Investigation on the interactions between amphiphilic copolymer and different surfactants

Abstract As a newly developed amphiphilic copolymer, poly (N-vinylpyrrolidone -co -methacrylic acid) (P(NVP- co -MAA)) has excellent lubricity and can be potentially employed in household detergents, personal cleaning and care. In this study, the interactions between P(NVP- co -MAA) and five different surfactants were investigated using the surface tension method. The results show that P(NVP- co -MAA) can interact with the two anionic surfactants which respectively contain COO − and SO 3 2− groups. In contrast, P(NVP- co -MAA) can’t interact with zwitterionic and cationic surfactants. The further study indicates that the electrostatic attraction between P(NVP- co -MAA) and the anionic surfactants benefits the formation of the mixed aggregation. However, as the surfactants contain quaternary ammonium groups, the electrostatic repulsion, steric hindrance and high interaction energy may hinder the binding of P(NVP- co -MAA) and these surfactants. Finally, the effect of NaCl on P(NVP- co -MAA)-anionic surfactant mixtures was studied. In the case that the surfactant has the SO 3 2− group, the addition of NaCl at the concentration not exceeding 0.5 g L −1 helps the formation of P(NVP- co -MAA)- surfactant aggregation. However, when the hydrophilic group of the surfactant is substituted by the COO − group, the addition of NaCl regardless of concentration inhibits the interaction of P(NVP- co -MAA) and the surfactants. This study offers a new guideline to select appropriate surfactants for P(NVP- co -MAA)-containing formulations.