Hindawi Publishing Corporation International Journal of Polymer Science Volume 2011, Article ID 109693, 11 pages doi:10.1155/2011/109693 Research Article RAFT Synthesis and Self-Assembly of Free-Base Porphyrin Cored Star Polymers Lin Wu, 1 Ronan McHale, 1 Guoqiang Feng, 2 and Xiaosong Wang 1, 3 1 Department of Colour Science, School of Chemistry, University of Leeds, Leeds LS2 9JT, UK 2 Laboratory of Pesticide and Chemical Biology, Ministry of Education, Central China Normal University, Wuhan 430079, China 3 Department of Chemistry and Institute of Nanotechnology, University of Waterloo, Waterloo, Canada N2L 3G1 Correspondence should be addressed to Xiaosong Wang, xiaosong.wang@uwaterloo.ca Received 25 March 2011; Accepted 11 May 2011 Academic Editor: Peng He Copyright © 2011 Lin Wu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Reversible addition fragmentation chain transfer (RAFT) synthesis and self-assembly of free-base porphyrin cored star polymers are reported. The polymerization, in the presence of a free-base porphyrin cored chain transfer agent (CTA-FBP), produced porphyrin star polymers with controlled molecular weights and narrow polydispersities for a number of monomers including N, N-dimethylacrylamide (DMA) and styrene (St). Well-defined amphiphilic star block copolymers, P-(PS-PDMA) 4 and P-(PDMA- PS) 4 (P: porphyrin), were also prepared and used for self-assembly studies. In methanol, a selective solvent for PDMA, spherical micelles were observed for both block copolymers as characterized by TEM. UV-vis studies suggested star-like micelles were formed from P-(PS-PDMA) 4 , while P-(PDMA-PS) 4 aggregated into flower-like micelles. Spectrophotometric titrations indicated that the optical response of these two micelles to external ions was a function of micellar structures. These structure-related properties will be used for micelle studies and functional material development in the future. 1. Introduction The controlled organization of functional dyes, such as por- phyrins, into polymer supramolecular systems has numerous potentially interesting material applications [1]. Porphyrin containing biological systems, where the dye usually works in aggregated structures, offer insights to these possibilities. Both the chemical structure of the dye and its cooperative interaction with other molecules accomplishes various com- plex functions such as photosynthesis and electron transfer [2]. Several porphyrin polymers have been synthesized [3– 17]. Micellization of these polymers offers the opportunity to organize the nanostructure of dyes in solution. For example, through the self-assembly of a porphyrin-centered amphiphilic star poly(oxazoline) in water/DMF, Jin observed vesicular aggregates [12]. Similar morphology aggregated from monofunctionalized metalloporphyrin polystyrene was also reported by de Loss et al. [14]. Despite these interesting discoveries, the self-assembly behaviour of porphyrin poly- mers is far from being understood and further research is required. We, therefore, are interested in the synthesis of well-defined free-base porphyrin polymers for self-assembly studies in an attempt at exploring porphyrin chemistry in polymer supramolecular assemblies. Among various options, living radical polymerization, which can be carried out under mild conditions and is compatible with a wide range of monomers, represents the best choice for this study [14–17]. As a matter of fact, several groups have explored similar syntheses using nitroxide medi- ated polymerization (NMP) [15] and atom transfer radical polymerization (ATRP) [14–17]. Zimmerman reported that NMP could be used to prepare porphyrin cored star copoly- mers. However, the resulting polymers usually had broad polydispersities and multimodal molecular weight distribu- tions [15]. ATRP catalyzed by transition metals has proven to be successful in the synthesis of well-defined porphyrin poly- mers. However, its use has been limited to metal ion (Zn(II) [16], Pd(II) [17]) coordinated porphyrin initiators and thus the production of metal complexed polymers. Attempts to synthesize polymers containing free-base porphyrin using ATRP was unsuccessful, because Cu(II) (formed by the Cu(I)