Synthesis of Triblock Copolymers Based on Two Isomer Acrylate Monomers by Atom Transfer Radical Polymerization ALEXANDRA MUN ˜ OZ-BONILLA, MARI ´ A L. CERRADA, MARTA FERNA ´ NDEZ-GARCI ´ A Instituto de Ciencia y Tecnologı ´a de Polı ´meros, Consejo Superior de Investigaciones Cientificas, Juan de la Cierva 3, 28006 Madrid, Spain Received 21 March 2005; accepted 23 May 2005 DOI: 10.1002/pola.20951 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The syntheses of triblock copolymers by the atom transfer radical poly- merization of tert-butyl and iso-butyl acrylates as inner blocks with cyclohexyl metha- crylate as outer blocks are reported. The living behavior and blocking efficiency of these polymerizations were investigated in each case. The use of difunctional macro- initiators led to ABA triblock copolymers with narrow polydispersities and controlled number-average molecular weights. These copolymers were prepared from bromo-ter- minated macroinitiators of poly(tert-butyl acrylate) and poly(iso-butyl acrylate), with copper chloride/N,N,N 0 ,N@,N@-pentamethyldiethylenetriamine as the catalytic system, at 40 8C in 50% (v/v) toluene solutions. The block copolymers were characterized with size exclusion chromatography and 1 H NMR spectroscopy. Differential scanning calo- rimetry measurements were performed to reveal the phase segregation. The glass transition of the inner block was not clearly detected, with the exception of the copolymer synthesized with the longest poly(iso-butyl acrylate) macroinitiator length. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4828–4837, 2005 Keywords: glass transition; phase separation; solution atom transfer radical polym- erization; triblock copolymers; molecular weight distribution INTRODUCTION The synthesis of (meth)acrylic block copolymers has industrial advantages because they can cover a large range of glass-transition tempera- tures (T g ’s) through the variation of the alkyl substituent of the ester group. In addition, poly (alkyl methacrylate)s and poly(alkyl acrylate)s are immiscible, except in the case of small alkyl groups and low molecular weights. 1 They have numerous industrial applications, including sur- factants, compatibilization agents in polymer blends, adhesives, additives in high-impact materials, and thermoplastic elastomers. 2 It is well known that block copolymers can exhibit microphase separation according to their molecular weight and composition, which deter- mine their final properties. 3 Moreover, block copolymers, when dissolved in a selective solvent (a good solvent for one block but a poor solvent for the other one), assemble into micelles with a core formed by the insoluble blocks, surrounded by a corona consisting of the soluble blocks. The micel- lization of block copolymers has been described in a wide range of copolymer/solvent systems. 4–12 In aqueous media, they form micelles that are Correspondence to: M. Ferna ´ ndez-Garcı ´a (E-mail: martafg@ ictp.csic.es) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 43, 4828–4837 (2005) V V C 2005 Wiley Periodicals, Inc. 4828