Atom transfer radical polymerization (ATRP) was applied to the synthesis of prototype copolymer brushes composed polystyrene/poly(t-butyl methacrylate) (PS/PBMA) alternating structure. Dilute solution properties of prototype copolymer brush were investigated by static and dynamic light scattering (SLS and DLS) in tetrahydrofuran (THF). As a result, such prototype copolymer brush composed of short aspect ratio formed a star-like single molecule in THE To discuss the intramolecular phase separation of PS/PBMA brushes in solution, we determined the radius of gyration (R-g) and cross-sectional radius of gyration (R-g,R-c) of prototype copolymer brush by small-angle X-ray scattering (SAXS) using Guinier's plots in THF and styrene. We used styrene as solvent to cancel each other Out with the electron density of PS side chains. Both R-g and R-g,R-c obtained in styrene decreased drastically compared with those obtained in THE These results indicated strongly that PS and PBMA side chains of prototype brushes formed intramolecular phase separation even in good solvent. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2298-2304, 2010