Surface modified layered double hydroxide

Abstract

Surface-modified layered double hydroxides (LDHs) are disclosed, as well as processes by which they are made, and uses of the LDHs in composite materials. The surface-modified LDHs of the invention are more organophilic than their unmodified analogues, which allows the LDHs to be incorporated in a wide variety of materials, wherein the interesting functionality of LDHs may be exploited.

Claims

1. A layered double hydroxide of formula (I) shown below: ##STR00008## wherein M is at least one charged metal cation; M′ is at least one charged metal cation different from M; z is 1 or 2; y is 3 or 4; 0<x<0.9; 0<b≤10; 0<c≤10; 0<d≤10 X is at least one anion; n is the charge on anion(s) X; a is equal to z(1−x)+xy−2; m ≥ a/n; and the solvent is an organic solvent capable of hydrogen-bonding to water; and the modifier is an organic moiety capable of covalent or ionic association with at least one surface of the layered double hydroxide, and which modifies the surface properties of the layered double hydroxide; and wherein the layered double hydroxide has a tap density of less than 0.35 g/mL.

2. The layered double hydroxide of claim 1, wherein the modifier is an organic moiety comprising at least 5 carbon atoms and at least one functional group that is capable of covalent or ionic association with at least one surface of the layered double hydroxide.

3. The layered double hydroxide of claim 1, wherein the modifier increases the lipophilicity of the layered double hydroxide.

4. The layered double hydroxide of claim 3, wherein the modifier is an organosilane or a surfactant.

5. The layered double hydroxide of claim 4, wherein the organosilane has a structure according to formula (II) shown below ##STR00009## wherein q is 1, 2 or 3; each R.sub.1 is independently hydrogen or an organofunctional group; each Y is independently absent, or is a straight or branched organic linker; and each R.sub.2 is independently hydrogen, halo, hydroxy, carboxy, (1-4C)alkyl or a group —OR.sub.3, wherein R.sub.3 is selected from (1-6C)alkyl, aryl(1-6C)alkyl, heteroaryl(1-6C)alkyl, cycloalkyl(1-6C)alkyl, heterocyclyl(1-6C)alkyl and (1-6C)alkoxy(l-4C)alkyl.

6. The layered double hydroxide of claim 5, wherein the organofunctional group is selected from acrylate, methacrylate, mercapto, aldehyde, amino, azido, carboxylate, phosphonate, sulfonate, epoxy, glycidyloxy, ester, halogen, hydroxyl, isocyanate, phosphine, phosphonate, alkenyl, aryl, cycloalkyl, heteroaryl and heterocyclyl.

7. The layered double hydroxide of claim 4, wherein the surfactant is a non-ionic, cationic, anionic or amphoteric surfactant.

8. The layered double hydroxide of claim 4, wherein the surfactant is a (4-22C)fatty acid or a salt thereof.

9. The layered double hydroxide of claim 1, wherein d has a value according to the expression 1≤d≤2.

10. The layered double hydroxide of claim 1, wherein z is 2, M is Mg, Zn, Fe, Ca, Sn, Ni, Cu, Co, Mn or Cd or a mixture of two or more of these, or when z is 1, M is Li.

11. The layered double hydroxide of claim 1, wherein y is 3, M′ is Al, Ga, Y, In, Fe, Co, Ni, Mn, Cr, Ti, V, La or a mixture thereof, or when y is 4, M′ is Sn, Ti or Zr or a mixture thereof.

12. The layered double hydroxide of claim 1, wherein M′ is Al.

13. The layered double hydroxide of claim 1, wherein the layered double hydroxide of formula (I) is a Zn/Al, Mg/Al, Mg,Zn/Al, Mg/Al,Sn, Ca/Al, Ni/Ti or Cu/Al layered double hydroxide.

14. The layered double hydroxide of claim 1, wherein X is an anion selected from at least one of halide, inorganic oxyanion, or an organic anion.

15. The layered double hydroxide of claim 14, wherein the inorganic oxyanion is carbonate, bicarbonate, hydrogenphosphate, dihydrogenphosphate, nitrite, borate, nitrate, sulphate or phosphate or a mixture of two or more thereof.

16. The layered double hydroxide of claim 1, wherein X is carbonate.

17. The layered double hydroxide of claim 1, wherein M is Mg, M′ is Al and X is carbonate.

18. The layered double hydroxide of claim 1, wherein the solvent is selected from the group consisting of acetone, acetonitrile, dimethylformamide, dimethyl sulphoxide, dioxane, ethanol, methanol, n-propanol, isopropanol, tetrahydrofuran, ethyl acetate, n-butanol, sec-butanol, n-pentanol, n-hexanol, cyclohexanol, diethyl ether, diisopropyl ether, di-n-butyl ether, methyl tert-butyl ether (MTBE), tert-amyl methyl ether, cyclopentyl methyl ether, cyclohexanone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methyl isoamyl ketone, methyl n-amyl ketone, furfural, methyl formate, methyl acetate, isopropyl acetate, n-propyl acetate, isobutyl acetate, n-butyl acetate, n-amyl acetate, n-hexyl acetate, methyl amyl acetate, methoxypropyl acetate, 2-ethoxyethyl acetate, nitromethane, and a mixture of two or more thereof.

19. The layered double hydroxide of claim 1, wherein the solvent is selected from the group consisting of acetone, ethanol, ethyl acetate, and a mixture of two or more thereof.

20. The layered double hydroxide of claim 1, wherein the layered double hydroxide also has a loose bulk density of less than 0.35 g/mL.

21. The layered double hydroxide of claim 1, wherein the layered double hydroxide also has a BET pore volume of at least 0.3 cc/g.

22. A process for the preparation of a layered double hydroxide of formula (I), the process comprising the steps of: a) providing a layered double hydroxide of formula (Ia): ##STR00010## where M, M′, z, y, x, b, c, X, m, and the solvent are as specified in claim 1; b) providing a modifier being an organic moiety of covalent or ionic association with at least one surface of the layered double hydroxide, and which is capable of modifying the surface properties of the layered double hydroxide; and c) contacting the layered double hydroxide of formula (Ia) provided in step a) with the modifier provided in step b), wherein the layered double hydroxide has a tap density of less than 3.5 g/mL.

23. A composite material comprising the layered double hydroxide as claimed in claim 1 dispersed throughout a polymer.

Description

EXAMPLES

(1) Embodiments of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which

(2) FIG. 1 shows possible interactions between organosilane modifiers and the LDH surface.

(3) FIG. 2 shows PXRD patterns for (a) acetone-washed AMO-MgAlCO.sub.3 (b) APTES, (c) GLYMO and (d) TEMS modified MgAlCO.sub.3-AMO-LDH. * is an aluminium peak from the sample holder.

(4) FIG. 3 shows FTIR spectrum of (a) acetone-washed AMO-MgAlCO.sub.3 (b) APTES-, (c) GLYMO- and (d) TEMS-modified MgAlCO.sub.3-AMO-LDH.

(5) FIG. 4 shows NMR spectra for (a) APTES-modified AMO-LDH, (b) GLYMO-modified AMO-LDH and (c) TEMS-modified AMO-LDH.

(6) FIG. 5 shows TEM images of (a) Acetone-washed MgAlCO.sub.3-LDH, (b) APTES-, (c) GLYMO- and (d) TEMS-modified MgAlCO.sub.3-LDH.

(7) FIG. 6 shows XRD pattern of the AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 7.

(8) FIG. 7 shows FTIR spectra of the AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 7.

(9) FIG. 8 shows FTIR spectra of the AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 8, using toluene as solvent.

(10) FIG. 9 shows FTIR spectra of the AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane.

(11) FIG. 10 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) without surface treatment against time.

(12) FIG. 11 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) with Zn stearate surface treatment after AMO wash against time.

(13) FIG. 12 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) with Zn stearate treatment on calcined LDH powder against time.

(14) FIG. 13 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 with Zn stearate surface treatment vs AMO-LDH.

(15) FIG. 14 shows XRD pattern of AMO-Mg.sub.3Al—CO.sub.3 LDH and Zinc stearate modified AMO-Mg.sub.3Al-CO.sub.3 LDH.

(16) FIG. 15 shows XRD pattern of AMO-Mg.sub.3Al—CO.sub.3 LDH and laurate modified AMO-Mg.sub.3Al—CO.sub.3 LDH.

(17) FIG. 16 shows FTIR spectrum of AMO-Mg.sub.3Al—CO.sub.3 LDH and laurate modified AMO-Mg.sub.3Al—CO.sub.3 LDH.

(18) FIG. 17 shows the XRD patterns of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(19) FIG. 18 shows the FTIR spectra of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(20) FIG. 19 shows the BET Surface Area plotted against Oil Absorption Number (OAN) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(21) FIG. 20 shows the loose bulk densities and tap densities of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(22) FIG. 21 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(23) FIG. 22 shows the oil absorption number (OAN) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(24) FIG. 23 shows the FTIR spectra of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 5.

(25) FIG. 24 shows the XRD patterns of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1.

(26) FIG. 25 shows the XRD patterns of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.2.

(27) FIG. 26 shows the BET Surface Area plotted against Oil Absorption Number (OAN) of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1 and 6.2.

(28) FIG. 27 shows the BET isotherm (A) and pore size distribution (B) of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1 and 6.2.

(29) FIG. 28 shows the loose bulk densities (black bars) and tap densities (white bars) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1 (A) and Example 6.2 (B).

(30) FIG. 29 shows the oil absorption number (OAN) before (black bars) and after (white bars) exposure to RH99 humidity at 20° C. for 120 hours of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1 (A) and Example 6.2 (B).

(31) FIG. 30 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1.

(32) FIG. 31 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.2.

(33) FIG. 32 shows FTIR spectra of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1.

(34) FIG. 33 shows FTIR spectra of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.2.

(35) FIG. 34 shows TGA curves of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.2

(36) FIG. 35 shows the XRD patterns of modified LDHs prepared according to Example 7.

(37) FIG. 36 shows the BET surface area of modified LDHs prepared according to Example 7.

(38) FIG. 37 shows the OAN of modified LDHs prepared according to Example 7.

(39) FIG. 38 shows the TGA curves of modified LDHs prepared according to Example 7.

(40) FIG. 39 shows the moisture uptake levels of modified LDHs prepared according to Example 7.

(41) FIG. 40 shows the XRD patterns of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.1.

(42) FIG. 41 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.1.

(43) FIG. 42 shows the XRD patterns of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2.

(44) FIG. 43 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2.

(45) FIG. 44 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2 (with 150° C. for 6 h thermal post-treatment).

(46) FIG. 45 shows TEM images of (a) unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and (b) Example 8.3.

(47) FIG. 46 shows the surface area (black bars) and pore volume (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and Example 8.3.

(48) FIG. 47 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.3 (MZA-TEVS).

(49) FIG. 48 shows TEM images of (a) unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and (b) Example 8.4.

(50) FIG. 49 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.4 (MZA-TEOS).

(51) FIG. 50 shows the surface area (black bars) and pore volume (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and Example 8.4.

(52) FIG. 51 shows the surface area (black bars) and pore volume (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and Example 8.5.

(53) FIG. 52 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.5 (MZA-TEAPS).

(54) FIG. 53 shows the surface area (black bars) and pore volume (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and Example 8.6.

(55) FIG. 54 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.6 (MZA-TMGPS).

(56) FIG. 55 shows the .sup.13C-NMR spectra of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH (bottom) and Example 8.6 (top).

(57) FIG. 56 shows the .sup.27Al-NMR spectra of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH (bottom) and Example 8.6 (top).

(58) FIG. 57 shows the XRD patterns of modified Mg.sub.3Al—CO.sub.3 LDHs prepared according to Example 9.1.

(59) FIG. 58 shows the FTIR spectra of modified Mg.sub.3Al—CO.sub.3 LDHs prepared according to Example 9.1.

(60) FIG. 59 shows the .sup.13C-NMR spectra of unmodified Mg.sub.3Al—CO.sub.3 AMO-LDH (top) and modified Mg.sub.3Al—CO.sub.3 LDHs prepared according to Example 9.1 (middle and bottom).

(61) FIG. 60 shows the FTIR spectra of modified Mg.sub.3Al—CO.sub.3 LDH prepared according to Example 9.2.

(62) FIG. 61 shows the moisture capacity of modified Mg.sub.3Al—CO.sub.3 LDH prepared according to Example 9.2 (MA-TEOS).

(63) FIG. 62 shows the .sup.13C-NMR spectra of unmodified Mg.sub.3Al—CO.sub.3AMO-LDH (bottom) and modified MA-TEOS prepared according to Example 9.2 (top).

(64) FIG. 63 shows TEM images of TEVS-modified LDH samples prepared according to Example 10.1 (left) and Example 10.2 (right).

(65) FIG. 64 shows XRD patterns of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b).

(66) FIG. 65 shows (A) the Si/Al molar ratio and (B) the carbon content of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b).

(67) FIG. 66 shows the surface area of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b).

(68) FIG. 67 shows the moisture capacity after exposure to RH60 humidity at 20° C. at various time points of TEVS-modified LDH samples prepared according to Example 10.1 (a), Example 10.2 (b) and unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c).

(69) FIG. 68 shows TEM images of TEVS-modified LDH samples prepared according to Example 10.3 (left) and Example 10.4 (right).

(70) FIG. 69 shows XRD patterns of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b).

(71) FIG. 70 shows (A) the Si/Al molar ratio and (B) the carbon content of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b).

(72) FIG. 71 shows the surface area of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b).

(73) FIG. 72 shows the moisture capacity after exposure to RH60 humidity at 20° C. at various time points of TEVS-modified LDH samples prepared according to Example 10.3 (a), Example 10.4 (b) and unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c).

(74) FIG. 73 shows XRD patterns of Example 11 stearic acid-modified LDH samples prepared according to the dry powder method (left) and the slurry method (right).

(75) FIG. 74 shows FTIR spectra of Example 11 stearic acid-modified LDH samples prepared according to the dry powder method (left) and the slurry method (right).

(76) FIG. 75 shows TGA curves of Example 11 stearic acid-modified LDH samples prepared according to the dry powder method, as well as unmodified AMO-LDH (LDH).

(77) FIG. 76 shows the yields of Example 11 stearic acid-modified LDH samples prepared according to the dry powder method (black bars) and the slurry method (striped bars).

EXAMPLE 1—PREPARATION OF LDHS

(78) AMO-LDH-1

(79) Mg(NO.sub.3).sub.2.6H.sub.2O (9.60 g, 37.4 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (4.68 g, 12.5 mmol) were dissolved in 50 mL of distilled water (Solution A). A second solution was made containing Na.sub.2CO.sub.3 (2.65 g, 25.0 mmol) and NaOH (4 g, 100 mmol) dissolved in 200 mL distilled water (Solution B). Solution A was added quickly to Solution B and stirred for 30 minutes. The LDH was washed twice with water and once with acetone by centrifuge-washing cycles. Six centrifuge tubes were used at 9000 rpm for five minutes. The resulting LDH slurry was dispersed in 200 mL acetone for 17 hours. The LDH slurry was then filtered, washed with 100 mL acetone and dispersed in 100 mL acetone for one hour. This procedure was repeated three times. The resulting LDH was dried overnight in a vacuum oven.

(80) AMO-LDH-2

(81) The mixed metal solution was prepared from 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O, 4.7 g of Al(NO.sub.3).sub.3.9H.sub.2O (4.68 g, 12.5 mmol) in 50 mL of de-carbonated water (Solution A). A second solution contained 2.65 g of Na.sub.2CO.sub.3 in 50 mL of deionised water. (Solution B). The solution A was added drop-wise (58 mL/min) to the Solution B. The system was kept at constant pH 10 by using 4 M NaOH and aged for 16 hours at room temperature. Then, the slurry was washed by de-carbonated water until the pH was close to 7 and followed by washing by using ethanol. The slurry was washed with 1000 ml of ethanol and then re-dispersed in 600 ml of this solvent for 1 hour. Then the obtained LDH solid was filtered, rinsed with 400 mL of ethanol, and dried in a vacuum oven for 24 hours.

EXAMPLE 2—MODIFICATION OF LDHS

(82) 2.1—Synthesis of Orqanosilane-Modified LDHs

(83) For organosilane modification, different silicon reagents were used; 3-aminotriethoxysilane (APTES), (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and triethoxymethylsilane (TEMS). 1 g of MgAlCO.sub.3-LDH (AMO-LDH-1, Example 1) was added to 50 mL of ethanol with stirring. A solution of 14 mmol of silicon reagent in 3 mL solvent (organic or aqueous) was added dropwise to the LDH solution. The resulting solution was stirred at room temperature for six hours. The LDH slurry was then washed three times with ethanol by centrifuge-washing cycles. Four centrifuge tubes were used at 4000 rpm for ten minutes. The resulting LDH was then dried overnight in a vacuum oven.

(84) 2.2—Synthesis of Stearate-Modified LDH

(85) Zn stearate (80 mg) was dissolved in 20 mL of xylene at 70° C. 200 mg of AMO-LDH-2 (Example 1) in 10 mL of xylene was added into Zn stearate solution. The mixture was stirred at 70° C. for 5 min. After cooling to room temperature, the solid was filtered and dried in the vacuum oven at room temperature.

(86) 2.3—Synthesis of Laurate-Modified LDH

(87) 200 mg of the obtained AMO-LDH-2 (Example 1) was dispersed in 10 mL of ethanol. 36 mg of sodium laurate was dissolved in ethanol at 70° C. Then the LDH slurry was quickly added to the laurate solution and kept stirring at 70° C. for 5 minutes. The final product was collected by filtration and dried in a vacuum oven overnight.

(88) 2.4—Alternative Modification Routes

(89) Aside from those protocols outlined in Examples 2.1-2.3, the LDHs of the invention can be prepared by a variety of other synthetic routes.

(90) Exemplary synthetic routes include:

(91) Route 7—Air sensitive technique: AMO-LDH (e.g. 1 g) is calcined at 150° C. for 6 h in the tube furnace under vacuum (or under N.sub.2). The calcined AMO-LDH is transferred into a glovebox. The AMO-LDH and the modifier (e.g. 1.8 mL) are introduced into an ampoule and a Schlenck respectively. Toluene (e.g. 10 mL) is added in both containers. The modifier/toluene solution is added onto the AMO-LDH/toluene slurry. The ampoule is heated at 100° C. overnight (16 h). The toluene is filtered away and the solid dried.
Route 8—RB flask under N.sub.2: AMO-LDH (e.g. 1 g) is calcined at 150° C. for 6 h under N.sub.2 in a RB flask. The calcined AMO-LDH is cooled to 25° C. Toluene (e.g. 10 mL) is added into the RB flask. Modifier (e.g. 1.8 mL) mixed with toluene (e.g. 10 mL) is added onto AMO-LDH slurry. The RB flask is heated at 100° C. overnight (16 h). The toluene is filtered away and the solid dried.

EXAMPLE 3—ORGANOSILANE MODIFIED LDHS

(92) 3.1—APTES-, GLYMO- and TEMS-Modified LDHs

THREE MODIFIED LDHS WERE PREPARED ACCORDING TO THE PROTOCOL DESCRIBED IN EXAMPLE 2.1. THE STRUCTURE OF THE 3 ORGANOSILANE MODIFIERS USED IS PROVIDED IN SCHEME 1 BELOW

(93) ##STR00007##

Scheme 1—Structures of (a) (3-aminopropyl)triethoxysilane (APTES); (b) (3-glycidyloxypropyl)trimethoxysilane (GLYMO); and (c) trimethoxylmethylsilane (TEMS)

(94) Powder X-ray Diffraction (PXRD)

(95) Structural changes can be observed from PXRD data. If the d-spacing of the 001 peaks is increased from the standard values for MgAlCO.sub.3-LDH, this will suggest that the silicon reagent has been inserted into the interlayer space. The PXRD patterns for all the organosilane-modified LDHs are shown in FIG. 2.

(96) The d.sub.003 values for all the organosilane-modified MgAlCO.sub.3-LDH are unchanged from the literature value of 7.9 Å for MgAlCO.sub.3-LDH. Relative to the PXRD patterns for unmodified acetone washed MgAlCO.sub.3-LDH, the LDH patterns for APTES- and TEMS-modified LDH are almost identical, with broad, weak reflections. This indicates that the products remain composed of just a few stacked layers of LDH nanosheets and the rigid stacking of LDHs prepared without acetone treatment has not been restored. The reflections for GLYMO-modified LDH appear slightly broader, indicating a reduction in crystallinity.

(97) Table 1 gives the average crystallite domain length (CDL) and average crystallite size for each of the samples.

(98) TABLE-US-00001 TABLE 1 Average crystallite sizes for the different organosilane-modified LDHs Average Size CDL (Å) size (Å) standard CDL (Å) (along a- and (Pielaszek deviation Sample (along c-axis) b-axes) method) (Å) Unmodified 127.3 636.4 68 21 MgAlCO.sub.3-LDH MgAlCO.sub.3- 157.6 623.8 70 28 LDH-APTES MgAlCO.sub.3- 134.8 734.2 97 27 LDH-GLYMO MgAlCO.sub.3- 164.9 632.6 76 23 LDH-TEMS

(99) Both sets of data show that when the LDH is modified with APTES and TEMS, the average crystallite size is not significantly changed, with a moderate increase along the c-axis. However, modification with GLYMO leads to a much larger crystallite size and an increase in the CDL along the a- and b-axes, whilst the CDL along the c-axis is similar to that of unmodified MgAlCO.sub.3-LDH. This shows that this modification leads to a change in how the LDH plates are arranged, with aggregation along the a- and b-axes rather than the c-axis.

(100) Fourier Transform Infrared Spectroscopy (FTIR)

(101) FIG. 3 shows the FTIR spectra for the LDH before and after modification with organosilane reagents.

(102) The characteristic absorptions of acetone treated MgAlCO.sub.3-LDH are visible for all four samples. These are the broad absorption at around 3400 cm.sup.−1 caused by —OH bonds, the band at around 1630 cm.sup.−1 corresponding to the bending mode of water, the absorption at 1366 cm.sup.−1 due to carbonate and the bands below 1000 cm.sup.−1 which are due to M-O vibrational modes.

(103) The series of bands around 2950 cm.sup.−1 in APTES-, GLYMO- and TEMS-modified LDH correspond to the asymmetric and symmetric stretching vibrations of —CH.sub.2 and the bands around 1040 cm.sup.−1 relate to the Si—O vibrations. For APTES-modified LDH, the band at 1568 cm.sup.−1 indicates the presence of —NH.sub.2. For GLYMO-modified LDH, the vibrations around 1200 cm.sup.−1 are due to the presence of C—O bonds in GLYMO. In the spectrum for TEMS-grafted LDH there are the correct absorptions relating to —CH.sub.2 and Si—O vibrations. Together with information from the XRD patterns, this suggests that the silicon reagents have grafted only on the outer surfaces of the LDH and are not present in the interlayer space, as the basal spacing was unchanged on modification.

(104) NMR Spectroscopy

(105) .sup.29Si-NMR spectroscopy can indicate how the organosilane reagents have been grafted onto the LDH. FIG. 4 shows the NMR spectra for the three different reagents.

(106) Transmission Electron Microscopy (TEM)

(107) FIG. 5 shows the TEM images for LDHs synthesised. For the APTES-modified sample, the sand-flower morphology has been maintained, but the darker patches on the TEM image indicate some degree of stacking perpedicular to the sample stage and the aggregates form much larger networks. This supports the suggestion that the T.sup.3 bonding mode increases aggreation of the LDH nanosheets.

(108) The TEMS-modified sample is comparable to the unmodified MgAlCO.sub.3-LDH, with similar shape and size aggregates of nanosheets.

(109) The GLYMO-modified sample has a very different morphology to the other samples. However, this does not agree with the NMR results of the GLYMO-modified sample, which showed the highest degree of T.sup.1 bonding. It may be that GLYMO does lead to a greater increase in hydrophobicity, leading to this new morphology, which is not related to the Si—O bonding mode or that there are additional interactions which lead to a greater aggregation of the LDH nanosheets.

(110) 3.2—TEVS-Modified LDHs

(111) A variety of triethoxyvinylsilane (TEVS)-modified LDHs were prepared according to Routes 7-8 outlined in Example 2.3.

(112) FIG. 6 shows the XRD pattern of the unmodified AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 7. FIG. 7 shows the FTIR spectra of the unmodified AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 7.

(113) FIGS. 6 and 7 shows that the LDH (TEVS-LDH) after Route 7 treatment retains a LDH structure. However, the d(003) spacing decrease due to the loss of water in the interlayer; new peaks at 1538, 1169, 1113, 1029 and 762 cm.sup.−1 highlight the presence of organosilane in the sample.

(114) FIG. 8 shows the FTIR spectra of the unmodified AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane using Route 8 using toluene as solvent. FIG. 9 shows the FTIR spectra of the unmodified AMO Mg.sub.3Al—CO.sub.3 LDH, and AMO Mg.sub.3Al—CO.sub.3 LDH modified with triethoxyvinylsilane.

EXAMPLE 4—STEARATE-MODIFIED LDHS

(115) 4.1. Water Content Studies

(116) Non-Calcined LDHs

(117) A series of LDHs were successfully made via co-precipitation in 20 L container. Each sample is isolated by vacuum filtration technique and washed by water till pH at 7. Then, the sample is dispersed in EtOH and isolated again. A selection of stearate salts have been used (stearic acid, Mg stearate, Ca stearate, Zn stearate, and all types of hydroxystearate salt), which has been separately dissolved in EtOH in the range of 2-10% weight of stearate salt to volume of EtOH. The LDH series is introduced into stearate salt/EtOH solution with a ratio in the range of 0.0005-0.4 of weight LDH powder to volume of EtOH used and mixed for 15 minutes to 24 hrs. The sample is then dried at 65-180° C.

(118) Calcined LDHs

(119) A series of LDHs were successfully made via co-precipitation in 20 L container. Each sample is isolated by vacuum filtration technique and washed by water till pH at 7. Then, the sample is dispersed by EtOH and isolated again. The resulting LDH is then dried and calcined at 100-300° C. for 4-20 hrs. A selection of stearate salts have been used (stearic acid, Mg stearate, Ca stearate, Zn stearate, and all types of hydroxystearate salt), which has been separately dissolved in EtOH in the range of 2-10% weight of stearate salt to volume of EtOH. The LDH powder is introduced into stearate salt/EtOH solution with a ratio in the range of 0.0005-0.4 of weight LDH powder to volume of EtOH used and mixed for 15 minutes to 24 hrs. The sample is dried at 65-180° C.

(120) Table 2 summarises the data for water content of stearate-modified Mg.sub.3Al—CO.sub.3 LDH.

(121) TABLE-US-00002 TABLE 2 Water content studies using stearate and stearic acid modified AMO-LDH Percentage a ratio of of stearate weight LDH salt/volume powder to Water Types of stearate of EtOH volume of content salt (% w/v) EtOH used (% w) Non- None — — 13.15 calcination Stearic acid 3% 0.2 11.48 4% 0.2 10.21 5% 0.2 9.95 Zn stearate 3% 0.2 9.85 4% 0.2 6.02 5% 0.2 5.85 Ca stearate 3% 0.2 8.75 4% 0.2 6.58 5% 0.2 6.34 Calcination Stearic acid 3% 0.2 8.20 4% 0.2 7.35 5% 0.2 7.10 Zn stearate 3% 0.2 5.67 4% 0.2 4.65 5% 0.2 4.43 Ca stearate 3% 0.2 6.97 4% 0.2 5.78 5% 0.2 4.98

(122) FIG. 10 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) without surface treatment against time.

(123) FIG. 11 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) with Zn stearate surface treatment after AMO wash against time. The stearate-modified LDH was prepared following the non-calcined protocol discussed in Example 4.1.

(124) FIG. 12 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 (100 m.sup.2/g of surface area) with Zn stearate treatment on calcined LDH powder against time. The stearate-modified LDH was prepared following the calcined protocol discussed in Example 4.1.

(125) FIG. 13 shows a plot of water adsorption of Mg.sub.3Al—CO.sub.3 with Zn stearate surface treatment vs AMO-LDH. The stearate-modified LDH was prepared according to the protocol set out in Example 2.2.

EXAMPLE 5—SODIUM STEARATE/STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH

(126) Preparation of AMO Mg.sub.4Al—CO.sub.3 LDH The mixed metal salts solution of Mg(NO.sub.3).sub.2.6H.sub.2O (80 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (20 mmol) in 50 mL deionised water was added dropwise into 50 mL of 25 mmol Na.sub.2CO.sub.3 solution while stirring for 1 hour. Constant pH of 10 was maintained by addition of 4 M NaOH to the reaction mixture. After stirring at room temperature for 24 hours, the product was filtered and washed with deionised water until pH 7. Then the wet cake was re-dispersed in 100 mL of deionised water and divided into four portions. Each portion was filtered and rinsed with 500 mL of ethanol then re-dispersed and stirred in 300 mL of ethanol at room temperature for 4 hours. The solvent was removed by filtration and the obtained LDH was further rinsed with 200 mL of ethanol. The product was dried at room temperature in a vacuum oven overnight.

EXAMPLE 5.1—SODIUM STEARATE-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH

(127) 1 g of Mg.sub.4Al—CO.sub.3 AMO LDH was added as a dry powder to 2.5 mmol of sodium stearate solution (0.7 g of stearic acid, 0.2 g NaOH, 100 mL EtOH, 50 mL deionised water) and stirred (750 rpm) at 80° C. for 18 hours. It was then filtered, washed with a warm (60° C.) solution of water/EtOH (1:1), and dried in vacuum overnight.

EXAMPLE 5.2—STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH

(128) 1 g of Mg.sub.4Al—CO.sub.3 AMO LDH was added as a dry powder to 2.5 mmol of stearic acid solution (0.7 g of stearic acid, 100 mL EtOH) and stirred (750 rpm) at 80° C. for 18 hours. It was then filtered, washed with a warm (60° C.) solution of water/EtOH (1:1), and dried in vacuum overnight.

EXAMPLE 5.3—STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH WITH ETHANOL WASH

(129) 1 g of Mg.sub.4Al—CO.sub.3 AMO LDH was added as a dry powder to 2.5 mmol of stearic acid solution (0.7 g of stearic acid, 100 mL EtOH) and stirred (750 rpm) at 80° C. for 18 hours. It was then filtered, washed with a warm ethanol (60° C.), and dried in vacuum overnight.

(130) Analysis of Sodium Stearate/Stearic Acid Modified AMO Mg.sub.4Al—CO.sub.3 LDHs

(131) FIG. 17 shows the XRD patterns of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3. When stearic acid treatment (Example 5.2) was used, impurity peaks from stearic acid were observed in XRD. Washing the modified LDH with warm ethanol (Example 5.3) more effectively removed excess stearic acid than washing with water/ethanol.

(132) FIG. 18 shows the FTIR spectra of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3. Very weak peaks of stearate were observed in Example 5.1 compared to Example 5.2 and Example 5.3. This might be due to the washing removing excessive stearate anion from the LDH surface. When stearic acid treatment with water/ethanol wash (Example 5.2) was used, impurity peaks from stearic acid were observed in FTIR. Washing with warm ethanol (Example 5.3) seems to be more effective at removing the excess fatty acid than the water/ethanol wash.

(133) FIG. 19 shows the BET Surface Area plotted against Oil Absorption Number (OAN) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). Surface area and oil absorption number (OAN) decreased after treatment. Both stearic acid treatments (Examples 5.2 & 5.3) significantly reduced the surface area and OAN of the AMO LDHs. This might be because of using high amounts of stearic acid so it coated and blocked the surface of LDHs, resulting in low surface area product. Example 5.3 in particular gave a slightly rigid product with a very low surface area.

(134) FIG. 20 shows the loose bulk densities and tap densities of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). The modified products show higher density than the unmodified AMO LDH, particularly Example 5.3.

(135) FIG. 21 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH) after exposure to RH99 humidity at 20° C. at various time points. The sodium stearate treatment (Example 5.1) did not help to slow down the moisture absorption rate of the LDH but it helped to decrease the maximum moisture uptake level from 50% for unmodified AMO LDH to 28%. Its uptake capacity was constant after 48 hours whereas ethanol-washed AMO LDH still continuously absorbed moisture up to 120 hours. Both stearic acid methods (5.2 and 5.3) help to retard the moisture uptake level of the LDHs.

(136) FIG. 22 shows the oil absorption number (OAN) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH) both before (black bars) and after (white bars) exposure to RH99 humidity at 20° C. for 120 hours. For both stearic acid methods (5.2 and 5.3), the OAN only slightly changes after exposure to moisture, indicating that stearic acid is more effective than stearate for preventing moisture uptake

(137) FIG. 23 shows the FTIR spectra of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 5.1, 5.2 and 5.3 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH) both before and after exposure to RH99 humidity at 20° C. for 120 hours. The FTIR results agree with moisture uptake level data as shown in FIG. 21. For AMO LDH and Example 5.1, the OH region peaks (3000-3600 cm.sup.−1) were broader and more intense after exposure to moisture, which indicates a higher moisture uptake level for these two LDHs compared to Examples 5.2 and 5.3.

EXAMPLE 6—STEARIC ACID MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDHS AT VARIOUS STEARIC ACID CONCENTRATIONS

EXAMPLE 6.1—STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH (DRY POWDER METHOD)

(138) Various amounts of stearic acid (0.05, 0.125, 0.25, 0.50, 1.00, 1.25, 2.50, 5.00 mmol) were dissolved in 100 mL of ethanol. 1 g of Mg.sub.4Al—CO.sub.3 AMO LDH as a dry powder was added to each solution and the mixtures were stirred (750 rpm) at 80° C. for 18 hours. The mixtures were filtered, washed with warm EtOH (60° C.), and dried in vacuum overnight. Products were noted as P-SA-X, where X=amount of stearic acid used in mmol and P refers to dry powder method.

EXAMPLE 6.2—STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH (SLURRY METHOD)

(139) Various amounts of stearic acid (0.05, 0.125, 0.25, 0.50, 1.00, 1.25, 2.50, 5.00 mmol) were dissolved in 70 mL of ethanol. 30 mL of Mg.sub.4Al—CO.sub.3 AMO LDH dispersed in ethanol (5% w/v; AMO LDH taken after AMO treatment process without drying; 1.5 g dry LDH) was added to each solution and the mixtures were stirred (750 rpm) at 80° C. for 18 hours. The mixtures were filtered, washed with warm EtOH (60° C.), and dried in vacuum overnight. Products were noted as S-SA-X, where X=amount of stearic acid used in mmol and S refers to slurry method.

(140) Analysis of Stearic Acid Modified AMO Mg.sub.4Al—CO.sub.3 LDHs at Various Stearic Acid Concentrations

(141) FIG. 24 shows the XRD patterns of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). No impurity phase was observed from XRD.

(142) FIG. 25 shows the XRD patterns of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.2, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). No impurity phase was observed from XRD.

(143) FIG. 26 shows the BET Surface Area plotted against Oil Absorption Number (OAN) of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1 and 6.2, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). At the same loading level of stearic acid, the slurry form treatment showed higher surface area and OAN value. For both methods, lower stearic acid loading corresponded to higher OAN and higher surface area of products.

(144) FIG. 27 shows the BET isotherm (A) and pore size distribution (B) of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1 and 6.2, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). Pore size decreased following stearic acid modification and decreased more at higher stearic acid concentration.

(145) FIG. 28 shows the loose bulk densities (black bars) and tap densities (white bars) of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1 (A) and Example 6.2 (B), as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). Lower stearic acid loading led to lower density. No significant difference in density was observed between both modification methods.

(146) FIG. 29 shows the oil absorption number (OAN) before (black bars) and after (white bars) exposure to RH99 humidity at 20° C. for 120 hours of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1 (A) and Example 6.2 (B), as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH). OAN generally decreased after exposure to moisture. Lower stearic acid loading gave higher OAN. At the same loading level of stearic acid, the slurry form treatment (B) showed higher OAN value than the powder form treatment (A)

(147) FIG. 30 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.1 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH), after exposure to RH99 humidity at 20° C. at various time points. The higher the stearic acid loading, the lower the moisture uptake of the modified LDH.

(148) FIG. 31 shows the moisture uptake levels of the modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Example 6.2 as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH), after exposure to RH99 humidity at 20° C. at various time points. The higher the stearic acid loading, the lower the moisture uptake of the modified LDH. At the same loading level of stearic acid, the slurry form post treatment seems to prevent LDH from moisture better than the powder form post treatment, especially at high loading level of stearic acid.

(149) FIG. 32 shows FTIR spectra of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.1, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH—bottom left panel) both before and after exposure to RH99 humidity at 20° C. for 120 hours. The lower the stearic acid loading, the broader the OH peak in the region 3000-3600 cm.sup.−1 after exposure to moisture. At low loadings of stearic acid (<0.25 mmol), the characteristic peaks of stearic acid cannot be observed.

(150) FIG. 33 shows FTIR spectra of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.2, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH—bottom left panel) both before and after exposure to RH99 humidity at 20° C. for 120 hours. The lower the stearic acid loading, the broader the OH peak in the region 3000-3600 cm.sup.−1 after exposure to moisture. At low loadings of stearic acid (<0.25 mmol), the characteristic peaks of stearic acid cannot be observed.

(151) FIG. 34 shows TGA curves of modified Mg.sub.4Al—CO.sub.3 LDHs prepared according to Examples 6.2, as well as unmodified Mg.sub.4Al—CO.sub.3 LDH (AMO LDH) both before (top curve) and after (bottom curve) exposure to RH99 humidity at 20° C. for 120 hours. Lower weight losses were obtained for products prepared with higher stearic acid loadings.

EXAMPLE 7—STEARIC ACID-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDHS, AMO MG.SUB.4.AL—CO.SUB.3 .LDHS AND AMO MG.SUB.5.AL—CO.SUB.3 .LDHS AT VARIOUS STEARIC ACID CONCENTRATIONS

(152) Preparation of AMO Mg.sub.3Al—CO.sub.3 LDH

(153) The mixed metal salts solution of Mg(NO.sub.3).sub.2.6H.sub.2O (75 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (25 mmol) in 50 mL deionised water was added dropwise into 50 mL of 25 mmol Na.sub.2CO.sub.3 solution while stirring for 1 hour. Constant pH of 10 was maintained by addition of 4 M NaOH to the reaction mixture. After stirring at room temperature for 24 hours, the product was filtered and washed with deionised water until pH 7. Then the wet cake was re-dispersed in 100 mL of deionised water and divided into four portions. Each portion was filtered and rinsed with 500 mL of ethanol then re-dispersed and stirred in 300 mL of ethanol at room temperature for 4 hours. The solvent was removed by filtration and the obtained LDH was further rinsed with 200 mL of ethanol. The product was dried at room temperature in a vacuum oven overnight.

(154) Preparation of AMO Mg.sub.5Al—CO.sub.3 LDH

(155) The mixed metal salts solution of Mg(NO.sub.3).sub.2.6H.sub.2O (90 mmol) and Al(NO.sub.3).sub.3.9H.sub.2O (10 mmol) in 50 mL deionised water was added dropwise into 50 mL of 25 mmol Na.sub.2CO.sub.3 solution while stirring for 1 hour. Constant pH of 10 was maintained by addition of 4 M NaOH to the reaction mixture. After stirring at room temperature for 24 hours, the product was filtered and washed with deionised water until pH 7. Then the wet cake was re-dispersed in 100 mL of deionised water and divided into four portions. Each portion was filtered and rinsed with 500 mL of ethanol then re-dispersed and stirred in 300 mL of ethanol at room temperature for 4 hours. The solvent was removed by filtration and the obtained LDH was further rinsed with 200 mL of ethanol. The product was dried at room temperature in a vacuum oven overnight.

EXAMPLE 7.1—STEARIC ACID-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDH

(156) Various amounts of stearic acid (1.25, 2.50 & 5.00 mmol) were dissolved in 70 mL of ethanol. 30 mL of Mg.sub.3Al—CO.sub.3 AMO LDH dispersed in ethanol (5% w/v; AMO LDH taken after AMO treatment process without drying; ˜1.5 g dry LDH) was added to each solution and the mixtures were stirred (750 rpm) at 80° C. for 18 hours. The mixtures were filtered, washed with warm EtOH (60° C.), and dried in vacuum overnight. Products were noted as Cop3-SA-X, where X=amount of stearic acid used in mmol.

EXAMPLE 7.2—STEARIC ACID-MODIFIED AMO MG.SUB.4.AL—CO.SUB.3 .LDH

(157) Various amounts of stearic acid (1.25, 2.50 & 5.00 mmol) were dissolved in 70 mL of ethanol. 30 mL of Mg.sub.4Al—CO.sub.3 AMO LDH dispersed in ethanol (5% w/v; AMO LDH taken after AMO treatment process without drying; ˜1.5 g dry LDH) was added to each solution and the mixtures were stirred (750 rpm) at 80° C. for 18 hours. The mixtures were filtered, washed with warm EtOH (60° C.), and dried in vacuum overnight. Products were noted as Cop4-SA-X, where X=amount of stearic acid used in mmol.

EXAMPLE 7.3—STEARIC ACID-MODIFIED AMO MG.SUB.5.AL—CO.SUB.3 .LDH

(158) Various amounts of stearic acid (1.25, 2.50 & 5.00 mmol) were dissolved in 70 mL of ethanol. 30 mL of Mg.sub.5Al—CO.sub.3 AMO LDH dispersed in ethanol (5% w/v; AMO LDH taken after AMO treatment process without drying; ˜1.5 g dry LDH) was added to each solution and the mixtures were stirred (750 rpm) at 80° C. for 18 hours. The mixtures were filtered, washed with warm EtOH (60° C.), and dried in vacuum overnight. Products were noted as Cop5-SA-X, where X=amount of stearic acid used in mmol.

(159) Analysis of Stearic Acid Modified AMO Mg.sub.3Al—CO.sub.3, Mg.sub.4Al—CO.sub.3 & Mg.sub.5Al—CO.sub.3 LDHs

(160) FIG. 35 shows the XRD patterns of modified LDHs prepared according to Examples 7.1, 7.2 and 7.3 as well as the unmodified LDH (AMO LDH) in each case. Impurities peaks from the excess stearic acid were observed at high loading level of stearic acid.

(161) FIG. 36 shows the BET surface area of modified LDHs prepared according to Examples 7.1 (striped bars), 7.2 (white bars) and 7.3 (black bars) as well as the unmodified LDH (AMO LDH) in each case. Surface area decreased after all the surface treatments.

(162) FIG. 37 shows the oil absorption number (OAN) of modified LDHs prepared according to Examples 7.1 (striped bars), 7.2 (white bars) and 7.3 (black bars) as well as the unmodified LDH (AMO LDH) in each case. OAN decreased after the surface treatments and lower OAN corresponded to higher stearic acid loading.

(163) FIG. 38 shows the TGA curves of (A) Cop3-SA-5, (B) Cop4-SA-5 and (C) Cop5-SA-5, surface-treated products plotted alongside the TGA curves for the corresponding unmodified LDH (AMO LDH) in each case.

(164) FIG. 39 shows the moisture uptake levels of the modified LDHs prepared according to Examples 7.1 (A), 7.2 (B) and 7.3 (C) as well as the unmodified LDH (AMO LDH) in each case, after exposure to RH99 humidity at 20° C. at various time points. The post treatment with stearic acid reduced the LDH uptake of moisture, especially at high loading levels of stearic acid.

EXAMPLE 8—MODIFICATION OF AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH

(165) Preparation of MgZn.sub.2Al—CO.sub.3 AMO-LDH

(166) MgZn.sub.2Al—CO.sub.3 (provided by SCG Chemicals) was slurried in ethanol, filtered, washed with ethanol and dried to give MgZn.sub.2Al—CO.sub.3AMO-LDH.

EXAMPLE 8.1—STEARIC ACID-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH

(167) Various amount of stearic acid (0.25, 0.5, 1.0, 2.0 mmol/g LDH) was dissolved in 300 mL of ethanol. 3 g of MgZn.sub.2Al—CO.sub.3AMO-LDH was introduced into stearic acid solution and mixed by homogenizer for 30 min. The mixture was then refluxed at 80° C. for 16 h. The solid was collect by filtration and washed with 600 mL of ethanol. Products were noted as MZA-SA-X, where X=amount of stearic acid used in mmol and MZA refers to MgZn.sub.2Al—CO.sub.3.

(168) FIG. 40 shows the XRD patterns of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.1, as well as the unmodified LDH (MZA-AMO-LDH). No impurity phase was observed after surface modification with loadings of stearic acid up to 1.0 mmol per g of LDH.

(169) FIG. 41 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.1, as well as the unmodified LDH (MZA-AMO-LDH), after exposure to RH99 humidity at 20° C. at various time points. Unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH exhibited a much faster moisture adsorption rate and higher adsorption capacity than the modified samples, reaching up to 37 wt % of dry LDH. As a result of stearic acid treatment, the moisture can be kept below 19 wt % of dry LDH. The lowest moisture capacity was 13 wt %, observed with the highest stearic acid loading of 2.0 mmol/g LDH (MZA-SA-2.0).

EXAMPLE 8.2—TRIETHOXYVINYLSILANE (TEVS)-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH (METHOD 1)

(170) 2 g of MgZn.sub.2Al—CO.sub.3 AMO-LDH was dispersed into 40 mL of Ethanol and purged with N.sub.2. TEVS with different loadings (8.5, 2.8 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 80° C. for 16 h. The solvent was evaporated. Half of solid was thermally treated at 150° C. for 6 h and the rest was used for characterisation. Products were noted as MZA-TEVS-X, where X=amount of TEVS used in mmol and MZA refers to Mg.sub.2ZnAl—CO.sub.3.

(171) FIG. 42 shows the XRD patterns of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2 (no thermal post-treatment), as well as the unmodified LDH (MZA-AMO-LDH). No impurity phase was observed after surface modification with TEVS.

(172) FIG. 43 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2 (no thermal post-treatment), as well as the unmodified LDH (MZA-AMO-LDH), after exposure to RH99 humidity at 20° C. at various time points. The MgZn.sub.2Al—CO.sub.3 AMO-LDH after modification with TEVS can effectively prevent the moisture adsorption as shown in FIG. 43. When the silane loading reached 8.5 mmol/g LDH, it kept moisture below 12 wt % of dry LDH for more than 4 days.

(173) FIG. 44 shows the moisture capacity of modified MgZn.sub.2Al—CO.sub.3 LDHs prepared according to Example 8.2 (with 150° C. for 6 h thermal post-treatment), as well as the unmodified LDH (MZA-AMO-LDH) which had also been subjected to the 150° C. for 6 h thermal post-treatment, after exposure to RH99 humidity at 20° C. at various time points. The silane-treated samples after thermal post-treatment at 150° C. for 6 h exhibited a much stronger ability to maintain moisture below 6 wt % in RH99 for more than 4 days. Thermal post-treatment on the sample with the higher TEVS loading exhibited better performance.

EXAMPLE 8.3—TRIETHOXYVINYLSILANE (TEVS)-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH (METHOD 2)

(174) 2 g of MgZn.sub.2Al—CO.sub.3AMO-LDH was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 100 mL acetone purged with N.sub.2. TEVS (5.6 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected and washed with acetone (300 mL) followed by drying in an oven at 80° C. overnight.

(175) FIG. 45 shows TEM images of (a) unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and (b) Example 8.3. After silane modification, there is no much difference in the morphology and aggregation degree.

(176) FIG. 46 shows the surface area in m.sup.2/g (black bars) and pore volume in cm.sup.3/g (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.3 (MZA-TEVS). The surface area and pore volume after silane modification were essentially unchanged.

(177) FIG. 47 shows the moisture capacity of unmodified MgZn.sub.2Al—COs AMO-LDH and Example 8.3 (MZA-TEVS) after exposure to RH60 humidity at 20° C. at various time points. After TEVS modification, the moisture level under these conditions could be kept below 5 wt %.

EXAMPLE 8.4—TRIETHOXYOCTYLSILANE (TEOS)-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH

(178) 2 g of MgZn.sub.2Al—CO.sub.3AMO-LDH was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 100 mL acetone purged with N.sub.2. Triethoxyoctylsilane (5.6 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected and washed with acetone (300 mL) followed by drying in an oven at 80° C. overnight.

(179) FIG. 48 shows TEM images of (a) unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and (b) Example 8.4. After silane modification, the particles are better dispersed and less aggregated.

(180) FIG. 49 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.4 (MZA-TEOS) after exposure to RH60 humidity at 20° C. at various time points. After TEOS modification, the moisture level under these conditions could be kept below 6 wt %, indicating reduced hydrophilicity compared to the unmodified LDH.

(181) FIG. 50 shows the surface area in m.sup.2/g (black bars) and pore volume in cm.sup.3/g (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.4 (MZA-TEOS). The surface area and pore volume after silane modification were slightly higher than unmodified LDH.

EXAMPLE 8.5—(3-AMINOPROPYL)TRIETHOXYSILANE (APTES)-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH

(182) 2 g of MgZn.sub.2Al—CO.sub.3AMO-LDH was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 100 mL acetone purged with N.sub.2. (3-aminopropyl)triethoxysilane (APTES, also referred to as TEAPS) (5.6 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected and washed with acetone (300 mL) followed by drying in an oven at 80° C. overnight.

(183) FIG. 51 shows the surface area in m.sup.2/g (black bars) and pore volume in cm.sup.3/g (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3AMO-LDH and Example 8.5 (MZA-TEAPS). The surface area and pore volume after silane modification were slightly lower than unmodified LDH.

(184) FIG. 52 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.5 (MZA-TEAPS) after exposure to RH60 humidity at 20° C. at various time points. After APTES modification, the moisture level under these conditions could be kept below 6 wt %, indicating reduced hydrophilicity compared to the unmodified LDH.

EXAMPLE 8.6—(3-GLYCIDYLOXYPROPYL)TRIMETHOXYSILANE (GLYMO)-MODIFIED AMO MGZN.SUB.2.AL—CO.SUB.3 .LDH

(185) 2 g of MgZn.sub.2Al—CO.sub.3 AMO-LDH was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 100 mL acetone purged with N.sub.2. (3-glycidyloxypropyl)trimethoxysilane (GLYMO, also referred to as TMGPS) (5.6 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected and washed with acetone (300 mL) followed by drying in an oven at 80° C. overnight.

(186) FIG. 53 shows the surface area in m.sup.2/g (black bars) and pore volume in cm.sup.3/g (striped bars) of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.6 (MZA-TMGPS). The surface area and pore volume after silane modification were essentially the same as unmodified LDH.

(187) FIG. 54 shows the moisture capacity of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH and Example 8.6 (MZA-TMGPS) after exposure to RH60 humidity at 20° C. at various time points. After GLYMO modification, the moisture level under these conditions could be kept below 6 wt %, indicating reduced hydrophilicity compared to the unmodified LDH.

(188) FIG. 55 shows the .sup.13C-NMR spectra of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH (bottom) and Example 8.6 (top). The functional group of silane can be clearly observed from .sup.13C NMR spectra, indicating the successful surface graft of 3-glycidoxypropylsilane on the LDH.

(189) FIG. 56 shows the .sup.27Al-NMR spectra of unmodified MgZn.sub.2Al—CO.sub.3 AMO-LDH (bottom) and Example 8.6 (top). The extra peak at around 50 ppm was observed, which is attributed to the migration of Al from LDH and the formation of tetrahedral Al—O—Si sites with the silane.

EXAMPLE 9—SILANE MODIFICATION OF AMO MG.SUB.3.AL—CO.SUB.3 .LDH

EXAMPLE 9.1—TRICHLORO(OCTADECYL)SILANE (TCODS)-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDH

(190) 1 g of Mg.sub.3Al—CO.sub.3 AMO-LDH (prepared as per Example 1, AMO-LDH-2) was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 20 mL acetone purged with N.sub.2. Different loadings of trichloro(octadecyl)silane (0.5, 1.0 & 2.0 mmol/g LDH) were injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected by centrifugation and washed with acetone (×3) followed by drying in vacuum overnight. Products were noted as MA-TCODS-X, where X=amount of TCODS used in mmol and MA refers to Mg.sub.3Al—CO.sub.3.

(191) FIG. 57 shows the XRD patterns of modified Mg.sub.3Al—CO.sub.3 LDHs prepared according to Example 9.1, as well as the unmodified LDH (MA-AMO-LDH). No impurity phase was observed after surface modification with loadings of TCODS up to 1.0 mmol/g of LDH.

(192) FIG. 58 shows the FTIR spectra of modified Mg.sub.3Al—CO.sub.3 LDHs prepared according to Example 9.1, as well as the unmodified LDH (MA-AMO-LDH). With increased TCODS-loading, the more obvious vibrations of CH.sub.2, CH.sub.3 (2919, 2850 cm.sup.−1) and Si—O—Si (900-1100 cm.sup.−1) can be observed (as indicated by the arrows), indicating the formation of silane on the AMO-LDH.

(193) FIG. 59 shows the .sup.13C-NMR spectra of unmodified Mg.sub.3Al—CO.sub.3 AMO-LDH (top) and modified Mg.sub.3Al—COs LDHs prepared according to Example 9.1 (middle and bottom). The octadecyl group of TCODS can be clearly observed in the TCODS-treated samples, as highlighted in the rectangular box.

EXAMPLE 9.2—TRIETHOXYOCTYLSILANE (TEOS)-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDH

(194) 1 g of Mg.sub.3Al—CO.sub.3 AMO-LDH was thermally treated at 180° C. for 6 h. The dry solid was dispersed in 20 mL acetone purged with N.sub.2. Triethoxyoctylsilane (3.22 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 60° C. for 16 h. The solid was collected by centrifugation and washed with acetone (×3) followed by drying in vacuum overnight.

(195) FIG. 60 shows the FTIR spectra of modified Mg.sub.3Al—CO.sub.3 LDH prepared according to Example 9.2, as well as the unmodified LDH (MA-AMO-LDH). After silane modification, the obvious vibrations of Si—O—Si (900-1100 cm.sup.−1) can be observed, indicating the formation of silane on the AMO-LDH.

(196) FIG. 61 shows the moisture capacity of modified Mg.sub.3Al—CO.sub.3 LDH prepared according to Example 9.2 (MA-TEOS), as well as the unmodified LDH (MA-AMO-LDH), after exposure to RH99 humidity at 20° C. at various time points. After silane modification, the moisture level does not exceed 20 wt %, indicating that the TEOS-treated sample is much less hydrophilic compared with the unmodified LDH.

(197) FIG. 62 shows the .sup.13C-NMR spectra of unmodified Mg.sub.3Al—CO.sub.3 AMO-LDH (bottom) and modified MA-TEOS prepared according to Example 9.2 (top). The NMR results show that the functional group (alkyl) of TEOS is present in the MA-TEOS sample, indicating the successful surface graft of TEOS on the LDH.

EXAMPLE 10—COMPARATIVE SILANE MODIFICATION OF AMO MG.SUB.3.AL—CO.SUB.3 .LDH AND MG.SUB.3.AL—CO.SUB.3 .LDH

EXAMPLE 10.1—TRIETHOXYVINYLSILANE-MODIFIED MG.SUB.3.AL—CO.SUB.3 .LDH (SLURRY METHOD)

(198) Water-Washed LDH Formation

(199) A mixed metal solution was prepared from 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O (37.4 mmol), 4.7 g of Al(NO.sub.3).sub.3.9H.sub.2O (12.5 mmol) in 50 mL of de-carbonated water (Solution A). A second solution contained 2.65 g of Na.sub.2CO.sub.3 (25.0 mmol) in 50 mL of deionised water (Solution B). The solution A was added drop-wise (58 mL/min) to the Solution B. The system was kept at constant pH 10 by using 4 M NaOH and aged for 16 hours at room temperature. The slurry was then filtered and the filter cake was washed with de-carbonated water until the pH was close to 7. The water-washed Mg.sub.3Al—CO.sub.3 LDH was dispersed in water to give a 29% w/v slurry.

(200) TEVS Modification

(201) Water washed Mg.sub.3Al—CO.sub.3 LDH slurry (29% w/v in water, equal to 1 g of dry LDH) was dispersed into 100 mL of ethanol purged with N.sub.2. Triethoxyvinylsilane (TEVS) (2.8 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 80° C. for 18 h. The solid was collected by filtration and washed with ethanol (300 mL) followed by drying for 16 h.

EXAMPLE 10.2—TRIETHOXYVINYLSILANE-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDH (SLURRY METHOD)

(202) Ethanol-Treated LDH Formation

(203) A mixed metal solution was prepared from 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O (37.4 mmol), 4.7 g of Al(NO.sub.3).sub.3.9H.sub.2O (12.5 mmol) in 50 mL of de-carbonated water (Solution A). A second solution contained 2.65 g of Na.sub.2CO.sub.3 (25.0 mmol) in 50 mL of deionised water (Solution B). The solution A was added drop-wise (58 mL/min) to the Solution B. The system was kept at constant pH 10 by using 4 M NaOH and aged for 16 hours at room temperature. The slurry was then filtered and the filter cake was washed with de-carbonated water until the pH was close to 7 and followed by washing with ethanol. It was then re-dispersed in ethanol and slurried for 1 hour. The slurry was filtered and rinsed with ethanol. The ethanol-treated Mg.sub.3Al—CO.sub.3 LDH was dispersed in ethanol to give a 29% w/v slurry.

(204) TEVS Modification

(205) Ethanol-treated AMO Mg.sub.3Al—CO.sub.3 LDH slurry (29% w/v in ethanol, equal to 1 g of dry LDH) was dispersed into 100 mL of ethanol purged with N.sub.2. Triethoxyvinylsilane (TEVS) (2.8 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 80° C. for 18 h. The solid was collected by filtration and washed with ethanol (300 mL) followed by drying for 16 h.

(206) Analysis of Comparative TEVS-Modified Mg.sub.3Al—CO.sub.3 LDHs Made by the Slurry Method

(207) FIG. 63 shows TEM images of TEVS-modified LDH samples prepared according to Example 10.1 (left) and Example 10.2 (right). Both samples show similar morphology. The TEVS-AMO-LDH (Example 10.2) shows slightly thinner particles.

(208) FIG. 64 shows XRD patterns of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b). Both samples show similar crystallinities and no impurity peaks.

(209) FIG. 65 shows (A) the Si/Al molar ratio and (B) the carbon content of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b). In (B) the carbon content of unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c) is also shown. Both samples can be grafted with silane using the same slurry method and showed similar Si content. However, after silane treatment, the AMO sample (b) contained more carbon, indicating more silane-derived functional groups are present in the AMO-treated sample.

(210) FIG. 66 shows the surface area of TEVS-modified LDH samples prepared according to Example 10.1 (a) and Example 10.2 (b). The surface area of unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c) is also shown. After silane modification both water-washed LDH (a) and AMO-LDH (b) had the same surface area.

(211) FIG. 67 shows the moisture capacity after exposure to RH60 humidity at 20° C. at various time points of TEVS-modified LDH samples prepared according to Example 10.1 (a), Example 10.2 (b) and unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c). AMO-LDH after TEVS-treatment (b) showed reduced moisture uptake compared to the equivalent water-washed LDH (a).

EXAMPLE 10.3—TRIETHOXYVINYLSILANE-MODIFIED MG.SUB.3.AL—CO.SUB.3 .LDH (DRY FORM METHOD)

(212) Water-Washed LDH Formation

(213) A mixed metal solution was prepared from 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O (37.4 mmol), 4.7 g of Al(NO.sub.3).sub.3.9H.sub.2O (12.5 mmol) in 50 mL of de-carbonated water (Solution A). A second solution contained 2.65 g of Na.sub.2CO.sub.3 (25.0 mmol) in 50 mL of deionised water (Solution B). The solution A was added drop-wise (58 mL/min) to the Solution B. The system was kept at constant pH 10 by using 4 M NaOH and aged for 16 hours at room temperature. The slurry was then filtered and the filter cake was washed with de-carbonated water until the pH was close to 7. The water-washed Mg.sub.3Al—CO.sub.3 LDH was dried in vacuum overnight.

(214) TEVS Modification

(215) Water-washed Mg.sub.3Al—CO.sub.3 LDH powder (1 g) was thermally treated at 180° C. for 6 h and was then dispersed into 100 mL of ethanol purged with N.sub.2. Triethoxyvinylsilane (TEVS) (2.8 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 80° C. for 18 h. The solid was collected by filtration and washed with ethanol (300 mL) followed by drying for 16 h.

EXAMPLE 10.4—TRIETHOXYVINYLSILANE-MODIFIED AMO MG.SUB.3.AL—CO.SUB.3 .LDH (DRY FORM METHOD)

(216) Ethanol-Treated LDH Formation

(217) A mixed metal solution was prepared from 9.6 g of Mg(NO.sub.3).sub.2.6H.sub.2O (37.4 mmol), 4.7 g of Al(NO.sub.3).sub.3.9H.sub.2O (12.5 mmol) in 50 mL of de-carbonated water (Solution A). A second solution contained 2.65 g of Na.sub.2CO.sub.3 (25.0 mmol) in 50 mL of deionised water (Solution B). The solution A was added drop-wise (58 mL/min) to the Solution B. The system was kept at constant pH 10 by using 4 M NaOH and aged for 16 hours at room temperature. The slurry was then filtered and the filter cake was washed with de-carbonated water until the pH was close to 7 and followed by washing with ethanol. It was then re-dispersed in ethanol and slurried for 1 hour. The slurry was filtered, rinsed with ethanol and dried in vacuum overnight.

(218) TEVS Modification

(219) Ethanol-treated AMO Mg.sub.3Al—CO.sub.3 LDH powder (1 g) was thermally treated at 180° C. for 6 h and was then dispersed into 100 mL of ethanol purged with N.sub.2. Triethoxyvinylsilane (TEVS) (2.8 mmol/g LDH) was injected dropwise into the suspension followed by reflux at 80° C. for 18 h. The solid was collected by filtration and washed with ethanol (300 mL) followed by drying for 16 h.

(220) Analysis of Comparative TEVS-Modified Mg.sub.3Al—CO.sub.3 LDHs Made by the Dry Form Method

(221) FIG. 68 shows TEM images of TEVS-modified LDH samples prepared according to Example 10.3 (left) and Example 10.4 (right). Both samples show similar morphology. The TEVS-AMO-LDH (Example 10.4) shows thinner particles.

(222) FIG. 69 shows XRD patterns of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b). Both samples show similar crystallinities and no impurity peaks.

(223) FIG. 70 shows (A) the Si/Al molar ratio and (B) the carbon content of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b). In (B) the carbon content of unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c) is also shown. Both samples can be grafted with silane using the same dry form method. However, the AMO-treated sample (b) contained more carbon and had a higher Si/Al ratio, indicating silane modification is more effective on AMO-LDH compared with water-washed LDH.

(224) FIG. 71 shows the surface area of TEVS-modified LDH samples prepared according to Example 10.3 (a) and Example 10.4 (b). The surface area of unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c) is also shown. After silane modification, the surface area of AMO-LDH (b) remained high, while the water-washed LDH (a) showed extremely low surface area.

(225) FIG. 72 shows the moisture capacity after exposure to RH60 humidity at 20° C. at various time points of TEVS-modified LDH samples prepared according to Example 10.3 (a), Example 10.4 (b) and unmodified AMO Mg.sub.3Al—CO.sub.3 LDH (c). After TEVS treatment, water-washed LDH (a) showed slightly better moisture resistance than that of AMO-LDH.

EXAMPLE 11—COMPARATIVE STEARIC ACID MODIFICATION OF AMO MG.SUB.3.AL—CO.SUB.3 .LDH AND MG.SUB.3.AL—CO.SUB.3 .LDH

EXAMPLE 11.1—STEARIC ACID-MODIFIED MG.SUB.3.AL—CO.SUB.3 .LDH (SLURRY METHOD)

(226) Stearic acid (2 mmol) was dissolved in 200 ml of ethanol. Water washed Mg.sub.3Al—CO.sub.3 LDH slurry (29% w/v in water, equal to 2 g of dry LDH) was added to this solution and the mixture was stirred (750 rpm) at 80° C. for 18 h. The solid was collected by filtration and washed with warm (60° C.) ethanol (600 mL) followed by drying in vacuum oven overnight. The resultant LDH is referred to as LDH-SA1.0-S.

EXAMPLE 11.2—STEARIC ACID-MODIFIED AMO-MG.SUB.3.AL—CO.SUB.3 .LDH (SLURRY METHOD)

(227) Stearic acid (2 mmol) was dissolved in 200 ml of ethanol. Ethanol-treated Mg.sub.3Al—CO.sub.3 LDH slurry (36% w/v in ethanol, equal to 2 g of dry LDH) was added to this solution and the mixture was stirred (750 rpm) at 80° C. for 18 h. The solid was collected by filtration and washed with warm (60° C.) ethanol (600 mL) followed by drying in vacuum oven overnight. The resultant LDH is referred to as AMO-LDH-SA1.0-S.

EXAMPLE 11.3—STEARIC ACID-MODIFIED MG.SUB.3.AL—CO.SUB.3 .LDH (DRY POWDER METHOD)

(228) Water washed Mg.sub.3Al—CO.sub.3 LDH powder (2 g) was thermally treated at 180° C. for 2 h. It was then added to a solution of stearic acid (2 mmol) in 200 ml of ethanol. The mixture was stirred (750 rpm) at 80° C. for 18 h. The solid was collected by filtration and washed with warm (60° C.) ethanol (600 mL) followed by drying in vacuum oven overnight. The resultant LDH is referred to as LDH-SA1.0-P.

EXAMPLE 11.4—STEARIC ACID-MODIFIED AMO-MG.SUB.3.AL—CO.SUB.3 .LDH (DRY POWDER METHOD)

(229) Ethanol-treated Mg.sub.3Al—CO.sub.3 LDH powder (2 g) was thermally treated at 180° C. for 2 h. It was then added to a solution of stearic acid (2 mmol) in 200 ml of ethanol. The mixture was stirred (750 rpm) at 80° C. for 18 h. The solid was collected by filtration and washed with warm (60° C.) ethanol (600 mL) followed by drying in vacuum oven overnight. The resultant LDH is referred to as AMO-LDH-SA1.0-P.

(230) Analysis of Comparative stearic acid-modified Mg.sub.3Al—CO.sub.3 LDHs

(231) FIG. 73 shows XRD patterns of stearic acid-modified LDH samples prepared according to the dry powder method (left) and the slurry method (right). No impurity phase was observed after surface modification with stearic acid.

(232) FIG. 74 shows FTIR spectra of stearic acid-modified LDH samples prepared according to the dry powder method (left) and the slurry method (right). The vibrations of CH.sub.2 and CH.sub.3 due to the presence of stearic acid can be observed for all four samples, but are more obvious in the sample made from AMO-treated LDH by the slurry method (AMO-LDH-SA1.0-S).

(233) FIG. 75 shows TGA curves of stearic acid-modified LDH samples prepared according to the dry powder method, as well as unmodified AMO-LDH (LDH). Stearic acid-modified samples showed reduced water content; LDH-SA1.0-P (13 wt %) and AMO-LDH-SA1.0-P (12 wt %) compared to the unmodified sample (19 wt %).

(234) FIG. 76 shows the yields of stearic acid-modified LDH samples prepared according to the dry powder method (black bars) and the slurry method (striped bars). Yields were calculated from the residual of stearic acid by .sup.1H-NMR. Modified samples prepared from AMO-LDH by both the dry powder and slurry methods resulted in higher yields than the equivalent samples prepared from the water washed LDH, indicating that the AMO-LDH can be more efficiently modified with stearic acid. The AMO-LDH modified by the slurry method exhibited the highest yield (95%).

(235) While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.