Synthesis of Functional Poly(styrene)-block-(methyl methacrylate/ methacrylic acid) by Homogeneous Reverse Atom Transfer Radical Polymerization: Spherical Nanoparticles, Thermal Behavior, Self-Aggregation, and Morphological Properties Guadalupe del C. Pizarro, 1 Manuel Jeria-Orell, 1 Oscar G. Marambio, 1 Andr  es F. Olea, 2 Daniela T. Vald  es, 1 Kurt E. Geckeler 3,4 1 Departamento de Quı ´mica, Universidad Tecnol ogica Metropolitana. Santiago, Chile 2 Departamento de Ciencias Quı ´micas, Facultad de Ciencias Exactas, Universidad Andr es Bello, Los Fresnos 52, Vi ~ na del Mar, Chile 3 Department of Nanobio Materials and Electronics (WCU), Gwangju Institute of Science and Technology (GIST), Gwangju 500- 712, South Korea 4 Laboratory of Applied Macromolecular Chemistry, School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, South Korea Correspondence to: G. d. C. Pizarro (E-mail: gpizarro@utem.cl) ABSTRACT: This study investigates the use of homogeneous reverse atom transfer radical polymerization for the synthesis of polysty- rene (PS) initiated by conventional radical peroxide with copper bromide in the lower oxidation state and a 2,2 0 -bypyridine complex as the catalyst. In a second stage, an amphiphilic block copolymer containing methyl methacrylate (MMA) was synthesized via nor- mal atom transfer radical polymerization in two steps, followed by partial hydrolysis of the methyl ester linkage of the MMA block under acidic conditions. The block copolymer PS 699 -b-P(MMA 232 /MAA 58 ) obtained had a narrow molecular weight dispersity (Ð < 1.3). The structure of the precursor, PS-b-PMMA, and resultant polymer, was characterized and verified by FTIR and 1 H-NMR spec- troscopy as well as size exclusion chromatography. The self-aggregation of PS 699 -b-P(MMA 232 /MAA 58 ) in organic solvents was moni- tored by UV spectroscopy, whereas the morphology and size of the formed microaggregates were investigated by transmission electron microscopy and dynamic light scattering. The results indicate that this copolymer formed regular spherical reverse micelles with a core–shell structure. The atomic force micrographs of PS 699 -b-P(MMA 232 /MAA 58 ) showed a rough surface morphology owing to microphase separation of the block copolymer. In addition, thermal characterization was performed by differential scanning calorime- try and thermogravimetric analysis. The glass transition temperature of PS 699 -b-P(MMA 232 /MAA 58 ) decreased significantly (65  C), when compared to PS and PMMA, suggesting that an enhanced movement of the polymer chains resulted by the segregation of the hydrolyzed P(MMA 232 /MAA 58 ) block. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 129: 2076–2085, 2013 KEYWORDS: micelles; morphology; nanostructured polymers; phase behavior; properties and characterization Received 8 October 2012; accepted 11 December 2012; published online 7 January 2013 DOI: 10.1002/app.38923 INTRODUCTION During the last decade, significant advancement has been made in the area of controlled free-radical polymerization, including atom transfer radical polymerization (ATRP), offering new syn- thesis routes to obtain well-defined polymers with low disper- sities 1 for applications ranging from next-generation separation media 2,3 to controlled release vehicles, 4,5 catalyst supports, 6 and nanoreactors. 7 ATRP has been successfully employed for the po- lymerization of a variety of monomers, such as styrene and its derivatives, 8 acrylates and methacrylates, 9–11 using a copper- based system and producing well-defined polymers in a relatively short period of time. There are several reports on the synthesis of amphiphilic block copolymers and the study of their properties, as these copolymers are important materials in the several fields of natural science, for example, colloid science and biochemistry, as well as in industrial fields. 12–15 In a normal ATRP reaction, the initiating radicals are generated from an alkyl halide in the presence of a transition metal in its V C 2013 Wiley Periodicals, Inc. 2076 J. APPL. POLYM. SCI. 2013, DOI: 10.1002/APP.38923 WILEYONLINELIBRARY.COM/APP