Preparation Of Polyacrylamide/Chitosan Composite Hydrogels

Due to their good hydrophilicity,flexibility and biocompatibility,hydrogels have a wide range of applications in agriculture,medicine,sensors,food,artificial skin and contact lenses.Compared with single-network hydrogels,double-network hydrogels have better mechanical properties with unique cross-linked network structure.Natural polymer chitosan is widely used as a biological material because of its good biocompatibility,nontoxicity,and antibacterial property.In this work,chitosan/acrylic acid（3CS/7AA）solution was prepared by dissolving chitosan in acrylic acid solution based on the acid-base interaction mechanism,which was used as a composite monomer solution with acrylamide（AM）and N,N’-methylene bisacrylamide（MBAA）to prepare poly（acrylamide-acrylic acid）/chitosan（P（AM-co-AA）/CS）semi-interpenetrating（semi-IPN）crosslinked network hydrogel.The prepared hydrogel is a three-dimensional crosslinked network with good mechanical and p H-sensitive properties confirmed by structural characterization and performance testing,which can be used as drug release agent and a dielectric layer of capacitive pressure sensor.The work can be divided as follow three parts:1.The CS/AA composite monomer solution was prepared by dissolving chitosan（CS）in acrylic acid（AA）solution using mechanical and ultrasonic stirring.A series of CS/AA composite monomer solutions were prepared by adjusting the mass ratio of AA and CS,which were analyzed by the chemical structure,viscosity,tyndall effect,storage stability and light transmittance.The results show that CS can be dissolved by AA and form a stable CS/AA composite monomer solution.When the mass ratio of CS:AA=3:7（noted as3CS/7AA）,the solubility,viscosity,light transmittance and storage stability of CS in the3CS/7AA composite monomer are best,lowest,75% and higher than 1 month respectively.2.The P（AM-co-AA）/CS semi-IPN hydrogel were prepared by the method of in-situ free radical copolymerization of 3CS/7AA composite monomer solution using AM as monomer,MBAA as crosslinking monomer and potassium persulfate（KPS）/sodium bisulfite（SBS）as composite initiators.Through mechanical property tests such as tensile,compression and rheology,the influence of the content of 3CS/7AA composite monomer on the mechanical properties of P（AM-co-AA）/CS hydrogel was investigated.The results showed that P（AM-co-AA）/CS-4 hydrogel has the best mechanical properties with 2.5 g of AM,4.0 g of 3CS/7AA composite monomer solution（20.0 wt%）,7.5 mg of MBAA,14.0mg of KPS,7.5 mg of SBS,and the total concentration of raw materials were 33.3%.Its elongation at break and strength reached 1178.0% and 161.7 k Pa,respectively.The compressive strength reached 5224.2 k Pa when the compressive strain was 90%.The chemical structure,surface morphology and thermostability of freeze-dried hydrogels were tested by infrared absorption spectroscopy,scanning electron microscopy and thermogravimetric characterization.The results show that P（AM-co-AA）/CS is prepared as the target product,and the hydrogel appears to have a three-dimensional network pore structure.The hydrogel presents a three-dimensional network pore structure and is temperature-and p H-sensitive.The swelling rate shows a linear increase with the increase of temperature and p H in the range of 20～60 ℃.3.A capacitive pressure sensor was assembled with P（AM-co-AA）/CS hydrogel as the dielectric layer,and the sensing performance of the hydrogel to different pressures was investigated.The results show that the hydrogel as dielectric layer exhibits excellent stability,sensitivity and fatigue resistance.P（AM-co-AA）/CS hydrogels were used as controlled drug release agent to investigate its release behavior of ranitidine hydrochloride in simulated gastrointestinal fluid,and the influence of the composition of hydrogel and the temperature and p H of buffer solution on the sustained release performance were evaluated.The results showed that the P（AM-co-AA）/CS hydrogel can be used as controlled drug release agent with sustained drug release performance.The drug release rate increases with the increase of temperature and p H in the range of 25～37 ℃.