A Comprehensive Review on Controlled Synthesis of Long‐Chain‐Branched Polyolefins: Part 2, Multiple Catalyst Systems and Prepolymer Modification

Long‐chain branching plays an important role in the performance of polyolefins (POs). The existence of a very small amount of long‐chain branches (LCBs), i.e., <1 per 10 000 carbons, can significantly improve processability of the polyolefin materials, which is highly desired for those intractable polyolefins with narrow molecular weight distribution and high degree of crystallinity. Numerous literatures have been published on the controlled synthesis of long‐chain‐branched POs. In the previous paper, the major literatures of single catalyst systems have been summarized. This paper provides a comprehensive review for the binary and multiple catalyst systems and a brief summary of some other methods for the controlled synthesis of long‐chain‐branched POs. The controllability of long‐chain‐branched structures in the various preparation procedures with single or two reactor systems, and in one or two‐step processes, is analyzed and compared in‐depth. The literatures pertinent to controlled synthesis of long‐chain‐branched polyolefins through two‐step processes with two or more catalysts are summarized and discussed. The two‐step processes can be implemented either in single‐reactor systems or in two‐reactor setups.