Stimuli-Responsive Capsules

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1、3634.4Stimuli-ResponsiveCapsulesYujieMa,MarkA.Hempenius,E.StefanKooij,Wen-FeiDong,HelmuthMçhwald,andG.JuliusVancso4.4.1IntroductionWiththerapiddevelopmentandmultidisciplinarybroadeningofmaterialsscience,manystructuralplatformsthatfeatureunprecedentedandcha

2、racteristicfunctionshavebeenintroduced.Newfunctionalstructurescouldbefabricatedbytheincorporationofclassicalmaterialsusingcontemporarytechniques.However,realbreakthroughsmaylieinthedesignandadvanceofnovelfunctionalmateri-als[1].Oneofthemostimportantclasses

3、ofthesematerialsarestimuli-responsivepolymers.Thesesmart’polymericmaterialscanrespondtospecificexternalstim-uliwithdrasticchangesintheirsizeandconformation[2–4].Inrecentyears,explorationofmolecularstructuresbasedonstimuli-responsivepolymersandtheircontrol

4、ledpropertiesinresponsetoexternalphysicalstimuli,suchastemper-ature,pH,ionicstrength,solventpolarityvariations,electricormagneticfieldsandlighthasflourished.Nevertheless,structure–propertymanipulationusingchemicalstimulistilllargelyremainsunexplored[5].Amo

5、ngthevariousstructuralplatforms,polyelectrolytemultilayers(PEMs)mayoffernewpropertieswhenconstructedfromstimuli-responsivepolymericmaterials[6].Polyelectrolytemultilayersarefabricatedusingtheelectrostaticlayer-by-layer(LBL)technique,basedonthesequentialads

6、orptionofchargedpoly-electrolytespecies.Inthisway,multilayeredpolymericthinfilmsarebuiltupwithcontrolledthicknessandcomposition[7].Oneofthemostattractivefeaturesofthismethodisthatthinfilmscanbetailor-madetodisplayspecificchemicalandphysicalpropertiesbythec

7、hoiceofthepolyelectrolytematerial[7,8].Aqueousprocessingenablessyntheticaswellasnaturalpolyelectrolytes[9,10]tobeassembledtothinfilmsforavarietyofapplications,rangingfromelectrolumines-centdevicestobiosensorarrays[7].Inordertobroadentheirapplicationpoten-t

8、ials,anumberofresponsivePEMsthatemploydifferentstimulihavebeenpro-posedduringthelastfewyears[8,11].Themostwidelyexploredarethosebasedontraditionalstimuli(e.g.pH[6e,12,13],ionicstrength[13,14],andsolventpolari