Surface selective and controllable photo-grafting for synthesis of tailored macroporous membrane adsorbers [Elektronische Ressource] = Oberflächenselektive und kontrollierbare Photopfropfung für die Synthese von maßeschneiderten makroporösen Membranadsorbern / by Dongming He

Hc0015

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• Publié par: universitat_duisburg-essen
• Publié le: 01 janvier 2008
• Nombre de lectures: 25
• Poids de l'ouvrage: 2 Mo

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Surface-selective and Controllable Photo-grafting for Synthesis
of Tailored Macroporous Membrane Adsorbers
(OberflächenselektiveundkontrollierbarePhotopfropfungfürdieSynthese
vonmaßgeschneidertenmakroporösenMembranadsorbern)







by

DongmingHe
Jiangxi, China


ThesissubmittedtotheDepartmentofChemistryof
UniversitätDuisburg&Essen,inpartialfulfillmentof
therequirementsofthedegreeof
Dr.rer.nat.






ApprovedbytheexaminingcommitteeonJuly 3, 2008:
Chair :Prof.Dr.HeinzWilhelmSiesler
Advisor :Prof.Dr.MathiasUlbricht
Reviewer :Prof.Dr.ThomasSchrader



Essen,2008

iAbstract
Photo&grafting is a straightforward and promisingetchnique for surface modification of
polymeric membranes. This work emphasized on the development and investigation of
surface&selectivephoto&graftingmethodfrompolaorrganicsolution;ontheotherhand,on
thepreparationofmembraneadsorbersviatheproposedgraftingmethodsandevaluation
oftheresultingmembraneadsorbers.
Two novel surface&selective photo&grafting methodshave been developed: synergist
immobilization and iniferter immobilization methods. Hydrophilized polypropylene (PP)
microfiltration(MF)membrane,whosesurface polymerlayercontains polyacrylate, was
usedasbasemembraneforbothmethods;track&etchdepolyethyleneterephthalate(PET)
MF membranes (PET200 and PET400) were used for extension of synergist
immobilization method and further investigation; methanol or acetonitrile solution of
acrylamide (AAm) with/without cross&linker (EDMA) was applied for investigation of
graftingmechanism.
For synergist immobilization method, the synergist (tertiary amino groups) for
photo&initiator benzophenone (BP) was introduced onto the membrane surface via an
aminolysisreactionwithdiethylethylenediamine(DEEDA).Thereactionconditionshave
been optimized. The proposed grafting mechanism was verified by the significant
difference in degree of grafting (DG) between original and aminolysed membranes. In
order to better understand and improve this novel method, detailed investigation of
functionalization parameters and affecting factors has been carried out. The grafted
membranes were characterized by ATR&IR, contact angle, SEM, permporometry, liquid
permeability and zeta potential. The obtained results demonstrated that the highest
surface&selectivity of photo&grafting could be acehvied only under the optimum grafting
conditions, i.e., inert solvent to excited BP should be used to reduce/avoid
homopolymerizationinbulksolution;appropriatelylowUVintensityshouldbeappliedto
excludetheuncontrolledsidegraftingreaction(anotherfunctionalizationmechanismwas
discoveredathighUVintensitybasedondirectgenerationofstarterradical);appropriately
low BP concentration was used to reduce the non&seelctive photo&grafting. Thus, the
grafted layer could be well controlled by immobilized synergist concentration, UV
irradiation time, monomer concentration and initiator concentration. In addition, this
method has been successfully applied to track&etchde PET membrane, and it is also
expectedtofunctionalizeotherpolymericmembraneswithsimilarchemicalstructure.
iiFor iniferter immobilization method, the reaction conditions for immobilization of
photo&iniferter(dithiocarbamategroup)havebeenoptimized.Thegraftingmechanismhas
beenverifiedbytherelationshipbetweenDGandphoto&iniferterconcentration.Detailed
investigation with respect to grafting efficiency, uniformity on the whole membrane
surfaceandcontrolled graftedlayerstructurehasbeencarriedout.This graftingmethod
exhibitedhighgraftingefficiency,uniformmodificationandhighcontrollability.However,
there&initiationefficiencywaslowfortheselecetdgraftingsystembasedonthesignificant
differenceinDGvalueobtainedbycontinuousandintermittentUVirradiation.
Via developed synergist immobilization method and conventional photo&initiator
adsorption method, three types of anion&exchange mme branes (low and high grafting
densityandslightlycross&linkedgraftedlayer)hvaebeenpreparedinaqueoussolutionof
(2&(methacryloyloxy)ethyl) trimethylammonium chlordie (MAETMAC) with/without
EDMA, using hydrophilized PP MF membrane as support. The effect of grafted layer
architecture on protein binding capacity and liquid permeability has been investigated.
Buffer/elution solution permeability, static and dynamic protein binding behaviors have
beendeterminedforselectedresultinganion&exchangemembranes.Analysesdemonstrated
that cross&linking of grafted layer and high graftnig density can improve the liquid
permeabilityofmembraneadsorbers.Buttheproteinbindingcapacitywasrelativelylow
for high grafting density membrane. In comparison, the membranes with slightly
cross&linkedgraftedlayerexhibitedimprovedoverlalperformance.Inaddition,compared
to conventional adsorption method, synergist immobilization method is a more efficient
and suitable grafting technique for the preparation of anion&exchange membranes with
three&dimensionalgraftedlayerbasedonthehighergraftingefficiencyandbetterdynamic
performanceformembraneadsorberspreparedviathismethod.
For the preparation of affinity membrane, track&ethced PET400 membrane was grafted
with a special functional copolymer with bisphosphonate ester groups via synergist
immobilizationmethodfromacetonitrilesolution.Theresultingaffinitymembraneshowed
highbindingcapacityforselectedproteins.Especially,itwasfoundthatmarkedlyhigher
binding capacity and affinity have been achieved for lysozyme than for cytochrome C,
both proteins with similar pI value and protein size. With this affinity membrane, the
protein separation has been realized in the 1:1 mixture solution of lysozyme and
cytochromeCwithaveryhighselectivity.
UsinghydrophilizedPPMFmembrane,MIPthin&layercompositemembraneshavebeen
prepared via synergist immobilization. However, the imprinting effect was not observed
iiiprobably due to the influence of synergist on the stability of formed complex between
functional monomer and template and template concentration in bulk solution. The
optimizationofcompositionforMIPhasbeenperformed.
Iniferter immobilization method would be a promising alternative. MIP thin&layer
composite membranes have been synthesized via this method, but the evaluation and
furtherinvestigationisstillinprogress.




























iv









This thesis is dedicated
to my wife (Liu Na)
for her love, endless support and encouragement.
















v


ThisworkwasperformedduringtheperiodfromJuly2005toMay2008attheInstituteof
Technical Chemistry (Lehrstuhl für Technische Chemie II), Department of Chemistry,
UniversitätDuisburg&Essen,underthesupervisionofProf.Dr.MathiasUlbricht.


















I declare that this dissertation represents my own work, except where due
acknowledgementismade.



DongmingHe




viAcknowledgement
This thesis could not be finished without the help and support of many people who are
gratefullyacknowledgedhere.
Attheveryfirst,I’mhonoredtoexpressmydeepestgratitudetomydedicatedsupervisor,
Prof. Dr. Mathias Ulbricht, with whose able guidance I could have worked out this
dissertation. He has offered me valuable ideas and suggestions with his profound
knowledge and rich research experiences. His patience and kindness are greatly
appreciated.Besides,becauseofthefinancialsupportprovidedbyhim,Icouldcontinue
andcompletemyPhDstudy.
I’m also extremely grateful to my reviewer Prof. Dr. Thomas Schrader (Organische
Chemie, UDuE) for his advice and discussion as well as giving a good opportunity for
cooperation.
IamgreatlyindebtedtotheHanns&Seidelfoundation(inGermany)forprovidingtwo&year
scholarshipandgivinganopportunitytostartmyPhDstudyinGermany.Iwouldliketo
givespecialthankstotheleadersfortheirunderstandingaboutmyspecialsituationduring
thetime.
I would like to thank Sun Wei (Organische Chemie, UDuE) for the very pleasant
cooperation and discussion, and to all members of our research group at Lehrstuhl für
Technische Chemie II, Universität Duisburg&Essen, namely, Inge, Claudia, Jun, Haofei,
Heru, Mehmet, Qian, Yu, Abdus, Marcel, Halim, Nico, Christian, Danuta, Alex, Falk,
Rafael, Monica, Nadia, Eva, Su&Hyoun, Dr. Illing, Polina, Frau Steffens and Frau
Nordmannforprovidingnicecompany,helpandexcellentworkingenvironment.
IampleasedtothankthegroupofProf.Dr.H.W.Siesler(PhysikalischeChemie,UDuE)
for help with the FTIR measurements, S. Boukercha (Anorganische Chemie, UDuE) for
theSEManalyses,andDr.T.Schaller(OrganischeChemie,UDuE)forSolidstateNMR
measurement.
Last but no least, I would love to pay my special gratitude to my wife, my parents and
parents&in&lawfortheirendles