The photophys. and energy transport properties of poly(p-phenylene ethynylene) were studied in thin films. Highly aligned films of a precise thickness, prepd. 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 studied as a function of the AO concn. and the no. of polymer layers. An increased efficiency of energy transfer to the traps was obsd. with increasing nos. of layers to an approx. thickness of 16 layers. This behavior is consistent with a transition to a three-dimensional energy migration topol. A phenomenol. model for the transport was proposed, and solns. 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 \AA in the Z direction (normal to the film surface). [on SciFinder(R)]