One-Pot Synthesis of Star-Block Copolymers Using Double Click Reactions HAKAN DURMAZ, AYDAN DAG, ALP HIZAL, GURKAN HIZAL, UMIT TUNCA Department of Chemistry, Istanbul Technical University, Maslak, Istanbul 34469, Turkey Received 23 May 2008; accepted 11 August 2008 DOI: 10.1002/pola.23014 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: 3-Arm star-block copolymers, (polystyrene-b-poly(methyl methacrylate)) 3 , (PS-b-PMMA) 3 , and (polystyrene-b-poly(ethylene glycol)) 3 , (PS-b-PEG) 3 , are prepared using double-click reactions: Huisgen and Diels–Alder, with a one-pot technique. PS and PMMA blocks with a-anthracene-x-azide- and a-maleimide-end-groups, respec- tively, are achieved using suitable initiators in ATRP of styrene and MMA, respec- tively. However, PEG obtained from a commercial source is reacted with 3-acetyl-N- (2-hydroxyethyl)-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxamide (7) to give furan-pro- tected maleimide-end-functionalized PEG. Finally, PS/PMMA and PS/PEG blocks are linked efficiently with trialkyne functional linking agent 1,1,1-tris[4-(2-propynyloxy)- phenyl]-ethane 2 in the presence of CuBr/N,N,N 0 ,N 00 ,N 00 -pentamethyldiethylenetri- amine (PMDETA) at 120  C for 48 h to give two samples of 3-arm star-block copoly- mers. The results of the peak splitting using a Gaussian deconvolution of the obtained GPC traces for (PS-b-PMMA) 3 and (PS-b-PEG) 3 displayed that the yields of target 3-arm star-block copolymers were found to be 88 and 82%, respectively. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7091–7100, 2008 Keywords: atom transfer radical polymerization; click reactions; Diels–Alder reaction; gel permeation chromatography (GPC); Huisgen reaction; NMR; one-pot technique; polyethers; polystyrene; star polymers; star-block copolymers INTRODUCTION A branched polymer structure is elucidated as a nonlinear polymer with multiple backbone chains growing from junction points. 1 It has been shown that branching results in a more compact struc- ture in comparison to linear counterparts of simi- lar molecular weight because of its high segment density, which changes the melt, solution, and solid-state properties of the polymer. 1 Nonlinear polymers primarily include star, miktoarm star, H-type, hyperbranched, dendrimers, and den- drimer-like star polymers. Star-block copolymers are star polymers in which each arm is a diblock or triblock copolymer. 2 Star-block copolymers have been mostly prepared using living anionic polymerization route until recently. In this tech- nique, the living block copolymers are first pre- pared via sequential anionic polymerization of two monomers and then linked with the core to provide star-block copolymers with many arms depending on the functional group numbers or the chemical nature of the core. 2 Multifunctional linking agent (chlorosilane) or difunctional mono- mer (divinyl benzene or ethylene glycol dimetha- crylate) can be employed as core. 2 However, recently a rapid growth in living/con- trolled radical polymerization techniques such as the reversible addition fragmentation chain trans- fer (RAFT) polymerization, the nitroxide-medi- ated free radical polymerization (NMP), and the metal-mediated living radical polymerization Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 46, 7091–7100 (2008) V V C 2008 Wiley Periodicals, Inc. Correspondence to: U. Tunca (E-mail: tuncau@itu.edu.tr) 7091