Inter- and intramolecular hydrogen bond in liquid polymers: a Fourier transform infrared response

Infrared (IR) absorption measurements are employed to investigate the vibrational spectra of propylene glycol (PG) and its oligomers the poly( propylene glycols) (PPGs) with different molecular weights (425 and 725 Da) in the OH stretching region. The goals are to identify the intramolecular, hydrogen bond imposed, sub-band and to connect the various sub-bands to different intermolecular aggregates originated by the existence of the hydrogen bond potential. The observed experimental data, compared with those of previous IR measurements on other similar polymers, ethylene glycol (EG) and poly( ethylene glycols) (PEGs), confirm the role played by the hydrogen bond in the structure of these liquids, discussed on the basis of current theories for associated systems.