Syntheses, Characterization, Optical Properties, and Charge-Transfer Complexation Study of Fluorescent Poly(aryl-ether-urea) Dendrimers MAHALINGAM VANJINATHAN, A. SULTAN NASAR Department of Polymer Science, University of Madras, Guindy Campus, Chennai 600025, India Received 15 March 2007; accepted 23 September 2007 DOI: 10.1002/pola.22419 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: An inexpensive and highly efficient synthesis of first example of fluorescent aromatic dendrimers having alternative ether and urea linkages without the need for protection and deprotection steps has been developed. Dendrons and dendrimers up to third generation, with amine end-groups, were prepared by convergent growth ap- proach in high yield. A repetitive synthetic sequence of nucleophilic addition reaction between amine and regenerated isocyanate and reduction of nitro groups into amine are adopted for the synthesis of these dendrimers. The peripheries of the dendrimers contained 6, 12, and 24 amino groups, for the first, second, and third generation, respec- tively. Materials were characterized by FTIR, NMR, and MALDI-TOF MS spectrometry. These dendrimers were soluble in amide solvents, THF and acetone and displayed fluorescence maxima in the 440–500 nm range with relatively narrow peak widths indi- cating that they had pure and intense fluorescence. These dendrimers form charge- transfer (CT) complexes with electron acceptor molecules such as 7,7,8,8,-tetracyano- quino-dimethane and 1,1,2,2 tetracyanoethane as evidenced by UV-visible absorption spectra. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 713–724, 2008 Keywords: charge transfer; dendrimers; fluorescence INTRODUCTION Dendrimers are mono disperse and perfectly branched macromolecules that find increasing interest because of their predetermined struc- ture at the nanoscale region and the resulting unique properties. 1 Generally, dendrimers are synthesized by the divergent or convergent syn- thetic methods. Thus, synthetic methods inevita- bly require repeated protection and deprotection steps for the synthesis of subsequent generation dendron. 2 Recently, high-performance dendritic polymers such as aromatic polyamides and poly (aryl-ethers) have been developed by several research groups. 3 For the synthesis of dendritic polyamides, the double stage convergent ap- proach, the orthogonal monomer approach and the unprotected AB 2 -monomer approach have been successfully exploited. 4 Two types of den- drimers were reported as light emitting materi- als; 5 one with conjugated skeleton and the other with embedded chromophores in the dendritic architectures. Highly branched and globular fea- tures improve the light emitting efficiency and also make the dendrimers to form good quality amorphous film. 6 Very few examples of ideal branching in poly- urethanes have been reported. Spindler and Frechet 7 were the first to demonstrate the Correspondence to: A. S. Nasar (E-mail: drasultannasar@ yahoo.com) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 46, 713–724 (2008) V V C 2007 Wiley Periodicals, Inc. 713