Polyethylene oxide as excipient

What is Polyethylene oxide?

Polyethylene oxide (PEO), also known as polyethylene glycol (PEG), is a versatile polymer that finds widespread applications in various industries, with a particular focus on pharmaceuticals. Its unique properties, such as water solubility, biocompatibility, and non-toxicity, make it an attractive choice for numerous applications.

PEO and PEG are both polymeric compounds, but they have some differences in terms of their molecular weight, applications, and characteristics, especially in the context of pharmaceutical use. Polyethylene Oxide is generally used to refer to high molecular weight polymers. It often has a molecular weight in the range of 100,000 to several million Daltons. PEGs can have a wide range of molecular weights, typically from around 200 to 20,000 Daltons.

Composition and properties of Polyethylene oxide

PEO belongs to the class of polyether polymers and is derived from ethylene oxide. The general formula H(OCH2CH2)nOH, where n represents the average number of ethylene glycol units. Polyethylene oxide is a linear, long-chain polymer composed of repeating ethylene oxide units. The molecular weight of PEO can vary, influencing its physical and chemical properties.


  • Solubility: PEO is highly soluble in water, contributing to its utility in pharmaceutical formulations.
  • Viscosity: The viscosity of PEO solutions is dependent on the molecular weight, with higher molecular weights resulting in higher viscosity.
  • Biocompatibility: PEO is biocompatible and is widely used in medical and pharmaceutical applications without causing adverse effects.
  • Thermoplasticity: PEO exhibits thermoplastic behavior, allowing it to be processed through various manufacturing techniques.

Excipient Characterization Services

Be in control of your product!

offers fast and flexible hands-on polyethylene oxide quantification and characterization services to reveal and compare hidden polyethylene oxide properties like :

the presence of potential reactive impurities or functional groups, degradation products and related substances, just like molecular weight distributions, reducing power and many other featured characteristics.

In addition, we can help users of excipients to pick the most appropriate polyethylene oxide manufacturer, select the most suitable PEO grade for their finished dosage form, or define customized polyethylene oxide specifications to control product performance, quality and safety.
Contact us

Polyethylene oxide manufacturing

The production of PEO involves the polymerization of ethylene oxide under controlled conditions. This process can be carried out using various catalysts, such as alkaline substances. The molecular weight of the polymer can be adjusted during production, allowing for the customization of PEO for specific applications.

Synthesis Route

The synthesis of PEO typically involves the ring-opening polymerization of ethylene oxide. Catalysts, such as alkali metal hydroxides or alkoxides, facilitate the polymerization reaction. The process is carefully controlled to achieve the desired molecular weight and polymer characteristics.

The synthesis of polyethylene oxide commonly involves the following steps:

  1. Initiation: Ethylene oxide is initiated by a catalyst, typically an alkaline substance like potassium hydroxide or an acidic compound.
  2. Propagation: Ethylene oxide molecules add sequentially to the growing polymer chain.
  3. Termination: The reaction is terminated to obtain the desired molecular weight of polyethylene glycol.

Figure 1 Structural formula of polyethylene oxide

Stability and Degradation of Polyethylene Oxide

PEO is generally stable under normal storage conditions. However, factors such as exposure to heat, pH, light, and certain chemicals or specific ions can affect its stability. The degradation of PEO can occur through hydrolysis of the polymer backbone. Like PEG polyethylene oxide is susceptible to oxidative degradation, which may occur over time. Proper storage and handling are crucial to maintaining the integrity of PEO-based products. Understanding the degradation kinetics is essential for ensuring the stability of pharmaceutical formulations.

Advantage and disadvantages of Polyethylene Oxide


  • Biocompatibility:
    PEO is well-tolerated by the human body, making it suitable for medical and pharmaceutical applications.
  • Water Solubility: Its excellent water solubility enhances its utility in drug formulations.
  • Controlled Drug Release: PEO’s ability to modulate drug release kinetics is valuable for developing sustained-release formulations.


  • Oxidative Degradation:
    PEO may undergo oxidative degradation over time, impacting its stability.
  • Sensitivity to Environmental Factors: PEO can be sensitive to environmental conditions such as heat and light, requiring careful handling and storage.
  • Limited Mechanical Strength: In certain applications, PEO may not possess the mechanical strength required, limiting its use in certain structural applications.

Be in control of your product!

Feel free to get in touch with our experts to quantify and characterize your polyethylene oxide and see how we can help you in making your products safe, robust and stable.

PEO Characterization Services

Excipia is an independent contract service platform that focuses on the quantification and physicochemical characterization of pharmaceutical excipients and food ingredients like PEO; as a pure substance, as a raw material or when processed into end products.

More than 25 years in the development of pharmaceutical formulations have taught us that the limited information available on an excipient Certificate of Analysis (CoA) often falls short of explaining observed product or excipient characteristics and that more in-depth knowledge of the actual chemical excipient composition is essential to meet and understand specific formulation challenges.

Over the past 15 years, Excipia analytical scientists have spent tens of thousands of hours establishing unique, specific analytical and physicochemical methods with ingenious sample preparation techniques to characterize polysaccharides and other pharmaceutical excipients.

In these years we have gained a lot of knowledge about many excipients, their properties and exact composition, the difference between batches, qualities, grades, and manufacturers, how to quantify them in medicines and how they can best be used in a formulation.

Excipia offers fast and flexible hands-on cellulose characterization services to reveal and compare hidden properties like:

    • the presence of potential reactive impurities or functional groups,
    • reducing power of excipients,
    • degradation products and related substances,
    • relative molecular weight distributions,
    • and many other excipient characteristics.

In addition, Excipia can help users of excipients to pick the most appropriate manufacturer, select the most suitable grade for their finished dosage form, or define customized cellulose specifications to control product performance, quality and safety.

Welcome to Excipia, a service platform dedicated to the composition, quality and quantity of excipients in medicinal products.

Discover our unique services such as quantitative excipient analysis, identification, selection or specific formulation development support. Don’t forget to check out our case studies.

Try us. Feel free to contact us using the “Contact”  button or by sending a message to Excipia@avivia.nl.

Menno Wiltink
Founder of Excipia.


Excipia, a division of Avivia BV

 Excipia as dedicated excipient knowledge platform is a division of Avivia BV, a Dutch independent specialized pharmaceutical development company that operates a hybrid business model combining CRO service activities with internal product development programs. The other complementary platforms of Avivia are Pharmaceutical R&D, Analytical R&D, and Biorelevant Dissolution Testing. For more information about Avivia and its pharmaceutical development CRO services, please visit the Avivia website.