Efficient amine functionalization of carbon nanotubes with triethylenetetramine through microwave assisted reaction for applications in nanofluids

Carbon nanotubes (CNT) exhibit outstanding physicochemical properties, which allow them to be used in several polymer applications, as reported previously by our group1-3. However, they tend to form stable aggregates, which lead to unwanted changes in their properties4. In order to counteract this, surface chemical functionalization of CNT with amino groups is as an alternative to improve dispersion behavior of CNT in polymer-water based fluids. Nevertheless, chemical routes for surface amino-modifications are still being optimized with respect to yield and environmental impact5. In this work, a low-cost and green chemistry route to functionalize oxidized-CNT (ONTC) with triethylenetetramine (TETA) was applied to control reaction parameters such reagents and time. The modified nanomaterial was fully characterized by all relevant techniques such as CHNO, FTIR, Raman, SEM, TEM, and others. Thermogravimetric curves showed 12% mass loss in the 120 - 400 °C range for ONTC-TETA, which is assigned to the thermal decomposition of the amino and carboxyl groups. Zeta potential measurements of aqueous dispersions displayed a surface charge of 21 ± 1 mV at 25 °C. Rheology measurements demonstrated the superior viscosity (increase of 180% at a shear rate of 1 s-1 ) in partially hydrolyzed polyacrylamide (HPAM) aqueous solutions when adding amounts of 1% of ONTC-TETA. These results indicate a great progress for the implementation of ONTC-TETA-HPAM nanofluids in energy applications such as enhanced oil recovery.