A composition having pH of 5 or less comprises composite particles dispersed in an aqueous continuous liquid phase. Each composite particle comprises a polymer core surrounded by a silicaceous shell. From 3 to 50 percent of silicon atoms in the silicaceous shells are bonded to respective organic groups via a silicon-carbon covalent bond. The weight ratio of the total amount of the silica in the composition to the total amount of the at least one polymer is from 0.1 to 19. The composition is useful for making various articles. A method for making the composition is also disclosed. Silicaceous particles dispersed in an aqueous phase, wherein from 3 to 50 percent of silicon atoms in the silicaceous particles are bonded to organic groups via a silicon-carbon covalent bond are also disclosed.