The multi-thermo-responsive block copolymer of poly[2-(2-methoxyethoxy)ethyl methacrylate]-block-poly[N-(4-vinylbenzyl)-N,N-diethylamine] (PMEO(2)MA-b-PVEA) displaying phase transition at both the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) in the alcohol/water mixture is synthesized by reversible addition-fragmentation chain transfer polymerization. The poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMEO(2)MA) block exhibits the UCST phase transition in alcohol and the LCST phase transition in water, while the poly[N-(4-vinylbenzyl)-N,N-diethylamine] (PVEA) block shows the UCST phase transition in isopropanol and the LCST phase transition in the alcohol/water mixture. Both the polymer molecular weight and the co-solvent/nonsolvent exert great influence on the LCST or UCST of the block copolymer. By adjusting the solvent character including the water content and the temperature, the block copolymer undergoes multiphase transition at LCST or UCST, and various block copolymer morphologies including inverted micelles, core-corona micelles, and corona-collapsed micelles are prepared. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4399-4412