A delicate ionizable-group effect on self-assembly and thermogelling of amphiphilic block copolymers in water

来自 dx.doi.org

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112

作者：

G Chang，Y Lin，Z Yang，J Ding

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摘要：

A carboxyl-capped PLGA–PEG–PLGA block copolymer (PLGA: poly(,-lactic acid--glycolic acid), PEG: poly(ethylene glycol)) was synthesized, and its self-assembly and thermogelling behaviors in water were studied at different pH values. While the aqueous solution of the virgin PLGA–PEG–PLGA block copolymer with the composition in this paper did not undergo sol–gel transition, that of the end-capped derivative exhibited four macroscopic states, sol, turbid sol, physical gel, and precipitate, dependent upon temperature and pH. Especially between pH 4.5 and 5.0, a concentrated aqueous system underwent sol–gel-(turbid sol)-precipitate transitions upon increase of temperature. Complex of dissociation constant p of weak-acid groups on the micelle surfaces was illustrated. Dynamic light scattering, hydrophobic dye solubilization, transmission electron microscopy, NMR, and potentiometric titration were used to examine the relationship between ionization of the end groups of the polymer chains on the molecular level, micellization of the amphiphilic block copolymers on the supermolecular level, and physical gelation on the macroscopic level. The present research reveals the complex of the multi-scale self-assembly of amphiphilic polymer ionomers in a selective solvent.Graphical abstract

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关键词：

Bibliography, Experimental/ ionisation nuclear magnetic resonance pH phase transformations polymer blends self-assembly sol-gel processing solubility transmission electron microscopy/ ionizable-group effect amphiphilic block copolymer thermogelling water carboxyl-capped PLGA-PEG-PLGA block copolymer poly(d,l-lactic acid-co-glycolic acid) poly(ethylene glycol) pH aqueous solution virgin PLGA-PEG-PLGA block copolymer sol-gel transition macroscopic states turbid sol physical gel sol-gel-(turbid sol)-precipitate transitions dissociation constant micelle surfaces dynamic light scattering hydrophobic dye solubilization transmission electron microscopy NMR potentiometric titration ionization polymer chains molecular level micellization amphiphilic block copolymers supermolecular level physical gelation macroscopic level multiscale self-assembly amphiphilic polymer ionomers/ A8120S Preparation of polymers and plastics A8245 Electrochemistry and electrophoresis A6470 Phase equilib