Boron-containing polymers have been widely used for applications such as catalysis, sensors, flame retardants, intermediates in the synthesis of functionalized polymers and device materials. Their preparation generally involves either direct polymerization of boron containing monomers or functionalization of the polymers. We have recently developed a highly efficient method to incorporate boron into the organic polymers via controlled polymerization of silylated monomers and a subsequent silicon boron exchange reaction. The polystyrene derivative with functionalized BH₂ moieties (PS-BH₂) has been prepared from poly(4-trimethylsilyl styrene) via post polymerization modification reactions. The polymer was successfully isolated in the form of its polymeric acid-base complexes PS-BH₂•D (D = ^tBuPy, PPh₂Me). Both polymers were fully characterized by multi-nuclear NMR spectroscopy and IR spectroscopy. Their thermal properties were studied by differential scanning calorimetry and thermogravimetric analysis. These polymers may find application as precursor to other functional polymers or as supported reducing agents.