Coating compositions are disclosed that include an alkoxide and a silica sol that includes silica nanoparticles and a polymerizable (meth)acrylate binding agent. The polymerizable (meth)acrylate binding agent remains substantially uncrosslinked after the coating composition has been cured to form a hard coat. Also disclosed are articles at least partially coated with a hard coat deposited from such a coating composition, methods for depositing a hard coat on at least a portion of a plastic substrate, and methods for improving the adhesion and abrasion resistance of a coating composition.