## 3 Results and Discussion  
### Functionalization of HSAG with Serinol Pyrrole via the Pyrrole Methodology  
Functionalization of HSAG was performed with SP, applying a method already described in previous publications [26], also named \"pyrrole methodology\", which is also shown, for the sake of clarity, in Figure 2 and is described in detail in the Section 2.  
In brief, SP was obtained by mixing and heating serinol and the diketone. Functionalization was then performed by simply adsorbing the pyrrole compound on the surface of the sp\({}^{2}\) carbon allotrope and then heating at 180 \({}^{\circ}\)C under air flux for 2 h. In this work, the functionalization reaction was performed by using a theoretical HSAG/SP mass ratio of 10:1. This functionalization method, from the synthesis of SP to the preparation of the HSAG/SP adduct, was characterized by a high atom economy, the only co-product being water. To check the efficiency of the functionalization reaction, thermogravimetric analysis (TGA) was employed, as described in the Section 2. Organic mass losses of the HSAG-SP  
Figure 1: **(a)** Sketch of shear sandwich configuration adopted in dynamic-mechanical tests; clamps are grey, rubber specimens are black colored; **(b)** geometry and nominal dimensions of a rubber sample for DMA tests; **(c)** loading configurations of DMA tests: rubber plate (grey broken line), specimens (full grey parallelepipeds), shear strains applied (arrows) and deformed shapes (black broken lines) are displayed.  
Figure 2: Scheme of the domino reaction for the functionalization of HSAG with serinol pyrrole [26].  
adduct before and after an exhaustive acetone washing were compared. Curves are shown in Figure 3. Mass losses are in Table 2.  
The mass losses detected below 150 \({}^{\circ}\)C, for both HSAG and HSAG-SP, were attributed to absorbed water or solvent. Mass losses detected between 150 \({}^{\circ}\)C and 700 \({}^{\circ}\)C for pristine HSAG were due to alkenylic defects present on the surface of the carbonaceous filler. Mass losses in the range 150-700 \({}^{\circ}\)C for the HSAG-SP adduct were attributed to the presence of SP [20]. As shown by the data in Table 2, organic mass losses remained appreciable after an exhaustive acetone extraction of the HSAG-SP adduct, thus giving evidence for the formation of a stable adduct. The functionalization yield was estimated according to Equation (1) reported in the Section 2. A high functionalization yield was achieved: 97.7%. It can be thus commented that the functionalization of HSAG with SP occurred with high atom efficiency [33]. The amount of SP in the adduct was calculated to be 8.7 parts per hundred parts of carbon. In the laboratory procedure, a solvent (acetone) was used to promote the dispersion of the reagents, but different methods, such as a spray dry, can be applied at a pre-industrial scale, thus avoiding the use (and the need of recycling) organic substances.  
The infrared characterization of the HSAG-SP adduct has been discussed elsewhere [23]. The expected spectral features of serinol pyrrole were identified for the HSAG-SP sample used in this work.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & & & & \\ \hline
**Temperature** & & & & & \\
**Range** & & & & & \\ \hline HSAG & (a) & 0.4 & 1.5 & 3.5 & 91.1 \\  & (c) & 0.0 & 0.1 & 0.4 & 99.5 \\ \hline HSAG-SP & (b) & 0.3 & 5.7 & 3 & 91.6 \\  & (c) & 0.4 & 5.4 & 3.1 & 91.1 \\ \hline \hline \end{tabular} (a) pristine, (b) after the functionalization reaction, and (c) after washing with acetone (see Section 2).  
\end{table}
Table 2: Mass losses for pristine HSAG and HSAG-SP adduct, determined via TGA.  
Figure 3: Thermogravimetric analysis of pristine HSAG (blue line), and HSAG-SP after acetone extraction (red line).