Structural characterization of low molecular weight polybutadiene synthesized using cationic initiation system

The microstructure of polymer chain of low molecular weight polybutadienes synthesized with cationic initiating systems has been investigated using one-dimensional (¹³C, ¹³C with a T₂-filter, and ¹³C DEPT-135°) and two-dimensional ¹H—¹³C (HSQC and HMBC) NMR spectroscopy. It was found that the unsaturated part of main polymer chain consists of 1,4-trans- and 1,2-structures with different combination of units. For the first time, structures of the head groups of polymers were identified, which are dimethylpropane fragments of the initiator (2-chloro-2-methyl-butane) connected with 1,4-trans- or 1,2-units of polybutadiene. Structures of two types (1,4-trans- and 1,2-) of chlorine-containing end groups were found. Methods for the calculation of the content of head and end groups, unsaturation and functionality of polybutadiene macromolecules on the terminal groups were developed.