Layered silicate/polymer composite and a method of forming the same

A method for forming a layered silicate/polymer composite, the composite comprising individual exfoliated silicate layers separated in a continuous polymer matrix, wherein the polymer is a hydrophobic polymer, the method comprising:

• exfoliating sheet silicate in water to form a silicate suspension;
• replacing the water in the silicate suspension by a first organic solvent to form a silicate/organic solvent suspension;
• carrying out rotary evaporation on the silicate/organic solvent suspension to form a concentrated silicate/organic solvent suspension;
• contacting the concentrated silicate/organic solvent suspension with a solution of a hydrophobic polymer precursor in a second organic solvent to form a silicate/polymer precursor suspension, the silicate layers randomly dispersed in the silicate/polymer precursor suspension, the polymer precursor containing hydroxyl or carboxylic acid groups;
• coating the silicate/polymer precursor suspension on a substrate;
• removing the first organic solvent and the second organic solvent;
• curing the hydrophobic polymer precursor of the coating of the silicate/polymer precursor using ultraviolet radiation to initiate cross-linking of hydroxyl or carboxylic groups of the polymer precursor with the silicate layers;
• and
• annealing the cured coating to form the layered silicate/polymer composite on the substrate, wherein the annealing forms chemical bonds between the silicate layers and the polymer matrix through cross-linking of the hydroxyl or carboxylic groups with the silicate layers;
• wherein coating the silicate/polymer precursor suspension on the substrate comprises applying a shearing force to the suspension to orient the dispersed silicate layers along a surface of the substrate, wherein the replacing the water by the first organic solvent is carried out by adding the first organic solvent to the silicate suspension in water, filtering the resulting suspension and re-suspending the silicate in the first organic solvent;
• and
• wherein adding the first organic solvent, filtering and re-suspending is repeated once to carry out solvent exchange for a total of two times so that the silicate layers in the silicate/organic solvent suspension are not coagulated together.