Elongation

(Sperling-400)

w is the work done by the network chains
is the change in Helmholtz free energy due to elastic deformation
n is the number chains in the network
R is the gas constant
T is temperature
is the average isotropic, unstrained end-to-end distance in the network
is the average isotropic end-to-end distance for a free chain in space (or in a vacuum, as opposed to in a solvent)
is the extension ratio [Sperling-389] (also called "elongation" Flory-444)