Using a classical density functional theory (DFT) based on Wertheim's first order thermodynamic perturbation theory (interfacial statistical associating fluid theory), we extend the DFT to include multiple hydrogen-bonding groups on polyatomic molecules. Since the theory already holds the ability to track each segment along a polymer chain separately, hydrogen-bonding groups can be assigned to any segment within the chain. The resulting theory will be demonstrated for model polymer systems to determine the effect of association/hydrogen-bonding on the molecular structure and phase behavior of the fluid.

Such an extension of the theory is important to many industrial and biological processes, where the function and stability of the macromolecular system is governed not only by the molecular size and shape and intramolecular interactions, but also by the temperature-dependent hydrogen-bonding forces and hydrophobicity of the system. Such processes can be found in many facets of chemistry and biology, most notably in self-assembly processes such as the formation of membranes and micelles in surfactant solutions, and the folding of proteins into stable, functional complexes.