Poly(N-isopropylacrylamide) (PNIPAM)
Poly(N-isopropylacrylamide) (PNIPAM) is a temperature-responsive polymer that undergoes a reversible
phase transition in water near its lower critical solution temperature (LCST). Below the LCST,
PNIPAM is generally water compatible; above the LCST, it becomes less water compatible and can
phase-separate from solution.
This thermoresponsive behavior is widely used in stimuli-responsive materials research, including
smart hydrogels and coatings where changes in temperature can be used to modulate swelling,
permeability, adhesion, or interaction with biomolecules and surfaces.
Key Properties
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Polymer type: Poly(N-isopropylacrylamide) (PNIPAM)
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Stimulus response: Temperature-responsive in aqueous environments
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Phase behavior: Reversible transition near the LCST (commonly reported around ~32 °C in water; can vary with formulation/conditions)
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Below LCST: Typically more hydrated / water compatible
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Above LCST: Typically less hydrated; can phase-separate/precipitate depending on conditions
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Typical use: Research and development applications
Applications
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Biomedical & Drug Delivery Research:
Studied in thermoresponsive hydrogels, drug carriers, and tissue engineering scaffold concepts where temperature can influence swelling and release behavior.
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Smart Coatings:
Incorporated into responsive coatings designed to alter surface wettability and adhesion as temperature changes.
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Bioseparations & Biointerfaces:
Used in affinity or surface-interaction studies (including cell culture and chromatography research) to enable temperature-controlled binding and release.
Synonyms / Acronyms
- PNIPAM
- Poly(N-isopropylacrylamide)
- Poly(NIPAm)
FAQs
Common questions about Poly(N-isopropylacrylamide) (PNIPAM).
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What does “LCST” mean for PNIPAM?
LCST stands for “lower critical solution temperature.” For PNIPAM in water, it refers to the
temperature region where the polymer’s solubility behavior changes and the system can transition
from a more hydrated, single-phase state to a less hydrated, phase-separated state.
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Why is PNIPAM called a temperature-responsive polymer?
PNIPAM’s polymer–water interactions change with temperature. This enables materials made with
PNIPAM (e.g., hydrogels or coatings) to reversibly change properties such as swelling, permeability,
or surface interaction as temperature shifts.
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Is the LCST always the same value?
Not necessarily. Reported LCST behavior depends on conditions such as polymer concentration,
molecular characteristics, additives (e.g., salts), and solvent composition. PNIPAM is commonly
reported near ~32 °C in water, but practical transition behavior can vary with formulation.
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What are common research uses for PNIPAM?
PNIPAM is widely studied in thermoresponsive hydrogels, smart coatings, and biointerface research
where temperature can be used as a trigger to influence swelling, adhesion, or binding/release behavior.
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Does PNIPAM “precipitate” above the LCST?
Above the LCST, PNIPAM becomes less hydrated and may phase-separate from aqueous solution. Whether
this appears as visible precipitation depends on the specific solution conditions and formulation.
