Crosslinked hydrogels comprising acrylamide (AAm) and maleic acid (MA) were synthesized by free radical polymerization in presence of a crosslinker using ammonium persulfate (APS) and N,N,N1,N1-tetramethylethylenediamine (TMEDA) as initiator and activator, respectively. The crosslinked hydrogel formation was confirmed by IR analysis. The swelling/de-swelling characteristics were studied in detail for crosslinked poly(acrylamide-co-maleic acid) [poly(AAM-co-MA)] hydrogels containing different amounts of maleic acid. Four different crosslinkers such as 1,2-ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), and diallyl phthalate (DP) were utilized to study their influence on the swelling behavior of the hydrogels. The effect of reaction parameters such as the concentration of crosslinker and initiator on swelling capacity of the crosslinked poly(AAm-co-MA) hydrogels was also investigated. Further, the influence of various salts, simulated biological fluids, and pH solutions on the swelling pattern of hydrogels was studied extensively. Phase separation morphology of crosslinked hydrogels was also studied by differential scanning calorimetry. The morphology of crosslinked hydrogels were revealed using scanning electron microscopy (SEM). 相似文献
A series of novel semi-interpenetrating polymer networks hydrogels composed of poly(ethylene glycol) and random copolymer of acrylamide/sodium methacrylate were prepared by polymerization of aqueous solution of acrylamide, sodium methacrylate using ammonium persulphate/N,N,N′,N′-tetramethylethylenediamine as a redox-initiating pair in the presence of poly(ethylene glycol) and poly(ethylene glycol)diacrylate as crosslinker. Fourier Transform Infrared spectroscopy was used to identify the presence of different repeating units in the semi IPNs. Water uptake and dye-sorption properties of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs were investigated as a function of chemical composition of the hydrogels. Cationic dye, Janus Green B have been used in sorption studies as a model molecule. This study has given the quantitative information on the swelling and sorption characteristic of acrylamide/sodium methacrylate hydrogels and acrylamide/sodium methacrylate/poly(ethylene glycol) semi IPNs in many potential applications. 相似文献
Stimuli-responsive poly(N-isopropylacrylamide-co-sodium acrylate) [poly(NIPAM-co-SA)] hydrogel networks were prepared by aqueous free-radical copolymerization using the ammonium persulfate/N,N,N1,N1-tetramethylethylenediamine (APS/TMEDA) redox-pair initiator system in the presence of different amounts of N,N1-methylenebisacrylamide (MBA) crosslinker. Higher swelling capacities were availed for these N-isopropylacrylamide-based hydrogels due to the presence of the hydrophilic poly(sodium acrylate) anionic units. In this the swelling phenomena of hydrogels in different surfactant and polymer solutions are investigated in a systematic way. The structural variation as well as the thermal stability of the surfactant-modified hydrogels were studied in detail. Further, the hydrogels swelling/diffusion kinetic parameters were investigated and a non-Fickian type of diffusion characteristics was found in all the swelling media for the diffusion of water into these hydrogels. 相似文献
The dual-sensitive, comb-type grafted hydrogels were synthesized by grafting polymeric chains with freely mobile ends, which were composed of both N,N-diethylacrylamide (DEA) and (2-dimethylamino) ethyl methacrylate (DMAEMA), onto the backbone of crosslinked poly(DEA-co-DMAEMA) networks. The structure of the poly(DEA-co-DMAEMA) macromonomer was characterized by Nuclear Magnetic Resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The effects of the feed components, temperature, and pH on the swelling behavior of the hydrogels were studied. With the increase of the poly(DEA-co-DMAEMA) macromonomer content, the thermo- and pH-sensitivity of the hydrogels improved. The G-PDD hydrogels exhibited improved thermo- and pH-sensitive characteristics, such as faster deswelling and reswelling rates and great oscillating deswelling/swelling behavior, and the level of improvement depended on the poly(DEA-co-DMAEMA) macromonomer content. The proposed dual thermo- and pH-sensitive, comb-type grafted poly(DEA-co-DMAEMA) hydrogel has various potential applications. 相似文献
Controlled release of L-ascorbic acid from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels is reported. PHEMA hydrogels were synthesized from 2-hydroxyethyl methacrylate (HEMA) monomer in an oven. We studied the swelling of PHEMA discs in water as a fuction of temperature and thickness of xerogel discs. The fractional swelling was linear in (time)1/2 at short times. Drug release has been examined as a fuction of temperature, initial drug load and thickness of the PHEMA discs. The fraction of avaible drug release was linear in (time)1/2 during the initial stage too. The release experiments were carried out at 308 K. These studies allow to determinate a diffusion coefficient for transport of water into the hydrogels and a diffusion coefficient for L-ascorbic acid release from the hydrogel. 相似文献
In this study, swelling behavior of polyelectrolyte poly(hydroxamic acid) (PHA) hydrogels have been investigated in aqueous thiazin dye solutions. PHA hydrogels were prepared by free radical polymerizations of acrylamide with some cross-linkers such as N,N′ methylenebisacrylamide (NBisA) and ethylene glycol dimethacrylate (EGDMA); then they were used in experiments on swelling and diffusion of some water-soluble cationic dyes such as methylene blue (MB), thionin (T), and toluidin blue (TB). Swelling experiments were performed in water at 25°C, gravimetrically. The equilibrium swelling percent (S%) values of PHA hydrogels were calculated as 238–2705%. Some swelling kinetic parameters such as initial swelling rate, swelling rate constant, and maximum (theoretical) swelling percent were found. Diffusional behavior of dye solutions was investigated. Dye diffusion into hydrogels was found to be non-Fickian in character. Diffusion exponent (n) is over 0.50. For sorption of thiazin cationic dyes, MB, T, and TB to PHA hydrogels were studied by batch sorption technique at 25°C. PHA hydrogels in the dye solutions showed the dark coloration. In the experiments of the adsorption, S-type adsorption in the Giles classification system was found. 相似文献
Stimulus-sensitive hydrogels are used as carriers for modified release of pharmaceuticals. The synthesis of thermosensitive hydrogels poly(N-isopropylacrylamide), p(NIPAM), and poly(N-isopropylacrylamide-co-2-hydroxypropyl methacrylate), p(NIPAM-HPMet), is performed. The synthesized hydrogels are characterized using FTIR and scanning electron microscope methods and swelling properties, and applied for modified release of ellagic acid (EA). This work presents the selective extraction of EA, as a natural antioxidant, from the aerial parts of Alchemilla vulgaris L. EA and A. vulgaris extract are incorporated into p(NIPAM) and p(NIPAM-HPMet) hydrogels and characterized by FTIR method. The EA content in the extract by the UHPLC–DAD–HESI–MS/MS method is determined (0.64?mg?cm?3). The total flavonoids content in the A. vulgaris extract was determined by the spectrophotometric method. Antioxidant activity of the A. vulgaris extract and EA is examined using the 2,2-diphenyl-1-picrylhydrazyl assay. The p(NIPAM-HPMet) shows a better incorporation and release at 37°C of EA standard and A. vulgaris extract (98.87 and 96.45% respectively), compared with p(NIPAM). 相似文献
The study reports a facile method of preparing poly(N-isopropylacrylamide)- based hydrogels by means of the Diels-Alder reaction. First, polymeric dienes were synthesized by free radical copolymerization between N-isopropylacrylamide (NIPA) and furfuryl methacrylate (FM), with 2, 2′-azobisisobutyronitrile (AIBN) as an initiator, and polymeric dienophile was obtained by a coupling reaction of poly(ethylene glycol) (PEG) and N-maleoyl-l-leucine (LMI) under N, N′-dicyclohexylcarbodiimide (DCC). Afterwards, the resultant dienes and dienophiles were dissolved in water and put in a refrigerator remaining a temperature of 9 °C, gelation via Diels-Alder reaction was observed after some time. The samples obtained at different steps were characterized by FTIR, NMR, GPC, SEM, CD, etc. It was found that LCST of copolymers decreases with the increase of FM content in copolymers. And the disassembly time of the hydrogels is closely related to the temperature and the solvents used. The swelling behavior study by gravimetric measurement indicates the hydrogels possess thermosensitivity and exhibit considerable swelling in water. Due to the simplicity of synthesis and no need for initiator or catalyzer and organic solvent, the strategy described here could find a promising application in the preparation of hydrogels. 相似文献
Novel intelligent hydrogels composed of biodegradable and pH-sensitive poly(l-glutamic acid) (PGA) and temperature sensitive poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNH) were synthesized and characterized for controlled release of hydrophilic drug. The influence of pH on the equilibrium swelling ratios of the hydrogels was investigated. A higher PNH content resulted in lower equilibrium swelling ratios. Although temperature had little influence on the swelling behaviors of the hydrogels, the changes of optical transmittance of hydrogels as a function of temperature were marked, which showed that the PNH part of hydrogel exhibited hydrophobic property at temperature above the lower critical solution temperature (LCST). The biodegradation rate of the stimuli-sensitive hydrogels in the presence of enzyme was directly proportional to the PGA content. Lysozyme was chosen as a model drug and loaded into the hydrogels. The in vitro drug release experiment was carried out at different pH values and the release data suggested that both the pH and PNH content played important roles in the drug release behaviors of the hydrogels. 相似文献
Summary: Polyelectrolyte hydrogels containing diprotic acid moieties sensitive to ionic strength changes of the swelling medium were synthesized from N,N‐diethylaminoethyl methacrylate (DEAEMA), N‐vinyl‐2‐pyrrolidone (VP) and itaconic acid (IA) by using ammonium persulfate (APS) as a free radical initiator in the presence of the cross‐linker, methylenebisacrylamide (MBAAm). The swelling behavior of the ionic poly[(N,N‐diethylaminoethyl methacrylate)‐co‐(N‐vinyl‐2‐pyrrolidone)] [P(DEAEMA/VP)] hydrogels were investigated in pure water; in NaCI solutions with pH 4 and 9; and in water‐acetone mixtures depending on the IA content in the hydrogel. The average molecular mass between cross‐links ( ) and polymer‐solvent interaction parameter (χ) of the hydrogels were determined from equilibrium swelling values. The pulsatile swelling behavior was also observed in response to solvent changes between the solution in water and in acetone. The equilibrium swelling ratio of these hydrogels was basically unaffected with change in temperature. The swelling variations were explained according to the swelling theory based on the hydrogel chemical structure.
Pulsatile swelling behavior of ionic P(DEAEMA/VP) hydrogels in response to solvent changes between water and acetone at 25 °C. 相似文献