Synthesis, reactivity, and pH-responsive assembly of new double hydrophilic block copolymers of carboxymethyldextran and poly(ethylene glycol) |
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Authors: | Oscar Suarez Hernandez,Ghareb Mohamed Soliman,Franç oise M. Winnik |
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Affiliation: | a Department of Chemistry, Université de Montréal, CP 6128 Succursale Centre Ville, Montréal QC H3C 3J7, Canada b Faculty of Pharmacy, Université de Montréal, CP 6128 Succursale Centre Ville, Montréal QC H3C 3J7, Canada |
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Abstract: | Double hydrophilic block copolymers (DHBC) were prepared by end-to-end coupling of two biocompatible water-soluble homopolymers: the polysaccharide dextran (Mw 8300 or 14,700 g mol−1) and ω-amino poly(ethylene glycol) (PEG-NH2, Mw 3000 or 7000 g mol−1). The synthesis involved, first, specific oxidation of the dextran terminal aldehyde group and, second, covalent linkage of PEG-NH2 via a lactone aminolysis reaction. The diblock copolymers dextran-PEG (DEX-PEG) were converted in high yield into the corresponding carboxymethyldextran-PEG (CMD-PEG) derivatives with control over the degree of substitution, from 30 to 85 mol% CH2COOH groups per glucopyranosyl unit. Further modifications of a CMD-PEG block copolymer led to N-(2-aminoethyl)carbamidomethyldextran-PEG yielding a pair of oppositely-charged DHBC of identical charge density, chain length, and neutral block/charged block content. The properties of CMD-PEG in aqueous solutions were studied by static and dynamic light scattering as a function of solution pH, providing evidence of the pH-sensitive assembly of the copolymers driven by inter- and intra-chain hydrogen-bond formation. |
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Keywords: | Polysaccharides Diblock copolymers Dextran |
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