Influence of amine groups in the chemical structure of photochromic dyes on the rheological and mechanical properties of poly(methyl methacrylate) (PMMA) Jos  e Kaio Max Alves do R ^ ego a, * , Jos  e Heriberto Oliveira do Nascimento b , Pankaj Agrawal c , Tom  as Jeferson Alves M  elo c , Maria Carolina Burgos Costa d , Edson Noriyuki Ito d a Postgraduate Program in Materials Science and Engineering, Federal University of Rio Grande do Norte e UFRN, Natal, 59078-970, RN, Brazil b Department of Textile Engineering, Federal University of Rio Grande do Norte e UFRN, Natal, 59078-970, RN, Brazil c Department of Materials Engineering, Federal University of Campina Grande e UFCG, 58429-900, Campina Grande, PB, Brazil d Department of Materials Engineering, Federal University of Rio Grande do Norte e UFRN, Natal, 59078-970, RN, Brazil article info Article history: Received 5 August 2016 Received in revised form 30 January 2017 Accepted 2 March 2017 Available online 30 March 2017 Keywords: PMMA Amine Azo dye Anthraquinone Reactivity abstract Polymer modification has been used as a means to improve the adhesion/bonding of compounds and/or particles to polymer chains, but this goal is not always achieved. Some compounds contain naturally reactive groups which, in contact with the polymer, can modify its properties. This work focused on the rheological (torque and parallel plates rheometry) and mechanical (tensile and impact) characterization of PMMA containing the DV31, DBL3 and DB79 aminic dyes and the DR73 inert dye. The rheological results indicated that the final torque (torque rheometry) varied in response to increasing dye concen- trations, and that the various dyes under study exhibited distinct behaviors (parallel plates rheometry). The mechanical tests revealed that, overall, the effect of the dyes on the properties of PMMA was negligible, except for DV31, that led to the decrease in the impact strength, possibly due to the bond between chains or segments of chains of the polymer. The presence, amount and type of amine in the dyes gave rise to significant rheological changes in PMMA because of the reactivity between the amine and the ether group of PMMA. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction From a commercial point of view, poly(methyl methacrylate) (PMMA) is the most important polymer among a variety of acrylics whose structures derive from acrylic acid [1]. The commercial use of PMMA is due in large part to the monomer production process from acetone developed by Crawford, which has allowed this polymer to be produced at competitive prices [2,3]. PMMA can be mixed with various additives, the most important of which are dyes and pigments, which must remain stable under both processing and service conditions. Two particular re- quirements are that they must not impair the polymerization re- action and/or the integrity of the polymeric chain when they undergo thermal processing (casting, extrusion mixing and/or in- jection molding), and that they must show good resistance during the molding cycle and to inclement weather conditions in which they are to be used [1]. Amine compounds, which are typically used for purposes of modification [4e6], tend to react with PMMA, forming bridge bonds between the polymer and the compounds it contains. Amines are typically basic organic compounds that react with various functional groups, among them the ketone groups, which include PMMA [4]. These reactions increase the basicity of these compounds, as illustrated in Fig. 1 [7e9]. More recently, the modification of polymers and compounds has been used as a method to establish or improve compatibility and/or reactivity between the polymer matrix and the fillers or compounds dispersed in it [10,11]. This enables changes to be made in dielectric [12] electrical and optical [13] properties, absorption of electromagnetic radiation [14], chemical bonding of polymer to metallic nanoparticles [4], compatibilization of polymer blends [6], * Corresponding author. E-mail addresses: kaiomax2000@gmail.com (J.K.M.A. R^ ego), ito@ufrnet.br (E.N. Ito). Contents lists available at ScienceDirect Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig http://dx.doi.org/10.1016/j.dyepig.2017.03.060 0143-7208/© 2017 Elsevier Ltd. All rights reserved. Dyes and Pigments 142 (2017) 350e357