  In this work we will derive an anisotropic generalisation of the finitely
extensible chain model, due to Kuhn and Gr\"un, which is well known in rubber
elasticity. This provides a chain energy that couples elastic behaviour to a
probability distribution describing the orientations of liquid crystal monomers
within a main chain elastomer. The key point is to invoke a maximum relative
entropy assumption on the distribution of bond angles in an observed chain. The
chain energy's fourth order Taylor expansion is also given, which couples to
the second and fourth moments of the nematic distribution function only.
