Copolymers consisting of acrylic acid (AA) and 12-acryloyldodecanoic acid (ADA) [poly(ADA-co-AA)] were synthesized, and their dissociation behaviors and binding characteristics with ionic surfactant, dodecylpyridinium. chloride, were investigated. The dissociation is strongly suppressed in the presence of ADA, and when the ADA molar fraction (F-ADA) is 0.5, the copolymer exhibits a distinct two-stage dissociation associated with AA and ADA. The binding process is also changed by the presence of ADA. When the ADA content is low, the surfactants bind cooperatively to form a stoichiometric complex. An increase in ADA content brings about noncooperative and nonstoichiometric complexion. The initiation constant (K-0) for an isolated surfactant binding to poly(ADA(F-ADA = 1.0)) is more than 3 orders of magnitude larger than that of poly(AA(FADA = 0)), indicating that the initiation of the binding is associated not only with the electrostatic interaction but also with the hydrophobic interaction between the alkyl chains of surfactant and ADA. The structure of surfactant-poly(ADA-co-AA) complexes changes from micelle-like to lamellar-like with the increase in F-ADA.