Positron annihilation study on thin-film compo

Positronannihilationstudyonthin-filmcompositepervaporationmembranes:CorrelationbetweenpolyamidefinestructureanddifferentinterfacialpolymerizationconditionsShu-HsienHuangb,**,Wei-SongHunga,Der-JangLiawc,Hui-AnTsaid,GeorgeJ.Jiangb,Kueir-RarnLeea,*,Juin-YihLaiaaR&DCenterforMembraneTechnology,DepartmentofChemicalEngineering,ChungYuanUniversity,ChungLi32023,TaiwanbDepartmentofChemicalandMaterialsEngineering,NationalIlanUniversity,I-Lan26047,TaiwancDepartmentofChemicalEngineering,NationalTaiwanUniversityofScienceandTechnology,Taipei10607,TaiwandDepartmentofMaterialandFiber,NanyaInstituteofTechnology,ChungLi32034,TaiwanarticleinfoArticlehistory:Received27June2009Receivedinrevisedform17January2010Accepted30January2010Availableonline4February2010Keywords:InterfacialpolymerizationPolyamidePositronannihilationspectroscopy(PAS)abstractToinvestigatethevariationinthefinestructureofpolyamidethin-filmcomposite(TFC)membranespreparedviatwodifferentinterfacialpolymerizationconditions(IP-IandIP-II),experimentsonScanningElectronMicroscopy(SEM),AtomicForceMicroscopy(AFM),watercontactangle,andpositronannihila-tionspectroscopy(PAS)coupledtoaslowpositronbeamwereconducted.PolyamideTFCmembraneswerepreparedviatheinterfacialpolymerizationreactionbetweentriethylenetetramine(TETA)andtrimesoylchloride(TMC)onthesurfaceofamodifiedpolyacrylonitrile(mPAN)membrane.ComparedwiththepolyamideTFCmembranepreparedviaIP-I,thepolyamidelayerpreparedviaIP-IIshowedashorterSplateaulength(thinnerthickness),ahighero-PsintensityI3value(higherfree-volumeconcentration),andasmallero-Pslifetimes3value(smallerfree-volumesize),resultinginhigherpermeationrateandsepa-rationfactorobtainedfromthepervaporativeseparationofa70wt%isopropanolaqueoussolutionat25�C.�2010ElsevierLtd.Allrightsreserved.1.IntroductionInterfacialpolymerizationisbasedonareactionthatformsapolymerfilmattheinterfacebetweentwoimmisciblephases.Ineachofthesephases,ahighlyreactivemonomerisdissolved.PolyamideTFCmembranes,whicharepreparedbytheinterfacialpolymerizati