AbstractFor most applications of polymer products, the modulus or stiffness, i.e. resistance to deformation under load, is of prime importance. The mechanical losses or damping reveal molecular movements of small groups of atoms, which movements can be significant for the impact strength.This review illustrates the effect of crosslinking, polarity, and steric features of both side‐groups and main molecular chain on both shear modulus and damping as functions of temperature.The examples are mainly taken from commercial or recently developed polymers.It is concluded that the most promising way of increasing the softening temperature of thermoplastics is to introduce rings into the main molecular chai