The synthesis of thermoassociative water-soluble copolymers, with polyether as pendant chains, was developed by macromonomer copolymerization and grafting techniques. The discussion was specially focused on the coupling reactions, between omega-methyl alpha-aminopolyethers and carboxylic units borne on the backbone, which provide in quantitative yield weil-defined grafted copolymer structures. According to the thermodynamical properties of poly(ethylene oxide) or poly(propylene oxide) side-chains (lower critical solution temperature), aqueous solutions of grafted copolymers exhibit a microphase separation of polyether grafts upon heating and generate, above C*, thermothickening properties of the solutions. The general basis of this behaviour is discussed, and the roles played by structural and external parameters highlighted.