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

Abstract

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.magnified imageRI 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.

Recent progress in the Lewis acid co-initiated cationic polymerization of isobutylene and 1,3-dienes

“…[80][81][82] In addition, it was also shown that strong nucleophiles were prone to give polymers with higher content of insoluble fraction and steric structure of nucleophilic additive strongly inuenced the reaction rate and polymer properties. [80][81][82] Interestingly, in the case of using a certain nucleophiles (butylamine 83 or triphenylamine 84 ) in conjunction with AlCl 3 as co-initiator in nonpolar solvents at 20 C, the increase of number average molecular weight from ca. 2000 g mol À1 to 12 000 g mol À1 with increasing polymer yield, one of the important features of controlled polymerization, 4,9 was observed.…”

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization I: Polymerization of 1,3‐Pentadiene with tBuCl/TiCl4 Initiating System: Kinetic and Mechanistic Study

“…It is known that the cationic polymerization of 1,3‐pentadiene is co‐initiated by a wide range of Lewis acids such as AlCl 3 , FeCl 3 , SnCl 4 , BF 3 OEt 2 , VOCl 3 , and TiCl 4 . The main feature of TiCl 4 ‐based initiating systems is their low activity in the polymerization of 1,3‐dienes in the absence of purposely added initiators such as water, hydrochloric acid, organic acids, and so on, while the addition to the system of protic compounds or cationogens allowed to increase the rate of polymerization of 1,3‐dienes significantly .…”

“…The TiCl 4 ‐co‐initiated cationic polymerization of 1,3‐dienes in conjunction with water, acetone, trichloroacetic acid, trifluoroacetic acid, tert ‐butyl esters of these acids, cumyl acetate, cumyl methyl ether, dimethylallyl bromide, and dimethylallyl alcohol has been investigated. The obtained poly(1,3‐diene)s are characterized by reduced unsaturation that was explained either by intramolecular cyclization or branching due to the chain transfer to polymer . The unsaturated part of the polymer chain consists mainly of trans ‐1,4‐structures …”

Cationic polymerization of 1,3‐pentadiene coinitiated by zinc halides

“…). The formation of HMWF and IF is observed during the cationic polymerization of 1,3‐pentadiene using the initiating systems based on AlCl 3 ,7–15 FeCl 3 ,16 SnCl 4 ,17 TiCl 4 ,1–6,18–20 and VOCl 3 21. Depending on the nature of Lewis acid used, the appearance of HMWF and IF is revealed at the different stages of the polymerization process.…”

“…Depending on the nature of Lewis acid used, the appearance of HMWF and IF is revealed at the different stages of the polymerization process. For example, HMWF and IF were formed at the beginning of the polymerization with AlCl 3 as coinitiator,8–15 while in the presence of TiCl 4 and VOCl 3 HMWF and IF were observed only when certain concentrations of polymer were achieved in the reaction medium 2,18–21…”