Can percolation theory explain the gelation behavior of diblock copolymer worms?

Lovett, Joseph R.; Derry, Matthew J.; Yang, Pengcheng; Hatton, Fiona L.; Warren, Nicholas J.; Fowler, Patrick W.; Armes, Steven P.

doi:10.1039/c8sc02406e

Cited by 72 publications

(137 citation statements)

References 76 publications

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“…This indicates the formation of highly anisotropic worms, with multiple inter-particle contacts producing a 3D network. 56 The storage modulus (G 0 ) exceeds the loss modulus (G 00 ) at 17 C, which corresponds to the critical gelation temperature (CGT) (Fig. S3, ESI, † for G 0 and G 00 data).…”

Section: Resultsmentioning

confidence: 99%

Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

et al. 2020

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Section: Resultsmentioning

confidence: 99%

Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

et al. 2020

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“…The effect of varying L c on gel strength has also been observed for surfactant worms 78 and has been recently rationalized in the context of percolation theory for this particular polymer formulation by Lovett and co-workers. 53 …”

Section: Resultsmentioning

confidence: 99%

“… 28 , 51 , 52 In each case, free-standing gels can be obtained above a certain critical copolymer concentration known as the critical gelation concentration (CGT). 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.…”

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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“…This convenient synthetic route allows for the direct derivatization of epoxy-containing diblock copolymer worms with 4-amino-TEMPO to give nitroxidefunctionalized diblock copolymer worms. Owing to their highly anisotropic nature, such diblock copolymer worms are expected to form a percolating network at relatively low volume fractions 32 and hence may exhibit superior charge transport properties. [9][10] Synthesis of diblock copolymer worms from GlyMA An initial aqueous emulsion of GlyMA was converted into an aqueous solution of GMA by heating at 85 °C for 9 h. 33 1 H NMR analysis indicated that the conversion of GlyMA to GMA was approximately 98%, see Fig.…”

Section: Resultsmentioning

confidence: 99%

Aqueous one-pot synthesis of epoxy-functional diblock copolymer worms from a single monomer: new anisotropic scaffolds for potential charge storage applications

et al. 2019

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Can percolation theory explain the gelation behavior of diblock copolymer worms?

Abstract: Physical gelation by block copolymer worms can be explained in terms of multiple inter-worm contacts using percolation theory, suggesting that worm entanglements are irrelevant in this context.

Cited by 72 publications

References 76 publications

Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

Unique aqueous self-assembly behavior of a thermoresponsive diblock copolymer

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

Aqueous one-pot synthesis of epoxy-functional diblock copolymer worms from a single monomer: new anisotropic scaffolds for potential charge storage applications

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