Activation and racemization of trifluoroacetate esters in the cationic polymerization of styrene

1-Phenylethyl trifluoroacetate ( 1 ) does not react directly with styrene but it is readily incorporated into polymer chains in the presence of an excess of trifluoroacetic acid. The proportion of the nondeuterated 1-phenylethyl end groups in the polymerization of deuterated styrene coinitiated with the acid was much higher than the proportion of the end groups formed by direct incorporation of the acidic protons ([CH₃? CHPh? CD₂? CDPh? …] > [HCD₂? CDPh? CH₂? CDPh? …]). The racemization of the optically active ester-(pseudo-first order rate constant at [HA]₀ = 0.79 mol/L at 20°C equals k^R = 1.7 × 10^?4 S^?1) is more rapid than the incorporation of the ester into polymer chains (k^E = 1.5 × 10^?4 mol^?1 Ls^?1, [M]₀ < 0.4 mol L^?1, i.e., k^R > k^E · [M]). These results and the complete loss of the optical activity in the final polymer indicate that the ester is activated by the acid but it is incorporated into polymer chain via ionic intermediates.