investigated by FT-IR and SEM (scanning electron microscopy), respectively. The effects of initial monomer concentration (0.5 and 1 M), the contents of crosslinker (0.25 and 1%) and comonomer (1-3 mol%), the absence/presence of pore-forming agent in the feed, and the molecular weight of pore-forming agent on the compressive elastic moduli and equilibrium swelling values (ESVs) of both polymers were investigated. While the use of a pore-forming agent during the polymer synthesis favored the formation of porous gels and increased the swelling values, it led to decrease in the compressive elastic moduli of PNIPAM and P(NIPAM-co-NHMAAM) gels. The swelling values of gels, which were prepared at high monomer (1 M) and crosslinker (1 %) contents, were not dependent on the comonomer NHMAAM incorporation to PNIPAM, the use of pore-forming agents, and the use of former and latter parameters together. The twice increase in initial monomer concentration at low NMBA (0.25%) content highly enhanced the elastic moduli of PNIPAM. One mol% NHMAAM incorporation into PNIPAM especially at low monomer (0.5 M) and crosslinker (0.25%) contents made the highest increase (4.7 times) in the elastic moduli of gel, and further increase in the NHMAAM content of gel decreased the moduli of gels at all crosslinker and monomer concentrations. It was concluded that the increase in the elastic moduli of copolymer gels with 1 mol% NHMAAM, which were prepared at low crosslinker and monomer concentrations, can be attributed to the increase in crosslinking through the condensation reaction between N-methylol groups or N-methylol and -NH groups in NHMAAM and NIPAM. Copyright (C) 2008 John Wiley & Sons, Ltd

Synthesis and swelling behavior of pH- and temperature-sensitive poly[2-(dimethylamino)ethyl methacrylate-co-2-acrylamido-2-methylpropane-1-sulfonic acid] hydrogels

Poly[2-(dimethylamino)ethyl methacrylate-co-2-acrylamido-2-methylpropane-1-sulfonic acid], poly(DMAEMA-co-AMPS), hydrogels were prepared by chain polymerization in water at 60 degrees C in the presence of tetraethyleneglycol diacrylate (TEGDA) as crosslinking agent. Ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamine (TEMED) were used as initiator and accelerator, respectively. Hydrogels with different feed compositions were prepared by keeping the total monomer concentration constant at 1 or 0.5 M. The concentration of TEGDA in the feed was adjusted so that it made for 3 or 2 mol % of the total monomer content while it was 1% for APS. In order to observe the effects of pH and ionic strength of the medium on swelling, the equilibrium swelling behavior of these hydrogels were investigated both in distilled water at various temperatures between 30 and 90 degrees C and in different buffer solutions with pH of 2.8, 5.3, 7.0, 10.0, and 12.4 at constant ionic strength (I=0.08 mol/l) at room temperature. The effects of temperature and co-monomer AMPS content on the swelling behavior of poly(DMAEMA-co-AMPS) in distilled water were also investigated

Synthesis and Characterization of Novel Poly(N-isopropylacrylamide-co-N,N '-dimethylaminoethyl methacrylate sulfate) Hydrogels

Poly(N-isopropylacrylamide-co-N,/N'-dimethylaminoethyl methacrylate sulfate) [P(NIPAM-co-DMAEMASA)] was prepared from N-isopropylacrylamide (NIPAM) and N,N-dimethylaminoethyl methacrylate sulfate (DMAEMASA) monomers, and its properties were compared with those of poly(N-isopropylacrylamide-co-N,/N'-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMAEMA)] The copolymers were characterized by swelling measurements in distilled water (10-40 degrees C) and buffer solutions (I = 0 1 M, pH = 2 2-10 0), FTIR, DSC, and SEM methods The ESV's of the NIPAM-DMAEMASA copolymers in distilled water were 5 times higher than those of P(NIPAM-co-DMAEMA), they decreased with an Increase in comonomer (DMAEMASA/DMAEMA) content for both copolymers While NIPAM-DMAEMASA copolymers did not display any phase transition with temperature, the LCST of the NIPAM-DMAEMA copolymer was determined as 20 degrees C Both copolymers displayed a phase transition at pH = 5 0, but the pH of the phase transition for NIPAM-DMAEMA gels shifted to 7 0 with increased DMAEMA content Glass transition temperatures of NIPAM copolymers did not change with the type and content of comonome

Synthesis and swelling behavior of thermosensitive poly(N-isopropyl acrylamide-co-sodium-2-acrylamido-2-methyl propane sulfonate) and poly(N-isopropyl acrylamide-co-sodium-2-acrylamido-2-methyl propane sulfonate-co-glycidyl methacrylate) hydrogels

The crosslinked copolymers and terpolymers of N-isopropyl acrylamide (NIPAm) with sodium-2acrylamido-2-methyl propane sulfonate (NaAMPS) and glycidyl methacrylate (GMA) were prepared in the presence of N,N'-methylene bisacrylamide (NMBA) as crosslinker by free radical solution polymerization at 4 degrees C. Potassium persulfate (KPS) and potassium bisulfide (KBS) were used as initiator and accelerator, respectively. While molar percentages of NaAMPS in copolymers feed were varied as 1, 2, and 3; NaAMPS and GMA were used in the molar percentages of 1 : 1, 2: 2, and 3: 3, respectively, for the terpolymer preparation. NMBA contents were kept constant as 1 or 1.5 mol % of total monomer moles in feed composition. The effects of the comonomer type, feed composition, and the crosslinker contents on the lower critical solution temperatures (LCST), equilibrium swelling values (Q) of polymers, swelling kinetics in water at room temperature, and deswelling kinetics at 55 degrees C were investigated. The results indicated that the higher the NaAMPS content in NIPAm/NaAMPS copolymer, the higher the Q and water uptake rate, but less the water release rate. However, the presence of hydrophobic GMA comonomer in the terpolymer of NIPAm/NaAMPS/GMA decreased the Q values, it increased both the water uptake and the water release rates. It was also observed that NIPAm/NaAMPS and NIPAm/NaAMPS/GMA polymers exhibit continuous phase transition behavior between 40 and 50 degrees C. (c) 2006 Wiley Periodicals, Inc

Competitive removal of heavy metal ions by cellulose graft copolymers

The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solution was investigated. The copolymers used were (1) cellulose-g-polyacrylic acid (cellulose-g-pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose-g-p(AA-NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of NN'-methylene bisacrylamide (NMBA); (3) cellulose-g-p(AA-AASO(3)H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2-acrylamido-2-methyl propane sulphonic acid (AASO(3)H) containing 10% (in mole) AASO(3)H; and (4) cellulose-g-pAASO(3)H obtained by grafting of AASO(3)H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose-g-pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/g(copolymer). Although the metal removal rate of cellulose-g-p(AA-NMBA) copolymer was lower than that of cellulose-g-pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/g(copolymer). Cellulose did not remove any ion under the same conditions. In addition, cellulose-g-pAASO(3)H removed practically no ion from the aqueous solution (0.02 mmol metal ion/g(copolymer)). The presence of AASO(3)H in the graft chains of cellulose-g-p(AA-AASO(3)H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose-g-pAA. All types of cellulose copolymers were found to be selective for the removal of Pb2+ over Cu2+ and Cd2+. (C) 2003 Wiley Periodicals, Inc

Effect of nickel, lanthanum, and yttrium addition to magnesium molybdate catalyst on the catalytic activity for oxidative dehydrogenation of propane

The catalytic performances of pure magnesium molybdate (MgMoO4) and MeMgMoOx (Me = Ni, La, or Y) for oxidative dehydrogenation of propane were investigated. Catalysts were characterized by nitrogen physisorption, XRD, FT-Raman, and temperature-programmed reduction measurements. Catalytic reactions were carried out at two different temperatures, 450 and 560 degreesC, under atmospheric pressure. The effects of the C3H8/O-2 molar ratio in the feed and bed residence time on propylene selectivity and on propane conversion were also investigated. Although the strong effect of Ni loading both on reducibility and on the catalytic activity of MgMoO4 catalyst was observed, Y and La modification did not show any significant effect as opposed to Ni. A 19.3% propylene yield was achieved over 5 mol % Ni-containing MgMoO4 catalyst at 560 degreesC

Room temperature carbon monoxide oxidation over Pt/Co2SnO4 and Pt/(Co3O4+SnO2) catalysts

Catalytic activities of Pt/Co2SnO4, Pt/(Co3O4+SnO2), Pt/SnO2, and Pt/Co3O4 catalysts for CO oxidation were investigated by varying CO concentration at room temperature. Reaction rates over Pt/Co2SnO4 and Pt/Co3O4 catalysts were not affected from increase in CO concentration