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  1. Article ; Online: A Hydrocarbon Soluble, Molecular and “Complete” Al-Cocatalyst for High Temperature Olefin Polymerization

    Gaia Urciuoli / Francesco Zaccaria / Cristiano Zuccaccia / Roberta Cipullo / Peter H. M. Budzelaar / Antonio Vittoria / Christian Ehm / Alceo Macchioni / Vincenzo Busico

    Polymers, Vol 15, Iss 1378, p

    2023  Volume 1378

    Abstract: The dinuclear aluminum salt {[ i Bu 2 (DMA)Al] 2 ( μ -H)} + [B(C 6 F 5 ) 4 ] − ( AlHAl ... DMA = N , N -dimethylaniline) is the prototype of a new class of molecular cocatalysts for catalytic olefin polymerization, its modular nature offering easy avenues ... ...

    Abstract The dinuclear aluminum salt {[ i Bu 2 (DMA)Al] 2 ( μ -H)} + [B(C 6 F 5 ) 4 ] − ( AlHAl

    DMA = N , N -dimethylaniline) is the prototype of a new class of molecular cocatalysts for catalytic olefin polymerization, its modular nature offering easy avenues for tailoring the activator to specific needs. We report here, as proof of concept, a first variant ( s-AlHAl ) bearing p -hexadecyl- N , N -dimethylaniline (DMA C16 ) units, which enhances solubility in aliphatic hydrocarbons. The novel s-AlHAl was used successfully as an activator/scavenger in ethylene/1-hexene copolymerization in a high-temperature solution process.
    Keywords olefin polymerization ; catalyst activation ; borate activators ; methylaluminoxane ; soluble cocatalyst ; Organic chemistry ; QD241-441
    Language English
    Publishing date 2023-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Chain Transfer to Solvent and Monomer in Early Transition Metal Catalyzed Olefin Polymerization

    Francesco Zaccaria / Peter H. M. Budzelaar / Cristiano Zuccaccia / Roberta Cipullo / Alceo Macchioni / Vincenzo Busico / Christian Ehm

    Catalysts, Vol 11, Iss 2, p

    Mechanisms and Implications for Catalysis

    2021  Volume 215

    Abstract: Even after several decades of intense research, mechanistic studies of olefin polymerization by early transition metal catalysts continue to reveal unexpected elementary reaction steps. In this mini-review, the recent discovery of two unprecedented chain ...

    Abstract Even after several decades of intense research, mechanistic studies of olefin polymerization by early transition metal catalysts continue to reveal unexpected elementary reaction steps. In this mini-review, the recent discovery of two unprecedented chain termination processes is summarized: chain transfer to solvent (CTS) and chain transfer to monomer (CTM), leading to benzyl/tolyl and allyl type chain ends, respectively. Although similar transfer reactions are well-known in radical polymerization, only very recently they have been observed also in olefin insertion polymerization catalysis. In the latter context, these processes were first identified in Ti-catalyzed propene and ethene polymerization; more recently, CTS was also reported in Sc-catalyzed styrene polymerization. In the Ti case, these processes represent a unique combination of insertion polymerization, organic radical chemistry and reactivity of a M(IV)/M(III) redox couple. In the Sc case, CTS occurs via a σ-bond metathesis reactivity, and it is associated with a significant boost of catalytic activity and/or with tuning of polystyrene molecular weight and tacticity. The mechanistic studies that led to the understanding of these chain transfer reactions are summarized, highlighting their relevance in olefin polymerization catalysis and beyond.
    Keywords olefin polymerization ; chain transfer ; solvent activation ; chain ends ; homolysis ; Ti(IV)/Ti(III) redox couple ; Chemical technology ; TP1-1185 ; Chemistry ; QD1-999
    Subject code 540
    Language English
    Publishing date 2021-02-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article: Unprecedented Large Hyperpolarizability of Twisted Chromophores in Polar Media

    Lou, Alexander J.-T / Alceo Macchioni / Christopher Barger / Cristiano Zuccaccia / Elena Cariati / Stefania Righetto / Tobin J. Marks

    Journal of the American Chemical Society. 2018 June 18, v. 140, no. 28

    2018  

    Abstract: Twisted intramolecular charge transfer (TICT) chromophores exhibit uniquely large second-order optical nonlinearities (μβ). However, their promise as electro-optic (E-O) materials is yet untapped, reflecting a strong tendency to aggregate in low-polarity ...

    Abstract Twisted intramolecular charge transfer (TICT) chromophores exhibit uniquely large second-order optical nonlinearities (μβ). However, their promise as electro-optic (E-O) materials is yet untapped, reflecting a strong tendency to aggregate in low-polarity media, leading to a dramatic fall in μβ. Until now, TICT chromophores in deaggregating polar solvents suffered decreased response due to polarity-driven changes in electronic structure. Here we report a new series of benzimidazolium-based TICT chromophores with interaryl torsional angles in the range of 64–77°. The most twisted, B2TMC-2, exhibits a large μβvec = −26,000 × 10–48 esu (at 1907 nm) in dilute nonpolar CH2Cl2 solution, which is maintained in polar DMF (μβvec= −20,370 × 10–48 esu) as measured by DC electric field-induced second harmonic generation (EFISH). Sterically enforced interaryl torsional angles are confirmed by single-crystal X-ray diffraction and solution phase Nuclear Overhauser Effect (NOE) NMR, and spectroscopic characterization reveals a zwitterionic/aromatic ground state electronic structure associated with the high μβ. We show that increasingly disrupted conjugation is correlated with increased μβ even at intermediate twist angles. The excellent performance and reduced aggregation in polar solvents opens new avenues for bridging microscopic and macroscopic chromophore performance.
    Keywords methylene chloride ; nuclear magnetic resonance spectroscopy ; solvents ; spectral analysis ; X-ray diffraction ; zwitterions
    Language English
    Dates of publication 2018-0618
    Size p. 8746-8755.
    Publishing place American Chemical Society
    Document type Article
    ZDB-ID 3155-0
    ISSN 1520-5126 ; 0002-7863
    ISSN (online) 1520-5126
    ISSN 0002-7863
    DOI 10.1021/jacs.8b04320
    Database NAL-Catalogue (AGRICOLA)

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