Ballistic energy transport in PEG oligomers

Energy transport between the terminal groups of the azido-PEG-succinimide ester compounds with a number of repeating PEG units of 0, 4, 8, and 12 was studied using relaxation-assisted two-dimensional infrared spectroscopy. The through-bond energy transport time, evaluated as the waiting time at which the cross peak maximum is reached, T-max, was found to be linearly dependent on the chain length for chain lengths up to 60 angstrom suggesting a ballistic energy transport regime. The through-bond energy transport speed is found to be ca. 500 m/s. The cross-peak amplitude at the maximum decays exponentially with the chain length with a characteristic decay distance of 15.7 +/- 1 angstrom. Substantial mode delocalization across the PEG bridge is found, which can support the energy propagation as a wavepacket.