What is Polyethylene Glycol Used For?

Polyethylene glycol (PEG) is an important class of polymer compounds, which is widely used in medicine, cosmetics, food, industry and other fields. The basic chemical structure of PEG is repeated -(CH2CH2O)- units, and the molecular weight ranges from hundreds to tens of thousands. PEGs of different molecular weights have significant differences in physical and chemical properties, which makes them have diverse applications in various fields.

What is a Polyethylene Glycol?

From the chemical properties, PEG is a water-soluble polymer, which is generated by addition polymerization of ethylene glycol. The structural characteristics of PEG determine that it has extremely good hydrophilicity and chemical stability. It is easily soluble in water and has good compatibility with many organic solvents. In addition, PEG molecules contain a large number of ether bonds, which make it highly flexible and film-forming. Since it usually appears as a liquid or soft solid state at room temperature (depending on the molecular weight), PEG can be adjusted into different forms as needed. The chemical reactivity of PEG is mainly concentrated in its terminal hydroxyl group. The terminal hydroxyl group of PEG can undergo various esterification, etherification and acetalization reactions to generate functionalized PEG, which are widely used in the development of drug delivery systems. For example, attaching a drug molecule to one end of a PEG chain through a reaction can improve the solubility and stability of the drug and extend its half-life in the body. In addition, PEG can react with isocyanates to form polyurethanes and with anhydrides to form esters, showing a variety of reaction possibilities.

Structure of Polyethylene Glycol

The basic structure of PEG consists of repeating ethylene glycol units connected by ether bonds. Its molecular formula reflects its linear chain structure with a hydroxyl group (-OH) at each end. Molecular weight is a key parameter of PEG, and PEGs of different molecular weights exhibit different physical and chemical properties. The molecular weight of PEG can range from hundreds to millions, and is usually expressed in the form of PEG-400, PEG-6000, etc., where the number represents the average molecular weight.

According to the molecular weight, polyethylene glycol can be roughly divided into low molecular weight polyethylene glycol (PEG 200 - PEG 600), medium molecular weight polyethylene glycol (PEG 1000 - PEG 4000) and high molecular weight polyethylene glycol (PEG 6000 - PEG 20000). PEGs of different molecular weights differ in physical form. Low molecular weight PEG (such as PEG-400) is usually a colorless liquid, while high molecular weight PEG (such as PEG-6000) is a waxy solid. In addition to the above classification, polyethylene glycol can also be derivatized with other chemical substances to generate various PEG derivatives (such as PEGylated drugs, PEG-liposomes, etc.) according to different application requirements to enhance its excellent properties, such as prolonging the half-life in the blood, improving drug stability, reducing immunogenicity, etc.

Polyethylene Glycol Uses

As a high molecular compound, polyethylene glycol has a wide range of applications in daily life and medicine. Its excellent performance and multifunctional characteristics make it play an irreplaceable role in various occasions. It has been proven to play an important role in many fields, including biological sciences, medicine, drugs, food, surfactants and cosmetics.

Industrial Applications

In the industrial field, polyethylene glycol is mainly used as a lubricant, dispersant, antistatic agent, defoamer and surfactant. Its excellent lubrication performance can effectively reduce the friction coefficient, reduce equipment wear and energy consumption. At the same time, the dispersing effect of polyethylene glycol can make the material more evenly dispersed in the liquid, improving the stability and quality of the product. In addition, it can also be used as a surfactant to reduce the surface tension of the liquid and improve the wettability and permeability of the liquid on the solid surface. For example, high molecular weight PEG is often used to prepare hydraulic fluids, which have good lubrication properties and temperature stability; while low molecular weight PEG is suitable for preparing moisturizers in cosmetics because it can effectively penetrate the skin and retain moisture.

Biomedical Applications

In the field of medicine, polyethylene glycol is non-toxic, non-irritating, and not easy to adsorb proteins, so it is widely used in pharmaceutical preparations. PEG is commonly used in a variety of dosage forms such as oral tablets, topical ointments, and injections. Especially in sustained-release tablets, PEG can regulate the gradual release of drugs to ensure the continuity of drug efficacy. PEG's biocompatibility and low immunogenicity make it a preferred choice for drug carriers. In recent years, the technology of polyethylene glycol modification (pegylation) has been widely used to improve the water solubility and stability of drug molecules, prolong their half-life in the body, effectively reduce the frequency of administration, and reduce side effects.

Cosmetic Applications

In cosmetics, polyethylene glycol is an important thickener, emulsifier and moisturizer. Due to its good solubility in water and oil, PEG can effectively stabilize the structure of the emulsion and improve the texture and feel of the product. For example, many creams, lotions, shampoos, shower gels and other products contain PEG ingredients, which can provide a comfortable moisturizing effect during use and enhance the softness and elasticity of the skin. In addition, PEG can also be used as a thickener and surfactant to make shampoo, soap, cosmetics and skin care products.

Food Additives

Polyethylene glycol is one of the common ingredients of food additives and is widely used to make lubricants, gels and thickeners. Due to its non-toxicity and good stability, PEG is considered a safe food processing aid. It is also often used to prevent food from spoiling during storage and transportation. For example, in fruit preservation, PEG can form a protective film to slow down the evaporation and oxidation of fruit water, thereby extending the shelf life.

Surfactants

Polyethylene glycol is an excellent surfactant that can be widely used in the manufacture of detergents and cleaning agents. Because PEG has excellent lubricity and permeability, many people use it as an important ingredient in detergents. Using PEG as a double-sided tape and adhesive is a common method because it can act as an adhesive when needed.