Foldamers can vary in size, but they are defined by the presence of noncovalent, nonadjacent interactions. This definition excludes molecules like poly(isocyanates) (commonly known as polyurethane) and poly(prolines) as they fold into helices reliably due to adjacent covalent interactions. Foldamers have a dynamic folding reaction (unfolded → folded), in which large macroscopic folding is caused by solvophobic effects (hydrophobic collapse), while the final energy state of the folded foldamer is due to the noncovalent interactions. These interactions work cooperatively to form the most stable tertiary structure, as the completely folded and unfolded states are more stable than any partially folded state.