Polyquaternium-7 is widely used in hair care products, such as shampoos and conditioners, and in skincare products, like shower gels and lotions. 

It is a water-soluble cationic polymer widely used in cosmetic and personal care products such as shampoos, conditioners, hair gels, lotions, and body washes. It is valued for its film-forming, conditioning, and antistatic properties, which improve hair manageability and leave the skin feeling silky smooth. As a cationic polymer, it carries a positive charge that binds to negatively charged surfaces like hair and skin, enhancing softness and reducing static electricity.

Chemical Composition and Structure
Polyquaternium-7 is a copolymer composed of acrylamide and diallyldimethylammonium chloride. Its chemical structure makes it water-soluble and highly attractive to negatively charged surfaces like damaged hair and dry skin. Its ability to form a thin film makes it effective in retaining moisture and providing a hydrated feel.

Physical Properties
Polyquaternium-7 typically comes in a clear or slightly opaque aqueous solution. It is highly soluble in water and has relatively low viscosity, making it easy to incorporate into cosmetic formulations. Once applied, it forms a smooth, soft film that helps improve hair combability and skin feel.

The name describes the structure of the molecule:

The term "Polyquaternium" is a combination of "polymer" and "quaternary ammonium salts". The number 7 in "Polyquaternium-7" refers to the specific type of polymer in the Polyquaternium series.

Since Polyquaternium-7 is a copolymer of acrylamide and the quaternary ammonium salt diallyldimethylammonium chloride (DADMAC), in the synthesis process, these two monomers are polymerized together to form the copolymer.

The general steps of the synthesis process are as follows:

• Monomer preparation. The monomers, acrylamide and DADMAC, are prepared for the polymerization process. This may involve dissolving them in a suitable solvent and purifying them to remove any impurities.
• Initiation. The polymerization process is initiated by adding a chemical initiator. The initiator starts the reaction by creating free radicals, which are highly reactive species that can react with the monomers to start the polymer chain.
• Propagation. The free radicals react with the monomers, adding them to the polymer chain. This process continues, with each monomer reacting with the end of the polymer chain to extend the chain.
• Termination. Eventually, the polymer chains will react with each other or with other free radicals to terminate the polymerization process. This results in the final polymer product.
• Purification and isolation. The final polymer product is then purified and isolated from the reaction mixture. This may involve processes such as filtration, washing, and drying.

It occurs as a white powder or colourless liquid.

What it is used for and where it is used

Cosmetics

Polyquaternium-7 is a restricted ingredient III/66 as relevant item in the Annexes of the European Cosmetics Regulation 1223/2009 and regulated by 2002/34/EC on Residual Polyacrylamides: 

• Body products: maximum residual acrylamide content 0.1mg/kg
• Other products: maximum residual acrylamide content 0.5mg/kg

Polyquaternium-7 is used as a conditioner and antistatic, with high charge density and good stability, in cosmetics to improve hair combability, increase volume and shine in shampoos, conditioners in a wide range of pH values between 5 and 8 for both dry and wet chemical hair treatment. 

Antistatic agent. Static electricity build-up has a direct influence on products and causes electrostatic adsorption. The antistatic ingredient reduces static build-up and surface resistivity on the surface of the skin and hair.

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

Improves clarity and compatibility in anionic surfactant systems.  

Other uses

In sludge regulation in municipal, industrial and waste water Polyquaternium-7 is also used as a flocculating agent.

Used as a retention aid in the paper industry, mining and mineral processing, for oil-water separation, crude oil dewatering and treatment of oily wastewater in oil fields and refineries.

The most relevant studies on this chemical compound have been selected with a summary of their contents:

Polyquaternium-7 studies

Typical optimal commercial product characteristics Polyquaternium-7

• Molecular Formula  C₁₁H₁₂ClN₂O      (C₈H₁₆NCl)n(C₃H₅NO)n
• Molecular Weight  232.752 g/mol
• Exact Mass   232.13400
• CAS  26590-05-6    108464-53-5
• UNII    0L414VCS5Y
• EC Number   200-700-9    618-347-7
• DSSTox Substance ID 
• IUPAC  dimethyl-bis(prop-2-enyl)azanium;prop-2-enamide;chloride
• InChI=1S/C8H16N.C3H5NO.ClH/c1-5-7-9(3,4)8-6-2;1-2-3(4)5;/h5-6H,1-2,7-8H2,3-4H3;2H,1H2,(H2,4,5);1H/q+1;;/p-1 
• InChl Key      XFOSBZOUUACCCN-UHFFFAOYSA-M
• SMILES   C[N+](C)(CC=C)CC=C.C=CC(=O)N.[Cl-]
• MDL number  MFCD00241413
• PubChem Substance ID    
• SCHEMBL126949

Synonyms : 

• Acrylamide diallyldimethylammonium Chloride
• 2-Propen-1-aminium, N,N-dimethyl-N-2-propenyl-, chloride, polymer with 2-propenamide
• Dimethyldiallylammonium chloride acrylamide polymer
• n,n-dimethyl-n-(prop-2-en-1-yl)prop-2-en-1-aminium chloride- prop-2-enamide(1:1:1)
• Quaternium-41
• N,N-Dimethyl-N-2-propenyl-2-propen-1-aminium chloride, polymer with 2-propenamide
• 2-Propen-1-aminium, N,N-dimethyl-N-2-propen-1-yl-, chloride (1:1), polymer with 2-propenamide