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| - Synthesis and Characterization of Water-Soluble AmphipaticPolystyrene-Based Dendrigrafts
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| - New water-soluble amphipatic hyperbranched organic polymers composed of a hydrophobicpolystyrene core and a hydrophilic shell have been synthesized and characterized. An arborescentpolystyrene core is first synthesized by the “graft-on-graft” technique based on the iterative grafting ofend-functional polystyryllithium chains onto reactive poly(chloroethyl vinyl) ether backbones. Chain-extension of the external branches of the hyperbranched polystyrene is then achieved by living cationicpolymerization of protected hydrophilic vinyl ethers. This yields polystyrene dendrigrafts surrounded bya dense poly(vinyl ether) shell that is made hydrophilic by deprotection of hydroxyl functions of vinylether units. The obtained nanometer-sized macromolecular structures are fully soluble in aqueous mediaand present unimodal and narrow size distribution with an average diameter of about 100 nm. Thedimensions and shape of the individual macromolecules before and after the deprotection step were furtherinvestigated in solution by dynamic light scattering (DLS) and as isolated unimolecular deposits usingatomic force microscopy and cryomicroscopy.The results obtained using both imaging techniques are inagreement with those obtained by DLS and provide additional information on the internal structure ofthe amphipatic dendrigrafts. Both the protected and the deprotected amphipatic polymers exhibit acomplex internal organization constituted by distinct subdomains. These peculiar morphologies resultfrom the internal segregation of chemically distinct macromolecular blocks that constitute the dendrigraftbranches and associate with neighboring blocks to form separate phases.
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