Dissipative particle dynamics simulation of the relaxation behaviour of a triblock copolymer supramolecular network

Wakimoto, Kohei; Sasaki, Hiroshi; Arai, Noriyoshi

doi:10.1080/08927022.2017.1403027

Cited by 1 publication

(1 citation statement)

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“…According to previous studies, the relaxation of physically associating triblock copolymer gels possesses two important time scales: , a short time scale controlled by the lifetime of end-block in the micelles and a long time scale representing the relaxation of whole gel network. The latter, which is the longest relaxation time of the gel, τ L , can be obtained from the frequency dependence of dynamic moduli.…”

Section: Resultsmentioning

confidence: 99%

Relaxation Dynamics and Underlying Mechanism of a Thermally Reversible Gel from Symmetric Triblock Copolymer

Cui

Indei

et al. 2019

Macromolecules

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We report a novel thermally responsive system from poly(butyl methacrylate)-b-poly(methacrylic acid)-b-poly(butyl methacrylate) (PBMA-b-PMAA-b-PBMA) triblock copolymer in dimethylformamide (DMF) solvent. This system shows a sol-gel transition by cooling below a critical temperature Tc. The network relaxation time of these gels rightly fall in the typical rheological experiment window, permitting us to investigate the relaxation dynamics and underlying mechanism, with a combination of linear rheology, time-resolved small-angle X-ray scattering (SAXS), and temperature-elevated nuclear magnetic resonance (NMR) measurements. Both time-temperature superposition (TTS) and time-concentration superposition (TCS) are well hold in this system. The relaxation dynamics at temperatures below and above Tc are quite different, giving two different activation energy E1a and E2a, respectively. The 2 E1a, being polymer concentration independent, is related to micelle formation of end blocks, while the concentration dependent E2a is related to the chain friction of entangled polymer solution. By coupling linear rheology, SAXS, and NMR, we quantitatively estimated the fraction of bridge, loop, and dangling chains. The longest relaxation time of the gel, τL, strongly depends on polymer concentration, attributing to the increased connectivity of micellar network. By combining the shift factors aT and aC determined from TTS and TCS, respectively, we can obtain the τL at any given temperature and concentration from that at reference temperature and concentration.

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Section: Resultsmentioning

confidence: 99%