MONITORING THE EFFECT OF FILLER IN ELASTOMERIC MATERIALS BY TIME DOMAIN NMR SPECTROSCOPY

In the last decades, many eorts have been dedicated to the improvement of the mechanical properties of elastomeric composite materials, as they are particularly attractive for several industrial applications. As a matter of fact, these properties are mainly related to the motional constraints of the polymer network, which are due to physical entanglements and chemical cross-linking between polymer chains, and may be in uenced by the presence of dierent additives and reinforcement llers (carbon black, nanosilica, clays) [1,2]. Usually, the mechanical properties of the materials are monitored by rheological measurements, which provide only macroscopic observables; however, also a description of the topology and dynamics of the polymer network at the molecular scale is needed in order to have a more complete comprehension of the factors that in uence these properties, with the nal aim to guide the design of optimized materials. In this context, low eld 1H time domain NMR (TD-NMR) can give an important contribution [3]. In this work, we studied dierent elastomeric materials with application in the tyre industry, by TD-NMR spectroscopy, with the aim of investigating the eect of ller particles on polymer structure and dynamics. 1H Multiple Quantum (MQ) experiments [4] were used to evaluate the residual 1H-1H dipolar couplings, which arise from the fast anisotropic motion of the polymer chains and are thus directly related to the amount of topological constraints within the polymer network. Moreover, 1H relaxation times (T1, T2) [5,6] were measured to probe a wide range of motional frequencies of the polymer chains. In particular, 1H spin-lattice relaxation times (T1) were evaluated by means of Fast Field Cycling [6] experiments at dierent temperatures, covering Larmor frequencies from 10 kHz to 35 MHz. References: [1] R. Scotti, M. D'Arienzo, B. Di Credico, L. Giannini and F. Morazzoni, in Hybrid Org. Interfaces, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 151-198, (2017). [2] G. Kraus Angew. Makromol. Chemie 60, 215-248, (1977). [3] S. Borsacchi, U. Sudhakaran, L. Calucci, F. Martini, E. Carignani, M. Messori and M. Geppi Polymers (Basel) 10, 822, (2018). [4] K. Saalw?achter Prog. Nucl. Mag. Res. Sp. 51, 1-35, (2007). [5] A. Maus, C. Hertlein and K. Saalw?achter Macromol. Chem. Phys. 207, 1150-1158k, (2006). [6] R. Kimmich, Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications, Royal Society of Chemistry, Cambridge, (2018).