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Front. Chem. | doi: 10.3389/fchem.2019.00176

Stereocomplexation of Poly(Lactic Acid)s on Graphite Nanoplatelets: from Functionalized Nanoparticles to Self-Assembled Nanostructures.

 Matteo Eleuteri1, Mar Bernal1, Marco Milanesio2, Orietta Monticelli3* and  Alberto Fina1*
  • 1Politecnico di Torino, Italy
  • 2University of Eastern Piedmont, Italy
  • 3University of Genoa, Italy

The control of nanostructuration of graphene and graphene related materials (GRM) into self-assembled structures is strictly related to the nanoflakes chemical functionalization, which may be obtained via covalent grafting of non-covalent interactions, mostly exploiting π-stacking. As the non-covalent functionalization does not affect the sp2 carbon structure, this is often exploited to preserve the thermal and electrical properties of the GRM and it is a well-known route to tailor the interaction between GRM and organic media. In this work, non-covalent functionalization of graphite nanoplatelets (GnP) was carried out with ad-hoc synthesized pyrene-terminated oligomers of polylactic acid (PLA), aiming at the modification of GnP nanopapers thermal properties. PLA was selected based on the possibility to self-assemble in crystalline domains via stereocomplexation of complementary poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) enantiomers. Pyrene-initiated PLLA and PDLA were indeed demonstrated to anchor to the GnP surface. Calorimetric and X-ray diffraction investigations highlighted the enantiomeric PLAs adsorbed on the surface of the nanoplatelets self-organize to produce highly crystalline stereocomplex domains. Most importantly, PLLA/PDLA stereocomplexation delivered a significantly higher efficiency in nanopapers heat transfer, in particular through the thickness of the nanopaper. This is explained by a thermal bridging effect of crystalline domains between overlapped GnP, promoting heat transfer across the nanoparticles contacts. This work demonstrates the possibility to enhance the physical properties of contacts within a percolating network of GRM via the self-assembly of macromolecules and opens a new way for the engineering of GRM-based nanostructures.

Keywords: PLA stereocomplex, Graphite nanoplatelets (GnP), interfacial thermal resistance, Thermal bridging, non-covalent functionalization

Received: 31 Jan 2019; Accepted: 06 Mar 2019.

Edited by:

Pellegrino Musto, Italian National Research Council (CNR), Italy

Reviewed by:

Vincenzo Venditto, University of Salerno, Italy
Tadeusz A. Biela, Polish Academy of Sciences, Poland  

Copyright: © 2019 Eleuteri, Bernal, Milanesio, Monticelli and Fina. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Prof. Orietta Monticelli, University of Genoa, Genoa, 16126, Italy,
Prof. Alberto Fina, Politecnico di Torino, Turin, 10129, Piedmont, Italy,