A comprehension of the phenomenon that controls the diffusion of an organic solvent to the pores of a polymeric matrix is fundamental for optimizing the operating conditions to distribute a homogeneous catalyst, which has to be supported on it. The traditional sessile drop method is impossible to use when a high polymer-solvent affinity exists. In this case, a different determination technique, similar to the Wilhelmy static mode method and based on the direct observation of the capillary raising curve of the solvent on the polymeric surface, has been set together with an experimental apparatus specifically built to perform measurements at a desired temperature and atmosphere. Such a technique has been demonstrated to be easy and promising for differentiating the behavior of different polyolefins [polypropylene (PP), high density polyethylene (HDPE), heterophasic copolymers (COPO)] at equal solvent and different temperatures. (C) 2007 Wiley Periodicals, Inc.