Hydroxyethyl Methacrylate (HEMA)

Basic Properties

Structural and Chemical Traits

Hydroxyethyl Methacrylate, commonly abbreviated as HEMA, has the chemical formula C₆H₁₀O₃ and a molecular weight of 130.14. Its preferred IUPAC name is 2 - hydroxyethyl 2 - methylprop - 2 - enoate, and it also has other aliases such as ethylene glycol methacrylate and glycol monomethacrylate. The molecule possesses two functional groups: a hydroxyl group (-OH) and an acrylate double bond (C=C), endowing it with both hydrophilicity and high chemical reactivity. It is typically synthesized through the reaction between ethylene oxide (EO) and methacrylic acid (MMA).

Physical Characteristics

Under normal temperature and pressure, HEMA presents itself as a colorless, transparent, and free - flowing liquid. It has a melting point of -12°C, a boiling point of approximately 189°C, and a flash point of 97.2°C. The density of HEMA is about 1.074 g/mL. It shows excellent solubility, being miscible with water and soluble in most polar solvents like ethanol and acetone. Additionally, it can be mutually soluble with most acrylate monomers, which lays a good foundation for its application in polymer synthesis.

Major Application Fields

Coatings Industry

As the largest consumer of HEMA, the coatings industry has a massive demand for this monomer. For UV - curable coatings, the double bond in HEMA can undergo rapid photopolymerization reactions, enabling the coatings to cure quickly under ultraviolet radiation. Such coatings are widely used in the painting of furniture, building materials, and electronic product casings. They not only enhance curing efficiency but also reduce volatile organic compound (VOC) emissions. In water - based industrial coatings, HEMA is used to produce acrylic resins with active hydroxyl groups. These resins improve the adhesion, chemical resistance, and flexibility of the coatings, making them suitable for automotive topcoats, primers, and protective coatings for marine engineering equipment. Moreover, in architectural coatings, HEMA can optimize film - forming properties and stability, preventing the coating from cracking or peeling under varying temperature and humidity conditions.

Biomedical Field

HEMA and its polymers are renowned for their excellent biocompatibility, making them indispensable in the biomedical sector. Back in 1960, Czech scientists synthesized polyhydroxyethyl methacrylate hydrogel via free radical polymerization using HEMA, which was successfully applied to soft contact lenses. This innovation revolutionized the contact lens market. Beyond contact lenses, HEMA is also utilized in dental fillings, burn dressings, and organ transplantation - related materials. It can serve as a carrier for drug delivery systems to achieve controlled drug release. Additionally, it plays a crucial role in cell culture and the immobilization of biomolecules and enzymes.

Cosmetics and Daily Chemicals

In the cosmetics field, HEMA functions as a film - forming agent and viscosity regulator. It is widely incorporated into products such as hairsprays, mascaras, and nail polishes. It aids in forming a thin, uniform protective film on the surface of hair or nails, enhancing the setting effect and long - lasting performance of the products. When added to skin care products, it also contributes to improving the moisture - retaining ability of the products and their compatibility with the skin.

Other Industrial Applications

In the plastic industry, HEMA is used to manufacture acrylic resins with active hydroxyl groups, which are further employed to modify the properties of plastics and fibers, such as enhancing their hydrophilicity and antistatic properties. Besides, it can be used in the preparation of water treatment agents like flocculants and scale inhibitors. In the textile printing and dyeing industry, it acts as an anti - wrinkle finishing agent, helping fabrics gain better durability and wrinkle resistance.