Based on a hydrophilic poly(ethylene oxide) macroinitiator (PEOBr), a novel amphiphilic diblock copolymer PEO-block-poly(11-(4-cyanobiphenyloxy)undecyl) methacrylate) (PEO-b-PMA(11CB)) was prepared by atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10-hexamethyltriethylenetriamine as a catalyst system. An azobenzene block of poly(11-[4-(4-butylphenylazo)phenoxyl]undecyl methacrylate) was then introduced into the copolymer sequence by a second ATRP to synthesize the corresponding triblock copolymer PEO-b-PMA(11CB)-b-PMA(11Az). Both of the amphiphilic block copolymers had well-defined structures and narrow molecular-weight distributions, and exhibited a smectic liquid-crystalline phase over a wide temperature range.