Polymetyyli

Polymetyyli is a term used in polymer chemistry to describe a family of polymers that contain methyl groups in their repeating units or as side chains. It is not a single compound, but a class of polymers derived from methyl-substituted monomers such as methyl methacrylate, methyl acrylate, or alpha-methyl styrene.

The most well-known member is polymethyl methacrylate (PMMA), commonly used as acrylic glass. Other examples include poly(methyl acrylate) (PMA) and poly(alpha-methyl styrene). These polymers share the characteristic presence of methyl groups that influence their physical properties, such as stiffness, solubility, and glass transition temperature, compared with polymers lacking such substituents.

Synthesis of polymetyyli polymers is typically achieved by chain-growth polymerization of the corresponding methyl-substituted monomers. Free-radical polymerization is the common route, with industrial processes often employing emulsion, suspension, or bulk polymerization for PMMA and related polymers. Controlled radical polymerization methods also enable more precise architectures for certain applications.

Key properties of polymetyyli polymers include relatively high glass transition temperatures, good optical clarity, and varying chemical resistance depending on the exact structure and substituents. The bulky methyl groups often reduce chain mobility, contributing to rigidity and hardness while potentially affecting solubility and processability.

Applications are broad and include transparent architectural glazing, automotive interiors, lenses and displays, coatings, and specialty adhesives. The history of PMMA, the archetypal polymetyyli polymer, dates to the early 20th century, with commercial development leading to the widely known Plexiglas in the 1930s.

See also: polymethyl methacrylate, poly(methyl acrylate), poly(alpha-methyl styrene).