Modified nano-clays and coating compositions including the same

1. A modified nano-clay, comprising:

a nano-clay platelet;

a plurality of haloalkylalkoxysiloxy moieties covalently bonded to a first surface of the nano-clay platelet, the haloalkylalkoxysiloxy moieties having a general formula:

wherein R 1 is haloalkyl and R 2 and R 3 are lower alkoxy; and

a plurality of polyatomic cations ionically bonded to a second surface of the nano-clay platelet, the polyatomic cations having displaced metal cations from the second surface of the nano-clay platelet and providing increased hydrophilicity of the modified nano-clay,

wherein the polyatomic cations are phosphorylcholine,

wherein the nano-clay platelet has a unit cell formula of Na 0.7 [(Si 8 Mg 5.5 Li 0.3 )O 20 (OH) 4 ], and

wherein the haloalkylalkoxysiloxy moieties are obtained from (tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane.

2. A modified nano-clay, comprising:

a nano-clay platelet;

a plurality of haloalkylalkoxysiloxy moieties covalently bonded to a first surface of the nano-clay platelet, the haloalkylalkoxysiloxy moieties having a general formula:

wherein R 1 is haloalkyl and R 2 and R 3 are lower alkoxy; and

a plurality of polyatomic cations ionically bonded to a second surface of the nano-clay platelet, the polyatomic cations having displaced metal cations from the second surface of the nano-clay platelet and providing increased hydrophilicity of the modified nano-clay,

wherein the polyatomic cations are phosphorylcholine, and

wherein the modified nano-clay has a haloalkylalkoxysiloxy moiety grafting efficiency of at least 20%.

3. A coating composition, comprising:

polyvinylidene fluoride (PVDF);

poly(methyl methacrylate) (PMMA), wherein the PVDF and PMMA have a weight ratio within a range of 50/50 to 70/30; and

0.4-0.6 wt % of a modified nano-clay based on a total mass of the modified nano-clay, the PVDF, and the PMMA, wherein the modified nano-clay comprises platelets having a unit cell formula of Na 0.7 [(Si 8 Mg 5.5 Li 0.3 )O 20 (OH) 4 ], a plurality of covalently bound haloalkylalkoxysiloxy moieties obtained from (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane, and a plurality of ionically bound phosphorylcholine ions.

4. The coating composition of claim 3 , wherein:

(i) the coating composition comprises nanoparticles of PVDF and PMMA, the nanoparticles having an average particle size of 100-300 nm; or

(ii) at least a portion of the modified nano-clay is disposed in voids between particles comprising PVDF and PMMA; or

(iii) the coating composition is an aqueous dispersion of (a) the modified nano-clay and (b) nanoparticles comprising PVDF and PMMA; or

(iv) any combination of (i), (ii), and (iii).

5. An object, comprising:

a metal component; and

a protective coating on at least a portion of the metal component, the protective coating comprising a layer of the coating composition according to claim 4 .

6. The object of claim 5 , wherein the protective coating further comprises:

a layer of a primer base coat;

a layer of a top coat comprising PVDF; or

a layer of a primer base coat and a layer of a top coat comprising PVDF,

wherein each layer of the protective coating has an average thickness of 5-20 μm.

7. The object of claim 5 , wherein the protective coating has:

(i) an average thickness of 20-40 μm;

(ii) an impedance of at least 3,000 MΩ·cm 2 at 0.1 Hz; or

(iii) both (i) and (ii).

8. The object of claim 5 , wherein the protective coating has:

(i) an initial impedance of at least 3000 MΩ·cm 2 at 0.1 Hz and an impedance of at least 1000 MΩ·cm 2 at 0.1 Hz after weathering for 4500 hours in an accelerated weathering tester;

(ii) an electrochemical stress index of less than 1.4 after weathering for 4500 hours in an accelerated weathering tester; or

(iii) both (i) and (ii).