Detailed Microstructure Analysis Through Monomeric Insertion Modes of Poly(propylene-Co-norbornene) Copolymers and Poly(propylene-Co-ethylene-co-norbornene) Terpolymers with Low Norbornene Contents

Polypropylene-based thermoplastic elastomers continue to be materials of enormous industrial interest because of their high mechanical performance and durability. These materials are especially important, for instance, in the automotive industry, where these polyolefins accounts for up to 32% of the total plastic used in a car. In the search for new grades, poly(propylene-co-ethylene-co-norbornene) terpolymers might be of interest for the production of a new class of thermoplastic elastomers, whose properties could be tailored by controlling the composition, as well as its distribution. Unfortunately, thorough characterization of these materials has not been possible so far, because of the complexity of their 13CNMR spectra. In this work, two series of poly(propylene-co-norbornene) copolymers and poly(propylene-co-ethylene-co-norbornene) terpolymers, containing low molar fractions of norbornene and ethylene-norbornene, respectively, have been synthesized and characterized in detail by NMR analysis. The comparison of 13CNMR spectra in both series and their respective changes with norbornene ratio in the feed enables a complete assignment of signals, which reveals that the terpolymers are featured by a well-defined microstructure, consisting of propylene sequences bound by both PEP triads and well-defined norbornene-ethylene sequences. Such a particular distribution results from an associated insertion of the ethylene and the norbornene that, in addition, accounts for the higher contents of both comonomers, when compared with their respective copolymers, obtained under the same reaction conditions.