Structure of terminal units of polybutadiene synthesized via anionic mechanism

The structure of head and end groups of the polybutadiene synthesized by anionic polymerization of butadiene using tert-butyllithium as an initiator has been established using methods of NMR spectroscopy with T2-filter as well as 2D 1H, 13C HMBC and HSQC NMR spectroscopy. The spectral signals of head groups, which consist of tert-butyl groups connected with cis-1,4, trans-1,4 or 1,2-units of polybutadiene chain, were identified for the first time. A new method for the quantitative calculation of the content of head and end groups with different microstructures was proposed. It was shown that the total content of 1,4-units (both cis-1,4 and trans-1,4) in terminal groups is considerably higher than that in a main chain of polybutadiene.