Abstract
The freely jointed chain is a simple off-lattice ideal model of a heteropolymer. We show how to compute the canonical partition function of this model exactly for all physical primary structures, degree of polymerization and space dimensions greater than or equal to 2. The canonical partition function of this model of a heteropolymer has an analytical expression involving a complicated multiple hypergeometric function. To obtain some accurate approximations we develop and use the independent motion approximation (IMA).