Energy Migration in a Poly(phenylene ethynylene): Determination of Interpolymer Transport in Anisotropic Langmuir−Blodgett Films

Abstract

The photophysical and energy transport properties of a poly(p-ethynylene), 1, were investigated in thin films. Highly aligned films of a precise thickness, prepared by sequential monolayer deposition using the Langmuir−Blodgett technique, were surface modified with luminescent traps (acridine orange, AO) for energy transfer studies. The degree of energy transfer to the traps was investigated as a function of the AO concentration and the number of polymer layers. An increased efficiency of energy transfer to the traps was observed with increasing numbers of layers until an approximate thickness of 16 layers. This behavior is consistent with a transition to a three-dimensional energy migration topology. A phenomenological model for the transport was proposed, and solutions were obtained by numerical methods. The model yields a fast (>6 × 1011 s-1) rate of energy transfer between polymer layers and a diffusion length of more than 100 Å in the Z direction (normal to the film surface).