Abstract
A series of semi-interpenetrating polymer network (semi-IPN) hydrogels based on N,N’-diethylacrylamide (DEA) and itaconamic acid (IAM) were synthesized by changing the molar ratio of linear copolymer P(DEA-co-IAM) and DEA monomer. Linear copolymer P(DEA-co-IAM) was introduced into a solution of DEA monomer to prepare pH-thermo dual responsive P(DEA-co-IAM)/PDEA semi-IPN hydrogels. The thermal gravimetric analysis (TGA) revealed that the semi-IPN hydrogel has a higher thermal stability than the conventional hydrogel, while the interior morphology by scanning electron microscopy (SEM) showed a porous structure with the pore sizes could be controlled by changing the ratio of linear copolymer in the obtained hydrogels. The oscillatory parallel-plate rheological measurements and compression tests demonstrated a viscoelastic behavior and superior mechanical properties of the semi-IPN hydrogels. Besides, the lower critical solution temperature (LCST) of the linear copolymers increased with the increase of IAM content in the feed, while the semi-IPN hydrogels increased LCSTs with the increase of linear copolymer content introduced. The pH-thermo dual responsive of the hydrogels was investigated using the swelling behavior in various pH and temperature conditions. Finally, the swelling and deswelling rate of the hydrogels were also studied. The results indicated that the pH-thermo dual responsive semi-IPN hydrogels were synthesized successfully and may be a potential material for biomedical, drug delivery or absorption applications. The further applications of semi-IPN hydrogels are being conducted.
Highlights
Smart hydrogel material is a three-dimensional network that is able to absorb a large amount of water without dissolving and can undergo a sharp change in volume or phase transition in response to small changes in environmental conditions, such as temperature, pH, ionic strength, light, pressure, redox and electric field [1,2,3,4,5,6,7]
The P(DEA-co-itaconamic acid (IAM))/PDEA semi-IPN hydrogels were synthesized by free radical polymerization of DEA monomer in the presence of linear copolymer P(DEA-co-IAM) using MBA, Ammonium persulfate (APS) and TEMED
The polymerization was initiated by sulfate free radicals, which were produced by the reaction between APS and TEMED [32]
Summary
Smart hydrogel material is a three-dimensional network that is able to absorb a large amount of water without dissolving and can undergo a sharp change in volume or phase transition in response to small changes in environmental conditions, such as temperature, pH, ionic strength, light, pressure, redox and electric field [1,2,3,4,5,6,7]. The hydrogels of several N-substituted polyacrylamides show thermo-responsive behavior, such as poly(N-isopropylacrylamide) (PNIPAM), poly(N-cyclopropyl-acrylamide) (PCPA), poly(N,N’-diethylacrylamide) (PDEA) and poly(N-ethylacrylamide) (PEAM) [12,13,14] These hydrogel materials are capable of reversible phase transition at a certain temperature and is commonly referred to as the lower critical solution temperature (LCST). A high hydrophilic pH-responsive system can be obtained by introduced a pH-sensitive segment such as acrylic acid [25] into the semi-IPN hydrogel This way, the resulting hydrogels have good mechanical properties, high response rate, and are thermo-pH dual-responsive. We combined LCST and swelling behavior measurements in various pH buffer solutions (PBS) and different temperatures to investigate the thermo-pH dual responsive of the obtained semi-IPN hydrogels. The further applications of obtained semi-IPN hydrogels are being conducted by our research group
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