The mechanism of obtaining a polymer with reduced unsaturation is proposed, which includes the formation of branched structures.

The microstructure of polyisoprene synthesized with t BuCl/TiCl 4 initiating system is investigated using 1D and 2D (HSQC and HMBC) NMR spectroscopy. It is found that trans-1,4-units with regular (head-to-tail) and inverse (tail-totail) and (head-to-head) enchainments are predominant structures of unsaturated part of polymer chain, while 1,2-and 3,4-units are presented in minor amounts. The new methodology for the quantitative calculation of the content of different structural units in polyisoprene chain including both types of inverse trans-1,4-addition (tail-to-tail and head-to-head) is proposed. It is shown that head groups consist of tert-butyl group connected to trans-1,4-unit of polyisoprene chain. In addition, two types of chlorine-containing end groups are found (trans-4,1-Cl and 4,3-Cl), while conjugated double bonds at the chain end are totally absent. The methodology for the calculation of number-average functionality by tertbutyl head and chlorine end groups, respectively, is developed.

The microstructure of polybutadiene synthesized via cationic polymerization using TiCl4‐based initiating systems has been investigated using 1D (1Н, 2Н, and 13С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans‐1,4‐unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2‐structures was also detected, while cis‐1,4‐units were totally absent. The signals of carbon atoms of three types of head groups (trans‐1,4‐, 1,2‐, and tert‐butyl) and two types of end groups (trans‐1,4‐Cl and 1,2‐Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert‐butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2‐units distributed randomly along the polybutadiene chain as separate units between trans‐1,4‐structures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 387–398

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