Ethylene/4-methyl-1-pentene copolymers by a "Constrained Geometry Catalyst": Advances in C-13 NMR assignment

Ethylene/4-methyl-1-pentene (E/4M1P) copolymers were synthesized by [Me2Si(?5-Me4C5) -(?1-N-tBu)TiCl2] and methylalumoxane (MAO) catalyst (CG) and analyzed by 13C NMR. The low regio- and stereoregularity of CG leads to spectral multiplicities which can be ascribed not only to differences in comonomer sequences but also to the presence of regio- and stereoirregularities. The tendency of CG to give a nearly random comonomer distribution gives rise to so far undetectable alternating sequences. The complete set of assignments proposed allows a satisfactory characterization of variously microstructured E/ 4M1P copolymers and the evaluation of the amount of regioirregular sequences in addition to the full determination of dyad and triad copolymer composition.