Cationic copolymers of isobutylene. 5. Copolymerization of isobutylene and cis-1,3-pentadiene

Abstract

The structure of cationic isobutylene (I)-c¿s-l,3-pentadiene (cP) copolymer was investigated by means of 13C NMR spectroscopy. The diene was present in the copolymer chains mainly as trans-1,4 units, but cis-1,2, trans-1,2, trans-4,1, and trans-4,3 units were also observed. The attack at position 4 of cP occurred by sterically unhindered carbenium ions arising from cP and not from I. The isomerization of cP to irons-1,3-pentadiene was ascertained to occur under mild conditions in the presence of BFg-OEtg. The evaluation of the fractions of triads centered on I was found to be in fair agreement with the calculated random distribution of the monomer units.

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

“…Unsaturation of PPD‐1, calculated through the comparison of intensities of protons or carbon atoms in olefinic and aliphatic regions of 1 H and 13 C NMR spectra, (a) were 89 and 91%, respectively. It should be noted that these values of unsaturation are the ones of the highest for PPDs synthesized by cationic polymerization . Owing to the low content of saturated structures in PPD‐1 sample, their structure is not investigated in this study.…”

“…Indeed, the absence of signal of methyl carbon atom of 3,4‐unit at 9–12 ppm in 13 C NMR spectrum indicates that PPD‐1 sample does not contain this structural unit. According to Rozentsvet et al, the signal 25 at 114.8–115.5 ppm (CH 2 group), which was misleadingly assigned to the structural fragment of 3,4‐unit, is in fact belonged to terminal groups of PPD chain, the exact structure of which is not identified up to date.

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“…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.…”

“…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. Moreover, the nature of head and end groups of cationic PPDs was investigated only in a few studies (b), and it was only reported that PPDs synthesized in the presence of AlCl 3 contained from 0.018 to 0.4% of chlorine, but the structure of chlorine‐containing units was not identified.…”

Cationic copolymerization of 1,3-pentadiene with α-pinene

“…Although there have been some reports about the cationic copolymer of PD with other monomers, such as olefin, styrene [4][5][6][7][8][9][10][11], research in the cationic copolymerization of PD with AP has rarely been reported. We are interested in the cationic PD-AP copolymerization because it is of significance for synthesis of the copolymer with high softening point and light color.…”