Comparing strategies for the synthesis of polyolefinic thermoplastic elastomers via macromonomer incorporation

Abstract

The microstructure of polyolefinic thermoplastic elastomers made with a combination of two single-site catalysts was analyzed by Monte Carlo simulation. The model can be used to describe the crystallizable fraction for both long-chain branched polypropylene (aPP-g-iPP) and long-chain branched ethylene/α-olefin copolymers (PEαO-g=PE). The simulations showed that at levels of 7.5% of comonomer incorporation, PEαO-g-PE samples reach a similar crystallizability level of aPP-g-iPP. From a topological point of view, it was demonstrated that the fraction of free arms and inner segments tend to the limit of 1/2 for highly branched chains and that the fraction of free arms reaches its maximum value when the Y-type chains are the predominant population. A mathematical correlation between the linear- and LCB catalyst probabilities was proposed to ensure the production of symmetrical branched chains.