Premium
Molecular weight distribution of metallocene polymerization with long chain branching using a binary catalyst system
Author(s) -
Zhu Shiping,
Li Dean
Publication year - 1997
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/mats.1997.040060409
Subject(s) - branching (polymer chemistry) , metallocene , molar mass distribution , polymerization , post metallocene catalyst , polymer chemistry , long chain , materials science , polymer science , catalysis , chemistry , chemical engineering , polymer , organic chemistry , engineering
In metallocene polymerization, termination by β‐hydride elimination generates polymer chains containing unsaturated vinyl groups at their chain ends. Further polymerization of these macromonomers produces branched polymers. Material properties of the branched polymers not only depend on molecular weight and branching density, but also on chain structure. This work presents analytical expressions to predict the bivariate distribution of molecular weight and branching density for polymer chains having dendritic and comb structures. It is shown that when a single metallocene catalyst is used the formation of dendritic polymers is favored with only a very small fraction of highly branched chains assuming comb structure. The use of a binary catalyst system is therefore proposed to obtain high content of comb polymers. One catalyst generates macromonomers and the other yields in‐situ branching. It is found that the comb polymers give much narrower molecular weight distributions than dendritic polymers with same branching densities.