Carbocationic Polymerization in the Presence of sterically Hindered Bases. VI. The Polymerization of Methylstyrene with the “H2O”/SnCl4Initiating System

The polymerization of α-methylstyrene has been investigated using the “H2O”/SnCl4 initiating system in the presence of 2,6-di-tert-butylpyridine (DtBP) in CH2Cl2 solvent at −60°C. In the absence of DtBP and at low DtBP concentrations conversions are about 100%, but with increasing amounts of DtBP conversions drop to 3–5%. Polydispersity decreases with increasing [DtBP], The [Mbar]n versus [DtBP] plot shows a maximum; thus [Mbar]n increases from ∼70,000 to ∼120,000 by increasing [DtBP] from 6 × 10−7 to 4.8 × 10−4 M and decreases to ∼ 10,000 on further increasing DtBP. The effect of DtBP on this polymerization system can be explained by assuming nonprotic initiation, termination only by DtBP, depressed chain transfer to monomer, and complex formation between the propagating carbocation and DtBP.