Grafting of Polypyrrole-3-carboxylic Acid to the Surface of Hexamethylene Diisocyanate-Functionalized Graphene Oxide

Abstract

A polypyrrole-carboxylic acid derivative (PPy-COOH) was covalently anchored on the surface of hexamethylene diisocyanate (HDI)-modified graphene oxide (GO) following two different esterification approaches: activation of the carboxylic acids of the polymer by carbodiimide, and conversion of the carboxylic groups to acyl chloride. Microscopic observations revealed a decrease in HDI-GO layer thickness for the sample prepared via the first strategy, and the heterogeneous nature of the grafted samples. Infrared and Raman spectroscopies corroborated the grafting success, demonstrating the emergence of a peak associated with the ester group. The yield of the grafting reactions (31% and 42%) was roughly calculated from thermogravimetric analysis, and it was higher for the sample synthesized via formation of the acyl chloride-functionalized PPy. The grafted samples showed higher thermal stability (~30 and 40 °C in the second decomposition stage) and sheet resistance than PPy-COOH. They also exhibited superior stiffness and strength both at 25 and 100 °C, and the reinforcing efficiency was approximately maintained at high temperatures. Improved mechanical performance was attained for the sample with higher grafting yield. The developed method is a valuable approach to covalently attach conductive polymers onto graphenic nanomaterials for application in flexible electronics, fuel cells, solar cells, and supercapacitors.

Tailorable Synthesis of Highly Oxidized Graphene Oxides via an Environmentally-Friendly Electrochemical Process

“…It should be noted that the C/O ratio influences structural properties like the degree of exfoliation and number of layers, amount of defects, flake size, and concentration of functional groups, among others [37], which, in turn, would tailor the band structure, hence the photoluminiscent behaviour, as well as the electrical and mechanical properties. In addition, the oxygenated moieties provide anchoring points for subsequent chemical modification [38].…”

Thermally Switchable Electrically Conductive Thermoset rGO/PK Self-Healing Composites

“…The residual functional groups remaining in the rGO structure make its dispersion easier and stable in water and polar organic solvents [ 32 , 33 , 34 , 35 ]. Furthermore, they increase the number of effective interactions with polymer matrices improving its homogeneous distribution in the solid host [ 36 , 37 ], leading to the preparation of polymeric nanocomposites [ 38 , 39 , 40 ], where rGO provides substantial electrical and mechanical properties [ 41 , 42 , 43 , 44 , 45 ]. Gudkov et al demonstrate that with only 0.6 wt% of rGO dispersed in a polymeric matrix an electrical conductivity of 0.5 S/m is achieved for the nanocomposite [ 46 ].…”

Electrically-Conductive Polyketone Nanocomposites Based on Reduced Graphene Oxide

“…The electric properties of GO can be recovered by reduction treatments (producing reduced graphene oxide (rGO)), which partially restores the graphitic network of sp 2 carbons [13,14]. Notably, the residual functional groups remained in the rGO structure make its dispersion easier in organic solvents [15] and increase the preparation of functional polymer nanocomposites [18][19][20] where rGO can provide enhanced electrical and mechanical properties [21][22][23][24][25]. In this sense, these materials have found a variety of applications such as supercapacitor electrodes [26], chemical sensor [27], and antibacterial scaffolds [28].…”