Thiophenol Derivatives as a Reducing Agent for In Situ Generation of Cu(I) Species via Electron Transfer Reaction in Copper-Catalyzed Living/Controlled Radical Polymerization of Styrene HUMEYRA MERT, UMIT TUNCA, GURKAN HIZAL Department of Chemistry, Istanbul Technical University, 34469 Istanbul, Turkey Received 8 May 2006; accepted 3 July 2006 DOI: 10.1002/pola.21672 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The copper-catalyzed living radical polymerization (LRP) of styrene (St) was carried out in the presence of thiophenol derivative such as sodium thiophenolate (PhSNa) or p-methoxythiophenol as a reducing agent for Cu(II) by using either 1- chloro-1-phenyl ethane or ethyl-2-bromoisobutyrate as an initiator and N,N,N 0 ,N@,N@- pentamethyldiethylenetriamine as ligand at 110 8C. Kinetic experiments were carried out to reveal the effect of PhSNa concentration on copper-catalyzed LRP of St. This technique was successfully applied for the preparation of both chain-extended polymer and block copolymer polystyrene-b-poly(methyl methacrylate). The obtained polymers were characterized using GPC, 1 H-NMR, and MALDI-TOF measurements. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5923–5932, 2006 Keywords: copper catalyzed living radical polymerization; electron transfer reaction; thiophenol derivatives INTRODUCTION Metal-catalyzed living/controlled radical polyme- rization (LRP), mediated by Cu, Ru, Ni, and Fe metal complexes, is one of the most efficient methods in various LRP. 1–3 Since this method consists of a catalytic process, the proper catalyst is the most important component in the polymer- ization. Copper-catalyzed LRP, often called atom transfer radical polymerization (ATRP), using Cu(I)/amine ligand as the catalyst system to- gether with an alkyl halide as an initiator has received much interest. Major disadvantages of copper-catalyzed LRP are high cost and easy oxidation of metal salt in lower oxidation state. These can be overcome by in situ Cu(I) generation via an electron transfer from a reducing agent to a more stable higher oxidation state metal salt. In this regard, Percec et al. reported for the first time the self-regulated catalytic system using a reaction between aryl sulfonyl chloride and Cu 2 O to give Cu(I). 4–6 This process was then success- fully applied for the preparation of dendritic structures, using a divergent synthesis method combined with a new concept called Terminator Multifunctional Initiator (TERMINI). 7,8 Later, Matyjaszewski and coworkers developed a me- thod based on in situ formation of Cu(I) from its higher oxidation state counterpart via combina- tion of ATRP and reverse ATRP processes. 9,10 In this process, a mixture of excess amount of alkyl halide and thermal radical initiator together with Cu(II) catalyst complex was used as a dual initia- tor (simultaneous reverse and normal initiation ATRP (SR and NI ATRP)). Recently, Hizal and Correspondence to: G. Hizal (E-mail: hizal@itu.edu.tr) or U. Tunca (E-mail: tuncau@itu.edu.tr) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 44, 5923–5932 (2006) V V C 2006 Wiley Periodicals, Inc. 5923