Association and physical gelation of ABA triblock copolymer in selective solvent

Inomata, Katsuhiro; Nakanishi, Daisuke; Banno, Ai; Nakanishi, Eiji; Abe, Yosuke; Kurihara, Ryuta; Fujimoto, Kentaro; Nose, Takeru

doi:10.1016/s0032-3861(03)00534-2

Cited by 46 publications

(69 citation statements)

References 25 publications

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“…A common architecture for block copolymer-based physical gels are ABA triblock copolymers, or analogously telechelic modified polymers, in a solvent selective for the midblock 1–4,6–8. In dilute solution, the polymers aggregate to form single “flowerlike” micelles.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle-Reinforced Associative Network Hydrogels

et al. 2008

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ABA triblock copolymers in solvents selective for the midblock are known to form associative micellar gels. We have modified the structure and rheology of ABA triblock copolymer gels comprising poly(lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA) through addition of a clay nanoparticle, laponite. Addition of laponite particles resulted in additional junction points in the gel via adsorption of the PEO corona chains onto the clay surfaces. Rheological measurements showed that this strategy led to a significant enhancement of the gel elastic modulus with small amounts of nanoparticles. Further characterization using SAXS and DLS confirmed that nanoparticles increase the intermicellar attraction and result in aggregation of PLA-PEO-PLA micelles.

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Section: Introductionmentioning

confidence: 99%

Nanoparticle-Reinforced Associative Network Hydrogels

et al. 2008

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“…However, ΔH app values of 400–500 kJ/mol have been reported for physical gels of poly(methyl methacrylate)-poly(tert-butyl acrylate)-poly(methyl methacrylate) by Inomata et al 1 . Activation energies obtained for associative triblock copolymer systems have been related to the activation energy for pullout of the terminal A block from the core of the aggregate, thereby breaking the junction formed by the polymer chain 1,18,19,25 . Effectively this is the energy cost for transferring the terminal block from the aggregate core to the solvent.…”

Section: Resultsmentioning

confidence: 99%

“…1–4 In dilute solution, the polymers typically assemble into flowerlike micelles. However, at higher concentrations the midblocks bridge between micelles, leading to formation of a three-dimensional network and gelation.…”

Section: Introductionmentioning

confidence: 99%

“…9 Although the most commonly-known use of time-temperature superposition is investigation of dynamics in polymer melts, it has also been applied to block copolymers 1,10–13 and polymer nanocomposites 14,15 in the presence of a solvent. In the present work we have studied the temperature dependence of the rheological behavior of gels formed by PLLA-PEO-PLLA triblock copolymers in water, both with and without added nanoparticles (figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Energetics of Association in Poly(lactic acid)-based Hydrogels with Crystalline and Nanoparticle−Polymer Junctions

et al. 2010

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We report the energetics of association in polymeric gels with two types of junction points: crystalline hydrophobic junctions and polymer-nanoparticle junctions. Time-temperature superposition (TTS) of small-amplitude oscillatory rheological measurements was used to probe crystalline poly(L-lactide) (PLLA)-based gels with and without added laponite® nanoparticles. For associative polymer gels, the activation energy derived from the TTS shift factors is generally accepted as the associative strength, or energy needed to break a junction point. Our systems were found to obey TTS over a wide temperature range of 15–70°C. For systems with no added nanoparticles, two distinct behaviors were seen, with a transition occurring at a temperature close to the glass transition temperature of PLLA, Tg. Above Tg, the activation energy was similar to the PLLA crystallization enthalpy, suggesting that the activation energy is related to the energy needed to pull a PLLA chain out of the crystalline domain. Below Tg, the activation energy is expected to be the energy required to increase mobility of the polymer chains and soften the glassy regions of the PLLA core. Similar behavior was seen in the nanocomposite gels with added laponite®; however, the added clay appears to reduce the average value of the activation enthalpy. This confirms our SAXS results and suggests that laponite® particles are participating in the network structure.

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“…Systems with other kind of blocks also proved to be efficient in the formation of organogels: for example, poly(methyl methacrylate)-block-poly(tert-butyl acrylate)-block-poly(methyl methacrylate) triblock copolymers formed associated micelles consisting of a PMMA associated core and a PtBA shell in 1-butanol at room temperature. [5] In this paper, we report the synthesis of triblock copolymers of polystyrene-block-poly(2-ethylhexyl acrylate)-block-polystyrene by atom-transfer radical polymerisation (ATRP) [6][7][8][9] to form elastic gels in paraffin oil which is a bad solvent for the endblocks (polystyrene) but a good one for the midblock [poly (2-ethylhexyl acrylate)]. ATRP was chosen as it allows the synthesis of polymers with well-defined compositions, architectures and functionalities without using such drastic conditions as in ionic methods.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterisation of Organogels from ABA Triblock Copolymers

Monge

Joly‐Duhamel

Boyer

et al. 2007

Macro Chemistry & Physics

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Polystyrene‐block‐poly(2‐ethylhexanyl acrylate)‐block‐polystyrene triblock copolymers with different molar masses were synthesised by atom transfer radical polymerisation which led to the formation of elastic gels in paraffin oil. Copolymers with control over molecular weight and low polydispersity were first obtained with different midblock lengths (10 000, 20 000, 60 000 g · mol−1). In paraffin oil, some triblock copolymers led to a gelation process due to appropriate chain length and concentration. We assumed that polystyrene endblocks aggregated into micelles whereas poly(2‐ethylhexanyl acrylate) midblocks formed loops or bridges between different micelles leading to the formation of a physical network of interconnected polymer chains. Rheological measurements proved that time and slow controlled cooling improved the elastic properties with the creation of new interactions in the network.

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Association and physical gelation of ABA triblock copolymer in selective solvent

Cited by 46 publications

References 25 publications

Nanoparticle-Reinforced Associative Network Hydrogels

Nanoparticle-Reinforced Associative Network Hydrogels

Energetics of Association in Poly(lactic acid)-based Hydrogels with Crystalline and Nanoparticle−Polymer Junctions

Synthesis and Characterisation of Organogels from ABA Triblock Copolymers

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