Polyethylene glycol dimethyl ether
[CAS# 24991-55-7]

Identification

• Classification: Catalysts and additives >> Polyethylene glycol derivative
• Name: Polyethylene glycol dimethyl ether
• Molecular Formula: CH₃O^.(C₂H₄O)_n^.CH₃
• CAS Registry Number: 24991-55-7
• EC Number: 607-475-9
• SMILES: O(CCOC)C

Properties

• Density: 1.07 g/mL (20 ºC) (Expl.)
• Melting point: 13 ºC (Expl.)
• Boiling point: >250 ºC (1013 hPa) (Expl.)
• Flash point: 254 ºC (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Hazard Statements: H302-H315
• Precautionary Statements: P264-P270-P280-P301+P312+P330-P332+P313-P501

Discovory and Applicatios

Polyethylene glycol dimethyl ether, often abbreviated as PEGDME, is a linear polyether compound composed of repeating ethylene oxide units terminated at both ends by methyl groups. Its general chemical formula can be expressed as CH3O–(CH2CH2O)_n–CH3, where n represents the number of ethylene oxide units. PEGDME is a colorless, hygroscopic liquid with low viscosity and high solubility in polar organic solvents such as methanol, ethanol, and dimethylformamide. The physical properties, including molecular weight and viscosity, vary depending on the number of repeating units, which can be tailored for specific applications.

The discovery and use of polyethylene glycol derivatives, including dimethyl ethers, are rooted in research on polyethers for industrial and chemical applications. The dimethyl ether functionality provides chemical inertness and prevents the terminal hydroxyl groups found in standard polyethylene glycols from participating in unwanted reactions. This makes PEGDME a versatile solvent, reaction medium, and component in formulations where a non-reactive, hydrophilic polymeric additive is desired.

Synthesis of polyethylene glycol dimethyl ether involves the reaction of polyethylene glycol with methylating agents, such as dimethyl sulfate or methyl iodide, under basic conditions. The hydroxyl end groups of the polyethylene glycol are converted to methyl ethers, producing a terminally protected polymer chain. Reaction parameters, including temperature, solvent, and base concentration, are carefully controlled to achieve high conversion and avoid degradation of the polyether chain. The resulting product can be purified by vacuum distillation or chromatography to remove unreacted reagents and by-products.

Chemically, PEGDME exhibits the properties of polyethers and alkyl ethers. The polymer backbone is resistant to hydrolysis under neutral conditions, and the methyl-terminated ends prevent hydrogen bonding at the termini, reducing intermolecular interactions. This enhances solubility in organic solvents and decreases viscosity compared with hydroxyl-terminated polyethylene glycols of similar molecular weight. PEGDME is chemically stable toward acids, bases, and many oxidizing and reducing agents, which allows it to function as an inert medium for reactions and as a stabilizer for sensitive compounds.

In industrial and laboratory applications, PEGDME is commonly used as a solvent, dispersing agent, and carrier. Its hydrophilic and non-reactive properties allow it to solubilize polar and moderately non-polar compounds, facilitating reactions, extractions, and coatings. PEGDME is also employed as a component in polymer blends, surface treatments, and as a plasticizer to modify the flexibility and processing properties of other polymers. The chain length and molecular weight can be adjusted to achieve desired viscosity, solubility, and surface activity for specific uses.

In chemical synthesis, PEGDME serves as a reaction medium for catalysis and organic transformations. Its ability to dissolve both organic and inorganic reagents, combined with its chemical inertness, makes it useful in nucleophilic substitutions, polymerizations, and metal-catalyzed reactions. Additionally, PEGDME is utilized as a phase-transfer agent, promoting interactions between hydrophilic and hydrophobic reagents. These properties make it particularly valuable in green chemistry applications, where traditional volatile organic solvents may pose environmental or safety hazards.

From a safety perspective, PEGDME is generally considered low in toxicity, but exposure can cause mild irritation to the skin or eyes. Handling guidelines recommend the use of gloves and eye protection, especially in concentrated forms. It is hygroscopic, and proper storage in tightly sealed containers is required to prevent water absorption, which could alter its physical properties and performance in chemical applications.

Overall, polyethylene glycol dimethyl ether is a chemically stable, hydrophilic polyether with versatile solvent and additive properties. Its inert methyl end groups, tunable chain length, and compatibility with polar solvents make it valuable in laboratory, industrial, and materials applications. The compound’s combination of solubility, chemical resistance, and low viscosity allows it to support chemical reactions, polymer processing, and formulation design, demonstrating its continued importance in both research and commercial settings.