Poly(N-isopropylacrylamide-co-maleic acid-co-1-vinylimidazole), (NIPAM-MA-VI), has been prepared in water by free radical polymerization. The aqueous solution of low-molecular-weight P(NIPANI-MA-VI) has four distinct phases above a critical concentration. Effects of monomer ratio, copolymer concentration, and pH on the phase transition temperatures of P(NIPAM-MA-VI) were studied. The addition of divalent metal ions promoted the gelation process of P(NIPAM-MA-VI). Therefore, the adsorption behavior of P(NIPAM-MA-VI) to Cu2+ ions was further investigated; this adsorption behavior was pH-dependent, and the adsorption isotherm could be well fitted by the Freundlich model. The maximum adsorption capacity reaches 21.1 mg g(-1) dried copolymer at 60 degrees C and pH S. The adsorbed P(NIPAM-MA-VI) can be regenerated by the treatment of hydrochloric acid and reused in the following adsorption process. X-ray photoelectron spectroscopy (XPS) and synchrotron radiation small-angle X-ray scattering (SAXS) were used to investigate the effect of Cu2+ ions on the phase transition behavior of P(NIPAM-MA-VI). O is and N is XPS spectra and SAXS results analyzed by the Ornstein-Zernike and generalized Ornstein-Zemike models are in agreement with the proposed mechanisms and adsorption behavior. As a thermo-, pH-, and metal ion-responsive copolymer, P(NIPAM-MA-VI) could be used for the ion recognition, water purification, and enrichment of heavy metal ions.