Statistical olefin block copolymers (OBCs) with "hard" and "soft" linear low-density polyethylene (LLDPE) blocks can be synthesized by tandem catalysis under "coordinative chain transfer polymerization" (CCTP) conditions. This process, disclosed in 2006 and commonly referred to as "chain shuttling copolymerization" (CSCP), is now exploited commercially by Dow Chemical, to produce thermoplastic elastomers with the Infuse trade name. Whereas the general kinetic principles of CSCP as well as the fundamental physical properties of the products are rather well-understood, the details are still poorly defined, to the point that even average block numbers and lengths of commercial Infuse grades are not available in the public domain. In this paper, we report the results of a molecular kinetic investigation in which high throughput experimentation tools and methods were employed to unravel the microstructure and architecture of these materials. The problem was factored in two parts. First, each of the two catalysts in the original Dow Chemical formulation was studied individually in ethene/1-hexene CCTP. Next, the two catalysts together were used in CSCP experiments under otherwise identical reaction conditions. The robust database thus obtained enabled us to disambiguate the interpretation of the results, and sort out system behavior as a function of the relevant variables. Plausibly, the process turned out to be governed by the relative probabilities of "self-shuttling" versus "cross-shuttling" (that is, of exchanging blocks of the same or different type). In particular, the synthesis of OBCs with long hard blocks and an excess of soft blocks, which are those featuring the most desirable application properties, requires a moderate chain shuttling rate and an excess of the catalyst with the higher comonomer incorporation ability; as a result, at practical average molecular weight values, these products are characterized by a pronounced interchain disuniformity, with an abundant fraction of chains undergoing exclusively "self-shuttling" at the aforementioned catalyst, and therefore consisting of just one soft block.

In this study, a state-of-the-art high-throughput experimentation (HTE) workflow for catalytic olefin polymerization, covering an unprecedented wide part of the polymer knowledge and value chains from catalytic synthesis all the way down to "engineering" microrheology, was thoroughly assessed with respect to its ability to prepare new materials and produce large and accurate databases for the investigation of quantitative structure−property relationships (QSPRs). Olefin blocks copolymers (OBCs) produced under chain-shuttling polymerization conditions were used as a demonstration case. The results of a thorough microstructural, structural, mechanical, morphological, and rheological characterization of OBC replicas prepared with the HTE synthetic platform and a commercial sample, chosen as a benchmark, demonstrate the robustness of the approach. The proposed workflow can become a paradigm for the high-throughput synthesis and investigation of novel materials, thus reducing the time to market of new products. In our opinion, this opens the door to integrated HTE and artificial intelligence approaches to QSPR problem solving in the numerous cases for which a thorough understanding of the theory is not sufficient to deterministically unravel the complexity of practical applications.

Efficient and economical plastic waste upcycling relies on the development of catalysts capable of polymer degradation. A systematic high-throughput screening of twenty-eight polymerization catalyst precursors, belonging to the catalyst families of metallocenes, ansa-metallocenes, and hemi-and post-metallocenes, in cis-1,4-polybutadiene (PB) degradation reveals, for the first time, important structure-activity correlations. The upcycling conditions involve activation of the catalysts (at 0.18 % catalyst loading) with tri-isobutyl aluminum at 50 °C in toluene. The data indicate the ability to degrade PB is a general reactivity profile of neutral group 4 metal hydrides. A simple quantitative-structure activity relationship (QSAR) model utilizing two descriptors for the distribution of steric bulk in the active pocket and one measuring the metal ion electrophilicity reveals the degradation ability improves with increased but not overbearing steric congestion and lower electrophilicity.

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High-impact polypropylenes (HIPPs) are complex blends, featuring a crystalline isotactic polypropylene matrix and a dispersed phase consisting of an amorphous ethylene/propylene copolymer (EPR). The relative amount of EPR and its composition heavily affect the application properties of the material and need to be accurately controlled. Standard analytical methods are time- and labor-intensive and require considerable amounts of sample and of a toxic solvent, xylene. Here, we introduce an analytical approach to HIPP characterization based on crystallization elution fractionation. The approach is fast, can be operated on just a few mg of sample, and does not require sophisticated and expensive techniques.