2-Hydroxyethyl methacrylate (HEMA) is a hydrophilic, hydroxy-functional methacrylate monomer used in polymer and copolymer synthesis. It combines one polymerizable methacrylate group with a pendant hydroxyl group, allowing HEMA to introduce hydrophilic character and reactive hydroxyl functionality into acrylic and methacrylic polymers.
Synonyms: HEMA; 2-HEMA; Glycol methacrylate; Methacrylic acid 2-hydroxyethyl ester.
Low Acid Grade HEMA, Cat. 03699, is specified at ≥98% purity with ≤0.10% acid content and ≤0.2% ethylene glycol dimethacrylate (EGDMA). Controlling these impurities is relevant to polymer synthesis because residual methacrylic acid can alter polymer acid content, while EGDMA can introduce unintended crosslinking and gel formation.
HEMA is water soluble, while poly(2-hydroxyethyl methacrylate) (pHEMA) is water-insoluble but can absorb water and swell. HEMA may be used as a homopolymer precursor or comonomer in formulations where hydrophilicity, hydroxyl functionality, or post-polymerization modification are important.
Key Properties
- Hydrophilic, hydroxy-functional methacrylate monomer
- Chemical purity: ≥ 98%
- Acid content: ≤ 0.10%
- EGDMA crosslinker content: ≤ 0.2%
- CAS Number: 868-77-9
- Molecular formula: C6H10O3
- Molecular weight: 130.1 g/mol
- Linear formula: H2C=C(CH3)CO2CH2CH2OH
- MEHQ inhibitor: 180–220 ppm
- Refractive index: n20/D 1.453
- Appearance: colorless liquid
- Catalog number: 03699
- Package sizes: 100 g, 500 g, and 1 kg
Applications
Polymer & Copolymer Synthesis
HEMA is used as a hydrophilic building block in free-radical polymerization and copolymerization. Incorporating HEMA introduces pendant hydroxyl groups that can influence polymer-water interactions and provide reactive sites for subsequent chemical modification.
Coatings, Resins & Adhesive Formulations
HEMA is used as a comonomer in acrylic coatings, resins, adhesives, printing inks, and related polymer formulations. Its hydroxyl functionality provides sites for hydrogen bonding and for additional reactions in appropriately designed polymer systems.
pHEMA & Hydrogel Research
HEMA is the monomer used to prepare poly(2-hydroxyethyl methacrylate) (pHEMA). The HEMA monomer is water soluble, while pHEMA is water-insoluble but can become plasticized and swollen in water. Crosslinked HEMA-based networks are widely studied as hydrophilic polymer and hydrogel systems.
Photopolymerization Research
HEMA can undergo photoinitiated free-radical polymerization when used with an appropriate photoinitiator system. Polymerization rate and conversion depend on initiator chemistry, HEMA concentration, oxygen exposure, irradiation conditions, temperature, and formulation composition.
Compatibility & Bonding Considerations
- Contains one polymerizable methacrylate group and one pendant hydroxyl group
- HEMA is a monofunctional polymerizable monomer and should not be treated as a conventional free-radical crosslinker
- The hydroxyl group can provide hydrogen-bonding interactions and may be used for post-polymerization functionalization under appropriate reaction conditions
- Acid content is limited to ≤0.10% to reduce variability associated with residual methacrylic acid
- EGDMA content is limited to ≤0.2% to reduce unintended crosslinking and gel formation
- Contains 180–220 ppm MEHQ inhibitor, which should be considered when establishing polymerization conditions
Final polymer properties depend on HEMA content, comonomer identity, molecular weight, conversion, crosslinker concentration, solvent or water content, and polymer architecture. Hydrophilicity, swelling, mechanical behavior, and adhesion should therefore be evaluated in the final polymer or formulation.
Application Tips
- Account for the 180–220 ppm MEHQ inhibitor level when establishing initiation and polymerization conditions
- Control oxygen exposure, initiator concentration, temperature, and monomer composition when comparing radical-polymerization experiments
- Select Low Acid Grade when reduced methacrylic acid content is important to polymer composition or polymerization consistency
- For crosslinked HEMA networks or hydrogels, incorporate an appropriate multifunctional crosslinker rather than relying on HEMA alone to form a covalent network
- When using pendant hydroxyl groups for subsequent functionalization, select reaction conditions appropriate for the polymer architecture and intended chemistry
Handling & Storage
- Store at 4°C in a cool, well-ventilated location
- Keep the material cool during storage
- Handle with good laboratory ventilation or in a chemical fume hood
- Avoid contact with skin and eyes
- Wear protective gloves, safety glasses, and suitable protective clothing during handling
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FAQ
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1. What is 2-hydroxyethyl methacrylate (HEMA) used for?
HEMA is a hydrophilic methacrylate monomer used in polymer and copolymer synthesis. Common research and formulation contexts include acrylic resins, coatings, adhesives, pHEMA synthesis, hydrophilic polymers, and crosslinked hydrogel systems.
2. What makes Cat. 03699 a Low Acid Grade HEMA?
Cat. 03699 is specified at ≥98% purity with acid content limited to ≤0.10%. EGDMA crosslinker content is also limited to ≤0.2%. Controlling these impurities can reduce variability in polymer composition, unintended crosslinking, and gel formation.
3. Is HEMA itself a crosslinker?
No. HEMA contains one polymerizable methacrylate group, so it is a monofunctional free-radical monomer rather than a conventional multifunctional crosslinker. Crosslinked HEMA-based networks typically require a separate multifunctional monomer such as a dimethacrylate.
4. Is HEMA the same as poly(2-hydroxyethyl methacrylate) (pHEMA)?
No. HEMA is the monomer. Poly(2-hydroxyethyl methacrylate) (pHEMA) is the polymer produced from HEMA. HEMA is water soluble, while pHEMA is water-insoluble but can absorb water and swell.
5. How does Low Acid Grade differ from Ophthalmic Grade HEMA?
Low Acid Grade HEMA, Cat. 03699, is specified at ≥98% purity, ≤0.10% acid, and ≤0.2% EGDMA. Ophthalmic Grade HEMA, Cat. 04675, has tighter purity and impurity specifications, including ≥99.5% purity and a lower MEHQ inhibitor level. Select the grade according to the requirements of the intended research or formulation.
Safety & Documentation
2-Hydroxyethyl methacrylate causes skin and serious eye irritation and may cause an allergic skin reaction. Use appropriate laboratory ventilation and personal protective equipment. Refer to the product Safety Data Sheet (SDS) for complete handling, storage, first-aid, and disposal guidance.
