Pluronic polymer induced transport of an organic cation across a negatively charged POPG membrane bilayer were studied using interfacial selective Second Harmonic (SH) spectroscopic technique. The length of either hydrophilic (poly-ethylene oxide) or hydrophobic (poly-propylene oxide) unit in the polymer was varied to investigate their effect on membrane transport. Membrane transport was observed to depend critically on the length of the hydrophobic segment present in the polymer. Membrane transport studies using polymers which were either 'incorporated' or 'incubated' with the lipid bilayer suggested that bilayer packing plays a critical role in the insertion of polymers having a long hydrophilic chain. (C) 2017 Elsevier B.V. All rights reserved.