This is interesting. Canon has come up with a way to enhance bokeh through the use of lens coatings. From PetaPixel.
"Canon says Defocus Smoothing is a new vapor-deposited coating that’s added to the front and rear surfaces of one or more of the elements in the lens (Canon says the 85mm features coating on two elements). This coating “has the effect of gradually decreasing the transmission factor from the center to the periphery of the lens,” Canon says."