The influence of secondary interactions on the development of interfacial structure in composites of wood and amorphous thermoplastic polymers is not well understood. This study used inverse gas chromatography to investigate the effect of different polymers on the surface energy of partially or fully coated white pine wood meal. In this way, the development of the interphase was monitored as a function of polymer depth on the wood surface. The polymers were selected to provide a range of functional groups and included polystyrene, poly(methyl methacrylate), poly(vinyl chloride), polymethacrylic acid, and polymethacrylonitrile. The overall variation of the dispersive component of the surface energy and the ratio of acceptor to donor coefficients appeared to group themselves into two categories based upon the polarity of the polymer's functional groups. In addition, the high loadings required for stabilization of the less polar polymers suggested that a relatively large volume of the matrix phase is affected by the wood filler.