Synthesis of block copolymers by the transformation of cationic polymerization into reversible atom transfer radical polymerization

Azo‐containing polytetrahydrofuran (PTHF) obtained by cationic polymerization was used as a macroinitiator in the reverse atom transfer radical polymerization (RATRP) of styrene and methyl acrylate in conjunction with CuCl2/2,2′‐bipyridine as a catalyst. Diblock PTHF–polystyrene and PTHF–poly(methyl acrylate) were obtained after a two‐step process. In the first step of the reaction, stable chlorine‐end‐capped PTHF was formed with the thermolysis of azo‐linked PTHF at 65–70 °C in the presence of the catalyst. Heating the system at temperatures of 100–110 °C started the polymerization of the second monomer, which resulted in the formation of block copolymers. The decomposition behavior of the azo‐linked PTHF and the structure of the block copolymers were determined by 1H NMR and gel permeation chromatography (GPC). Kinetic studies and GPC analyses further confirmed the controlled/living nature of the RATRP initiated by the polymeric radicals.