## 1 Introduction  
Poly(1,4-cis_-isoprene) from _Heeva Brasiliensis_, known as natural rubber (NR) [1, 2], is the most important rubber, with a worldwide production of almost 14 million tons in 2018; it represents about 40% of the total rubber consumption [3; 4]. Such a great success is based on the outstanding properties of NR: tack [5; 6] and strength [7] in the uncured state and, upon vulcanizing, tensile strength [8; 9] and resistance to fatigue and crack growth [10; 11; 12; 13]. In particular, the latter properties are due to a peculiar property of NR, strain induced crystallization [14; 15; 16; 17]. Indeed, NR is the selected rubber for demanding applications, for instance those in tire compounds (for cars, heavy trucks, and airplanes), anti-seismic base isolators, and anti-vibrating mounting pads. Moreover, NR is produced with a far lower energy input with respect to synthetic rubber: 15-16 MJ/kg versus a typical value of 100 MJ/kg [4]. It is also worth mentioning the efficient carbon sequestration performed by the _Hevea_ tree: the photosynthetic rate of _Hevea_ leaves is of about 11 umol/m\({}^{2}\)-s versus a value of 5-13 umol/m\({}^{2}\)-s in other trees [18]. Thus, the large amount of research performed on NR and NR-based composites can be easily understood. In spite of its remarkable properties, NR is unable to meet the requirements of the above-mentioned applications. Better mechanical properties are required and achieved with the addition of reinforcing fillers [19; 20]. Carbon black (CB) has been used for over a century [21]. After the discovery of fullerenes [22], an impressive amount of nanosized sp\({}^{2}\) carbon allotropes has been prepared: single [23; 24] or multi-walled [25; 26] carbon nanotubes, graphene [27; 28; 29; 30], and graphene-related materials [31; 32; 33; 34]. Graphene is of particular interest because of its outstanding properties: an elastic modulus larger than 1 TPa, exceptional thermal and electrical conductivity [35; 36]. Papers and reviews on rubber composites with graphene and related materials (GRM), mainly dedicated to isoprene rubber, are available in the scientific literature [37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58]. The basic objective of the reported researches is to obtain an ultimate distribution and dispersion of the graphene layers. Indeed, it is widely acknowledged that, by increasing filler distribution and dispersion, superior mechanical and ultimate properties and abrasion resistance can be achieved [59]. Moreover, the amount of filler can be reduced, thus preparing lighter materials. In the field of rubber composites, the filler dispersion can be improved by applying mechanical energy. However, such an approach can alter the structure of the rubber and even of the filler. Melt blending is used to promote the dispersion of nanographite, even with a very high surface area [39; 44; 50]. The solution mixing has been documented [58], but this approach is troublesome, particularly in view of an industrial scale up. The favored technology reported in the literature is the dispersion of graphene layers in latexes of NR [37; 38; 41; 45; 46; 48; 50; 51; 52; 55] or of poly(styrene-_co_-butadiene) (SBR) [40], combined with the rational design of the surface chemistry of the filler [40]. In fact, to prepare latex dispersions, polar graphitic materials, in most cases graphene/graphite oxide (GO), are used [23; 24; 25; 26; 37; 38; 40; 41; 44; 45; 46; 48]. GO, which is typically prepared by means of the Hummers and Offeman method [60; 61; 62; 63] is then reduced, typically with chemical methods [64; 65; 66]. In such an oxidation-reduction method, the main disadvantage is the use of dangerous and even toxic chemicals (such as potassium permanganate, sulphuric acid, hydrazine), and harsh reaction conditions. Moreover, it is acknowledged that the bulk graphene structure is only partially restored: an appreciable amount of sp\({}^{3}\) defects is present in the final product.