Preparation and characterization of magnetic field and thermo-sensitive poly (n-t-butylacrylamide-co-acrylamide)/poly(vinyl methyl ether) semi-interpenetrating networks ferrogels

In this study, temperature and magnetic field sensitivepoly(N-t-butylacrylamide-co-acrylamide)/poly(vinyl methyl ether)P(TBAAm-co-AAm)/PVME semi-IPN hydrogels were synthesized byfree-radical crosslinking copolymerization of N-t-butylacrylamide(TBAAm) and acrylamide (AAm) in methanol by using N,N?-methylene(bis)acrylamide (MBAAm) as crosslinker, ammoniumpersulfate (APS) as an initiator and N,N,N?,N?-tetramethylethylenediamine (TEMED) as an activator; in the presence ofPVME. Following the swelling period in concentrated aqueous solutionof FeCl3.6H2O/FeSO4.7H2O for one week, the gels were heated in nitricacid (HNO3) solution for half an hour. Magnetic gels with embedded(Fe3O4) magnetite nanoparticles were prepared by treating these gelswith concentrated aqueous solution of KOH/KNO3. Magnetic propertiesof these gels were determined by electron spin resonancespectroscopy (ESR). The presence of magnetite particles in the polimergel was confirmed by ESR. The maximum signal intensity values ofmagnetic gel and of the magnetite were determined from ESR spectra.The effects induced by electric field on the motility and the shape ofpolymer gels was investigated. Under an external electric field, thesegels were observed to respond by quick and reversible bending. Someof the magnetic and non-magnetic P(TBAAm-co-AAm)/PVME hydrogelswere prepared to contain definite amount of PVME and differentamounts of MBAAm crosslinker; the others were prepared to containdefinite amount of MBAAm and different amounts of PVME. Theswelling ratios of both type of hydrogels were determined in pure wateras a function of temperature and time. Dependence of the swellingbehaviour of temperature sensitive P(TBAAm-co-AAm)/PVME hydrogelson the amounts of crosslinker (MBAAm), PVME and magnetic particles(Fe3O4) was investigated. There observed remarkable decrements in theswelling ratios of the hydrogels with increasing amount of crosslinker.On the other hand, increasing the amount of PVME caused todecrements in the swelling ratio of the hydrogels. The amount ofmagnetic particles (Fe3O4) in the hydrogel also affected the swellingratio of the hydrogels. Swelling ratio of the hydrogels was decreasedwith increasing magnetite/polymer mass ratio. In addition, the pulsatileswelling behaviour in pure water was observed at alternatingtemperatures between 10 and 40 0C. Thermal properties of the plain andmagnetic hydrogels were examined by TGA analyses. TGA resultsshowed that the termal stability of the hydrogels with embeddedmagnetite (Fe3O4) was more than those of the plain hydrogels. Thestructure characterization of these gels as mode realized performed byusing an FT-IR spectrophotometer. The surface characterization offerrogels and hydrogels were invastigated by using SEM and EDSimages which were obtained from surface and intermediate-surface ofthese gels