Curing reactions and thermal stability of nanocomposites with DNA/graphene nanoplatelets by differential scanning calorimetry

Nanocomposite materials containing DNA-functionalized graphene are characterized by multifunctional properties that make them potentially useful for applications in biomedical devices, such as cell-instructive devices, or in radiation monitoring systems. In this work, DNA-graphene fillers were embedded in a silicone-based polymer matrix made of polydimethylsiloxane (PDMS) or its mixtures with hydroxyl-terminated polydimethylsiloxane (PDMS-OH). Double stranded DNA was selected because of its sensitivity to UV radiation and, at the same time, efficient exfoliation ability for the graphene nanoplatelets. Differential scanning calorimetry (DSC) was conducted at different heating rates to investigate the curing reactions of the PDMS and PDMS/PDMS-OH matrices filled with DNA/graphene nanoplatelets. The thermal stability of the nanocomposites in a wide temperature range (from -40°C to 250 °C) was also tested, providing information for the application of these materials in extreme environments, such as in space, where large temperature gradients are present. Results by DSC showed larger activation energies for the curing reactions (determined using the maximum reaction rate method) of the PDMS/PDMS-OH matrices filled with pure GNP as compared to the same matrices filled with the DNA-functionalized GNP. This result revealed a favorable contribution of the DNA element on the curing behaviour of the nanocomposites. In order to test the effects of UV exposure on the nanocomposite properties, the thermal analysis was also conducted after irradiation under UV light. Results revealed a change in the behaviour of the nanocomposites containing DNA upon UV exposure. In fact, these exhibited a shift of the DNA denaturation peak to higher temperatures, which could be ascribed to a DNA crosslinking promoted by UV radiation.