三嵌段共聚物的合成.pdf

950Biomacromolecules2009,10,950–958

RAFTSynthesisandStimulus-InducedSelf-AssemblyinWater
ofCopolymersBasedontheBiocompatibleMonomer
2-(Methacryloyloxy)ethylPhosphorylcholine

BingYu,†AndrewB.Lowe,*,‡andKazuhikoIshihara§
DepartmentofChemistryandBiochemistry,andSchoolofPolymersandHighPerformanceMaterials,
UniversityofSouthernMississippi,118CollegeDrive,No.10076,Hattiesburg,Mississippi39406,and
DepartmentofMaterialsEngineering,SchoolofEngineering,TheUniversityofTokyo,7-3-1,Hongo,
Bunkyo-ku,Tokyo113-8656,Japan
ReceivedDecember23,2008

Reversibleaddition-fragmentationchaintransfer(RAFT)radicalpolymerization,mediatedby4-cyanopentanoic
aciddithiobenzoateand4,4′-azobis(4-cyanovalericacid)(V-501)inwaterat70°C,ofbiocompatible2-(meth-
acryloyloxy)ethylphosphorylcholine(MPC)yieldsamacro-chaintransferagent(CTA)thatwasemployedinthe
synthesisofarangeofstimulus-responsiveABdiblockcopolymersinproticmedia.Well-definedblockcopolymers
ofvaryingmolarcomposition,withnarrowmolecularweightdistributions(Mw/Mn)1.10-1.24)wereprepared
withN,N-diethylacrylamide(DEAm),4-vinylbenzoicacid(VBZ),N-(3-sulfopropyl)-N-methacryloyloxyethyl-
N,N-dimethylammoniumbetaine(DMAPS),andthenewlysynthesizedN,N-di-n-propylbenzylvinylamine(Dn-
PBVA)ineithermethanol,2,2,2-trifluoroethanol,oraqueousmedia.Whenacombinationof1HNMRspectroscopy
anddynamiclightscatteringisused,itisshownthatallblockcopolymersarecapableofexistingasmolecularly
dissolvedchainsinaqueousmediawithaveragehydrodynamicdiametersof∼6-7nmprovidedtheaqueous
environmentisappropriatelytuned.Similarly,theseunimerscanbeinducedtoundergoself-assemblyinthe
sameaqueousenvironmentprovidedthecorrectexternalstimulus(changeintemperature,pH,orelectrolyte
concentration)isapplied.Insuchinstances,aggregateswithaveragesizesintherangeof∼22-180nmare
formedandaremostlikelyduetotheformationofpolymericmicellesandvesicles.Suchself-assemblyisalso
completelyreversible.Removal,orreversal,oftheappliedstimulusresultsinthereorganizationtotheunimeric
state.

Introductionselective,and