Cationic Polymerization of β‐Pinene Using B(C6F5)3 as a Lewis Acid for the Synthesis of Tackifiers in Pressure Sensitive Adhesives

β‐pinene is a well‐known bio‐based monomer that can be polymerized via cationic polymerization to give low molecular weight resins that find use commercially as tackifiers. However, the controlled synthesis of these polymers by cationic polymerization is challenging due to the reactivity of commonly used Lewis acid catalysts and the propagating carbocationic species with water. Here, the cationic polymerization of β‐pinene under mild conditions using the water stable Lewis acid tris(pentafluorophenyl)borane is demonstrated. It is shown that when combined with a suitable alcohol initiator the molecular weight of the polymer can be tuned while the kinetics are largely controlled by the concentration of tris(pentafluorophenyl)borane. The final poly(β‐pinene) is shown to perform well as a tackifier in the formation of pressure sensitive adhesives based on polystyrene‐b‐polyisoprene‐b‐polystyrene triblock copolymers. β‐pinene is polymerized in solution using a water tolerant Lewis acid, B(C6F5)3, as catalyst. The molecular weight can be controlled by the addition of an alcohol initiator leading to low molecular weight polymers that can be used as tackifiers in pressure sensitive adhesives.