Cationic polymerization of 1,3‐pentadiene I. infrared, ¹H‐NMR and ¹³C‐NMR investigations on the microstructure of poly(1,3‐pentadiene) synthesized with cationic catalysts

Abstract

This study deals with cationic polymerization of the cis‐ and trans‐isomers of 1,3‐pentadiene. The microstructure of the polymer chains is studied by 1H‐NMR, 13C‐NMR and IR spectroscopies. It is shown that the trans‐diene gives strictly trans‐1,4 and trans‐1,2 residual linear insaturations, whereas the cis‐isomer yields also cis‐1,4, cis‐1,2 and 3,4‐units whose overall content can reach 10 mol‐%. According to the cyclization degree of the macromolecules, ranging from 30 to 70 mol‐%, the number of trans‐(1,2+1,4) units varies between 33 to 65 mol‐% and that of trans‐1,2 units between 4 and 20 mol‐%. An analytical method is proposed to evaluate the average number of rings present in the polycyclic sequences. It is found that the cyclic fragments of the polymer chains consist of bi‐ or tri‐cyclohexane fused rings containing α tetrasubstituted double bond.

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

“…The decrease of the unsaturation of the poly(1,3‐diene)s during the cationic polymerization is usually explained by an intramolecular cyclization leading to a rigid polymer backbone . However, for the cationic polymerization of 1,3‐pentadiene with the t BuCl/TiCl 4 initiating system, the intramolecular cyclization is unlikely.…”

“…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 …”

A new insight into the mechanism of 1,3‐dienes cationic polymerization. II. Structure of poly(1,3‐pentadiene) synthesized with tBuCl/TiCl4 initiating system

“…PPDs synthesized by cationic polymerization possess the most complicated microstructure of the polymer chain . Cationic PPDs are characterized by reduced unsaturation, which is explained either by chain transfer to polymer with the formation of branched structures or by intramolecular cyclization . The literature data on the microstructure of unsaturated part of polymer chain of cationic PPDs are quite ambiguous.…”

“…Based on the obtained results, an important conclusion has been made by Rozentsvet et al that the nature of Lewis acid used and polymerization conditions (temperature, solvent) did not influence the microstructure of unsaturated part of chain of cationic PPDs. On the other hand, in a series of publications, along with aforementioned units, the significant amount of 3,4‐ , and cis −1,4‐units was identified in the structure of cationic PPDs, whereas the units with inverse monomer addition were not detected. Finally, in known studies devoted to the investigation of microstructure of cationic PPDs, only the signals of methyl carbon atoms were identified in 13 C NMR spectra, whereas data on position of the signals of other carbon atoms of corresponding structural units were almost absent.…”

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

“…The signals of the carbons of the alkylated ED aromatic rings indeed overlapped with the polymer olefinic carbons ones. Some authors [14] studied the cyclization reactions by IR and defined a cyclization degree (t) as the loss of linear units (t ¼ 1 -fraction of the linear units). Based on this paper, the microstructure of the purified polymers obtained at 20 8C was investigated by 1 H NMR and IR focusing on the proton unsaturation loss, the cyclization degree and the content of linear units.…”