Linear conditions in chain systems with neighbour interaction. I. Theory and general applications

The general combinatorial expression of the partition function for a polymer chain with neighbour interactions is given. It is shown how to take into account the existence of linear relationships connecting the frequencies of some conformational states of the monomer units. Such restrictions may be introduced when external factors influence the conformational equilibrium. The equivalence of the combinatorial and the matrix approach is proved; applications to the copolymer problem as well as to polyelectrolytes in solution are discussed.