Synthesis and characterization of a novel star polycaprolactone to be applied in the development of graphite nanoplates-based nanopapers

Abstract The work was focused on the synthesis and characterization of a polymer designed with suitable features to be applied in the development of graphite nanoplates (GNP)-based nanopapers, prepared by using a solution blending approach, followed by filtration, drying and pressing treatments. Indeed, the polymer was tailored to possess: i) pyrenic functionalities, potentially capable of interacting with the graphite surface; ii) a star shape to promote the formation of a physical networking among the GNP layers; iii) arms made of a semicrystalline biopolymer, namely polycaprolactone (PCL), to obtain a mechanically robust and sustainable system. The polymer structure, synthesized by applying a three-step procedure, was validated by IR and 1H NMR measurements. The presence of the pyrenic end groups turned out to decrease the crystallinity of the polymer, compared to the starting PCL with hydroxylic and carboxylic functionalities, while significantly increasing its thermal stability at high temperature. The star shape structure of the synthesized PCL, together with its pyrene functionality, allowed introducing into the nanopapers structure a greater amount of polymer than that which can be inserted by using a high-molecular weight linear PCL. Moreover, GNP was found to promote significantly the pyrenic-PCL crystallization, acting as a nucleating agent. The strong interaction between the functionalized PCL and GNP delivered nanopapers exhibiting remarkable thermomechanical stability, up to well above the PCL melting temperature, coupled with noticeable heat spreading performance. Indeed, the developed nanopapers, being also based on a biopolymer, represent novel promising high performance and sustainable materials.