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Methoxy-polyethylene glycol-polycaprolactone, also known as MPEG-PCL, is a block copolymer composed of methoxy polyethylene glycol (MPEG) and polycaprolactone (PCL).
Catalog W888515

Property	Details
Chemical Name	Methoxy – polyethylene glycol – polycaprolactone
CAS Number	Similar to the previous PEG – related compound, the CAS number can vary based on the lengths of the polyethylene glycol (PEG) and polycaprolactone (PCL) segments. Different degrees of polymerization for both the PEG and PCL chains result in a range of specific compounds, each potentially having its own CAS number. Precise identification requires knowledge of the exact molecular weights of the PEG and PCL components.
Molecular Formula	The molecule has a methoxy group (-OCH₃) at one end, followed by a polyethylene glycol chain with the general formula (C₂H₄O)ₙ, which is then linked to a polycaprolactone chain. The polycaprolactone segment is composed of repeating units of -[O-(CH₂)₅-CO]- with a general formula of (C₆H₁₀O₂)ₘ. So the overall formula can be written as CH₃O(C₂H₄O)ₙ[O-(CH₂)₅-CO]ₘH, where ‘n’ represents the number of ethylene oxide units in the PEG chain and’m’ represents the number of caprolactone units in the PCL chain.
Molecular Weight	The molecular weight is determined by the values of ‘n’ and’m’. The methoxy group has a molecular weight of approximately 31 g/mol. Each ethylene oxide unit in the PEG chain contributes about 44 g/mol, and each caprolactone unit in the PCL chain has a molecular weight of around 114 g/mol. Thus, the molecular weight of Methoxy – polyethylene glycol – polycaprolactone is \(31 + 44n+114m\) g/mol. This can span a wide range, from a few hundred to several thousand daltons depending on the lengths of the PEG and PCL chains.
Molecular Structure	It has a block – copolymer structure. The methoxy – terminated PEG chain is a hydrophilic segment, characterized by its flexible, water – soluble nature due to the repeating ethylene oxide units. The polycaprolactone chain is a hydrophobic segment, with a linear arrangement of the caprolactone repeating units. The two segments are covalently linked, creating a molecule with both hydrophilic and hydrophobic properties.
Appearance	Usually appears as a white to off – white solid. The physical state can be influenced by the relative lengths of the PEG and PCL segments. If the PEG content is relatively high, it may have a more waxy or soft – solid appearance. Higher PCL content can lead to a harder, more crystalline – like solid.
Solubility	Solubility depends on the ratio of PEG to PCL. The PEG segment imparts water – solubility, so if the PEG chain is long enough relative to the PCL chain, the compound will show some solubility in water. It also dissolves well in polar organic solvents such as ethanol, methanol, and DMSO due to the PEG component. However, as the PCL content increases, solubility in non – polar organic solvents like chloroform and toluene improves, while water – solubility decreases.
Function in Industry	Biomedical Applications: Drug Delivery: Widely used in drug delivery systems. The hydrophobic PCL segment can encapsulate hydrophobic drugs, protecting them and controlling their release. The hydrophilic PEG segment provides stealth properties, reducing the recognition of the drug – carrier complex by the immune system and improving solubility in biological fluids. This combination allows for the delivery of a wide range of drugs, including poorly – soluble ones. Tissue Engineering: Can be used to fabricate scaffolds. The hydrophobic PCL provides mechanical strength and can be tailored to have appropriate degradation rates. The PEG component improves cell adhesion and biocompatibility. By controlling the ratio of PEG to PCL, scaffolds can be designed with specific properties for different tissue engineering applications. Cosmetics: In cosmetics, it can act as an emollient and a thickening agent. The hydrophobic PCL part can provide a smooth, non – greasy feel on the skin, while the PEG part helps in retaining moisture and improving the spreadability of cosmetic products.
Stability	Stable under normal storage conditions, typically at room temperature in a dry and dark place. However, the PCL segment is susceptible to hydrolysis, especially under acidic or basic conditions. Hydrolysis can lead to the breakdown of the PCL chain into smaller units, affecting the integrity of the molecule. The PEG segment can also be oxidized over time, particularly in the presence of strong oxidizing agents or at high temperatures and humidities. Antioxidants and pH – buffering agents may be added to formulations to enhance stability.
Safety Considerations	In biomedical and cosmetic applications, it is generally considered safe. The PEG component has a long – established safety profile. The PCL is also biocompatible and biodegradable. However, as with any chemical, there is a potential for individual sensitivity or allergic reactions. In industrial settings, proper handling procedures should be followed to avoid contact with eyes and skin. Adequate ventilation should be maintained when handling large quantities, especially if there is a risk of inhalation of dust or vapors.

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