In poly(propylene glycol) (PPG) the polymer chains are terminated by hydroxy groups. These polar ends are capable of coordinating to both cations and anions when a salt is dissolved in the polymer. This coordination has been monitored using shifts in the OH stretching vibration band at about 3400cm-1, as measured by Fourier transform infra-red spectroscopy. In the LiCF3SO3-PPG(3000 ) system, the Li ? ions preferred to coordinate to OH groups rather than to ether oxygens; at the composition LiCF3SOaPPGlo, all OH groups were coordinated by both lithium and triflate ions, suggesting that the properties of these electrolytes depend to a large extent on metal ion to OH end-group interactions. Solvent-shared ion pairs, where the ions are separated by an OH group rather than free triflate ions, are present in these samples. The triflate ions in the solvent-shared ion pairs are suggested to have a 1,'(SO3) s absorption band at 1032 cm-1, i.e. at the same position as has been found for non-coordinated triflate ions.
Посилання на статтю:
OH end-group coordination to cations and triflate ions in PPG systems / Annika Bernson and Jan Lindgren // Polymer. – 1994. – Vol 35. – P. 4842-4847.