Synthetic Metals 160 (2010) 2397–2403 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Structural characterization of poly-para-phenylenediamine–montmorillonite clay nanocomposites Gustavo M. do Nascimento ∗ , Ricardo H. Sestrem, Marcia L.A. Temperini Departamento de Química Fundamental, Instituto de Química, Universidade de SãoPaulo, CP 26.077, CEP 05513-970, São Paulo, SP, Brazil article info Article history: Received 4 June 2010 Received in revised form 8 September 2010 Accepted 16 September 2010 Available online 14 October 2010 Keywords: Polyaniline Raman spectroscopy Nanocomposites para-Phenylenediamine abstract The structure of the poly-(para-phenylenediamine) (PpPD) formed by oxidative polymerization of 1,4- phenylenediamine (p-PD) into the galleries of the Montmorillonite (MMT) clay was determined by different spectroscopic techniques. According to X-ray diffraction (XRD) pattern the polymer is formed between the clay layers. In addition, the composite morphology, visualized by electron microscopy (SEM), is similar to the pristine clay. The UV–vis–NIR data of PpPD–MMT sample shows strong absorption bands at 620 and 670 nm, being related to groups with protonated phenazine-like rings. The resonance Raman spectrum of PpPD–MMT displays bands at 1179, 1201, 1347, 1412, and 1630 cm -1 , which are related to phenazine-like rings modes. X-ray absorption (XANES) at Nitrogen K edge of PpPD–MMT confirms the presence of azo, hydrazo and phenazinic nitrogens. The intercalated material is EPR silent, confirming that the charge carriers, responsible for the conductivity of ca. 10 -4 S cm -1 , have diamagnetic behavior. Hence, the results confirm that when aniline or its derivates are polymerized in confined environments, it causes preferentially the formation of diamagnetic segments having protonated phenazine and azo segments. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The intrinsically conducting polymers (ICPs), more commonly known as “synthetic metals”, form one of the largest classes of molecular conductors [1,2]. The development of the conducting polymer field has continued to accelerate at an unexpectedly rapid rate. This development has been stimulated not only by the funda- mental synthetic novelty and importance but also mainly because this field is a cross-disciplinary section of many areas [1]. More recently, the interest of conducting polymer derivates from aro- matic diamines has increased [3]. These polymers can show more multifunctionality and better mechanical and thermal properties than poly(aniline) (PANI) [3]. Among the great diversity of diamines that are suitable to the oxidative polymerization, the phenylenedi- amines (PDs) are the most employed [4–11]. In the literature, it has been suggested that the poly-ortho-phenylenediamine, poly-para- phenylenediamine and poly-meta-phenylenediamine have ladder structure with fenazine units [4–8], when the polymers are syn- thesized in acid aqueous media by oxidation with ammonium persulfate. ∗ Corresponding author. Present address: Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 6627, CEP 31270-901, Belo Horizonte, BH, Brazil. Tel.: +55 1156712419; fax: +55 1156712419. E-mail addresses: morari@yahoo.com, gustavo.morari@gmail.com (G.M. do Nascimento). Resonance Raman (RR) scattering has been employed as main tool in the elucidation of polymeric structure derivates from different aromatic amines [12–16]. Our interest is to carry out the vibrational and electronic characterization of conducting polymers, in order to give subsidies for the understanding the structure–property relationships in these materials. Recently, the use of the RR spectroscopy was essential in the elucidation of the chromophoric segments present in the oligomers and poly- mer derivates from ortho-phenylenediamine [12]. It was proposed that poly-ortho-phenylenediamine (PoPD) is formed by phenazine- like rings having different protonation and oxidation levels, but the polymeric backbone also presents some segments with struc- ture similar to that of quinoid rings of PANI (see Scheme 1). On the contrary, the structure of chemically prepared poly-para- phenylenediamine (PpPD) is PANI-like (see Scheme 1), being formed by dication units, similar to polyaniline in its pernigrani- line base form and radical cations, similar to the polyaniline in its emeraldine salt form [13]. Nowadays, nanocomposites between conducting polymers and inorganic layered materials have been extensively prepared in order to improve the polymer bulk properties [17,18]. Among the different types of layered hosts, smectite clays have received great attention. Clay minerals such as montmorillonite (MMT) are layered silicates, able to exchange cationic ions and intercalate neutral molecular species between the interlayer regions. Layered silicates like MMT clay have layer thickness of about 10 ˚ A. These negative charged layers are stacked face to face forming crystallites known as tactoids. 0379-6779/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2010.09.016