Polymerization of 1,3‐Pentadiene Initiated by Aluminium Trichloride in Nonpolar Solvent: Pseudo‐Control is Explained by Continuous Grafting

Summary: The cationic polymerization of 1,3‐pentadiene initiated by AlCl₃ was studied in nonpolar solvent. It was previously shown that at room temperature the active species were long‐lived and that the number‐average molar mass of the polymer chains was increasing with the polymerization yield. In order to explain this apparent control, the macromolecules were labeled with a transfer agent, triphenylamine (NPh₃). The latter binds to active species by electrophilic aromatic substitution. The labeling of the polymer chains indicated that at 20 °C the polymer chains mainly contained one NPh₃ molecule per macromolecule while the NPh₃ content was higher for the high molar mass chains due to a “grafting from” polymer transfer mechanism. Thus, the pseudo‐control was assigned to the branching reactions. The labeling process by NPh₃ also succeeded at ?10 °C. Whereas at ?10 °C a dialkylation of NPh₃ was observed, a trialkylation at 20 °C was obtained. The analysis of the polymer microstructure at both temperatures highlighted an interaction between the active centers and NPh₃. This paper also describes a process to synthesize tri‐arm stars polymers by cationic polymerization.

RI SEC chromatograms of soluble polymers synthesized at 20 °C in the presence of NPh₃ with increasing reaction times (r = [NPh₃]/[AlCl₃] = 1); (a) t = 0.25 h, (b) t = 0.5 h, (c) t = 1 h, (d) t = 2 h, (e) t = 18 h, (f) t = 48 h; [AlCl₃] = 2.3 × 10^?2 mol · L^?1, [1,3‐pentadiene] = 1.6 mol · L^?1, pentane.