Abstract:

The amphiphilic polymer was used as a conditioner in a silicone-free hair conditioner. The amphiphilic random copolymer poly （styrene-co-acrylic acid） was synthesized by free radical polymerization. Through the cation-π electron interaction between the cationic surfactant behenyl trimethyl ammonium chloride and the benzene ring in the copolymer, the amphiphilic random copolymer poly （styrene-co-acrylic acid） would be adsorbed on the hair surface to give more smoothness to hair. The hair conditioner with excellent combing performance was prepared by adjusting the molar ratio of styrene in poly （styrene-co-acrylic acid） to behenyl trimethyl ammonium chloride, the concentration of behenyl trimethyl ammonium chloride as well as the dosage. The prepared conditioner was evaluated and compared with silicone conditioner. The results show that, the amphiphilic random polymer poly（styrene-co-acrylic acid） is successfully synthesized; the molecular weight of the polymer is 11 824 and the polydispersity coefficient is 1.67; the optimized molar ratio is close to the feeding ratio of 7∶3. The residual amount of the amphiphilic polymer on the hair is positively correlated with the viscosity of the compound solution, i.e., the greater the viscosity of the compound solution, the greater the cation-π electron interaction, and thus the more easily the amphiphilic polymer would stay on the hair surface. The optimized conditions are as follows: the usage amount of BTAC is 1 mL; the mass fraction is 2.0%; the molar ratio is 1.2. Under this condition, the residual amount of the amphiphilic polymer on the hair is 102 μg/ghair. The analysis of the significant difference in the maximum friction force and the combing work show that the wet combing performance is significantly improved by adding the amphiphilic polymer into the hair conditioner, and the wet combing performance of the self-made conditioner is better than that of the commercially available silicone-containing conditioners. SEM images show that the hair scales after treatment with the prepared conditioner are regular and without curling. The amphiphilic polymer has no cumulative effect on hair.

Key words: amphiphilic polymer, cation-π electron interaction, conditioner