Osmotic Delamination: A Forceless Alternative for the Production of Nanosheets Now in Highly Polar and Aprotic Solvents

Dudko, Volodymyr; Ottermann, Katharina; Rosenfeldt, Sabine; Papastavrou, Georg; Breu, Josef

doi:10.1021/acs.langmuir.0c03113

Cited by 17 publications

(26 citation statements)

References 48 publications

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“…The melt synthesized crystals of sodium fluorohectorite [Na 0.5 ] inter [Li 0.5 Mg 2.5 ] oct [Si 4 ] tetr O 10 F 2 spontaneously delaminate into singular NSs by osmotic swelling in water. [ 47 , 48 , 49 ] The NSs have high aspect ratio of ≈20 000 and high charge density of 1.1 nm −2 . In addition, the NSs have anisotropic mechanical properties; they are stiff in the in‐plane direction with the modulus of 150 GPa and flexible in the cross‐plane direction.…”

Section: Resultsmentioning

confidence: 99%

Patterned Electrode Assisted One‐Step Fabrication of Biomimetic Morphing Hydrogels with Sophisticated Anisotropic Structures

et al. 2021

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Anisotropic structures are ubiquitous in nature, affording fascinating morphing behaviors. Biomimetic morphing materials can be developed by spatially controlling the orientations of molecules or nanofillers that produce anisotropic responses and internal stresses under external stimuli. However, it remains a serious challenge to fabricate materials with sophisticated anisotropic architectures. Here, a facile strategy to fabricate morphing hydrogels with elaborately ordered structures of nanosheets, which are oriented under distributed electric field and immobilized by polymerization to form a poly(N-isopropylacrylamide) matrix, is proposed. Diverse sophisticated anisotropic structures are obtained by engineering the electric field through the patterns and relative locations of the electrodes. Upon heating, the monolithic hydrogels with through-thickness and/or in-plane gradients in orientation of the nanosheets deform into various three-dimensional configurations. After incorporating gold nanoparticles, the hydrogels become photoresponsive and capable of programmable motions, for example, dynamic twisting and flipping under spatiotemporal stimuli. Such a strategy of using patterned electrodes to generate distributed electric field should be applicable to systems of liquid crystals or charged particles/molecules to direct orientation or electrophoresis and form functional structures. The biomimetically architectured hydrogels would be ideal materials to develop artificial muscles, soft actuators/robots, and biomedical devices with versatile applications.

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Section: Resultsmentioning

confidence: 99%

Patterned Electrode Assisted One‐Step Fabrication of Biomimetic Morphing Hydrogels with Sophisticated Anisotropic Structures

et al. 2021

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“…XRD patterns from the nanocomposite films taken in reflection mode show a 00l series (Figure S1, Supporting Information) with a spacing of 17.7 Å (2 θ = 4.99°), indicating that 18C6 remain complexed to the hectorite sheets during film production and that within the hectorite tactoids, there is an absence of PLA. The previously reported d‐spacing of a pure 18C6Hec is even larger (18.3 Å), [ 31 ] while without a complexed 18C6, NaHec has a d‐spacing of 12.5 Å. [ 35 ] Although pure NaHec is sensitive to humidity, the complexation by 18C6 reduces hydrophilicity, thus reducing its ability to swell in the presence of water vapor.…”

Section: Resultsmentioning

confidence: 99%

“…[ 35 ] Although pure NaHec is sensitive to humidity, the complexation by 18C6 reduces hydrophilicity, thus reducing its ability to swell in the presence of water vapor. [ 31 ] As water acts as a plasticizer, swelling will increase segment mobility and consequently permeability. Therefore, the moisture sensitivity of 18C6Hec stacks in the PLA nanocomposite was systematically evaluated by monitoring changes in d‐spacing as a function of RH (Figure 2d).…”

Section: Resultsmentioning

confidence: 99%

“…Our group also recently published a method which for the first time, extends the rare phenomenon of osmotic delamination within NaHec into organic, aprotic solvents. [ 31 ] Previously limited to aqueous suspensions, osmotic delamination of NaHec was obtained spontaneously in various organic solvents, including N ‐methylformamide (NMF) by the simple addition of crown ethers. The complexation of interlayer sodium with, for example, 18‐crown‐6 (18C6) renders the hectorite (18C6Hec) surface more hydrophobic.…”

Section: Introductionmentioning

confidence: 99%

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High Barrier Nanocomposite Film with Accelerated Biodegradation by Clay Swelling Induced Fragmentation

Timmins

Kumar

Röhrl

et al. 2021

Macro Materials & Eng

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Conventional biodegradable polymers such as poly(lactic acid) (PLA) are an attractive alternative to replace traditional nondegradable food packaging films which plague the environment. However, PLA has shown to not be degradable in some environmentally relevant conditions, including within the freshwater systems. Additionally, PLA suffers from very poor barrier properties, which could result in food spoilage. Compositing with clay has been used to improve barrier properties according to tortuous path theory. Here a synthetic, large aspect ratio Na-Hectorite is used that may be utterly delaminated in an organic solvent and composited with PLA by modification with 18-crown-6 (18C6Hec), yielding a castable, homogeneous nematic suspension. Upon drying, thermodynamics drive the suspension toward segregation into sublayers of PLA and partially restacked 18C6Hec in situ. This unique self-assembled nanostructure combines the best of two worlds: The aspect ratio remains high and results in a 99.3% reduction in oxygen permeability. Additionally, the film shows surprisingly high resistance to swelling at elevated humidity, but once soaked in water, clay swelling is triggered, which fragments the film and drastically increases the surface area by 2500%. Accelerated degradation is observed under controlled enzymatic conditions and in an environmentally relevant wastewater medium during CO 2 evolution testing.

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“…Due to superb charge homogeneity, these synthetic clay minerals show sharp transitions between crystalline swelling steps and from crystalline to osmotic swelling. We previously studied a swelling of 0.5 Hec in binary and ternary water–organic solvent mixtures and in pure organic solvents . The aspect ratio is of prime importance in various applications, in particular, in nanocomposite barrier liners, , and as the diameter of the pristine clay minerals tends to increase with charge density, we here extend studying repulsive osmotic swelling to 0.7 Hec.…”

Section: Introductionmentioning

confidence: 97%

Delamination by Repulsive Osmotic Swelling of Synthetic Na-Hectorite with Variable Charge in Binary Dimethyl Sulfoxide–Water Mixtures

et al. 2022

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Swelling of clays is hampered by increasing layer charge. With vermiculite-type layer charge densities, crystalline swelling is limited to the two-layer hydrate, while osmotic swelling requires ion exchange with bulky and hydrophilic organic molecules or with Li+ cations to trigger repulsive osmotic swelling. Here, we report on surprising and counterintuitive osmotic swelling behavior of a vermiculite-type synthetic clay [Na0.7]inter[Mg2.3Li0.7]oct[Si4]tetO10F2 in mixtures of water and dimethyl sulfoxide (DMSO). Although swelling in pure water is restricted to crystalline swelling, with the addition of DMSO, osmotic swelling sets in at some threshold composition. Finally, when the DMSO concentration is increased further to 75 vol %, swelling is restricted again to crystalline swelling as expected. Repulsive osmotic swelling thus is observed in a narrow composition range of the binary water–DMSO mixture, where a freezing point suppression is observed. This suppression is related to DMSO and water molecules exhibiting strong interactions leading to stable molecular clusters. Based on this phenomenological observation, we hypothesize that the unexpected swelling behavior might be related to the formation of different complexes of interlayer cations being formed at different compositions. Powder X-ray diffraction and 23Na magic angle spinning-NMR evidence is presented that supports this hypothesis. We propose that the synergistic solvation of the interlayer sodium at favorable compositions exerts a steric pressure by the complexes formed in the interlayer. Concomitantly, the basal spacing is increased to a level, where entropic contributions of interlayer species lead to a spontaneous thermodynamically allowed one-dimensional dissolution of the clay stack.

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Osmotic Delamination: A Forceless Alternative for the Production of Nanosheets Now in Highly Polar and Aprotic Solvents

Cited by 17 publications

References 48 publications

Patterned Electrode Assisted One‐Step Fabrication of Biomimetic Morphing Hydrogels with Sophisticated Anisotropic Structures

Patterned Electrode Assisted One‐Step Fabrication of Biomimetic Morphing Hydrogels with Sophisticated Anisotropic Structures

High Barrier Nanocomposite Film with Accelerated Biodegradation by Clay Swelling Induced Fragmentation

Delamination by Repulsive Osmotic Swelling of Synthetic Na-Hectorite with Variable Charge in Binary Dimethyl Sulfoxide–Water Mixtures

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