Ethylene-1-dodecene copolymers were synthesized with novel low-Ti-loading (0.8 wt %,) Ziegler-Natta catalysts prepared by a one-pot balling method. C-13-NMR was applied for the quantitative determination of the composites and microstructures of the resultant ethylene-1-dodecene copolymers. The results showed that (1) the ethylene-ldodecene copolymers obtained from both the MgCl2/supported low-Ti-loading Ziegler-Natta catalyst and the MgCl2/ SiO2-bisupported low-Ti-loading Ziegler-Natta catalyst at a 0.6M 1-dodecene concentration had high levels of 1-dodecene and (2) most of the 1-dodecene units were separated by ethylene units in the copolymer chains obtained from the MgCl2- supported low-Ti-loading Ziegler-Natta catalyst, whereas there were some continuous I-dodecene repeat units in the copolymer chain obtained from the MgCl2/SiO2-bisupported low-Ti-loading Ziegler-Natta catalyst. (c) 2007 Wiley Periodicals, Inc.