N-Isopropylacrylamide (NIPAM) is an acrylamide monomer used to synthesize poly(N-isopropylacrylamide) (PNIPAM) and related thermoresponsive copolymers. PNIPAM exhibits lower critical solution temperature (LCST) behavior in water, making NIPAM an important building-block monomer for temperature-responsive polymer research.
In aqueous systems, PNIPAM typically undergoes a reversible transition near 32°C, although the observed transition temperature depends on polymer composition, molecular weight, concentration, end groups, ionic environment, and other solution conditions. NIPAM can be used in linear polymers, crosslinked hydrogels, microgels, copolymers, and surface-grafted polymer architectures.
Synonyms: NIPAM; NIPAAm; N-isopropyl acrylamide; N-(1-methylethyl)acrylamide.
Key Properties
- Hydrophilic, monofunctional acrylamide monomer
- Chemical purity: ≥98.0%
- CAS number: 2210-25-5
- Molecular formula: C6H11NO
- Linear formula: H2C=CHCONHCH(CH3)2
- Molecular weight: 113.2 g/mol
- Melting point: 64–67°C
- Poly(N-isopropylacrylamide) homopolymer Tg: approximately 85°C
- Storage temperature: 4°C
- Polysciences catalog number: 02455
Applications
Thermoresponsive Polymer Synthesis
NIPAM is the monomer used to prepare PNIPAM, one of the most extensively studied thermoresponsive polymers. In water, PNIPAM undergoes a temperature-dependent change in hydration and chain conformation associated with its lower critical solution temperature.
PNIPAM Hydrogel Research
NIPAM can be polymerized in the presence of an appropriate crosslinker to prepare temperature-responsive hydrogel networks. Network composition, crosslink density, water content, and polymerization conditions influence swelling, deswelling, mechanical behavior, and the observed thermal transition.
Thermoresponsive Microgels
NIPAM is widely used in the synthesis of PNIPAM-based microgels. Crosslinked PNIPAM particles undergo temperature-dependent changes in hydration and particle volume, with the volume-phase transition determined by network composition and solution conditions.
Copolymerization & LCST Tuning
NIPAM can be copolymerized with compatible vinyl monomers to modify the composition and thermal response of PNIPAM-based materials. Hydrophilic and hydrophobic comonomers, ionic functionality, sequence distribution, and comonomer content can shift or broaden the observed phase transition.
Thermoresponsive Surface & Brush Research
NIPAM is also used to prepare PNIPAM-containing grafted polymers and polymer brushes for studies of temperature-dependent surface hydration, conformation, and interfacial behavior.
Polymerization & LCST Considerations
- NIPAM is the monomer; LCST behavior is a property of PNIPAM and NIPAM-containing polymers in appropriate solution environments
- PNIPAM commonly exhibits an aqueous transition near 32°C, but the exact value is formulation- and method-dependent
- Polymer molecular weight, concentration, architecture, and end groups can influence phase-transition behavior
- Comonomer identity and composition can shift the LCST of NIPAM-containing copolymers
- Salts, cosolvents, surfactants, and other dissolved species can alter PNIPAM hydration and transition temperature
- Crosslinked PNIPAM networks are generally characterized by a volume-phase transition rather than treating the behavior as identical to that of a linear polymer solution
- Select initiator, crosslinker, polymerization temperature, and oxygen-control conditions according to the intended polymer architecture
Thermoresponsive behavior should be characterized for the actual polymer composition and experimental environment rather than inferred solely from the NIPAM content. PNIPAM phase behavior reflects interactions among polymer structure, water, temperature, additives, and network architecture.
Application Tips
- Use clean, dry equipment appropriate for acrylamide monomer polymerization
- Define the desired polymer architecture before selecting initiator, crosslinker, and reaction conditions
- Control oxygen when using free-radical polymerization methods that are sensitive to radical inhibition
- Keep monomer concentration, comonomer composition, and crosslinker level consistent when comparing thermoresponsive behavior among formulations
- Characterize transition temperature under the same solvent, ionic-strength, concentration, and heating conditions used in the intended experiment
- Distinguish the LCST or cloud-point behavior of linear PNIPAM solutions from the volume-phase transition of crosslinked PNIPAM gels or microgels
- Use small-scale polymerization studies when establishing new copolymer compositions or crosslinking conditions
Handling & Storage
- Store at 4°C in a cool, well-ventilated location
- Keep the container tightly closed when not in use
- Handle with good laboratory ventilation or in a chemical fume hood
- Wear protective gloves, safety glasses, and suitable protective clothing
- Avoid contact with the skin and eyes
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FAQ
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1. What is N-isopropylacrylamide used for?
N-Isopropylacrylamide is used to synthesize PNIPAM and related copolymers for research involving temperature-responsive polymer solutions, hydrogels, microgels, and surface-grafted polymers.
2. Are NIPAM and NIPAAm the same compound?
Yes. NIPAM and NIPAAm are abbreviations used for N-isopropylacrylamide, CAS number 2210-25-5.
3. Does NIPAM itself have an LCST?
The commonly discussed LCST behavior refers to poly(N-isopropylacrylamide), or PNIPAM, in aqueous solution rather than the NIPAM monomer itself. NIPAM is the polymerizable building block used to prepare the thermoresponsive polymer.
4. What is the LCST of PNIPAM?
Linear PNIPAM commonly exhibits an aqueous phase transition near 32°C. The measured value can vary with molecular weight, polymer concentration, end groups, comonomer composition, salts, cosolvents, and the analytical method used.
5. What happens to PNIPAM above its LCST?
As temperature rises through the transition region, PNIPAM becomes less hydrated and undergoes a coil-to-globule transition followed by association or phase separation in solution. Crosslinked PNIPAM hydrogels and microgels instead exhibit temperature-dependent changes in network hydration and volume.
6. What are the purity and CAS number of NIPAM?
N-Isopropylacrylamide has a chemical purity of ≥98.0% and CAS number 2210-25-5. Its molecular weight is 113.2 g/mol.
7. What package sizes are available?
N-Isopropylacrylamide is available in 25 g and 100 g sizes. For larger quantities, use the bulk-quote option.
Safety & Documentation
N-Isopropylacrylamide is harmful if swallowed and can cause serious eye irritation. Use appropriate laboratory ventilation and personal protective equipment. Refer to the Safety Data Sheet, product specification, and lot-specific documentation for complete handling, storage, disposal, and quality information.
