Examining polyquaternium polymers deposition on human excised hair fibers

Background Polyquaterniums (PQs) as important ingredients of hair products are synthetic cationic polymers and are used in commercial hair volumizers and conditioners. Methods Three different grades of polymers including PQ 87, 68, and 46 with various concentrations were used, and their hair deposition efficacy was measured at 5 different pH values using hair diameters measurements by digital micrometer. Deposition durability of polymer layer on the hair surface was tested by a defined washing test. Optical microscopic images and polarized light images were also taken from treated and untreated samples for further investigation. Attenuated total reflectance (ATR) spectral were recorded from hair samples to prove the polymer deposition and probable interaction with hair fibers. Results PQ-68 with the highest molecular weight (300 kDa) at pH = 9 exhibited the best hair deposition efficacy. The results revealed that the deposition of polymers is directly proportional to the pH values. The best results were seen at pH = 9, and at the lowest pH (pH = 5), the efficiency of polymers was approximately equal to zero. The best resistance against washing was shown by PQ-44 at pH = 6. ATR successfully tracked the presence of the polymers on the hair fibers and also proposed specific wave numbers for each polymeric agent, individually. Conclusions In general, two main parameter which can mainly influence the deposition efficacy of PQs are the type of polymer or its molecular weight and also the positive charge density on the polymer molecules.