The Preparation Of PH-Responsive Microgel Cationic Microgel-Pd Nanoparticle As Catalyst In-Situ Synthesis

Noble metal nanoparticles have a large surface area,high surface energy and adsorption capacity.It has excellent optical,electrical,magnetic and catalytic performance.However,because of the large surface energy,it needed to be combined with suitable stabilizer in order to prevent agglomeration of particles to exsist stablely.Microgels are lightly crosslinked polymers with special 3D network structures,which offer the role of confinement for the growth of nanoparticle.Microgels are ideal template for the preparation of the organic-inorganic hydrid materials.pH-responsive cationic microgel-nano metal particle composite system can be pepared by in situ synthesis and be catalyst for catalyst which proceed under acidic conditions.The composite system of the microgel and the metal nanoparticles form homogeneous phase with the chemical reaction,which can effectively improve the catalytic efficiency and Aftercompletion of the reaction,the system can be adjust at alkaling condition in order to recycle using a simple method such as centrifugation.2-(diethylamino)ethyl methacrylate(DEA)solved in most organic solvents,lauryl sodium sulfate(SDS)as emulsifier,poly(ethylene glycol)methacrylate as stabilizer,water as disperse agent,Ammonium persulfateor 2,2'-azobis[2-methylpropionamidine]dihydrochloride as initiator were used to prepare the pH-resonsive microgel.The solid content was determined,1H NMR spectroscopy(1H NMR),potential conductometric titration and scanningelectron microscopy(SEM)were used to characterize and analyse the chemical structure,amine content and morphology of the microgel.The behavior of response and swelling were analyzed by ultraviolet-visible absorption spectrophotometry(UV-vis)and dynamic light scattering(DLS).The microgelsprepared have better stabilitywhen AIBA as initiator compared with(NH4)2S2O8 and the respective parameters are kept constant.1H NMR chart showed that the macromolecular stabilizers PEGMA successfully grafted to the the PDEA polymeric microspheres.The pKa value is approximately 6.7 when AIBA as initiator and crosslinking agent mass 1%based monomer.The mole of N is 3.26 mmol per gram polymer.The SEM photograph show that the particlesare non-spherical and the number average particle diameter of about 60 nm.This is because Tg of PDEA is only around 16 ? and the polymer has better film-forming properties.Absorbance at different pH values were detected using UV-vis,which proves better pH-respone of the microgel.The microgel dispersion PDEA as the template,Na2PdCl4 as precursor,and NaBH4 as reducing agent were used to prepare Pd nanopaticle in-situ synthesis.Transmission electron microscopy(TEM),UV-vis,Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and TGA(TGA)were used to characterize Pd particle size,the microgel-Pd composite microspheres interaction,Pd crystal form,Pd loadings.TEM photograph showed the Pd particle diameter of about 3.1 nm.UV absorption spectrum showed the absorption of the PDEA-Na2PdCl4 composite system spectrum acromion and the absorption curves of PDEA,PDEA-Pd composite system are smooth curves.PDEA-Pd curve occur blue shift relative to the curve of the PDEA absorption peak by the FT-IR.The XRD spectrum does not appear on the crystal peak of Pd,this may be due to the Pd loading smaller or Pd is Amorphous at N:Pd= 2:1.Allowing' for the possible oxidation of Pd upon polymer decomposition,which would result in an oxidized Pd residue after TGA,and given the difference in mass between the platinum and oxygen atoms,a maximum and a minimum Pd loading of 5.74%and 4.99%was calculated for this sample.For a model reaction of catalysis of microgel-based metal nanoparticles,we chose the reduction of 4-nitrophenol by an excess of NaBH4.The kinetics of 4-nitrophenol reduction in presence of PDEA-Pd nanocomposite particles was studied by UV-vis spectroscopy.The result shows the values of the apparent rate constant kapp is 1.48×10-3 s-1,which suggest the PDEA-Pd nanocomposite particles have good catalytic activity.