Solubility and diffusion of ethylene and 1-hexene mixtures in linear amorphous polyethylene (modeled as C-70) are studied using a recently proposed united atom force field. It is found that the presence of 1-hexene increases the solubility of ethylene in polyethylene. These results are also compared to the solubility predictions of the SAFT equation of state. It is also observed that, in the polymer phase, both ethylene and 1-hexene molecules prefer to reside in the vicinity of the polymer chain ends. This aggregation effect may be important in determining penetrant solubilities in longer polymers and polymers with short chain branches.