Effect of the molecular mass distribution on the thermomechanical properties of linear polymers

A relationship between the shape of thermomechanical curves and the molecular mass distribution of linear polymers is established on the basis of a model of the physical lattice sites. A formula is derived that relates the temperature of the yield onset (the end of a plateau of the rubberlike elasticity) to the molecular mass, which proves to be universally valid for a wide class of polymers. A method is proposed that allows the molecular mass distribution to be estimated proceeding from an analysis of the shape of the thermomechanical curve of a polymer in the region of transition from glassy state to viscous flow. A relation is obtained that generalizes the Flory formula, describing the effect of chain ends on the high elasticity modulus, to the case of low-crosslinked polymers.