Rutile pigment was surface-modified by the adsorption of various diblock copolymers and used as a component in two- and three-component polymer blends involving the incompatible pair of linear, low-density polyethylene (LLDPE) and poly(vinyl chloride) (PVC). Stress-strain analyses and electron microscopy show that the copolymer tethered to the rutile surface affects both mechanical and morphological properties of the blends. Inverse gas chromatography was used to evaluate dispersion surface energies and acid-base interaction parameters of the various solids. The mechanical and morphological characteristics of the blends can be rationalized by the concepts of acid-base and dispersion-force interaction. Of the copolymer modifiers used, the diblock based on polyisoprene and poly(4-vinyl pyridine) (PIP-P4VP) was best suited for use in LLDPE/PVC blends, ostensibly because of strong acid-base interaction between PVC and P4VP and mechanical interlocking between LLDPE and the PIP moiety. The properties of ternary blends were shown to be dependent on the method used for mixing the components. All mixing procedures used here resulted in time-dependent variations of mechanical properties, suggesting that none gave rise to equilibrium morphology in the compounds.