Translating Thermal Response of Triblock Copolymer Assemblies in Dilute Solution to Macroscopic Gelation and Phase Separation

Sun, Zhe; Tian, Ye; Hom, Wendy L.; Gang, Oleg; Bhatia, Surita R.; Grubbs, Robert B.

doi:10.1002/ange.201609360

Cited by 5 publications

(1 citation statement)

References 38 publications

(11 reference statements)

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“…53 Moreover, such worm gels can exhibit interesting thermoresponsive behavior: adjusting the solution temperature leads to a worm-to-sphere transition, which leads to in situ degelation. 8,21,28,32,47 For example, poly(glycerol monomethacrylate)−poly(2-hydroxypropyl methacrylate) (PGMA− PHPMA) diblock copolymer worm gels undergo degelation on cooling from 20 to 5 °C. 21 This morphological transition is reversible at a sufficiently high copolymer concentration, with worm gels being re-formed on returning to 20 °C.…”

Section: ■ Introductionmentioning

confidence: 99%

Critical Dependence of Molecular Weight on Thermoresponsive Behavior of Diblock Copolymer Worm Gels in Aqueous Solution

et al. 2018

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Reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate was used to prepare three poly(glycerol monomethacrylate)x–poly(2-hydroxypropyl methacrylate)y (denoted Gx-Hy or PGMA-PHPMA) diblock copolymers, namely G37-H80, G54-H140, and G71-H200. A master phase diagram was used to select each copolymer composition to ensure that a pure worm phase was obtained in each case, as confirmed by transmission electron microscopy (TEM) and small-angle x-ray scattering (SAXS) studies. The latter technique indicated a mean worm cross-sectional diameter (or worm width) ranging from 11 to 20 nm as the mean degree of polymerization (DP) of the hydrophobic PHPMA block was increased from 80 to 200. These copolymer worms form soft hydrogels at 20 °C that undergo degelation on cooling. This thermoresponsive behavior was examined using variable temperature DLS, oscillatory rheology, and SAXS. A 10% w/w G37-H80 worm dispersion dissociated to afford an aqueous solution of molecularly dissolved copolymer chains at 2 °C; on returning to ambient temperature, these chains aggregated to form first spheres and then worms, with the original gel strength being recovered. In contrast, the G54-H140 and G71-H200 worms each only formed spheres on cooling to 2 °C, with thermoreversible (de)gelation being observed in the former case. The sphere-to-worm transition for G54-H140 was monitored by variable temperature SAXS: these experiments indicated the gradual formation of longer worms at higher temperature, with a concomitant reduction in the number of spheres, suggesting worm growth via multiple 1D sphere–sphere fusion events. DLS studies indicated that a 0.1% w/w aqueous dispersion of G71-H200 worms underwent an irreversible worm-to-sphere transition on cooling to 2 °C. Furthermore, irreversible degelation over the time scale of the experiment was also observed during rheological studies of a 10% w/w G71-H200 worm dispersion. Shear-induced polarized light imaging (SIPLI) studies revealed qualitatively different thermoreversible behavior for these three copolymer worm dispersions, although worm alignment was observed at a shear rate of 10 s–1 in each case. Subsequently conducting this technique at a lower shear rate of 1 s–1 combined with ultra small-angle x-ray scattering (USAXS) also indicated that worm branching occurred at a certain critical temperature since an upturn in viscosity, distortion in the birefringence, and a characteristic feature in the USAXS pattern were observed. Finally, SIPLI studies indicated that the characteristic relaxation times required for loss of worm alignment after cessation of shear depended markedly on the copolymer molecular weight.

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Section: ■ Introductionmentioning

confidence: 99%

Critical Dependence of Molecular Weight on Thermoresponsive Behavior of Diblock Copolymer Worm Gels in Aqueous Solution

et al. 2018

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Exploiting the Structural Metamorphosis of Polymers to ‘Wrap’ Micron‐Sized Spherical Objects

Higgs

Appleton

Turnbull

et al. 2021

Chemistry A European J

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There is growing interest in developing methods to 'wrap' nano-and micron-sized biological objects within films that may offer protection, enhance their stability or improve performance. We describe the successful 'wrapping' of lectindecorated microspheres, which serve as appealing model micron-sized objects, within cross-linked polymer film. This approach utilizes polymer chains able to undergo a structural metamorphosis, from being intramolecularly cross-linked to intermolecularly cross-linked, a process that is triggered by polymer concentration upon the particle surface. Experiments demonstrate that both complementary molecular recognition and the dynamic covalent nature of the crosslinker are required for successful 'wrapping' to occur. This work is significant as it suggests that nano-and micron-sized biological objects such as virus-like particles, bacteria or mammalian cells-all of which may benefit from additional environmental protection or stabilization in emerging applicationsmay also be 'wrapped' by this approach.

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Stimuli-responsive polymer wormlike micelles

Tian

Fei

Yin

et al. 2019

Progress in Polymer Science

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Translating Thermal Response of Triblock Copolymer Assemblies in Dilute Solution to Macroscopic Gelation and Phase Separation

Cited by 5 publications

References 38 publications

Critical Dependence of Molecular Weight on Thermoresponsive Behavior of Diblock Copolymer Worm Gels in Aqueous Solution

Critical Dependence of Molecular Weight on Thermoresponsive Behavior of Diblock Copolymer Worm Gels in Aqueous Solution

Exploiting the Structural Metamorphosis of Polymers to ‘Wrap’ Micron‐Sized Spherical Objects

Stimuli-responsive polymer wormlike micelles

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