Polyethylene glycol, also known as Polyoxyethylene (PEG), is a polymer made from the polymerization of ethylene oxide. It is commonly used in various industries, including cosmetics, pharmaceuticals, and industrial applications, due to its versatility as a surfactant, emulsifier, solubilizer, and carrier for active ingredients.
Chemical Composition and Structure
Polyoxyethylene is composed of repeating units of ethylene oxide (C₂H₄O) that form long chains. These chains are connected by oxygen atoms and hydroxyl groups (-OH), which give the polymer its hydrophilic (water-attracting) properties.
The general chemical structure of polyoxyethylene can be represented as:
The length of the polymer chain (the value of n) can vary, which influences the properties of the polyoxyethylene, such as its solubility and viscosity. Polyoxyethylene with shorter chains is typically liquid, while longer chains form solid or wax-like substances.
Physical Properties
Appearance: Polyoxyethylene can range from a liquid to a solid, depending on the molecular weight (or chain length) of the polymer. It is typically colorless and odorless.
Solubility: Polyoxyethylene is highly soluble in water and many organic solvents. It is often used to enhance the solubility of ingredients that are poorly soluble in water.
Viscosity: The viscosity of polyoxyethylene increases with the length of the polymer chain, which means that lower molecular weight versions are more fluid, while higher molecular weight forms are thicker.
Stability: Polyoxyethylene is stable under normal conditions, though it can degrade when exposed to high heat or extreme pH conditions over prolonged periods.
Benefits and Functions
Surfactant: Polyoxyethylene is used as a surfactant in various formulations, reducing surface tension and improving the spreadability of products on skin or other surfaces.
Emulsifier: It helps to form stable emulsions by combining oil and water, making it useful in products like creams, lotions, and shampoos.
Solubilizer: It can solubilize hydrophobic ingredients (such as oils or fragrances) in aqueous solutions, making it easier to incorporate them into water-based formulations.
Carrier for active ingredients: Polyoxyethylene is often used as a carrier to help deliver active ingredients in pharmaceutical and cosmetic products to enhance their absorption and effectiveness.
Applications
Cosmetics and Personal Care
Moisturizers: Polyoxyethylene is commonly used in lotions, creams, and serums to improve texture, stability, and hydration.
Shampoos and conditioners: It is used as an emulsifier and conditioning agent to ensure proper mixing of ingredients and to improve hair softness.
Face cleansers and toners: It acts as a solubilizer for oils and helps remove dirt and impurities.
Deodorants: Polyoxyethylene is used in deodorant formulations to help dissolve active ingredients and ensure even application.
CAS: 25322-68-3
Pharmaceuticals
Topical creams and ointments: Polyoxyethylene is included in formulations to enhance the delivery of active ingredients and improve the consistency of the product.
Oral medications: It is used in tablet formulations as a binder and solubilizer to ensure proper absorption of active compounds.
Industrial Applications
Environmental and Safety Considerations
Biodegradability: Polyoxyethylene is biodegradable, making it environmentally friendly when disposed of properly. However, it may accumulate in aquatic environments if not managed properly.
Safety: Generally considered safe for use in cosmetics and pharmaceuticals, polyoxyethylene is non-toxic and non-irritating in low concentrations. However, it is important to use it within recommended guidelines to avoid potential adverse effects.
Sustainability: Polyoxyethylene is derived from ethylene oxide, which is a petrochemical product. Although it is widely used, its sustainability depends on the source of ethylene oxide and the production process.
PEG (Polyethylene glycol) polymerize condensed ethylene oxide and water and are referred to as polyethylene glycols, but they are actually complex chemical components, polymers bonded together. For example, plastic is polyethylene and has a hard consistency, while polyethylene aggregated with glycol forms a liquid. PEGylation is produced not only as heterification but also as transesterification, which is the transformation of an alcohol by an ester.
The number that appears after the abbreviation PEG represents the molecular weight, and the higher this number is, the less it penetrates the skin.
The term 'eth' refers to the ethoxylation reaction with ethylene oxide after which residues of ethylene oxide and 1,4-dioxane, chemical compounds considered carcinogenic, may remain. The degree of safety therefore depends on the degree of purity of the compound obtained. No manufacturer appears to provide this information on the label, at least as of the date of this review.
Kim MC, Park SY, Kwon SY, Kim YK, Kim YI, Seo YS, Cho SM, Shin EC, Mok JH, Lee YB. Application of Static Headspace GC-MS Method for Selective 1,4-Dioxane Detection in Food Additives. Foods. 2023 Sep 2;12(17):3299. doi: 10.3390/foods12173299.
Abstract. "Efficient detection methods must be developed for 1,4-dioxane due to its suspected status as a human carcinogen, which is highly mobile in food and environmental resources. In this regard, this experiment has been conducted to develop reliable and selective detection and measurement methods by using static headspace (SH) isolation, followed by gas chromatography-mass spectrometry (GC-MS). A new method was developed for determining the spiked 1,4-dioxane contents in a polyethylene glycol 600 (PEG 600). The optimal condition for SH-GC-MS was discussed. The representative ions of 1,4-dioxane and 1,4-dioxane-d8 in the SIM mode of MS are 88 and 96, respectively, and the peaks of the SIM mode were separated and confirmed. The linear range for the method covers 0.25 to 100 mg/L with a coefficient of determination (R2) ≥ 0.999. The method applicability was demonstrated by spike recovery across a variety of food additives (i.e., chlorine bitartrate, choline chloride, polysorbate 20 and 60, and PEG 1000). All spike recovery from the tested samples was in the range of 89.50-102.68% with a precision of 0.44-11.22%. These findings suggest a new analytical method for food safety inspection, and could be applicable for ensuring the safety of foods and environmental and public health on a broad scale."
Polyethylene glycol 
