Energy Transport in PEG Oligomers: Contributions of Different Optical Bands

Abstract

The transport of high-frequency vibrational energy in linear oligomer chains can be fast and efficient if specific conditions which permit ballistic transport are satisfied. These conditions include high delocalization and slow dephasing rate of chain states. We present new experimental results probing the energy transport in linear polyethylene glycol (PEG) oligomers of 0, 4, 8, and 12 PEG units terminated with IR-active end groups, N3 and succinimide ester. The energy transport was initiated by vibrational excitation of one of the end groups and the energy arrival to another end group was detected using dual-frequency, two-dimensional infrared spectroscopy. In addition to end-group to end-group energy transport dynamics, the end-group-to-chain-state and chain-state-to-chain-state waiting-time dynamics are reported. The results show that despite rather short lifetimes for several IR-active chain states, the end-to-end energy transport occurs with a constant and rather high speed of 5.5 A/ps, regardless o...