Block and star block copolymers by mechanism transformation. I. Synthesis of PTHF-PSt-PTHF by the transformation of ATRP into CROP

Polystyrene (PSt) with end-terminal bromine (Br-PSt-Br) was synthesized by the atom transfer radical polymerization of styrene with the difunctional initiator 1,2-bis(2′-bromobutyryloxy)ethane in combination with CuBr and bipyridine. The Br-PSt-Br reacted with silver perchlorate at −78 °C, and the resulting macromolecular initiator was used to initiate the polymerization of tetrahydrofuran. Triblock poly(tetrahydrofuran)-polystyrene-poly(tetrahydrofuran) (PTHF-PSt-PTHF) diol was obtained after propagation at −15 °C. The conversion of the polymerization was measured by gas chromatography. The structures of the triblock copolymer PTHF-PSt-PTHF diol were characterized by 1H NMR and gel permeation chromatography. The mechanism of cationic ring-opening polymerization is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 337–344, 2000