The difference between small molecular weights of polyethylene glycol

Polyethylene glycol (PEG) is a series of polymer compounds formed by the polymerization of ethylene oxide monomers. Depending on the degree of polymerization, different molecular weights of PEG products are formed. Polyethylene glycol 200, 300, 400, and 600 are all liquid grade polyethylene glycol, and their main differences lie in the following aspects:

1. Molecular weight:

The average molecular weight of PEG200 is approximately 200 g/mol.

The average molecular weight of PEG300 is approximately 300 g/mol.

The average molecular weight of PEG400 is approximately 400 g/mol.

The average molecular weight of PEG600 is approximately 600 g/mol.

2. Physical properties:

Viscosity: As the molecular weight increases, the viscosity of polyethylene glycol also increases accordingly. Therefore, PEG200 has the lowest viscosity, while PEG600 has the highest viscosity.

Solubility: Although all of these polyethylene glycols are easily soluble in water, higher molecular weight polyethylene glycols may have slightly decreased solubility in certain solvents.

Volatility: Polyethylene glycol with lower molecular weight, such as PEG200, may have higher volatility, while polyethylene glycol with higher molecular weight, such as PEG600, has lower volatility.

3. Application areas:

Polyethylene glycol with different molecular weights has different application ranges. For example, PEG400 is commonly used in liquid formulations such as oral liquids, eye drops, etc. due to its good solvability and compatibility with other solvents.

PEG with lower molecular weight, such as PEG200 and PEG300, may be more commonly used as solvents or diluents, while PEG with higher molecular weight, such as PEG600, may be more suitable as thickeners or stabilizers.

4. Chemical reactivity:

PEG with lower molecular weight may be more prone to participate in chemical reactions due to their higher terminal hydroxyl activity. As the molecular weight increases, the proportion of terminal hydroxyl groups relatively decreases, and the chemical reactivity also decreases.

When selecting polyethylene glycol with specific molecular weight, consideration should be given to its performance requirements in specific applications, such as viscosity, solubility, stability, and contribution to the final product.