Nanocelluloses： A New Family of Nature-Based Mater

GreenNanomaterialsDOI:10.1002/anie.201001273Nanocelluloses:ANewFamilyofNature-BasedMaterialsDieterKlemm,*FriederikeKramer,SebastianMoritz,TomLindstrm,*MikaelAnkerfors,DerekGray,*andAnnieDorrisAngewandteChemieKeywords:cellulose·nanocellulose·nanomaterials·nature-basedmaterials·polymersD.Klemmetal.Reviews54382011Wiley-VCHVerlagGmbH&Co.KGaA,WeinheimAngew.Chem.Int.Ed.2011,50,5438–54661.IntroductionCelluloseisoneofthemostimportantnaturalpolymers,analmostinexhaustiblerawmaterial,andakeysourceofsustainablematerialsonanindustrialscale.Formillennia,cellulosehasbeenusedintheformofwoodandplantfibersasanenergysource,forbuildingmaterials,andforclothing.SincetheEgyptianpapyri,celluloseproductshaveplayedacentralroleintherecordingandtransmissionofhumanculture.Asachemicalrawmaterial,cellulosehasbeenusedforabout150years.Advancinginsightintothestructuralfeaturesandreactivityofcellulosehasdriventhestep-by-stepcreationofnoveltypesofmaterials.Highlightswerethedevelopmentofcelluloseestersandcelluloseethersaswellasofcelluloseregeneratesandthediscoveryofthepolymericstateofmolecules.ThereactionofcellulosewithnitricacidtoformcellulosenitratewasthebasisofaprocesscarriedoutbytheHyattManufacturingCompanyin1870tomakecelluloid,theveryfirstthermoplasticpolymermaterial.Thechemicalmodificationofcelluloseonanindustrialscaleledtoabroadrangeofproductsbasedoncellulosefromwood.Thefirstexamplewasthefabricationofregeneratedcellulosefila-mentsbyspinningasolutionofcelluloseinamixtureofcopperhydroxideandaqueousammonia.Thisdevelopmentwasfollowedbytheparticularlyimportantlarge-scaleviscoseprocessforproducingrayonfiberandfilament.Novelmaterialsforcoatings,films,membranes,buildingmaterials,drillingtechniques,pharmaceuticals,andfoodstuffswereobtainedbythelarge-scaleproductionofcelluloseestersandethers.Theelucidationofthepolymericstructureofcellulosecanbetracedbackto1920andthepioneeringworkofStaudinger.Thesestudies,alongwithStaudingersresearchonotherchainmolecules,markedthediscoveryofthepolymericstateofmoleculesandtheoriginofpolymerscience.Currently,theisolation,characterization,andsearchforapplicationsofnovelformsofcellulose,variouslytermedcrystallites,nanocrystals,whiskers,nanofibrils,andnanofib-ers,isgeneratingmuchactivity.Novelmethodsfortheirproductionrangefromtop-downmethodsinvolvingenzy-matic/chemical/physicalmethodologiesfortheirisolationfromwoodandforest/agriculturalresiduestothebottom-upproductionofcellulosenanofibrilsfromglucosebybacteria.Suchisolatedcellulosicmaterialswithonedimensioninthenanometerrangearereferredtogenericallyasnanocellu-loses.Inauniquemanner,thesenanocellulosescombineimportantcelluloseproperties—suchashydrophilicity,broadchemical-modificationcapacity,andtheformationofversatilesemicrystallinefibermorphologies—withthespecificfeaturesofnanoscalematerials:featuresmainlycausedbytheverylargesurfaceareaofthesematerials.Onthebasisoftheirdimensions,functions,andpreparationmethods,whichinturndependmainlyonthecellulosicsourceandontheprocessingconditions,nanocellulosesmaybeclassifiedinthreemainsubcategories(Table1).Typicalstructuresofthesecellulosetypesonthenanoscalecanbeseenintheelectronmicro-graphsinFigure1.AsapparentfromTable1,thenomenclatureofnano-celluloseshasnotbeenusedinacompletelyuniformmanner[*]Prof.Dr.D.Klemm,Dr.F.Kramer,S.MoritzPolymetJenaAssociationandJenpolymerMaterialsLtd.&Co.KGWildenbruchstrasse15,07745Jena(Germany)Fax:[phone]E-mail:[e-mail]:m,M.AnkerforsMaterialProcesses,InnventiaABBox5604,11486Stockholm(Sweden)Fax:[phone]E-mail:[e-mail]:(Canada)Fax:[phone]E-mail:[e-mail]:(MFC)RetrievedfromWood-BasedFibers54423.NanocrystallineCellulose(NCC):ASustainableReinforcingAgent54504.BiofabricationofBacterialNanocellulose(BNC):PotentialandPerspectives54545.SummaryandOutlook5460Nanocelluloses5439Angew.Chem.Int.Ed.2011,50,5438–54662011Wiley-VCHVerlagGmbH&Co.KGaA,Weinheiminthepast.Her