Polyethylene oxide(PEO) were widely used as a surfactants or rheology control agents. In this study, telechiric type associative copolymers were prepared by end-capping of polyethylene oxide(PEO) with various alkylphenols and the viscosity behavior of the copolymer solutions was measured. Phenol or p-Dodecylphenol(pC12P) or o-Dodecylphenol(oC12P) was introduced at the end of PEO having various molecular weight(2K,9K,15K,and 20K). The viscosity of solution were greatly affected by the end-capping ratio and length and position of alkyl chain of the alkyl phenol induced. And the phase separations were observed at low concentration due to the structure of the formed micelle.