A barrier coating composition including: a monomer combination including a first monomer having at least two thiol groups at its terminal end and a second monomer having at least two carbon-carbon unsaturated bond-containing groups at its terminal end; and a plurality of organo-modified clay particles dispersed in the monomer combination, wherein the organo-modified clay particles include a compound having a hydrocarbyl group linked to a heteroatom, and wherein the compound is a primary, secondary, or tertiary amine, a quaternary organoammonium salt, a primary, secondary, or tertiary phosphine, a quaternary organophosphonium salt, a thiol including an amine group, or a combination thereof.