Abstract
In this work, the synthesis, selective chemical modifications, and self-assembly behavior in aqueous media of a novel poly(2-(dimethylamino)ethyl acrylate)20-b-poly(N-isopropylacrylamide)11-b-poly(oligo ethylene glycol methyl ether acrylate)18 (PDMAEA20-b-PNIPAM11-b-POEGA18) dual-responsive (pH and temperature) and triply hydrophilic amino-based triblock terpolymer are reported. The amine functional triblock terpolymer was synthesized by sequential reversible addition fragmentation chain transfer polymerization (RAFT) polymerization and molecularly characterized by size exclusion chromatography (SEC) and 1H-NMR spectroscopy that evidenced the success of the three-step polymerization scheme. The tertiary amine pendant groups of the PDMAEA block were chemically modified in order to produce the Q1PDMAEA20-b-PNIPAM11-b-POEGA18 as well as the Q6PDMAEA20-b-PNIPAM11-b-POEGA18 quaternized triblock terpolymers (Q1 and Q6 prefixes show the number of carbon atoms (C1 and C6) attached on the PDMAEA groups) using methyl iodide (CH3I) and 1-iodohexane (C6H13I) as the quaternizing agents and the SPDMAEA20-b-PNIPAM11-b-POEGA18 sulfobetainized triblock terpolymer using 1,3 propanesultone (C3H6O3S) as the sulfobetainization agent. The self-assembly properties of the triblock terpolymers in aqueous solutions upon varying temperature and solution pH were studied by light scattering and fluorescence spectroscopy experiments. The novel triblock terpolymers self-assemble into nanosized aggregates upon solution temperature rise above the nominal lower critical solution temperature (LCST) of the temperature-responsive PNIPAM block. The remarkable stimuli-responsive self-assembly behavior of the novel triblock terpolymers in aqueous media make them interesting candidates for biomedical applications in the fields of drug and gene delivery.
Highlights
Diblock copolymers have garnered the ever-increasing scientific interest over the past decades regarding the design and synthesis of novel copolymer systems by implementing facile polymerization techniques as well as the in-depth comprehension of behavioral motifs intending to their utilization in a wide range of applications [1,2,3,4,5]
The chosen chain transfer agent (CTA) was the DDMAT, because it is known from other studies [63,64] that it is reactive for these kinds of monomers, resulting in well-defined polymers with controlled molecular weights, as well as rather narrow and symmetrical molecular weight distributions
A dual-responsive PDMAEA20 -b-PNIPAM11 -b-POEGA18 triblock terpolymer was successfully synthesized via sequential reversible addition fragmentation chain transfer polymerization (RAFT) polymerization
Summary
Diblock copolymers have garnered the ever-increasing scientific interest over the past decades regarding the design and synthesis of novel copolymer systems by implementing facile polymerization techniques as well as the in-depth comprehension of behavioral motifs intending to their utilization in a wide range of applications [1,2,3,4,5]. The addition of one more stimuli-responsive block to the AB type diblock copolymers can provide novel linear stimuli-responsive triblock terpolymers of the ABC type with ameliorated functionality and structural complexity at the molecular and supramolecular. Controlled radical polymerization methodologies such as nitroxide-mediated radical polymerization (NMP) [11], atom transfer radical polymerization (ATRP) [12,13] and reversible addition fragmentation chain transfer polymerization (RAFT) [14,15] have been utilized for the synthesis of linear triblock terpolymers. RAFT polymerization demonstrates some significant advantages, which include the synthesis of well-defined polymers with controlled molecular characteristics and complex architectures, under less strict experimental conditions, the compatibility with a wide variety of functional and biocompatible monomers, as well as the absence of non-biocompatible inorganic catalysts [16,17,18,19,20]. Based on the above-mentioned features, RAFT polymerization has been used widely for the synthesis of several stimuli-responsive triblock terpolymers [21,22,23,24] that can be utilized for advanced biomedical applications, such as drug and/or gene delivery [25,26]
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