Cationic copolymerization of norbornadiene with styrene by AlEtCl2/tert‐butyl chloride catalyst system, 2. Effect of polymerization conditions on “crosslinking” and “polymer linking” reactions

The cationic copolymerization of norbornadiene (NBD) and styrene (St) was carried out with the AlEtCl2/tert-butyl chloride catalyst system under various conditions. Detailed analyses were focused on the effect of reaction conditions on the two types of intermolecular reactions, that is, the “crosslinking” reaction to form an insoluble polymer and the “polymer linking” reaction to form a soluble polymer with a molecular weight higher than that of the non-crosslinked polymer. The two types of crosslinking processes can explain the unique dependency of the polymer solubility on the NBD/St feed ratio. The “polymer linking” reaction is initiated after complete consumption of the monomers and is strongly affected by the polymerization conditions. For example, longer polymerization time, lower temperature, an initial monomer concentration [M]0 around 1,0–1,5 mol/L, a [t-BuCl]0/[AlEtCl2]0 ratio around 0,75–1,0 and increasing [AlEtCl2]0 are the factors that facilitate the “polymer linking”.