Block and star block copolymers by mechanism transformation. IV. Synthesis of S-(PSt)2(PDOP)2 miktoarm star copolymers by combination of ATRP and CROP

Abstract

A new tetrafunctional initiator, di(hydroxyethyl)-2,9-dibromosebacate (DHEDBS) [HOCH 2 CH 2 OOCCHBr(CH 2 ) 6 CHBrCOOCH 2 CH 2 OH], was synthesized and used in preparation of A 2 B 2 miktoarm star copolymers, (polystyrene)2/ [poly(1,3-dioxepane)] 2 [S-(PSt) 2 (PDOP) 2 ], by transformation of atom transfer radical polymerization (ATRP) to cationic ring-opening polymerization (CROP). First, two-armed PSt with two primary hydroxyl groups sited at the center of macromolecule [(PStBr) 2 (OH) 2 ] was obtained by ATRP of St with the initiation system of DHEDBS/CuBr/bpy, and used as a chain-transfer agent in the CROP of DOP with triflic acid as the initiator. Therefore, A 2 B 2 miktoarm star copolymer S-(PSt) 2 (PDOP) 2 was formed. Its structure was confirmed by the 1 H NMR spectrum. Gel permeation chromatography (GPC) curves show that the polymers obtained have a relatively narrow molecular weight distribution. The hydrolysis product of S-(PSt) 2 (PDOP) 2 was also characterized by 1 H NMR and GPC.