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High temperature performance of polymers depend mainly on their glass transition temperature Tg. Polymers with high Tg, however, often tend to have low toughness. In this work, a model polyethylene like polymer is analysed to understand the reason for this phenomenon. To this end, molecular dynamics simulations are performed to investigate the effect of various factors on glass transition and yielding. Two generic modifications to the model polymer are suggested for enhancing its Tg and the effect of these modifications on the stress–strain behaviour are studied. Results indicate that when non-bonded interactions govern the energetics of the deformation process, a polymer with a high energetic barrier to torsional changes will lead to a higher Tg without significantly compromising the toughness. On the other hand, strong non-bonded interactions also promote high Tg but lead to a brittle material. [ABSTRACT FROM AUTHOR]