Abstract: The compositions of sixteen diads of random butadiene-styrcne copolymers were calculated by using aliphatic carbon portion of the ¹³C-NMR spectra, based on the assignment in the previous paper. Compositions of the four monomer units deduced from the calculation were consistent with the results obtained from ¹H-NMR spectra. In the polymerization system, the average sequence lengths of diads and the average permanence ratio of four monomer units indicate that the styrcne unit (S) tends to form short block polymers, vinyl unit (v) shows a tendency to combine with the other three monomer units, trans-1, 4-butadiene unit (t) and cis-1, 4-butadiene unit (c) show tendency to form structures containing alternating units besides the block polymers formed from themselves. The results prove that ¹³C-NMR is a powerful tool for investigating the microstructure of butadiene-styrcne copolymers.

Key words: butadiene-styrene copolymer, NMR, block length, permanence ratio