Polymers are high molecular mass compounds formed by polymerization of monomers. Block copolymers are made up of blocks of different polymerized monomers. Inverse emulsion polymerization requires water, monomers, and a surfactant. Many polymers are copolymers, meaning that they are derived from two different monomers. Synthetic polymers are human made through chemical reactions of monomers. Epoxy resins produced from such epoxy monomers are called glycidyl-based epoxy resins. Some polymers may also decompose into the monomers or other toxic substances when heated. Vinyl polymers are a group of polymers derived from vinyl monomers of the type CH=CHR. All polymers are made of repetitive units called monomers. SBR is derived from two monomers, styrene and butadiene. Amino acids are the monomers of proteins. Macromolecules are formed by many monomers linking together, forming a polymer. Glucans are polysaccharides derived from glucose monomers. There's not any crystallographic data available describing the crosslinking of monomers. Polyethylene terephthalate can be depolymerized to yield the constituent monomers.