Copolymerization kinetics of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene: A test of the penultimate model

The propagation kinetics for the copolymerization of 4‐methoxystyrene with methyl methacrylate and 4‐methoxystyrene with styrene have been investigated using a pulsed laser technique. The dependence of the copolymerization propagation rate constant on the monomer feed ratio shows a diviation from classic Mayo–Lewis model kinetics for 4‐methoxystyrene with methyl methacrylate but not for 4‐methoxystyrene with styrene. These results have been interpreted to indicate that a penultimate effect is apparent in the first monomer pair but not in the second. With r1r2 = 0.092 for the copolymerization of 4‐methoxystyrene with methyl methacrylate and r1r2 = 0.95 for 4‐methoxystyrene with styrene, it is suggested that a deviation of the product of the coplymerization reactivity ratios from unity may be an indication of the presence of a penultimate effect.