Fe(III)-containing mesoporous poly-(p-phenylenediamine): Synthesis, characterization and magnetic properties Mahasweta Nandi a,b , Swapan Kumar Das a , Saurav Giri c , Asim Bhaumik a,⇑ a Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India b Integrated Science Education and Research Centre, Siksha Bhavana, Visva-Bharati, Santiniketan 731235, India c Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India article info Article history: Received 11 November 2009 Received in revised form 8 December 2010 Accepted 30 December 2010 Available online 13 January 2011 Keywords: Aqueous polymerization Fe(III)-containing polymer Magnetic material Mesoporous material Surfactant templating abstract A new mesoporous polymer constituting of Fe(III)-poly-(p-phenylenediamine) (Fe-MPPD) has been syn- thesized by using the supramolecular assembly of anionic surfactant sodium dodecylsulphate (SDS) as template under mild conditions. The polymeric framework resulted via simultaneous oxidative polymer- ization of p-phenylenediamine (PPD) and cross-linking in the presence of Fe(III) ion using water as reac- tion medium. Upon removal of template SDS molecules through solvent extraction this material has retained the 2D-hexagonal nanostructure. The presence of Fe(III) in the polymeric material has been con- firmed by atomic absorption spectroscopy (AAS, 18.3 and 10.2 wt% for two samples) and 57 Fe Mössbauer spectroscopy. The temperature dependence of zero-field cooled magnetization showed spin freezing temperature at 3.5 K, below which there is a large coercivity due to significant contribution of surface anisotropy. The porosity and the magnetic property of the material are found to be dependent on the molar ratio Fe(III):PPD and SDA content. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction Porous organic polymers [1] have huge possibilities when it can be coupled with semiconductor nanostructures [2] exploiting the void space and this can find novel applications in optoelectronics [3,4], light-harvesting [5,6] and so on. Introducing porosity in poly- meric networks containing metal atoms on the other hand can find numerous potential applications in gas storage [7–9], ion exchange [10], sensors [11], drug delivery [12], magnetic materials [13], optoelectronics [14], etc. Compared to their inorganic analog, zeo- lites [15] and related mesoporous materials [16,17], the organic building blocks in porous polymers have more versatile potential to tune the pore architecture and functionality [18]. Porous poly- mers of organic compounds e.g. polyaniline, [19] polypyrrole [20], etc. have many unique advantages, like easy to prepare, suit- able for making composites with different types of binders, envi- ronmentally stable, special chemical and physical properties. Aqueous phase oxidative polymerization of the monomers are usually carried out by using ammonium persulphate [20,21] as oxi- dizing agent. When metal salts are used as the oxidizing agents [22], metal ions may get incorporated in the polymer matrix through metal–ligand coordination, which further stabilize the nanostructure leading to metal-incorporated polymeric material having some unusual properties. Mesoporous materials with dif- ferent framework compositions [23–25] can be synthesized by using supramolecular assembly of surfactant molecules, which act as structure-directing agent (SDA) through ionic or H-bonding interaction with the framework species. SDA molecules can be re- moved from the composite mesophase through solvent extraction to generate mesoporosity in the material. Herein, we have employed the supramolecular templating chemistry of mesoporous solids to design a novel mesoporous polymeric material containing a magnetic element. We have cho- sen p-phenylenediamine (PPD) as monomer because it can poly- merize easily in the presence of an oxidant under mild acidic conditions and multiple donor sites within the poly-(p-phenylene- diamine) macromolecule [26] makes it a suitable organic node for the construction of a metal-doped porous polymeric material. An- ionic surfactant sodium dodecylsulphate (SDS) has been used here as template or SDA, which could make electrostatic interaction with protonated –NH 3 + groups of the framework during the oxida- tive polymerization of PPD [26] under mild acidic conditions. We have used ferric chloride as the oxidizing agent as well as metal ion source. Subsequent removal of the template molecule gives the mesoporous polymeric material. Surface chemical analysis of this material revealed the presence of uniformly grafted iron (III) species in the framework. The specific surface area of the material has been found to be comparable to the other mesoporous organic polymers previously reported. The existence of iron in the poly- meric framework prompted us to study its magnetic behavior un- der variable temperature. It showed a spin freezing temperature at 1387-1811/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.micromeso.2010.12.048 ⇑ Corresponding author. Tel.: +91 33 2473 4971; fax: +91 33 2473 2805. E-mail address: msab@iacs.res.in (A. Bhaumik). Microporous and Mesoporous Materials 142 (2011) 557–563 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso