Decisive Progress in Metallocene-Catalyzed Elastomer Synthesis

Abstract

Within the last 2 decades a large number of metallocene/MAO copolymerization catalysts has been developed, targeting tailor-made high-quality ethylene−propylene elastomers. However, under the widely used EP(D)M solution polymerization process temperatures, conventional metallocene catalysts give only access to the lower 15% of the commercial molecular weight range, established with Ziegler−Natta catalysts, which extends to about 106 g/mol. The novel class of donor−acceptor metallocenes makes a quantum leap in enhancing in EP(D)M molecular weights by orders of magnitude. Thus, the full molecular weight range of tailor-made polyolefin elastomers up to ultra high molecular weights is now accessible. At lower temperatures the D−A metallocene catalyst systems approach 100% chain growth selectivity in living olefin homo- and copolymerizations.

Isotactic poly(propylene‐co‐1‐pentene‐co‐1‐hexene) terpolymers: Synthesis, molecular characterization, and evidence of the trigonal polymorph

“…The use of metallocene catalysts from the late 1980s for the olefin polymerization introduced important changes as their single‐site characteristics leaded to produce polymers with nearly the same chain architecture, that is polyolefins with narrower molecular weight distributions rather than those synthesized using Ziegler–Natta catalysts and, consequently, with new properties. There are a variety of materials that, for the first time, could be prepared with high activity by these metallocene catalysts such as long‐chain‐branched polyethylene, polypropylenes with low amounts of oligomers and different tacticities (atactic, isotactic, isoblock, stereoblock, and syndiotactic), copolymers based on ethylene or propylene with a high proportion (5–30%) of long chain α‐olefins; elastomers made of ethylene, propene, and dienes (EPDM), syndiotactic polystyrene with a high melting point, homo‐ and copolymerization of cyclo‐olefins; and polymerization in the presence of fillers, filled polyolefins, or blends …”

Comparing elastomeric behavior of block and random ethylene–octene copolymers

“…Polyolefin‐based thermoplastic elastomers (TPEs) have received considerable attention due to their chemical inertness, low density, and low cost compared with other TPEs 1. Since olefin copolymers became commercially available in the 1960s,2 a sizable effort has been expended to develop catalyst technology3 and structure–property relationships for very low crystallinity olefin copolymers 4–11. To obtain elastomeric properties of low modulus and high recovery from large deformations, the crystallinity is usually less than 20 wt %.…”

Copolymerization of Propylene with Higher α-Olefins by a Pyridylamidohafnium Catalyst: An Effective Approach to Polypropylene-Based Elastomer

“…Since the first commercial POE developed by the copolymerization of ethene and 1-octene, many kinds of olefin-based elastomers with different multi-block or graft structures have been prepared by using different catalytic systems or synthetic strategies [10][11][12][13][14]. In these olefin-based elastomers, the crystalline PE chain domains (hard segments) acting as physical cross-links is indispensable for good strength, while the amorphous ethene/α-olefin chain domains (soft segments) endows the POE with an excellent elastic recovery [15,16].…”