In situ-polymerization of fluorinated polyoxadiazole with carbon nanotubes in poly(phosphoric acid) Marcio R. Loos, Dominique Gomes ⁎ GKSS Research Centre Geesthacht GmbH, Institute of Materials Research, Max Planck Str.1, D-21502, Geesthacht, Germany abstract article info Article history: Received 18 April 2008 Accepted 25 November 2008 Available online 3 December 2008 Keywords: Polyoxadiazole Carbon nanotubes Nanocomposites Synthesis In the present work, in-situ polymerizations of fluorinated polyoxadiazole through a polycondensation reaction of A–A (hydrazine sulphate) and B–B (aromatic dicarboxylic acid) monomers with multiwalled carbon nanotubes (MWCNT) in poly(phosphoric acid) were performed in the frame of time 3 to 48 h. The effect of acid treatment in polyphosphoric acid on the CNT structure was analyzed by SEM, TGA and FTIR. Fluorinated polyoxadiazole/MWCNTs soluble in organic solvents with high molecular weights (around 200 000 g/mol) could be synthesized in 3 h. The fluorinated polyoxadiazole/MWCNTs exhibits high thermal stability with degradation temperature at about 460 °C. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Carbon nanotubes (CNTs) have been the subject of considerable attention because of their exceptional unique electronic, physical, mechanical and optical properties [1,2]. Although the addition of CNT into polymeric materials exhibits a high potential of application in different research fields, there are still many limitations and challenges to be met such as the manufacturing route and surface properties of nanoparticles, which influence the resulting degree of dispersion and interfacial adhesion with the polymer matrix. Various physical, chemical, or combined approaches have been reported to afford homogeneous dispersion of CNTs in polymer solution or melt [1–5]. Functionalization of fillers has been shown to reduce agglom- eration and to improve the interaction between the fillers and the polymeric matrix [3,4]. Recently, Oh et al. [4] described a grafting of polyetherketone onto multi-walled carbon nanotube (MWCNT) by in-situ polycondensation of the AB monomers, 3- and 4-phenoxybenzoic acids in viscous PPA at 130 °C for 48 h. In the present work, in-situ polymerizations of fluorinated polyoxadiazole through a polycondensation reaction of A–A (hydrazine sulphate) and B–B (aromatic dicarboxylic acid) monomers with MWCNT in polyphosphoric acid were performed in the frame of time 3 to 48 h. For that, the effect of acid treatment in polyphosphoric acid on the CNT structure was analyzed. Polyoxadiazoles have a great potential as structural material because of their superior thermal, chemical and mechanical properties [6–8]. It has been shown that fluorinated polyoxadiazole/MWCNTs soluble in organic solvents with high molecular weights (around 200 000 g/mol) can be synthesized in 3 h. 2. Experimental section 2.1. Materials 4,4′-dicarboxyphenyl-hexafluoropropane, HF (99%, Aldrich), hydra- zine sulfate, HS (N 99%, Aldrich), sodium hydroxide, NaOH (99%, Vetec), poly(phosphoric acid), PPA (115% H 3 PO 4 , Aldrich), multiwalled carbon nanotubes, MWCNTs (N 95%, Bayer MaterialScience). All chemicals were used as received. 2.2. In-situ polymerization of fluorinated polyoxadiazole/carbon nanotube composites Initially polyphosphoric acid, PPA, was added to the flask and heated up to 60 °C under dry nitrogen atmosphere. Then, 1 wt.% multiwalled carbon nanotube, MWCNT, was added to the polyphosphoric acid and homogenized through stirring and heating up to 160 °C. After 0.5–48 h for CNT functionalization, hydrazine sulfate salt, HS, was added to this mixture. After dissolving the HS, 4,4′-dicarboxyphenyl-hexafluoropro- pane, HF, was added to the flask. The molar dilution rate (PPA/HS) and the molar monomer rate (HS/HF) were kept constant and equal to 10 and 1.2, respectively. After reacting the mixture for 3–48 h, the reaction medium was poured into water containing 5% w/v of sodium hydroxide, for precipitation of the polymer composite. The pH of this suspension was controlled according to literature [9]. Composite polyoxadiazoles soluble in the solvents NMP, DMAc, DMSO, THF and chloroform were obtained (Yield: 97–99%). (C 16.9 H 8 N 2 O 1 F 6 ) (367): Calcd. N/C 0.137; FoundN/C 0.130. Materials Letters 63 (2009) 694–696 ⁎ Corresponding author. Tel.: +49 4152 871974; fax: +49 4152 871909. E-mail addresses: dominique.gomes@gkss.de, mdmdefigueiredogomes@gmx.de (D. Gomes). 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.11.042 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet