Magnetic Responsive Clay/PNIPam Nanocomposite Hydrogels

In recent ten years,nanocomposite hydrogels?NC gels?,which employ inorganic clay as a multifunctional cross-linker,have been draw more attentions due to its excellent mechanical properties,optical transparency and swelling/deswelling behavior.NC gels are composed of organic polymer matrix and inorganic clay,the hydrogel matrix like PNIPAm exhibit themal sensitivity in aqueous solution.The inorganic clay reinforce the NC gels and improve its mechanical performance,but they add no additional properties such as response to light,electric and magnetic field to the hydrogels.The directly incorporation of functional nanoparticles into PNIPAm hydrogels endow their specific functionalization,but may cause negative effect on the mechanical properties of hydrogels and can inefficient for trapping the functional nanoparticles due to the absence of cross-linking interaction and to a pore size larger than the size of nanoparticles.In this paper,from the views of functionality and mechanical properties of hydrogels,the functionlized Fe₃O₄ nanoparticles are successfully utilized as cross-linkers to prepare magnetic nanocomposite hydrogels with reinforced mechanical properties.?1?Firstly,the Fe₃O₄ nanoparticles were synthesized via chemical co-precipitation method.Then,azide-functional Fe₃O₄ nanoparticles were obtained by a two-step chemical modification process using 3-chloropropyltriethoxysilane and NaN3 respectively.The 2-?Dimethylamino?ethyl methacrylate?DMA?was quaternized using propargyl bromide under mild conditions to yield a quaternized2-?Dimethylamino?ethyl methacrylate?QDMA?molecule which contained vinyl and alkynyl groups.In 1H NMR studies,comparison of the peak integrals of the characteristic signals indicated a degree of quaternization of ?100%.Finally,theQDMA molecules were directly reacted with azide-functional Fe₃O₄ nanoparticles to acquire Fe₃O₄@QDMA nanoparticles.The Fe₃O₄ nanoparticles were characterized by XRD?FTIR?TEM?Tg?DLS and SQUID.The QDMA molecules were successfully grafted onto the magnetite nanoparticles and the surface functionalization process did not change magnetite phase.The diameter of Fe₃O₄@QDMA nanoparticles was about12.2 nm and can be homodispersed in water.In addition,the Fe₃O₄@QDMA nanoparticles exhibited superparamagnetic behavior and the Ms of Fe₃O₄@QDMA nanoparticles was 49.07 emu/g.?2?Fe₃O₄@QDMA nanoparticles were successfully utilized cross-linkers to prepare novel magnetic nanocomposite hydrogels?m NC gels?using NIPAm as monomer and clay as additional cross-linking agents via in suit free radical polymerization.The mechanical properties,swelling/deswelling behavior,magnetic properties and temperature variation in alternating magnetic field of the mNC gels have been investigated in details.The incorporation of Fe₃O₄@QDMA into NC hydrogels strengthen the mechanical properties of mNC gels without negatively affecting the magnetic properties of Fe₃O₄ and the themal sensitivity of PNIPAm.Crosslinking of Fe₃O₄@QDMA in the hydrogel network provides a way to reduce the loss of magnetic nanoparticles.The temperature of mNC8 gel can rise to about44.5 ??reach hyperthermia temperature,above LCST of PNIPAm?in a magnetic AC field?300KHz?.These properties make it possible for mNC hydrogels to realize dual hyperthermia and pulsatile drug delivery.