PEG-8/SMDI Copolymer is a synthetic polymer formed by the reaction of polyethylene glycol (PEG-8) with succinic acid and 1,3-bis(aminomethyl)cyclohexane (SMDI). This copolymer is widely used in cosmetic formulations for its emulsifying, thickening, and film-forming properties.

Chemical Composition and Structure

The chemical composition of PEG-8/SMDI Copolymer includes:

• PEG-8: A polyethylene glycol that provides moisture-retaining properties and enhances solubility.
• SMDI: A compound that contributes to the copolymer’s film-forming and stabilizing properties.

Structurally, the copolymer consists of long chains of PEG linked with SMDI units, allowing it to function effectively as an emulsifier and thickener in various cosmetic applications.

Physical Properties

• Appearance: Typically a clear to slightly opaque gel or viscous liquid.
• Solubility: Soluble in water, making it easy to incorporate into aqueous formulations.
• pH: Generally neutral to slightly acidic, around 6-7.
• Odor: Mild, characteristic of synthetic polymers.
• Stability: Stable under normal storage conditions; should be protected from extreme temperatures.

Production Process

• Synthesis: PEG-8/SMDI Copolymer is produced through a chemical reaction that combines PEG-8 with SMDI under controlled conditions.
• Purification: The resulting copolymer is purified to remove any unreacted materials and by-products.
• Formulation: The purified copolymer is incorporated into cosmetic products, often combined with other ingredients to enhance performance and stability.

Applications

• Medical: Limited use in formulations requiring emulsifying and thickening properties.
• Cosmetics: Commonly included in creams, lotions, and hair care products for its emulsifying, thickening, and skin-conditioning effects.

INCI Functions:

Film-forming agent. It produces, upon application, a very thin continuous film with an optimal balance of cohesion, adhesion and stickiness on skin, hair or nails to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.

CAS   39444-87-6

• Industrial Uses: Occasionally utilized in formulations where thickening and emulsifying properties are needed.

Environmental and Safety Considerations

Responsible sourcing and production practices are essential to ensure that the ingredient is free from harmful contaminants and produced sustainably. 

Cosmetic Safety

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."