Oxidative fabrication of spherical polycarbazole-based microparticles Maria Naddaka, Ejabul Mondal, Jean-Paul Lellouche ⁎ Department of Chemistry, Nanomaterials Research Center, Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900, Israel abstract article info Article history: Received 7 September 2010 Accepted 14 January 2011 Available online 1 February 2011 Keywords: Functional organic polymers Microparticles Polycarbazoles Oxidative liquid polymerization A straightforward oxidative liquid phase polymerization (LPP) method has been successfully developed for the fabrication of spherical functional (polyCOOH) polycarbazole-based microparticles from corresponding carbazole-containing monomers. The influence of the chemical structure of starting carbazole monomers on the LPP-based microparticle formation has been deeply examined using scanning electron microscopy (SEM). © 2011 Elsevier B.V. All rights reserved. 1. Introduction The straightforward fabrication of polymeric nano and microparti- cles (NPs & MPs) is a constant subject of major scientific interest. The availability of a wide range of polymerization methods, of monomeric source materials, and of tunable NP/MP surface functionalities makes these particles attractive for numerous applications [1]. However, when dealing with conducting polymers (CPs) for which the preparation of polyaniline (PANI)-, polypyrrole (polyPyr)-, and polythiophene (polyTh)-based particles is well documented [1,2], polycarbazole (polyCbz) -based [3–6] ones are by far less studied. This phenomenon is likely due to a difficult synthetic access to corresponding Cbz- monomers. A 2nd reason is that such Cbz-monomers possess higher oxidation potentials causing increasingly difficult or even ineffective oxidative electrochemical/chemical polymerizations. In such a context, isolated literature data described the fabrication of thin polyCbz-films and composite blends only [3–6]. Herein, we describe the oxidative liquid phase polymerization (LPP) and characterization of spherical polyCbz MPs using specifically designed oxidizable Cbz-monomers of type 1-6 and 8-9 (Fig. 1A). To the best of our knowledge, the work developed below is the first report that deals with the fabrication of polyCbz –based MPs using oxidative polymerization. 2. Experimental 2.1. Synthesis of the Cbz-based monomers 1-9 The preparation of the whole set of Cbz-based monomers (Fig. 1A) involved a modified Clauson-Kass [7] reaction for heterocyclic Cbz- based systems that has been developed in our laboratory [8,9]. That one-step reaction transforms the free amine (-NH 2 ) group of appropriate amino-acids/amino-acid derivatives into the requested Cbz-heterocycle using 2,5-dimethoxy-tetrahydrofurane in mixtures of 1,4-dioxane/AcOH/12M HCl at reflux for 1-4h [8,9]. In this way, Cbz-monomers 1-3 as well as the intermediate ω-NH 2 Cbz-methyl ester 7, have been synthesized in a 20-32% yield range (monomer syntheses and characterizations, Supporting Information (SI), 2S-9S). Coupling of this same key intermediate 7 in parallel with (i) three corresponding monoacyl chlorides (PhCOCl, MeCOCl, Br(1,4)- PhCOCl), and with (ii) both iso- and terephthaloyl dichlorides (CHCl 3 /TEA, 20 °C, 2 h) followed by saponification (KOH, MeOH/ PhMe, 60-80 °C, 1-2 h) readily afforded the mono- and diacidic Cbz- monomers 4-6 (SI, 2S-9S) and ortho-8/para-9 [9], respectively (12-15 & 15-21% global yields respectively). All these Cbz-monomers including the synthetic intermediate 7 have been fully characterized using a combination of FT-IR spectroscopy, 1 H/ 13 C-NMR, and mass spectrometry (SI, 2S-9S). 2.2. Preparation of polyCbz-based MPs using an oxidative LPP method In a typical optimized LLP procedure, the monoacidic Cbz- monomer 1 (0.112 g, 0.25 mmol) was vortexed in 2.5 mL of CH 3- COCH 3 for dissolution (~ 1 min). Bi-distilled water (2.5 mL) was added to the monomer solution followed by solid APS (0.285 g, 1.25 mmol, 1 min-long vortexing, room temperature). Then, the reaction mixture was stirred for 15 min at 15 °C, and centrifuged (10,000 rpm, 10 min, 4 °C). The resulting brown-colored precipitate was washed with a 1/1 v/v CH 3 COCH 3 /H 2 O mixture (3 × 10 mL, sequential vortexing-redis- persion followed by centrifugation) in order to eliminate any excess of monomer/reagents. Finally, the obtained polymeric dark precipitate was dispersed in CH 3 COCH 3 (5.0 mL) for poly(1)-MP sampling and analysis (SEM, HR-SEM). The rest of the same acetone-dispersed Materials Letters 65 (2011) 1165–1167 ⁎ Corresponding author. Tel.: +972 3 531 83 24; fax: +972 3 738 40 53. E-mail address: lellouj@biu.ac.il (J.-P. Lellouche). 0167-577X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2011.01.028 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet