Excellent Hydration Lubrication Based on Zwitterionic Poly (N-vinylpyrrolidone-co-methacrylic acid) for Hair Combing Improvement

In the present work, Poly (N-vinylpyrrolidone-co-methacrylic acid) (P(NVP-co-MAA)) was synthesized with free radical polymerization, and the hydration lubrication of the zwitterionic copolymer were investigated. P(NVP-co-MAA) as a lubricant to improve hair combing was also explored. The contact angle measurement showed that P(NVP-co-MAA) could adsorb onto both PDMS and hair surfaces. Adsorption equilibrium was achieved at the polymeric concentration of 0.2% and 0.3% on the surfaces of PDMS and hair, leading to a decrease in the contact angles by 5° and 11°, respectively. The hydration lubricity of P(NVP-co-MAA) was tested, and the results demonstrated that P(NVP-co-MAA) exhibited excellent lubricity properties in both boundary lubrication and mixed lubrication. It provided stable lubricity for up to 2 hours with continuous friction. Scanning electron microscope (SEM) and atomic force microscope (AFM) showed that the copolymer adsorbed on hair surfaces, mainly concentrated around the cuticles. It implied that the adsorption of the copolymer on hair surfaces relied on electrostatic interactions as well as hydrophobic interactions. The polymeric solution could lower the friction coefficient of wet hair compared to polyquaternium-10 (JR-400), a commonly used hair conditioner. When the concentration of copolymer was greater than 0.2%, the friction coefficient of wet hair was 0.129. At this concentration, copolymer molecules formed a hydration layer on the hair surface, which reduced the friction coefficient by 34.1%.