t Butyl pyrene containing poly(arylene ethynylene)s for highly sensitive and selective sensing of TNT Siddheshwar B. Jagtap a , Darshna D. Potphode a , Tanaji K. Ghorpade a , Akshaya K. Palai b , Manoranjan Patri a , Sarada P. Mishra a, * a Polymer Science and Technology Centre, Naval Materials Research Laboratory (DRDO), Shill-Badlapur Road, Anand Nagar P.O., Ambernath (E) 421506, Maharastra, India b Department of Chemical Sciences, Tata Institute of Fundamental Research, Colaba, Homi Bhabha Road, Mumbai 400005, India article info Article history: Received 21 January 2014 Received in revised form 7 April 2014 Accepted 15 April 2014 Available online xxx Keywords: Sensor Nitroaromatics Fluorescence abstract A series of poly(arylene ethynylene)s (PAEs) containing t butyl pyrene in the main chain were synthesized for nitroaromatic sensors. As control, similar polymers containing unsubstituted pyrene were also syn- thesized. The sensory properties of the polymers were studied towards various nitroaromatic com- pounds like trinitrotoluene (TNT), dinitrotoluene (DNT), nitrotoluene (NT), nitrobenzene (NB) and picric acid (PA) in solution as well as vapor state. Interestingly, all the t butyl substituted pyrene containing polymers showed higher sensitivity than the corresponding unsubstituted pyrene containing polymers. Moreover, the polymers showed high sensitivity towards TNT as compared to the other nitroaromatic compounds. The sensitivity of one of the polymer PB was found several folds higher than that of the similar reported polymer containing unsubstituted pyrene ring. In addition, t butyl pyrene containing polymers were found to have improved molecular weight, thermal stability, fluorescence quantum yield, film forming properties and solubility in common organic solvents as compared to the control polymers. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Selective detection of nitroaromatic compounds used in various explosive devices becomes the areas of interest due to the security concern worldwide. [1] Currently, the methods used for the detection of nitroaromatic compounds are surface enhance Raman spectroscopy, gas chromatography, amperometry, energy disper- sive X-ray analysis and fluorescence spectrometry [2]. Amongst, fluorescence detection method became very popular as it can provide an affordable process suitable for a real time explosive sensor [3]. In this regard, there are number of reports on small molecules as well as polymers used as fluorescence chemo-sensors both in so- lution as well as solid state [4]. However, as compared to the small molecular sensors, research on polymeric counterpart becoming more focused because of it improved sensitivity by ‘molecular wire effect’ or ‘super quenching effect’ [5]. In fluorescence based sensor, facile energy migration process in conjugated polymers is used to amplify the signals [6]. The general design of these kind of polymers is consist of electron rich aromatic systems and fluorescent polynuclear aromatic hydrocarbon linked through ethynylene bridge. Among the p conjugated polymers, those containing polyaromatic hydrocarbons like fluorene, anthracene, perylene, pyrene, carbazole etc. linked specifically with an acetylene linkage are more attractive because of flat p-stacking organization in the solid state [7]. Although greater tendency of migration in solid leads to better sensory activity, that also coun- tered by a decreased fluorescence quantum yield. Therefore, a sensory material having high fluorescence quantum yield without compromising the p-stacking is always desirable. Pyrene based functional materials have been explored exten- sively almost every field of electronics [8]. Because of its promising optical and electrochemical properties like high absorption coeffi- cient, high quantum yield and stability with respect to heat and oxidation they have been used in the field of organic light emitting diode [9], organic photo voltaics [10], organic thin film transistors [11] and organic sensors [12]. Another advantage of pyrene is the facile selective substitution at different positions by which a library of materials (e.g. mono, di and poly substituted pyrenes) can be generated [8,13]. * Corresponding author. E-mail addresses: sarada.nmrl@yahoo.com, bunu_2001@yahoo.com (S. P. Mishra). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer http://dx.doi.org/10.1016/j.polymer.2014.04.028 0032-3861/Ó 2014 Elsevier Ltd. All rights reserved. Polymer xxx (2014) 1e7 Please cite this article in press as: Jagtap SB, et al., t Butyl pyrene containing poly(arylene ethynylene)s for highly sensitive and selective sensing of TNT, Polymer (2014), http://dx.doi.org/10.1016/j.polymer.2014.04.028