This thesis focuses on the progress in the field of block copolymers self-assembly in an aqueous environment. It is well known that AB diblock copolymers comprising a hydrophilic A segment and a hydrophobic B block, under proper conditions, are able to self-assemble in water into polymeric micelle, supramolecular assemblies of block copolymers with a characteristic core-shell structure. Poly(ethylene glycol) (PEG) is so far the most adopted hydrophilic polymer to provide colloidal stability to polymer nano-assemblies. The so-called PEGylation is usually obtained by covalently linking a PEG chain to a hydrophobic polymer or insoluble compound that is wanted to be dispersed in water. However, the advent of PEG based macromonomers, that is to say PEG chains functionalized with a vinyl group, paved the way to more complex polymer structures. In this thesis, PEG based AB diblock copolymers showing a reversible micellization in water have been produced and their properties widely investigated. Production of block copolymers with well-defined structures and composition was achieved via reversible addition fragmentation chain transfer (RAFT) polymerization although in some cases also different synthesis methods were investigated. The possibility to finely tune the copolymer hydrophobicity acting on its structure and the peculiar ability of these systems to undergo a reversible expansion/collapse of the PEG portion, allowed the formation of amphiphilic materials. As a consequence, these polymers in aqueous environment formed micelle whose size and chemistry was controlled via the adoption of different RAFT macromolecular agents. Potential application possibilities of block copolymer as nanoreservoir in aqueous environment are also discussed.
Il presente elaborato si focalizza sull’analisi dei progressi nel campo del self-assembly di copolimeri a blocchi in ambiente acquoso. E’ risaputo infatti che i copolimeri diblocco AB, costituiti da una porzione A idrofilica e da B idrofobica, dispersi in mezzo acquoso in opportune condizioni e concentrazioni, tendono ad auto-assemblare spontaneamente in micelle polimeriche, aggregati sopramolecolari caratterizzati da una particolare struttura “core-shell”. Ad oggi, il polietilenglicole (noto anche con la sigla PEG) risulta essere il polimero idrofilo più utilizzato per favorire la stabilità colloidale di nanoparticelle polimeriche. Il cosiddetto processo di PEGilazione si realizza generalmente legando covalentemente una catena polimerica di glicole polietilenico ad un polimero idrofobo o ad un composto insolubile che si vuole disperdere in fase acquosa. I macromonomeri a base di PEG, ovvero catene di polietilenglicole funzionalizzate con un gruppo vinilico, hanno così aperto la strada alla sintesi di polimeri con strutture molto complesse. Nell’ambito di questa tesi, sono stati sintetizzati e ampiamente caratterizzati copolimeri diblocco AB a base di PEG che mostrano una micellizzazione reversibile in acqua. La tecnica di polimerizzazione principalmente usata per la produzione di questi copolimeri è la cosiddetta reversible addition fragmentation chain transfer (RAFT) polymerization, che permette di ottenere polimeri con strutture piuttosto complesse, nonostante in alcuni casi anche altri metodi di sintesi siano stati utilizzati. La possibilità di calibrare accuratamente l’idrofobicità del copolimero modificandone la struttura e la particolare abilità di questi sistemi di subire un processo reversibile di espansione/collasso della porzione contente PEG, ha permesso di produrre materiali anfifilici. Di conseguenza, questi polimeri in ambiente acquoso si sono assemblati formando micelle con caratteristiche differenti, definite dall’utilizzo di diversi agenti RAFT macromolecolari. Inoltre, sono state studiate le potenziali applicazioni di questi copolimeri a blocchi come nano contenitori.
Study of the micellization of PEG based polymers in aqueous environment
ARENA, CHIARA
2016/2017
Abstract
This thesis focuses on the progress in the field of block copolymers self-assembly in an aqueous environment. It is well known that AB diblock copolymers comprising a hydrophilic A segment and a hydrophobic B block, under proper conditions, are able to self-assemble in water into polymeric micelle, supramolecular assemblies of block copolymers with a characteristic core-shell structure. Poly(ethylene glycol) (PEG) is so far the most adopted hydrophilic polymer to provide colloidal stability to polymer nano-assemblies. The so-called PEGylation is usually obtained by covalently linking a PEG chain to a hydrophobic polymer or insoluble compound that is wanted to be dispersed in water. However, the advent of PEG based macromonomers, that is to say PEG chains functionalized with a vinyl group, paved the way to more complex polymer structures. In this thesis, PEG based AB diblock copolymers showing a reversible micellization in water have been produced and their properties widely investigated. Production of block copolymers with well-defined structures and composition was achieved via reversible addition fragmentation chain transfer (RAFT) polymerization although in some cases also different synthesis methods were investigated. The possibility to finely tune the copolymer hydrophobicity acting on its structure and the peculiar ability of these systems to undergo a reversible expansion/collapse of the PEG portion, allowed the formation of amphiphilic materials. As a consequence, these polymers in aqueous environment formed micelle whose size and chemistry was controlled via the adoption of different RAFT macromolecular agents. Potential application possibilities of block copolymer as nanoreservoir in aqueous environment are also discussed.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/137640