Clinical tests with an 8% solution indicated that Polyquaternium-7 is not a photosensitiser. Given its structure, the material is considered not to be at risk of being significantly absorbed into the skin and is therefore unlikely to produce general toxicity, developmental toxicity, or mutagenic/carcinogenic effects under conditions of use. The presence of Acrylamide monomer is considered to be sufficiently low to be of no toxicological significance. Based on the available data, it is concluded that Polyquaternium-7 is safe for use in cosmetic formulations (1).

It is used as a conditioning agent in shampoos to improve the uniformity and efficiency of deposition of conditioning agents on the hair and to lubricate (2) and soften the hair to avoid frizzing (3).

Polyquaternium-7 has been used, as it is nontoxic, in an antibacterial superabsorbent hydrogel (4).

References_____________________________________________________________________

(1) Final Report on the Safety Assessment of Polyquaternium-7   International Journal of Toxicology - December 1995 vol. 14 no. 6 476-484

(2) Erazo-Majewicz P, Roberts-Howard C, Oldham E, Lynch C, Graham J, Usher CR, Joneja S. Linking enhanced deposition agent functionality with aesthetic performance. J Cosmet Sci. 2011 Mar-Apr;62(2):101-8. 

Abstract. This study examines the cationic polymers 1) guar hydroxypropyltrimonium chloride polymers (GHPTC), 2) acrylamidopropyltrimonium chloride/acrylamide copolymer (APTAC/Acm), 3) polyquaternium polymers (PQ-10, PQ-7, PQ-67), and 4) a new polymer system approach for their a) deposition efficiency (as measured by quantifying oils deposited on virgin hair) and b) ability to deliver good wet and dry lubricity to the hair from a cleansing formulation as measured by comb energy and friction characteristics of the hair samples. Conditioning polymer technology approaches 1) acrylamidopropyltrimonium chloride/acrylamide copolymer, 2) a guar hydroxypropyltrimonium chloride polymer, and 3) the new polymer system approach deliver superior deposition of natural conditioning oils and dimethicone materials from anionic/amphoteric surfactant cleansing formulations. These new polymer technologies offer formulators the ability to improve uniformity of deposition as well as deposition efficiency of conditioning agents onto hair, and target the desired hair lubricity.

(3) Gao T. Evaluation of hair humidity resistance/moisturization from hair elasticity. J Cosmet Sci. 2007 Jul-Aug;58(4):393-404.

(4)  Shen J, Li B, Zhan X, Wang L. A One Pot Method for Preparing an Antibacterial Superabsorbent Hydrogel with a Semi-IPN Structure Based on Tara Gum and Polyquaternium-7. Polymers (Basel). 2018 Jun 22;10(7):696. doi: 10.3390/polym10070696. PMID: 30960621; PMCID: PMC6403564.

Abstract. An antibacterial superabsorbent polymer was prepared by graft polymerization of acrylic acid onto tara gum polysaccharide, by adding N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride and a polymer with 2-propenamide (polyquaternium-7, PQ7) as an antibacterial agent. The effects of the amount of PQ7 in the hydrogel on its swelling ratio were investigated and maximum swelling ratios of 712 g/g and 68 g/g, in distilled water and 0.9 wt % NaCl solution were attained with 0.5 g PQ7 per gram of tara gum. The superabsorbent hydrogel was characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. The results showed that poly (acrylic acid) was successfully grafted onto tara gum and a three-dimensional network structure formed with PQ7 chains penetrated in the networks. The antibacterial properties of these superabsorbent hydrogels against Staphylococcus aureus and Escherichia coli improved with increasing PQ7 content. This study demonstrates a method of preparing novel functional superabsorbent hydrogels.

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