Polyisobutylene-containing Stimuli-responsive Amphiphilic Diblock Copolymers: Synthesis, Characterization, And Self-assembly

Amphiphilic block copolymers have potential applications in nanoscience andnanotechnology （drug and gene carriers, diagnostic imaging and nano-reactors, etc.）, bythe extensive attention and research. Polyisobutylene is recognized for its environmentalstability, bio-security, excellent biocompatibility, as well as superior gas-barrier inrecent years in industry area, amphiphilic block copolymers containing polyisobutylenereported very rarely. This paper focuses on the synthesis and characterization ofresponsive amphiphilic diblock copolymers based on polyisobutylene （PIB） and theirsolution behaviors. The monomers used in this work include poly [2-（N,N-dimethylamino） ethyl methacrylate]（PDMAEMA）, tert-butyl methacrylate （tBMA）,MePEG.The main content and conclusions of this dissertation are summarized in threeparts:（1） The preparation, characterization and behavior of containingpolyisobutylene polycationic amphiphilic block copolymersA kind of commercial exo-olefin-terminated high reactive polyisobutylene （HRPIB）was first changed to hydroxyl-terminated PIB via hydroboration-oxidation of C=Cdouble bond in the chain end, and then reacted with potassium hydride to yield anoxyanion-capped PIB （PIB-O-K+）. Using PIB-O-K+as a macroinitiator to polymerize2-（N, N-dimethylamino） ethyl methacrylate, we can obtain a kind of diblock copolymerPIB-b-PDMAEMA. The composition and chemical structures of the functional PIB andthe copolymers have been characterized by1H NMR, fourier transform infraredspectroscopy （FT-IR） and thermogravimetric analysis （TGA）. The average molecularweight and polydispersity index （PDI） were determined by gel permeationchromatography （GPC）. The results obtained from transmission electron microscopy （TEM） revealed that these diblock copolymers are able to self-assemble into vesicles，spheres and cylindrical aggregates with different particle sizes.The morphologiesdepended on the variation of concentrations, solvent polarity, pH value and the blockcopolymer composition.（2） The preparation, characterization and behavior of containingpolyisobutylene polyanion amphiphilic block copolymersThe HTPIB was also prepared by hydroboration/oxidation of commercialexo-olefin-terminated highly reactive polyisobutylene （HRPIB）. The polyanionPIB-b-PMAA can be prepared via a combination of oxyanion-initiated polymerization（OIP） of tert-butyl methacrylate （tBMA） and subsequent hydrolysis of ester groups inPtBMA segment. The composition and chemical structures of the copolymers have beencharacterized by1H NMR, fourier transform infrared spectroscopy （FT-IR） andthermogravimetric analysis （TGA）. The average molecular weight and polydispersityindex （PDI） were determined by gel permeation chromatography （GPC）. The resultsobtained from transmission electron microscopy （TEM） revealed that these diblockcopolymers were able to self-assemble into micelles, vesicles, spherical, lamellaraggregates or cylindrical with different particle sizes. The morphologies depended onthe concentration and ratio of the mixed solution, the block copolymer composition,solvent polarity and pH value.（3） Preparation and Characterization of Amphiphilic block copolymer PIB-b-MePEGFirstly, The HTPIB was also prepared by hydroboration/oxidation of commercialexo-olefin-terminated highly reactive polyisobutylene （HRPIB）. Secondly, thealkynyl-capped PIB was prepared by HTPIB and Propyne acid through esterificationreaction. Thirdly, MePEG-acetal-Cl was synthesized by MePEG and2-Chloroethylvinyl ether, and then reacted with NaN₃to generate the azide-capped MePEG-acetal-N₃.Finally, amphiphilic block copolymers PIB-b-MePEG were prepared by alkynyl-cappedPIB and azide-capped MePEG-acetal-N₃via “Click” reaction. The composition andchemical structures of the copolymers PIB-b-MePEG were characterized by1H NMR,FT-IR. The results shown we obtained the amphiphilic block copolymers by the “Click”reaction successfully.