A facile and low environmental impact approach to prepare thermally conductive nanocomposites based on polylactide and graphite nanoplatelets

TL;DR

This study introduces a low environmental impact reactive extrusion method to create polylactide/graphite nanoplatelet nanocomposites with enhanced thermal conductivity, utilizing stereocomplexation and surface interactions.

Contribution

It is the first to apply reactive extrusion with pyrene-based molecules for synthesizing PLA/GNP nanocomposites, demonstrating improved thermal properties and scalable, eco-friendly production.

Findings

Thermal conductivity increased in stereocomplexed nanocomposites.

Electrical conductivity remained similar across different nanocomposites.

Stereocomplexation influenced local crystallinity and thermal performance.

Abstract

In this work, the preparation of nanocomposites based on poly(L-lactide) PLLA and graphite nanoplatelets (GNP) was assessed, by applying, for the first time, the reactive extrusion (REX) polymerization approach, which is considered a low environmental impact method to prepare polymer systems and which allows an easy scalability. In particular, ad hoc synthesized molecules, constituted by a pyrene end group and a poly (D-lactide) (PDLA) chain (Pyr-D), capable of interacting with the surface of GNP layers as well as forming stereoblocks during the ring opening polymerization (ROP) of L-lactide, were used. The nanocomposites were synthesized by adding to L-lactide the GNP/initiator system, prepared by dispersing the graphite in the acetone/Pyr-D solution, which was dried after the sonication process. DSC and X-ray diffraction measurements evidenced the stereocomplexation of the systems synthesized by using the pyrene-based initiators, whose extent turned out to depend on the PDLA chain length. All the prepared nanocomposites - including those synthesized starting from a classical initiator, that is 1-dodecanol - retained similar electrical conductivity, whereas the thermal conductivity was found to increase in the stereocomplexed samples. Preferential localization of stereocomplexed PLA close to the interface with GNP was demonstrated by Scanning Probe Microscopy (SPM) techniques, supporting for an important role of local crystallinity in the thermal conductivity of the nanocomposites.