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

Abstract

Repulsive osmotic delamination is thermodynamically allowed "dissolution" of two-dimensional (2D) materials and therefore represents an attractive alternative to liquid-phase exfoliation to obtain strictly monolayered nanosheets with an appreciable aspect ratio with quantitative yield. However, osmotic delamination was so far restricted to aqueous media, severely limiting the range of accessible 2D materials. Alkali-metal intercalation compounds of MoS 2 or graphite are excluded because they cannot tolerate even traces of water. We now succeeded in extending osmotic delamination to polar and aprotic organic solvents. Upon complexation of interlayer cations of synthetic hectorite clay by crown ethers, either 15-crown-5 or 18-crown-6, steric pressure is exerted, which helps in reaching the threshold separation required to trigger osmotic delamination based on translational entropy. This way, complete delamination in water-free solvents like aprotic ethylene and propylene carbonate, N-methylformamide, N-methylacetamide, and glycerol carbonate was achieved.

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

“…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.…”

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

“…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.…”

“…[ 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).…”

“…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.…”

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

“…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.…”