Acrylics are probably the most versatile family of monomers. They can be used to prepare polymers with rigid, flexible, ionic, nonionic, hydrophobic, or hydrophilic properties. The monomers are classified into 9 groups based on composition and functionality. They are polymerized primarily by a free radical process, and to a lesser extent by anionic polymerization. Note that additional acrylic macromonomers can be found in the Poly(ethylene glycol) and Poly(ethylene oxide) section.