The grafting of luminescent side groups onto poly(vinyl chloride) and the identification of local structural features Nuria Garcı ´a a , Mario Hoyos a , Gilbert Teyssedre b , Rodrigo Navarro a , Helmut Reinecke a , Pilar Tiemblo a, * a Instituto de Ciencia y Tecnologı ´a de Polı ´meros, Consejo Superior de Investigaciones Cientı ´ficas (CSIC), Juan de la Cierva 3, 28006 Madrid, Spain b Laboratoire de Ge ´nie Electrique, Universite ´ Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France Received 30 November 2006; received in revised form 15 January 2007; accepted 15 January 2007 Available online 11 August 2007 Abstract The phosphorescence and fluorescence emitted by both the chromophores existing in raw PVC (allylic and ketoallylic structures and poly- enes) and luminescent probes introduced by substitution of chlorine atoms have been used to study local features of the chain microstructure, namely the formation of blocky sequences during the nucleophilic substitution of chlorine atoms and the length and nature of the chain segments relaxing below T g , i.e., the b relaxation. The comparison with results obtained by dynamic mechanical analysis of some of the copolymers has been carried out. Blocky sequences are found to exist and all isotactic sequences over a diad together with their heterotactic associated triads are found to participate in the b motions. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: PVC; Beta relaxation; Tacticity; Luminescence; Phosphorescence decay 1. Introduction In preceding work, the possibility of using grafted aromatic groups as luminescent probes for the study of local features in poly(vinyl chloride) was studied [1,2]. PVC was chosen because the nucleophilic substitution of chlorine atoms allows the introduction of grafted groups in a very controlled manner when appropriate reaction conditions are used [3,4]. The dependence of microstructure, chemical composition distribu- tion and stereoregularity on modification with nucleophiles is well-known and the resulting copolymers have been exhaus- tively studied. This is absolutely necessary as the grafted probe alters the local structure of the polymer, this being a possible drawback and one of the main differences with methods which do not require the introduction of a probe. In addition to studying the local motions of PVC by intro- ducing luminescent chemical groups, other interesting local features can be investigated by means of the luminescent decay. For instance, it is possible to analyse the local structure of PVC by means of its own (scarce) chromophores and to study the products of modification reactions, especially at very low modification degrees, via the study of the light emit- ted by the grafted groups. As regards the first, PVC, like most polymers, contains de- fective structures [5], which in many cases are phosphorescent and fluorescent: ketoallylic chlorines [6], allylic chlorines [7], polyene sequences [8,9] and a,b-unsaturated ketones. Allylic chlorine in PVC may occur at chain ends as a result of dispro- portionation or transfer to monomer, or also in the chains as a result of random dehydrochlorination or of copolymerization with acetylenic impurities in the monomer [7]. All of these species are to some extent labile structures which promote the zipping degradation of the polymer, resulting in polyene * Corresponding author. Tel.: þ34 9 1 5622900; fax: þ34 9 1 5644853. E-mail address: ptiemblo@ictp.csic.es (P. Tiemblo). 0141-3910/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymdegradstab.2007.01.033 Available online at www.sciencedirect.com Polymer Degradation and Stability 92 (2007) 2300e2307 www.elsevier.com/locate/polydegstab