Study On The Preparation And Application Of The Polymer Nanocomposites Based On Functionalized Graphene

Graphene,a two-dimensional(2D)carbonaceous material with sp2-bonded carbon atoms,has attracted more and more attention since its experimental discovery in 2004 by Geim et al.Its unique electrical properties,excellent mechanical performance,excellent thermal conductivity,extraordinary thermal properties,low density,and high surface area offer great promise for many practical applications including super-capacitors,microelectronics,catalyze,active materials for energy storage and conversions,sensors and composite reinforcements.Polyimide(PI)is considered as an important high-performance polymer owing to its excellent properties,such as its high mechanical properties,superior thermal stability,good processability,good chemical resistance,low dielectric constant and so on.Therefore,it has been widely used in the aerospace industries,gas separation,fuel cell,automotive,microelectronic,optic and membrane fields.However,the accumulation of electrostatic charge as well as its poor heat dissipation must be resolved in certain PI applications.Hyperbranched polymer has attracted an increasing attention because of its unique structural characteristic,outstanding physical and chemical properties and potential application.In addition to keep the superior high-temperature stabilities,high strength and modulus of polyimides,various introduction of hyperbranched structure into PIs endow their products with good organo-solubilities,low solution viscosity and amorphism In addition to keeping the superior high-temperature stabilities,high strength and modulus of PIs,introduction of hyperbranched structure into PIs also endow their products with good organo-solubilities,low solution viscosity and amorphism.But some performance of the hyperbranched polyimides(HBPIs)which have been reported leaves more or less to be desired.As is known to all,based on polyimides,various organic or inorganic hybrid or composite materials,including graphene oxide and graphene,have been studied widely due to obtain improved comprehensive properties.Graphene(GE)has been proved to be one of the most effective enhanced additives for linear PI-based composites,but the improvements is extremely limited due to the compatibility problem with PI.The individual or few properties of GE/PI nanocomposites which are derived from the precursor of GE(graphene oxide,GO)or its chemical modified product(CMG)with heavy oxygen-containing decoration,are very obviously promoted or improved for the good compatibility of the matrix and additive.Though the interfacial interaction problem of GE/PI nanocomposites could be settled by the incorporation of modified GO with various free reactive groups and PI backbones with strong covalent bonding between the host and guest,but the practical improvements of the nanocomposites are not as good as expected.Because of its diverse functional groups and stable aqueous suspension,GO has been used to compound with various polymers,such as poly(methyl methacrylate),poly(vinyl alcohol),epoxy,polyaniline and polypyrrole,to improve their mechanical properties,thermal properties,electrical properties,and gas barrier properties.It is a pity that they cannot stably suspend in water.Seed emulsion polymerizations have largely advanced in recent years for preparing polymer nanoparticles and emulsions.For these reasons,the following works have been carried out in the paper:First,the hydroxyl groups on GO nanosheet mainly are grafted with the silicon hydroxyl groups,which are hydrolyzed from APTMS.And a series of reduced graphene oxide/polyimide(rGO/PI)nanocomposites are prepared via in situ random co-polycondensation of chemically modified and reduced graphene oxide(rGO-NH2)with commercial ODA,ODPA and BPADA,as well as casting on glasses and thermal imidization,successively.The chemical structure and composition,as well as the microstructure characterized with FTIR,SEM,XPD,XPS and Raman spectroscopy,which are employed to confirm that GO is chemically modified and further reduced successfully for rGO-NH2.It was found that the glass transition temperature(T8),the initial degradation temperature of for 5%weight loss(Tds%)in N2 and air of the resulting rGO/PI nanocomposites were increased,as well as tensile strength,modulus and elongation at break increased in turn compared with neat PI.Second,the hydroxyl groups on GO nano sheet mainly are grafted with the silicon hydroxyl groups,which are hydrolyzed from 3-aminopropyltriethoxy silane coupling agent(KH550).And a series of reduced graphene oxide/polyimide(rGO/PI)nanocomposites are prepared via in situ random co-polycondensation of chemically modified and rGO-NH2 with commercial ODA,PMDA,NTADA,and then the PAA was subsequently converted to polyimide through a thermal imidization process as well as casting on glasses,successively.The chemical structure and composition,as well as the microstructure characterized with FTIR,SEM and XRD which are employed to confirm that GO is chemically modified and further reduced successfully for rGO-NH2.The thermal properties of the resulting rGO/PI nanocomposites meet the optimum results with Td5%and Td10%raising at least 20? or 10?,respectively.Third,based on the aforementioned results,GO colloidal dispersion in DMF and then used to react with excess KH550 to afford KH550-modified GE(KH550-GE).The anhydride-terminated hyperbranched polyimides(AD-HBPIs)was successfully prepared with commercial dianhydrides,4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)and a novel BB2'-type aromatic triamine(TAPP),2,4,6-tris[3-(4-aminophenoxy)phenyl]pyridine,.The KH550-GE is used as a multi-functional crosslinker,which makes the precursor of AD-HBPAA derived from the TAPP and 6FDA,link with each other by in situ solution cross-linking reaction and the same subsequent process,The anhydride-terminated HBPAA was subsequently converted to HBPI through a chemical imidization process,to prepare(KH550-GE)-g-anhydride-terminated-HBPI((KH550-GE)-g-AD-HBPI)nanocomposites.At the same time,KH550-GE is used as a multi-functional co-monomer to prepare KH550-GE modified HBPI((KH550-GE)-co-HBPI)nanocomposites with TAPP and 6FDA,via in suit random solution poly-condensation and subsequent synchronous thermal imidization and reduction.Compared with the pure HBPI,the(KH550-GE)-co-HBPI nanocomposites meet the optimum results with Td5%and Td10%raising at least 58.9? or 20?.On the contrary,KH550-GE)-g-AD-HBPI nanocomposites meet the optimum results with Tds%and Td10%decreasing at least 45.8? or 15?.Fourth,the styrene-acrylic emulsion for canvas coating can be synthesized by seed emulsion polymerization adjusting the proportion of monomers,such as MMA,BA,St,AA And so on,and controlling the variety and quantity of initiators and new emulsifiers.To improve the dispersion and the strength of filler-matrix interface in acrylic resin,the functional graphene oxide(rGO)was obtained by surface modification of graphene oxide(GO)by oleic acid/sodium dodecyl sulfonate(OA-SDS)and then the acrylic nanocomposites containing OA-SDS-GE were prepared.Compared with the neat styrene-acrylic emulsion,OA-SDS-GE modified styrene-acrylic emulsion nanocomposites meet the optimum results with Ta5%and Td10%decreasing at least 29? or 30?.Fifth,the acrylic resin I and II of high brightness and high gloss can be synthesized by seed emulsion polymerization,adjusting the proportion of monomers,such as MMA,BA,St and AA,and controlling the variety and quantity of initiators and new emulsifiers,using sodium persulfate as the initiator and using N-methylol acrylamide as the cross-linking agent.The structure,morphology the acrylic resin I and II were characterized by FTIR,PCS,SEM,TEM and et al.Sixth,based on the aforementioned results,to improve the dispersion and the strength of filler-matrix interface in acrylic resin,the functional graphene oxide was obtained by surface modification using oleic acid/sodium dodecyl sulfonate(OA-SDS)and then the acrylic nanocomposites containing OA-SDS-GO and OA-SDS-GE were prepared.The OA-SDS-GO modified acrylic emulsion nanocomposites and OA-SDS-GE modified acrylic emulsion nanocomposites can be synthesized by seed emulsion polymerization,adjusting the proportion of monomers and controlling the variety and quantity of initiators and new emulsifiers,using sodium persulfate as the initiator and using N-methylol acrylamide as the cross-linking agent.The chemical structure and composition,the microstructure as well as the relevant thermoanalysis are characterized to confirm that the OA-SDS was successfully grafted onto the surface of GO sheets.Furthermore,the corresponding thermal,chemical resistance properties of the acrylic nanocomposites filled with the OA-SDS-GO and OA-SDS-GE nanocomposites were studied and compared with those of neat acrylic emulsion.Over and above all,graphene oxide(GO)was modified by APTMS,KH550 and OA/SDS to produce a series of rGO-NH2.Polymer nanocomposites with high performance were prepared via in situ solution random copolycondensation and seed emulsion polymerization.Thus,it provides a beneficial attempt in the field of developing multifunctional nanocomposites.