P (nipam-co-aa), Preparation And Properties Of Hydrogel-based Inorganic / Organic Nanocomposites

Assembly of inorganic-organic nanocomposites and relative nanotechnology have taken great advantage in the synthesis of novel nanocomposites and therefore aroused increasing attention among researchers.Due to the synergism of the polymer matrix and nanoinorganics,polymer based composites combined the advantages of the inorganic materials(rigidity,high module,good dimension stability,high thermal stability,unique optical property,electronic and magnetic properties) and the organic polymers(flexibility,ductility,electrical insulation,toughness and processability),which are different from the single material and conventional composite materials. Moreover,these polymer based organic/inorganic nanocomposites have potential application in mechanical,thermal,electronic,optical,and nanolinear optical fields because the inorganic particles are well dispersed in polymer matrix in nanometer scale.The properties of composite were extremely determined by the dispersed particle size and the interracial action among the components in the nanocomposites,in order to increase the interfacial action among the components in the nanocomposites,the dispersion phase dimension was desired for nanometer level or molecule level. The properties of nanocomposites were improved greatly for the fine dispersion structure and strong interfacial interaction,even they owned some new special properties.In-situ polymerization is probablely a feasible method to prepare the inorganic-organic nanocomposite for its convenient condition and two phases could disperse homogeneously in composite system.The substance of the mentioned technic is polymerization or copolymerization happened during the monomers via external stimulation such as oxygenation,electricity,heat,ray, radiation and initiation.The superiorities of the in-situ polymerization are as follows:the first advantage is that the technic of preparation is simple,the second one is that this technic can be used to prepare the nanocomposites of the multi-system components,the third one is its variety types, uniform dispersion,lustration surface and high volume content of the second phase or enhanced phase in composite system,besides the forenamed merits,it is also can be applied for preparing the nanocomposite based on polymer matrix by using metal or ceramic as enhanced phase.Based upon above studies,in this thesis,we have prepared several kinds of polymer/inorganic nanocomposites,which are composed of PNIPAM,P(NIPAM-co-AA) as polymer matrix and nano TiO₂,Clay as enhanced phase via in-situ polymerization respectively.The thesis mainly includes following three parts:(1) Nano TiO₂ powder was prepared via sol-gel route,using TBT as precursor,HAc as chelated reagent,HCI as catalyzer,ethanol as solvent,also the mechanism of sol-gel route and the influenced preparation factors were discussed.The silane coupler was used to modify the surface of nano TiO₂, and the modified nano TiO₂ can be bond to the polymer by Si-O-Ti bond with the help of Si-OH of silane coupler.The SEM and TEM micrographs showed that the size of the nano TiO₂ particles dispersed uniformly and their distribution of particle size was really narrow.The IR spectrum revealed the Si-O-Ti bond between nano TiO₂ and silane coupler was formed.EDX results exhibited that the product was what we desired.XRD curves indicated the crystalloid of TiO₂ was affected mainly by the calcine temperature.(2) The composite hydrogels of poly(N-isopropylacrylamide)(PNIPAM) with nano-TiO₂ were prepared with PNIPAM as polymer matrix and nano TiO₂ as enhanced phase by the coupling copolymerization between PNIPAM and the pre-treated nano-TiO₂ particles with a silane coupling agent.The N,N' -methylene bisacrylamide was used as crosslinking agent.The morphology,optical and mechanical properties of the composite hydrogels were studied by SEM,UV-VIS,FT-IR,and Dynamic Mechanical Analysis(DMA) method,respectively.The UV results showed that the composite hydrogels had a good absorption of UV,and TG curves revealed the thermal stability of nanocomposite increased largely,more over,their mechanical strength and toughness were improved markedly through DMA tests.(3) A series of P(NIPAM-co-AA)/Clay nanocomposite hydrogels(abbreviated as NAC) with high swelling ratio and excellent mechanical strength were prepared with PfNIPAM-co-AA) as polymer matrix,inorganic clay as enhanced phase via in-situ polymerization,and their characterization were tested by DMA,SEM,TG/DSC,IR and XRD.During the preparation process, the clay dispersed uniformly in water via the hydration of the cation between the layers,the separated layers penetrated further with polymer matrix,then the nanocomposite hydrogels were formed.In unique NAC gels network,the inorganic clay acted as a multifunctional crosslinker in place of an organic cross-linker(BIS) used in OR gels.The NAC gels exhibited excellent swelling ratio and it had no detectable change as altering the clay concentration,while the swelling ratio of NAC decreased slightly when the clay concentration was up to 25 wt%,which was consistent with the conclusion of SEM micrographs.XRD curves and IR spectrums showed that the clay was exfoliated and intercalated by copolymers,and the sandwich structure was formed.Furthermore, DMA results revealed the composite hydrogel had an excellent mechanical strength in a wide range of clay concentration,while the hydrogel moduli was improved with increasing clay concentration.