(165v) Rheological Properties of Hydrogels for Controlled Drug Delivery

In this research paper we report the rheological properties of hydrogels for drug delivery systems which are highly elastic based on N-isopropylacrylamide (NIPAM), cationic (3-acrylamidopropyl) trimethylammonium chloride (AMPTMA) and nanoscopic clay. Cationic copolymer hydrogels based on NIPAM and AMPTMA were prepared by aqueous free radical polymerization. The thermoresponsive hydrogels have served as powerful tools in drug delivery and tissue engineering. The effect of some salts, chemical cross-linker (BIS), the concentration of AMPTMA, and clay content on the viscoelastic properties, volume phase transition temperature, and the thermal behavior of the prepared hydrogels were investigated as a function of temperature. Synthetic clay and anionic groups of the salts such NTF₂ and Cl bind to the cationic comonomer units and significantly affected the viscoelasticity and thermal properties of the hydrogels. DSC measurements showed that the volume phase transition temperature of cationic copolymer hydrogels depends on clay content. By introducing of comonomer, 250 mM solution of NaCl- 15 mM Bis (trifluoromethane) sulfonimide lithium salt (LiNTF₂) and laponite clay,a 10-fold, 4-fold and 3.8 fold increase in elastic modulus was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With a temperature change from 20 °C to 45 °C for the homopolymer PNIPAM hydrogel in 15mM LiNTF₂, the elastic modulus grew 5 times larger.