Solvent quality and nonbiological oligomer folding: revisiting conventional paradigms.

We report on extensive molecular dynamics atomistic simulations of a -substituted poly-phenylacetylene (pPA) foldamer dispersed in three solvents, water HO, cyclohexane cCH, and -hexane CH, and for three oligomer lengths 12mer, 16mer and 20mer. At room temperature, we find a tendency of the pPA foldamer to collapse into a helical structure in all three solvents but with rather different stability character, stable in water, marginally stable in -hexane, unstable in cyclohexane. In the case of water, the initial and final number of hydrogen bonds of the foldamer with water molecules is found to be unchanged, with no formation of intrachain hydrogen bonding, thus indicating that hydrogen bonding plays no role in the folding process.