(Hydroxyethyl)methacrylate

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Hydroxyethyl methacrylate (HEMA) is a colorless, viscous liquid that easily forms polymers. It is a reactive monomer used to make polyhydroxyethyl methacrylate (pHEMA), a hydrophilic polymer that can absorb a lot of water.

Key points
- Uses: Mainly used to make hydrogels and soft contact lenses (pHEMA is highly water-absorbent). Also used in 3D printing resins, cosmetics (nail products and eyelash/hair extension glues), and certain crosslinked paints.
- Properties: Mixes well with water and ethanol; viscosity about 0.07 Pa·s at 20°C; during polymerization it shrinks by about 6%. Boiling point is around 213°C.
- How it’s made and history: First made in the 1920s. It’s famous for enabling hydrophilic, crosslinked networks used in soft contact lenses.
- How it can be used: Cures quickly with UV light when a photoinitiator is present; can act as a matrix with silica particles for specialized 3D printing; can form foams with blowing agents.
- Safety: It can irritate the skin and eyes and may cause allergic reactions; labeling and professional handling are common in cosmetics.
- Other notes: Used as an embedding medium in microscopy and can form acrylic resins when crosslinked with polyisocyanates.