The regularities of dispersion radical polymerization of n-butylacrylate in water-alcohol medium under the action of polymer tritiocarbonates based on copolymers of acrylic acid and N-isopropylacrylamide have been investigated. The conditions for the formation of a block copolymer with controlled molecular weight and high yield have been found. The conditions of formation of stable suspensions of block copolymers with unimodal particle size distribution have been determined.