Thermal decomposition of polystyrene-b-poly(2-vinylpyridine) coordinated to co nanoparticles Ays ¸ egu ¨ l Elmaci a , Jale Hacaloglu a, * , Ceyhan Kayran a , Georgios Sakellariou b , Nikos Hadjichristidis b a Chemistry Department, Middle East Technical University, Ankara 06531, Turkey b Chemistry Department, University of Athens, Athens 15771, Greece article info Article history: Received 11 March 2009 Received in revised form 9 July 2009 Accepted 17 July 2009 Available online 3 August 2009 Keywords: Metal nanoparticles coordinated to block polymers Metal polystyrene-b-poly(2-vinylpyridine) Thermal degradation Pyrolysis mass spectrometry abstract Direct pyrolysis mass spectrometry analyses of polystyrene-block-poly(2-vinylpyridne), PS-b-P2VP, indicated that the thermal degradation of each component occurred independently through the decomposition pathways proposed for the corresponding homopolymers; depolymerization for PS and depolymerization and loss of protonated oligomers for P2VP by a more complex degradation mechanism. On the other hand, upon coordination to cobalt nanoparticles, thermal decomposition of the P2VP blocks was initiated by loss of pyridine units, leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction During the last decades, the incorporation of nanomaterials with block polymers has been the subject of many studies because of the potential applications in optics, catalysis, biosensors, microelectronics and magnetic data storage [1–9]. As a conse- quence of the strong affinity of amines to various ions and polar groups, polymers containing a pyridine moiety can make strong bonds with various metal ions or nanoparticles and have attracted increasing attention. PS-b-P2VP copolymer has been extensively studied and has also been used in nanoparticle assembly into block copolymers. Enhancement of thermal stability of the polymer is expected as a result of metal and/or metal ion coordination [10–15]. Khairou investigated the thermal stability of poly(4-vinylpyridine) and its complex with transition metal chlorides and found that the degradation products mainly consist of 4-vinylpyridine monomer and traces of pyridine [11]. Lyons and co-workers studied the thermal degradation characteristics of poly(2-vinylpyridine) (P2VP) and its complexes with copper chloride via TGA and GC–MS and proposed changes in the thermal degradation mechanism of P2VP [12], but they were unable to propose related thermal degradation mechanisms. In the case of pyrolysis GC–MS analysis, since thermal decomposition occurs in a closed container/system, secondary reactions cannot be avoided and only low molecular weight volatile species can be detected. Thus, in most cases, with the use of pyrolysis GC–MS data, the investigation of the thermal decomposition mechanism is almost impossible [16]. In the present study we applied direct pyrolysis mass spec- trometry to investigate the thermal degradation behaviour of polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, and PS-b- P2VP coordinated to cobalt nanoparticles in order to elucidate the effect of metal coordination on thermal characteristics by direct pyrolysis mass spectrometry to investigate the changes in thermal behaviour. 2. Experimental 2.1. Materials and synthesis The block copolymers PS-b-P2VP, were synthesized by sequen- tial polymerization of the corresponding monomers by anionic polymerization using high vacuum techniques [17]. After the complete polymerization of styrene in tetrahydrofuran at 78  C with n-BuLi as initiator, 2-vinylpyridine was distilled into the reactor and the polymerization was allowed to proceed for 1 h before being terminated with degassed methanol. The block copolymers were recovered by precipitation in methanol. The molecular * Corresponding author. Tel.: þ90 312 210 5148; fax: þ90 312 210 3200. E-mail address: jale@metu.edu.tr (J. Hacaloglu). Contents lists available at ScienceDirect Polymer Degradation and Stability journal homepage: www.elsevier.com/locate/polydegstab 0141-3910/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymdegradstab.2009.07.026 Polymer Degradation and Stability 94 (2009) 2023–2027