Synthesis And Characterization Of Nanocomposite Hydrogels Based On Inorganic Nanoparticles

Hydrogels are insoluble polymeric materials with three dimensional networks, containing a large number of hydrophilic groups which endow these materials with the ability of loading a large amount of water. Hydrogels have been reported as a kind of versatile materials in many fields, such as drug delivery system, encapsulation of living cells, and carrier of active compounds. Nanomaterials have been the hot research focus due to their high surface/volume ratio. Some absolutely mind-blowing advances are being made because of the highly interdisciplinary combinations of hydrogels and nanomaterials, which makes up the hydrogels’ developmental deficit and eliminates the agglomeration of nanomaterials. It might also open up new avenues of discovery in materials science.1. Uniform and transparent poly(methacrylic acid) (MAA)/Laponite nanocomposite hydrogels were prepared by in situ polymerization using Laponite as crosslinker. They possessed excellent ductility and adhesion. It was found that the elastic modulus (G’)、 viscosity and the 180° peel strength were all increased with the increasing Laponite and mononer (MAA) content. JKR instrument was also used to characterize the surface adhesion energy.2.Thermosensitive poly(NIPAAm-co-AMPS) hydrogels were prepared by copolymerization of N-isopropyl acrylamide (NIPAAm) and 2-acrylamido-2-methyl 1-propansulfonic acid (AMPS) by employing N, N’-methylenebis(acrylamide) (BIS) as cross-linker. Uniformly distributed silver nanoparticles (Ag-NP) were obtained within hydrogel networks as nanoreactors via in-situ reduction of silver nitrate (AgNO3) using sodium borohydride (NaBH4) as reducing agent. Swelling experiments showed the effect of hydrogel composition on the LCST value. The TEM test showed that the Ag nanoparticles were well distributed and uniformed in size centered at 3.5 nm by Nanomeasure.3.The catalytic properties of Ag-NP-poly(NIPAAm-co-AMPS) hydrogels presented obvious temperature dependence upon the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBHH4 in aqueous solution. The rate constant k and SR at different temperatures were the same tendency. k increased as the temperature increased, while when the temperature reached a level, around the LCST, k would decrease dramatically, which could be caused by the thermosensitive shrinkage of the poly(NIPAAm-co-AMPS) hydrogels.Interestingly, the addition of a-cyclodextrin (a-CD) could further enhance the reduction rate and change the associated activation parameters.