Multifunctional Stimuli Responsive ABC Terpolymers: From Three‐Compartment Micelles to Three‐Dimensional Network

Katsampas, Ilias; Roiter, Yuri; Minko, Sergiy; Tsitsilianis, Constantinos

doi:10.1002/marc.200500387

Cited by 42 publications

(15 citation statements)

References 23 publications

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“…[28,29] Temperature-sensitive ABC triblock copolymers were studied by Hamley and co-workers. These systems, however, proved to be moderately effective gelators, with a required copolymer concentration around 20 wt %.…”

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Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

et al. 2007

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Self-assembly of block copolymers in a solvent selective for one block is at the origin of unique behaviors of micellar particles, such as stimuli responsiveness. [1][2][3][4] ABC triblock copolymers are very versatile precursors of micelles, whose internal structure is dictated by the constitutive blocks and their sequential arrangement. Accordingly, smart materials can be contemplated, including multiresponsive ones. Herein, we report on pH-and temperature-sensitive gels formed by an amphiphilic ABC triblock copolymer, polystyrene-bpoly(2-vinylpyridine)-b-poly(ethylene oxide). The selfassembly of this copolymer into core-shell-corona (CSC) micelles [5,6] is observed in N,N-dimethylformamide upon addition of water. The micellar solution forms a soft gel at a lower threshold copolymer concentration (8 wt %) than other systems. [7][8][9] This soft gel is reversibly converted into an optically clear hard gel by merely decreasing the pH value or increasing the temperature. The ordered packing of the CSC micelles and the fast response to pH value were investigated by small-angle neutron scattering (SANS) and rheological measurements.Block copolymers consist of two or more chemically different polymer chains covalently bonded at their chain ends to form one single linear macromolecule.[10] The freeenergy-driven micellization of these copolymers takes place in a selective solvent, that is, a nonsolvent for one block and a good solvent for another. This self-association phenomenon is based on the phase separation of the insoluble blocks, which is, however, restricted to the nanometric scale by a surrounding shell of soluble blocks. Depending on the nature, length, and number of constitutive blocks and their interaction with the solvent, a variety of nanoobjects can be formed in dilute solutions, ranging from typical core-shell nanospheres [11][12][13] to cylinders, [12,14] vesicles, [12,15,16] and tubules, [16] as well as multilayered (onion), [5,17] non-centrosymmetric ("Janus"), and segregated structures. [18,19] Quite importantly, although less extensively studied, higher levels of organization can be observed, that is, assembly into clusters, networks, and gels. Stimulus-triggered aggregation of micelles has been reported for ABA triblock copolymers in a solvent selective for the B block, [9,[20][21][22][23][24] with special attention paid to the well-known polyoxyalkylene-type ABA copolymers (mainly Pluronics). [9,20,21] Among other responsive systems, Armes and coworkers synthesized biocompatible ABA triblocks, where A is poly(N-isopropylacrylamide) and B is poly(2-methacryloyloxyethyl phosphorylcholine).[24] Because of the thermosensitivity of the outer A blocks, micellization and ultimately gelation occurred above a lower critical solution temperature (LCST) of 37 8C. In recent years, increasing attention was paid to sol-to-gel transitions exhibited by multitalented ABC terpolymers. In addition to the synthesis of several isomers of a triblock terpolymer (ABC, BAC, and ACB) by Patrickios and co-workers that were...

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Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

et al. 2007

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“…2) prepared by living anionic polymerisation exhibited rich phase behaviour. 75 At low pH, the PAA block is protonated and relatively hydrophobic, whereas the P2VP block is cationic and highly hydrophilic; this leads to formation of PAA-core micelles. Increasing the pH leads to deprotonation of the PAA chains, which become highly anionic.…”

Section: Ph-responsive Gelatorsmentioning

confidence: 99%

(Meth)acrylic stimulus-responsive block copolymer hydrogels

Madsen

Armes

2012

Soft Matter

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“…In particular, controlling the exchange time of the B blocks may lead to soft hydrogels or viscoelastic fluids with tunable viscosities relevant for applications such as in enhanced oil recovery (EOR) , or cosmetics. , However, few attempts have been made at controlling the exchange time which increases exponentially with the length of the B blocks and with their hydrophobic character. , Most amphiphilic triblock copolymers studied in the literature actually form so-called “frozen” networks with extremely long exchange times . Stimuli-responsive triblocks − actually often consist of B blocks which switch from fully hydrophilic, leading to a low-viscosity fluid containing unassociated chains, to very hydrophobic, leading to a nonflowing gel where the B blocks are not able to exchange.…”

Section: Introductionmentioning

confidence: 99%

pH-Controlled Rheological Properties of Mixed Amphiphilic Triblock Copolymers

et al. 2016

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Aqueous mixtures of pH-sensitive block random BAB triblock copolymers with different hydrophobic B blocks connected to the same hydrophilic A block were studied in order to investigate comicellization and the impact on the dynamic mechanical properties. The B blocks were statistical copolymers of acrylic acid (AA) and n-butyl acrylate (nBA) with varying AA contents, whereas the A block was a pure PAA. Neat triblocks self-assembled into transient networks for which the mechanical relaxation time depended both on the AA content within the B blocks and on the pH, which affected the ionization of the AA units. Static and dynamic light scattering measurements were done on mixtures of equivalent AB diblock copolymers that showed that comicellization occurred only at conditions at which both copolymers considered separately self-assemble. When comicellization occurred, the characteristic escape time of both types of B blocks from the mixed hydrophobic cores impacted the rheological properties of the binary triblock mixture. Using binary mixtures of BAB triblock copolymers exhibiting pH-controlled dynamics thus allows control and fine-tuning of the viscoelastic properties at constant pH by formulation without the need to synthesize a large number of different polymers. Moreover, the more dynamic B blocks were slowed down in the presence of the less dynamic ones, and vice versa, so that a frozen network could be transformed into a transient one by coassembly with very dynamic chains.

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Multifunctional Stimuli Responsive ABC Terpolymers: From Three‐Compartment Micelles to Three‐Dimensional Network

Cited by 42 publications

References 23 publications

Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

(Meth)acrylic stimulus-responsive block copolymer hydrogels

pH-Controlled Rheological Properties of Mixed Amphiphilic Triblock Copolymers

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