ON THE COMBINATION OF GRAPHITE NANOPLATELETS WITH PCL

The issue to improve the properties and to expand the application fields of biopolymers, such as poly(ε-caprolactone) (PCL), which is the object of the present work, represents a significant challenge of the Circular Economy. Indeed, the combination of graphene-related materials (GRM), such as graphite nanoplatelets (GNP), with biopolymers represents an appealing and effective approach to enlarge the exploitation of such systems. In particular, from one hand, the addition of the above nanofillers could potentially improve the features of the polymer matrix and disclose novel properties and from the other, the low environmental impact of both the components make the resulting composite/nanocomposites “green”. For the development of these systems, GRM dispersion represent a key issue, as it is necessary to reach a fine distribution to transfer the properties of the nanofiller to the polymer matrix. As such, in order to promote specific interactions of the nanofiller with the polymer, graphene oxide can be used. While the oxidation of graphite and possible subsequent organic functionalization may allow better interactions with the polymer matrix, enabling the easier nanofiller dispersion, the chemical modification of GRM introduces disruptions of the sp2 structure, thus affecting their physical properties, particularly in terms of electrical and thermal conductivity. An alternative approach to guarantee for strong interactions between non functionalized GRM consists in the modification of the chemical structure of the macromolecules to promote non-covalent bonding with graphitic surfaces. With this mind and taking into account the specific interactions, that occur between pyrene molecules and the surface of the graphite lamellae, PCL bearing these functionalities were developed and used for the preparation of different composite systems. In particular, a novel polymer additive, consisting of a low molecular mass PCL ending with a pyrene group (Pyr-PCL), to be applied in the preparation of nanocomposites based on a commercial PCL and GNP, was developed. Indeed, a significant improvement of the electrical conductivity was found in the systems based on Pyr-PCL, this peculiar phenomenon being related to the optimized nanofiller dispersion and to the ameliorate compatibility with the polymer matrix. Moreover, playing also with the polymer architecture, a star PCL ending with pyrene groups was synthesized and applied in the preparation of GNP-based nanopapers. In this case, the main aim was to achieve a physical crosslinking among the graphitic layers thanks to the peculiar star architecture and to the polymer functionalities. Indeed, the developed nanopapers, consisting of well organized and packed graphitic layers connected by the star PCL polymer, were characterized by high thermal and electrical conductivity as well as by improved mechanical properties with respect to the neat GNP-based systems.