A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization III: Polymerization of 1,3‐Pentadiene with CF3COOD/TiCl4 Initiating System: Chain‐Ends Structure and Kinetics

A novel method for the investigation of the chain‐end structure of poly(1,3‐pentadiene)s synthesized using the CF3COOD/TiCl4 initiating system is developed. It is shown for the first time that the content of trans‐1,2‐structures in the first monomer unit is considerably higher than the content of trans‐1,4‐structures, whereas the content of trans‐1,4‐units is substantially higher than trans‐1,2‐units for the polymer chain as a whole. Another important observation is that chain transfer to monomer is significant even at the earlier stages of the 1,3‐pentadiene polymerization (after 1 s of reaction). The very low functionality at the ω‐end (Fn (Cl) < 0.15) confirms the intensive chain transfer to monomer. This method is also applied for the estimation of the concentration of active species and the rate constant for propagation (k p) for the cationic polymerization of 1,3‐pentadiene using the CF3COOD/TiCl4 initiating system: rate constants for propagation, k p, of 1.5 × 103 and 3.3 × 103 L mol−1 min−1 are determined for 1,3‐pentadiene polymerization at 20 and –78 °C, respectively. image