2.1. Dataset. In this study, we employ multiple datasets to evaluate the UQ capabilities of ML models in predicting polymer properties, with a particular focus on linear polymers. These datasets, summarized in Table , include four training and testing datasets (𝑇 𝑔 , 𝐸 𝑔 , 𝑇 𝑚 , 𝑇 𝑑 ) and OOD datasets ( 𝑇 𝑔 𝐸𝑋𝑃 and 𝑇 𝑔 𝑀𝐷 ), ensuring a comprehensive evaluation of the models' generalizability and reliability. The selection of these datasets is motivated by the need to systematically assess the performance of ML models on both in-distribution and OOD data, a critical aspect for their deployment in polymer informatics and materials discovery workflows.