The surface free energy of diblock copolymer, composed of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA-b-PFEMA), was compared with that of PFEMA homopolymer (P-PFEMA) in correlation with their structures in the solid state and in the solution using dynamic contact angle, X-ray photoelectron spectroscopy, X-ray diffraction, and dynamic light scattering. The PMMA-b-PFEMA film cast from chloroform solution was found to possess very low surface free energy (7.8 mJ/m(2)) compared with the Surface free energies of the P-PFEMA (8.5 mJ/m(2)) and the PMMA-b-PFEMA (9.8 mJ/m(2)) films cast from CF3CF2CHCl2 solutions. These differences in the surface free energy were brought about by the variations in their surface structures. The very low surface free energy was considered to have originated from the surface segregation of the PFEMA segments highly self-assembled by the presence of chloroform. (C) 2004 Elsevier Inc. All rights reserved.