Hi everybody,

I have a question about the shear modulus of polymers. As we know, the general engineering polymers （,rubbers）, are highly extensible and elastic. The shear modulus，,G，, for the polymers subjected to the small-strain conditions, can be defined by G=NkT, where N is the number of network chains, k is Boltzmanns constant and T is temperature in Kelvins.

It can be seen from the formula,the modulus increases with temperature. That is to say, the polymer gets stiffer rather than softer when increasing environment temperature. However in reality, (to my limited knowledge) the polymer would become softer as temperature increases, and the modulus is expected to decrease.

so,my question is how to understand the dependence of shear modulus on temperature? Maybe the formula, G=NkT, is limited to a special range of application. (entropic

elasticity)

Can anyone give me more details about this?

Thanks in advance!

Lianhua