Mechanism of Shear Thickening in Reversibly Cross-Linked Supramolecular Polymer Networks

Xu, Duanfu; Hawk, Jennifer L.; Loveless, David M.; Jeon, Sung Lan; Craig, Stephen L.

doi:10.1021/ma100093b

Cited by 129 publications

(229 citation statements)

References 46 publications

(149 reference statements)

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“…53,54,60 They attribute the observed shear thickening in these systems to a shear-induced increase in the number of elastically effective network strands, which stems from the conversion of intrachain crosslinks to interchain crosslinks at high strains. 60 In collagen-based materials, Rajagopalan and co-workers ascribed a similar strain stiffening to deformation-induced reorganization of the dynamic noncovalent crosslinks to increase the number of elastically effective strands. 55 In the latter study, the dynamic crosslinks originate from H-bonding interactions between the collagen fibrils.…”

Section: ■ Discussionmentioning

confidence: 99%

Synthesis and Rheological Characterization of Poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) Triblock Copolymer Hydrogels

Speetjens

Mahanthappa

2015

Macromolecules

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We report the synthesis and shear rheology of a series of hydrogels derived from poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) (PVAc-b-PVOH-b-PVAc) triblock copolymers. Bidirectional, reversible-addition−fragmentation chain transfer free radical polymerizations of vinyl acetate (VAc) and vinyl chloroacetate (VClAc) are optimized to produce a series of relatively narrow dispersity PVAc-b-P(VAcran-VClAc)-b-PVAc triblock copolymers with controlled molecular weights and compositions. Rapid and selective hydrolysis of P(VAc-ran-VClAc) blocks with K 2 CO 3 /CH 3 OH furnishes access to a series of PVAc-b-PVOH-b-PVAc amphiphiles. Hydration of solvent-cast films of these copolymers, comprising PVAc blocks of comparable degrees of polymerization with variable PVOH segment lengths, yields soft hydrogels (G′(ω) ∼ 1−10 kPa). Synchrotron small-angle and wide-angle X-ray scattering reveals that these hydrogels microphase separate into spherical hydrophobic PVAc domains that are interconnected by solvated PVOH network strands. The strain-dependent rheology of these hydrogels depends sensitively on the length of the center PVOH segment. This gel rheology is shown to stem from the hydrogen bond donor−acceptor capabilities of PVOH, which leads to the formation of weak, dynamic noncovalent crosslinks in the aqueous domains of these gels. Thus, the observed gel rheology may be rationalized in terms of the shear-induced reorganization of these H-bonding crosslinks as a function of the applied strain.

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Section: ■ Discussionmentioning

confidence: 99%

Synthesis and Rheological Characterization of Poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) Triblock Copolymer Hydrogels

Speetjens

Mahanthappa

2015

Macromolecules

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“…Craig and coworkers extensively studied the relationship of bond kinetics and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13 polymer relaxation timescales, demonstrating that disadvantageous shear-thickening behavior arises if polymer relaxation occurs more rapidly than reconnection of broken crosslinks. [78][79] As such, the decreased polymer relaxation may be accomplished through formation of multifold junctions in highly modified guest-host hydrogels to enforce shear-thinning behavior and ease of injection. 80 The physical chemistry underlying the flow process, as well as other fundamental behaviors of supramolecular networks have been recently reviewed.…”

Section: Injectable Hydrogelsmentioning

confidence: 99%

Supramolecular Guest–Host Interactions for the Preparation of Biomedical Materials

2015

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Supramolecular chemistry has emerged as an important technique for the formation of biomaterials, including nano- and microparticles and hydrogels. One specific class of supramolecular chemistry is the direct association of guest-host pairs, which involves host macrocycles such as cyclodextrins and cucurbit[n]urils and a wide range of guest molecules, where association is typically driven by molecule size and hydrophobicity. These systems are of particular interest in the biomedical field due to their dynamic nature, chemical diversity, relative ease of synthesis, and ability to interact with biological or synthetic molecules. In this review, we discuss aspects of polymeric material assembly mediated by guest-host interactions, including the fundamentals of assembly into functional biomedical materials. Additionally, applications of biomaterials that utilize guest-host interactions are discussed with a focus on injectable material formulations, the sequestration and delivery of encapsulated cargo (i.e., drugs, biomolecules), and the investigation of cell-material interactions (i.e., adhesion, differentiation, and delivery). While methodologies for guest-host mediated assembly and biological interaction have rapidly evolved in recent years, they remain far from realizing their full potential in the biomaterials field.

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“…They observed the shear thickening in a colloidal system with attractive interactions and found the transition to shear thickening flow is stress controlled and results in a fine suspension microstructure that produces enhanced modulus gels. Xu et al [9] added bis-Pd(II) or bis-Pt(II) complexes cross-linker to semidilute unentangled solutions of poly(4-vinylpyridine) (PVP) in dimethyl sulfoxide (DMSO). They reported that the onset and magnitude of the shear thickening depend on the amount of cross-linkers added.…”

Section: Introductionmentioning

confidence: 99%

Study of shear-stiffened elastomers

Tian

Ding

et al. 2012

Smart Mater. Struct.

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Shear thickening fluids, which are usually concentrated colloidal suspensions composed of non-aggregating solid particles suspended in fluids, exhibit a marked increase in viscosity beyond a critical shear rate. This increased viscosity is seen as being both 'field-activated', due to the dependence on shearing rate, as well as reversible. Shear thickening fluids have found good applications as protection materials, such as in liquid body armor, vibration absorber or dampers. This research aims to expand the protection material family by developing a novel solid status shear thickening material, called shear-stiffened elastomers. These new shearstiffened elastomers were fabricated with the mixture of silicone rubber and silicone oil. A total of four SSE samples were fabricated in this study. Their mechanical and rheological properties under both steady-state and dynamic loading conditions were tested with a parallel-plate. The effects of silicone oil composition and angular frequency were summarized. When raising the angular frequency in dynamic shear test, the storage modulus of conventional silicone rubber shows a small increasing trend with the frequency. However, if silicone oil is selected to be mixed with silicone rubber, the storage modulus increases dramatically when the frequency and strain are both beyond the critical values. © 2013 AIP Publishing LLC. Abstract. Shear thickening fluids, which are usually concentrated colloidal suspensions composed of non-aggregating solid particles suspended in fluids, exhibit a marked increase in viscosity beyond a critical shear rate. This increased viscosity is seen as being both 'field-activated', due to the dependence on shearing rate, as well as reversible. Shear thickening fluids have found good applications as protection materials, such as in liquid body armor, vibration absorber or dampers. This research aims to expand the protection material family by developing a novel solid status shear thickening material, called shear-stiffened elastomers. These new shear-stiffened elastomers were fabricated with the mixture of silicone rubber and silicone oil. A total of four SSE samples were fabricated in this study. Their mechanical and rheological properties under both steady-state and dynamic loading conditions were tested with a parallel-plate. The effects of silicone oil composition and angular frequency were summarized. When raising the angular frequency in dynamic shear test, the storage modulus of conventional silicone rubber shows a small increasing trend with the frequency. However, if silicone oil is selected to be mixed with silicone rubber, the storage modulus increases dramatically when the frequency and strain are both beyond the critical values.

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Mechanism of Shear Thickening in Reversibly Cross-Linked Supramolecular Polymer Networks

Cited by 129 publications

References 46 publications

Synthesis and Rheological Characterization of Poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) Triblock Copolymer Hydrogels

Synthesis and Rheological Characterization of Poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) Triblock Copolymer Hydrogels

Supramolecular Guest–Host Interactions for the Preparation of Biomedical Materials

Study of shear-stiffened elastomers

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