Poly(ethylene glycol)
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Product Description
Poly(ethylene glycol) (PEG) is a versatile polyether compound composed of repeating ethylene glycol units, with the general formula H–(O–CH₂–CH₂)ₙ–OH. It is a high-molecular-weight polymer formed by the stepwise addition polymerization of ethylene oxide and water or ethylene glycol. PEG's properties vary significantly with molecular weight: lower molecular weights (200–600) result in colorless, odorless, viscous liquids, while higher molecular weights (>600) produce semi-solid or waxy solids. PEG is highly soluble in water and ethanol but insoluble in ether. It is non-toxic, biocompatible, and chemically stable, with a melting point ranging from -15°C (low molecular weight) to 64-66°C (high molecular weight) and a boiling point above 250°C. PEG is widely used in pharmaceuticals as a laxative, drug carrier, and PEGylation agent to enhance drug stability and half-life. In cosmetics, it serves as a moisturizer and emulsifier. Industrially, PEG is used as a plasticizer, lubricant, and anti-foaming agent. It is also employed in biotechnology for protein crystallization and nucleic acid precipitation. PEGs of different molecular weights, such as PEG-400 and PEG-6000, have distinct applications and should be selected based on specific needs.
Recent Developments (as of 2025)
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Advanced Drug Delivery Systems: PEG derivatives are being explored for targeted nanoparticles in cancer therapy.
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Sustainable Alternatives: Research focuses on developing PEG alternatives due to environmental persistence concerns.
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mRNA Vaccine Alternatives: Studies are exploring non-PEGylated alternatives to address rare allergic reactions observed in some mRNA vaccines.
Synthesis Methods
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Anionic Ring-Opening Polymerization: Ethylene oxide is polymerized using nucleophiles like water or alcohols. This method allows control over molecular weight and polydispersity.
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RAFT Polymerization: Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization is used to create PEG alternatives with specific functionalities and controlled molecular weights.
Uses
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Pharmaceuticals & Medicine:
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Drug Delivery: PEGylation (attaching PEG chains to proteins or drugs) increases drug stability, half-life, and reduces immunogenicity.
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Solvent and Excipient: Used in ointments, laxatives, and as pill binders.
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Hydrogels: Used in tissue engineering and wound dressings.
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Protein Conjugation: Enhances stability and circulation time of biologics.
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mRNA Vaccines: Used in lipid nanoparticles to stabilize formulations, as seen in COVID-19 vaccines (e.g., Pfizer-BioNTech Comirnaty).
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Cosmetics & Personal Care:
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Moisturizers and Emulsifiers: Found in creams, lotions, toothpaste, and shampoos.
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Humectants and Thickeners: Enhances product viscosity and water retention.
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Industrial Uses:
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Lubricants: Used in various industrial processes.
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Plasticizers: Improves plasticity in adhesives, resins, and ceramics.
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Surfactants and Dispersants: Used in paints, coatings, and inks.
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Mold Release Agent: Facilitates the removal of molded products.
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Biotechnology:
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Protein Purification: Used in protein precipitation and purification.
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Surface Coating: Reduces protein adsorption and cell adhesion.
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Stabilization: Preserves biologics during storage.
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Protein Crystallization: Facilitates the formation of protein crystals.
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Properties
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Molecular Weight: Ranges from a few hundred g/mol to over 20,000 g/mol. The physical state varies from viscous liquids (MW < 600 g/mol) to waxy solids (MW > 1000 g/mol).
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Solubility: Highly soluble in water and many organic solvents such as ethanol. Insoluble in non-polar solvents like oils.
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Biocompatibility: Non-toxic, non-immunogenic, and FDA-approved for various uses. Generally recognized as safe (GRAS).
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Hydrophilicity: Strong affinity for water, making it hygroscopic.
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Chemical Stability: Chemically inert but can be functionalized (e.g., with methoxy groups as mPEG) for specific applications.
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Viscosity: Adjustable based on molecular weight, with liquid PEGs being viscous and high molecular weight PEGs being solid at room temperature.
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Melting Point: Varies with molecular weight; low molecular weight PEGs are liquids, while high molecular weight PEGs are semi-solid or waxy solids.
Safety and Environmental Notes
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Safety: Generally regarded as safe (GRAS) for oral, topical, and intravenous use. High doses may cause mild gastrointestinal irritation (e.g., diarrhea in laxatives).
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Environmental: PEG is biodegradable under certain conditions, but high molecular weight PEGs degrade slowly. Environmental persistence concerns have led to research into sustainable alternatives.