Multiblock copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were investigate for use as a model coupling agent for wood-based polymer composites. The PS-PMMA copolymers with approximately 50/50 composition and 150,000 molecular weight were synthesized using atom transfer radical polymerization. The ability of the copolymers to improve the interfacial properties was evaluated in lignin/PS PMMA and PS blend systems. The interaction of model films based on wood's main chemical components, lignin and cellulose, was investigated using calorimetric techniques and atomic force microscopy. Small addition levels of the triblock PS-PMMA-PS copolymer reveals improved phase behavior in PS-lignin blends. These results will lead to a new class of wood compatibilizers where the polymer chain architecture and functionality can be dialed in for the desired application.