Climate models struggle to accurately represent polar regions, particularly during polar night, when cloud cover is especially prevalent. The uncertainty budget is dominated by cloud and cloud-aerosol interactions, but the difficulty in maintaining robust field observations means a lack of long-term validative datasets for key cloud parameters. A large component of the Earth's outgoing energy budget resides in the far-infrared region of the spectrum, which interacts with numerous components of the atmosphere, including with trace gases and clouds/aerosols. Notably scattering by clouds and aerosols contribute significant uncertainty in our understanding of polar radiative interactions, and in the broadband energy budget. Long-term measurements of the downwelling thermal infrared (400 - 3000 cm-1) have been recorded since 2008 at Eureka, Canada, with an Atmosphere Emitted Radiance Interferometer (AERI) instrument, operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC), while a similar instrument was deployed at McMurdo Station for 2016 as part of the ARM [Atmosphere Radiation Measurement] West Antarctic Radiation Experiment (AWARE) program. We analyse the downwelling infrared emission of the polar atmosphere recorded by AERI instruments, with supplementary data from active lidar, surface meteorology, chemical transport models to derive microphysical and optical properties of clouds at Eureka (2008 - ) and McMurdo (2016) including optical depth, thermodynamic phase, temperature, liquid droplet and ice crystal effective scattering radii. A comparison between Arctic and Antarctic cloud properties is made, to demonstrate the abundance of cloud morphology between the two poles and consequences of these differences, while challenges in performing these retrievals are also discussed.