Within ASML’s extreme ultraviolet (EUV) lithography machines, a photomask defines the pattern on the silicon wafer. To protect the photomask from particles that are shed from inside the machine and to ensure the quality of the printed patterns, a highly EUV-transparent pellicle is suspended in front of the photomask. Various materials have been explored to meet the stringent requirements for such pellicles. One potential material is a random carbon nanotube (CNT) network, due to its favorable mechanical and thermodynamical properties. Despite the high EUV transmission rate of around 90%, the 10% of absorbed EUV radiation can lead to a temperature increase of the pellicle on the order of several hundred kelvin. It is essential to remove this heat as quickly as possible to prevent the pellicle from becoming thermally instable. Therefore, a thorough understanding of the thermodynamics of CNT pellicles at elevated temperatures - up to around 900 K - is required. In this thesis, the optomechanical method is successfully applied to extract key thermal properties such as the thermal expansion coefficient, specific heat capacity, and the thermal conductivty of 2D CNT networks up to 1300 K.