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HTE-based opportunities for mastering olefin polymerization catalysts and processes
No full textChemistry in general is not an exact science. Chemical catalysis, moreover, is a purely kinetic phenomenon. This translates into the fact that discovering and even optimizing a catalyst for a desired application heavily relies on trial-and-error, and serendipitous advances are not rare.
In recent years, we spent a considerable effort to extend the scope of HTE from discovery to mechanistic investigations. The general objective was to introduce protocols for ‘smart’ applications of an existing HTE workflow to complex chemical problems in polyolefin catalysis. In particular, methods for the rapid and accurate determination of the Quantitative Structure-Activity Relationship (QSAR) of representative molecular or heterogeneous catalyst formulations were implemented as the basis for statistical modeling with predictive ability.
A high-performance polymerization platform (Freeslate PPR48) was integrated with state-of-art polymer characterization tools (including GPC, 13C NMR and A-CEF), and the workflow was optimized for the fast acquisition of large structure-properties databases. The approach was successfully applied to Ziegler-Natta and molecular olefin polymerization catalysts. Chain shuttling chemistry represented an extreme challenge, because operating reliably in solution at high temperature under controlled kinetic conditions in HTE scale is highly demanding; on the other hand, exploring exhaustively the complex variables hyperspace of this chemistry with conventional methods is also challenging, and requires a very long time.
In the present talk, we want to share the idea that innovation in chemistry is not over even in areas that are considered mature, like e.g. catalytic olefin polymerization. Many chemical problems, including long standing ones, can rapidly find a solution as soon as adequate information becomes available. This simple and – in a way – trivial concept is often overlooked because the actual complexity of chemical systems tends to be under-estimated
Highly Regioselective Transition-Metal-Catalyzed 1-Alkene Polymerizations: A Simple Method for the Detection and Precise Determination of Regioirregular Monomer Enchainments
Full text linkHTE-aided QSAR modeling of olefin polymerization catalysts: another step towards catalyst design
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Catalyst Design Using HTE Tools and DFT QSAR Modeling: A Case Study on C2-symmetric Bis-Indenyl Type Zirconocenes in Propene Polymerization
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High-Field 13C NMR Characterization of Ethene-1-13C/Propene Copolymers Prepared with Cs-Symmetric ansa-Metallocene Catalysts: A Deeper Insight into the Regio- and Stereoselectivity of Syndiotactic Propene Polymerization
Full text linkIn this paper, we report the results of a 150 MHz 13C NMR characterization of ethene-1-
13C/propene copolymers at low (<5 mol %) ethene content prepared in the presence of the syndiotacticselective
ansa-metallocene catalyst (Me)(Ph)C(cyclopentadienyl)(9-fluorenyl)ZrCl2 (cocatalyst, MAO). In
particular, from the fine structure of the resonances of the ethene-1-13C units we conclude that the
enantioselectivity of 1,2-propene insertion is substantially lower and the probability of chain back-skip
substantially higher after an ethene insertion than after a propene one. Moreover, we find that the
regioirregular 2,1-propene units (whose concentration is higher than claimed in the literature) are also
substantially stereoirregular
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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