Molecular stiffness and aromatic ring position – crucial structural factors in the self-assembly processes of phenyl alkohols

Abstract The combination of dielectric, infrared, and diffraction studies was used to study the impact of the phenyl ring and molecular stiffness on the self-assembly phenomena in four model aromatic alcohols: 1-phenyl-1-propanol, 3-phenyl-1-propanol, 1-phenyl-2-propyn-1-ol and 3-phenyl-2-propyn-1-ol. Firstly, it is shown that even highly sterically hindered molecules can associate and organize themselves into nanosized clusters. However, their size, concentration, and degree of order decrease with growing steric hindrance and intramolecular stiffness. Secondly, a twofold intermolecular assembly via O-H…π and O-H…O schemes is proved to exist in the aromatic alcohols. Consequently, the mechanism of hindering effect of the phenyl ring on the self-assembly is ascribed to its double role: (i) as a steric hindrance and (ii) as a source of O-H…π interactions, competitive with the hydrogen bonds of O-H…O scheme. Finally, it is shown that the growing tendency to self-association does not implicate the increase in the intermolecular ordering on a scale greater than one nanometer.