Novel Regular Polyimide-graft-Poly(methacrylic acid) Brushes: Synthesis and Possible Applications as Nanocontainers of Cyanoporphyrazine Agents for Photodynamic Therapy Alexander V. Yakimansky, 1 Tamara K. Meleshko, 1 Dmitrii M. Ilgach, 1 Maria A. Bauman, 1 Tatiana D. Anan’eva, 1 Larisa G. Klapshina, 2 Svetlana A. Lermontova, 2 Irina V. Balalaeva, 3 William E. Douglas 4 1 Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, St. Petersburg 199004, Russia 2 G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinin Street 49, GSP-445, Nizhny Novgorod 603600, Russia 3 Research Institute of Living Systems, Lobachevsky State University of Nizhny Novgorod, Gagarin pr. 23/1, GSP-20, Nizhny Novgorod 603950, Russia 4 CNRS UMR 5253, Universit e Montpellier II, Place E. Bataillon, 34095 Montpellier cedex 5, France Correspondence to: A. V. Yakimansky (E - mail: yak@hq.macro.ru) Received 16 April 2013; accepted 19 June 2013; published online 19 July 2013 DOI: 10.1002/pola.26846 ABSTRACT: An approach to the synthesis of new regular graft- copolymers polyimide (PI)-graft-polymethacrylic acid is elabo- rated, including (1) synthesis of multicenter PI macroinitiators, (2) controlled ATRP of tert-butylmethacrylate on the prepared macro- initiators, and (3) protonolysis of tert-butyl ester groups of side chains of the resulting PI-graft-poly(tert-butylmethacrylate). Experimental conditions for attaining complete conversions of the first and the third stages of the process are determined by means of 1 H NMR and FTIR-spectroscopy. Polymer products of the first and the second stages of the process, as well as poly(tert- butylmethacrylate) side chains cleaved from the PI-graft-poly(tert- butylmethacrylate) copolymers by complete decomposition of the PI backbone under alkaline hydrolysis conditions, are charac- terized by GPC. The kinetics of poly(tert-butylmethacrylate) chain growth on a PI macroinitiator under ATRP conditions are studied. The results obtained provide evidence for the controlled character of the ATRP process and the regular structure of the synthesized graft-copolymers. It is shown that PI-g-PMAA PI brushes are sig- nificantly more efficient intracellular delivery agents for the potential photosensitizer [tetra(4-fluorophenyl)tetracyanoporhyr- azine free base] than are the commonly used PEG-micelles. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4267–4281 KEYWORDS: amphiphilic copolymers; atom transfer radical poly- merization (ATRP); biological applications of polymers; graft copolymers; photodynamic therapy; poly(tert-butylmethacrylate); polyimide macroinitiators; polymer brushes; polymethacrylic acid INTRODUCTION Graft-copolymerization is an efficient method for directed modification of polymer properties due to the branched structure of graft-copolymers and various functional properties of side chains covalently bound to the backbone. At present, controlled ATRP from multicenter macroinitiators is one of the most important and widely used tools for the realization of the graft-copolymerization processes. This method makes it possible to obtain regular graft-copolymers known as macromolecular or cylindrical brushes, which are characterized by a rather uniform and dense grafting of narrow dispersed side chains. 1–4 Among such macromolecular brushes, those with different natures of the backbone and side chains are of special interest, because they may adopt a wide variety of conformations in selective solvents. 5 Water is the most important selective solvent. It is not sur- prising, therefore, that many amphiphilic polymer brushes with a hydrophilic backbone and hydrophobic side chains 6 or vice versa 7 have been synthesized and studied. In the vast majority of such systems, the backbone is represented by a vinyl polymer 2,3 with a monomer unit length of about 0.25 nm. Therefore, the side chain can barely change its confor- mation, remaining always almost fully extended due to steric repulsion from its neighbors along the backbone. It is inter- esting to increase the backbone monomer unit length, to provide side chains with more space and to make their con- formational transitions in selective solvents more pro- nounced. In this context, aromatic polyimide (PI) backbones with a monomer unit length of 1.5–2.0 nm are promising. To the best of our knowledge, although there are a few reports V C 2013 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2013, 51, 4267–4281 4267 JOURNAL OF POLYMER SCIENCE WWW.POLYMERCHEMISTRY.ORG ARTICLE