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Natta chionogaster (Simon, 1901) Cyllobelus chionogaster Simon, 1901a: 151. Cyllobelus australis Peckham & Peckham, 1902: 334. Cyllobelus chionogaster – Simon 1901c: 541, 549, fig. 665. — Peckham & Peckham 1903: 195, pl. 21 fig. 1. Cyllobelus australis – Peckham & Peckham 1903: 194, pl. 21 fig. 2. Natta chionogaster – Wesołowska 1993: 18, figs 1–16. For full reference list see World Spider Catalog (2022). Material examined IVORY COAST • 1 ♂; Lamto; 16 Sep. 1975; “savane, base des herbes”; MNHN • 1 ♂; same collection data as for preceding; 3 Jan. 1975; “savane non-brulée, base des herbes”; MNHN • 1 ♂; Mt Niangbo; 16 Oct. 1975; “savane arborée, sol et herbes”; MNHN. Description For both sexes see Wesołowska (1993). Distribution Widespread in the Afrotropical Region., Published as part of Wesołowska, Wanda & Russell-Smith, Anthony, 2022, Jumping spiders from Ivory Coast collected by J. - C. Ledoux (Araneae, Salticidae), pp. 1-143 in European Journal of Taxonomy 841 (1) on page 69, DOI: 10.5852/ejt.2022.841.1943, http://zenodo.org/record/7195354, {"references":["Simon E. 1901 a. Descriptions d'arachnides nouveaux de la famille des Attidae (suite). Annales de la Societe entomologique de Belgique 45: 141 - 161. Available from https: // www. biodiversitylibrary. org / page / 36148105 [accessed 16 Aug. 2022].","Peckham G. W. & Peckham E. G. 1902. Some new genera and species of Attidae from South Africa. Psyche 9 (312): 330 - 335. https: // doi. org / 10.1155 / 1902 / 13502","Simon E. 1901 c. Histoire naturelle des Araignees. Deuxieme edition, tome second. Roret, Paris. https: // doi. org / 10.5962 / bhl. title. 51973","Peckham G. W. & Peckham E. G. 1903. New species of the family Attidae from South Africa, with notes on the distribution of the genera found in the Ethiopian region. Transactions of the Wisconsin Academy of Sciences, Arts and Letters 14: 173 - 278.","Wesolowska W. 1993. Notes on the genus Natta Karsch, 1879 (Araneae, Salticidae). Genus 4: 17 - 32.","World Spider Catalog. 2022. Version 23.0. Natural History Museum Bern. Available from http: // wsc. nmbe. ch [accessed 6 Jan. 2022]. https: // doi. org / 10.24436 / 2"]}

Natta horizontalis Karsch, 1879 Natta horizontalis Karsch, 1879: 362. Natta horizontalis – Wesołowska 1993: 25, figs 22–41. For full reference list see World Spider Catalog (2022). Material examined IVORY COAST • 1 ♂; Lamto; 22 Aug. 1975; “sous bois, au sol”; MNHN • 1 ♀; same collection data as for preceding; 12 Aug. 1975; “savane gruyére, hautes des herbes”; MNHN • 1 ♂; same collection data as for preceding; 12 Aug. 1975; “lisière, savane du rocher 1 km E de la station”; MNHN • 1 ♀; same collection data as for preceding; 6 Sep. 1975; “savane, base des herbes”; MNHN • 1 ♀; same collection data as for preceding; 13 Oct. 1975; “savane, au sol”; MNHN • 1 ♀; same collection data as for preceding; “savane, base des herbes”; MNHN • 1 ♀; same collection data as for preceding; 15 Sep. 1975; “sur un nid de magnans aux environs de la station”; MNHN • 1 ♀; Man; 7°24′ N, 7°33′ W; 9 Apr. 1978; “derièrre l’hôpital, forêt secondaire”; MNHN. Description See Wesołowska (1993). Distribution Widely distributed in Africa., Published as part of Wesołowska, Wanda & Russell-Smith, Anthony, 2022, Jumping spiders from Ivory Coast collected by J. - C. Ledoux (Araneae, Salticidae), pp. 1-143 in European Journal of Taxonomy 841 (1) on page 69, DOI: 10.5852/ejt.2022.841.1943, http://zenodo.org/record/7195354, {"references":["Karsch F. 1879. West-afrikanische Arachniden, gesammelt von Herrn Stabsarzt Dr. Falkenstein. Zeitschrift fur die Gesammten Naturwissenschaften 52: 329 - 373.","Wesolowska W. 1993. Notes on the genus Natta Karsch, 1879 (Araneae, Salticidae). Genus 4: 17 - 32.","World Spider Catalog. 2022. Version 23.0. Natural History Museum Bern. Available from http: // wsc. nmbe. ch [accessed 6 Jan. 2022]. https: // doi. org / 10.24436 / 2"]}

Heterogeneous derivatives of catalysts discovered by Ziegler and Natta are important for the industrial production of polyolefin plastics. However, the interaction between precatalysts, alkylaluminum activators, and oxide supports to form catalytically active materials is poorly understood. This is in contrast to homogeneous or model heterogeneous catalysts that contain resolved molecular structures that relate to activity and selectivity in polymerization reactions. This study describes the reactivity of triisobutylaluminum with high surface area aluminum oxide and a zirconocene precatalyst. Triisobutylaluminum reacts with the zirconocene precatalyst to form hydrides and passivates −OH sites on the alumina surface. The combination of passivated alumina and zirconium hydrides formed in this mixture generates ion pairs that polymerize ethylene., A zirconium precatalyst, alkylaluminum, and oxide support interact to form catalytic sites.

In this study, commercially available, milled, and heat-treated Mg(OEt)2 were used as the precursors in the synthesis procedure of industrially-favorable supported Ziegler–Natta catalysts. The effects of milling and heat-treatment of the support were completely investigated during the catalyst synthesis and polymerization using SEM, PSD, BET, DCS, and XRD techniques. It was found that despite the support treatments had no significant effect on the elemental analysis results of the catalysts, the morphology of the catalyst pores was very sensitive to support manipulation, and bottleneck-type pores were predominated in the catalysts which were made using the non-manipulated supports. On the other hand, the catalysts which were made using the milled and not-milled supports showed a clear difference between the activity, particle size, and particle size distribution of the catalysts. Also, a high level of stacking disorder and high grain size was observed in the crystal structure of the catalyst made using the commercially available support. In the following, competition between fragmentation and replication was investigated in the synthesized samples, and an attempt was made to link the stacking disorder (in the catalyst structure) to the ease of the fragmentation process. Finally, using practical observation, a mechanism was proposed to justify the changes in the morphology of the catalysts during synthesis procedures. We claimed that milling and especially heat-treating of the support leads to the ordering of the MgCl2 stacking structure.

A full elucidation of chemisorbed donor behavior is of fundamental importance for tailoring the active species but has not yet been achieved for Ziegler–Natta catalysts. Herein, by exploiting the s...

Although Ziegler-Natta catalysts were discovered more than four decades ago, many aspects of their characteristics are not fully understood. The effect of the support particle size on the final pro...

Many researchers have studied the effects of donors, promoters and alkyl aluminum compounds on the polymerization catalysts, the polymerization process and the final properties of polymers. Neverth...

The effect of nanosize and structural disorder on the MgCl2 support of Ziegler–Natta catalysts has been investigated in terms of induced changes to their vibrational spectroscopic fingerprint. In p...

Herein, we study comparatively melt-memory effects on recrystallization of two sets of linear low-density polyethylenes (LLDPE) synthesized with Ziegler–Natta (ZN-LLDPE) and with metallocene cataly...

A multivariate aspect has hampered the clarification of structure-performance relationships in heterogeneous Ziegler-Natta olefin polymerization catalysis. Here, 16 catalyst samples were prepared using Mg(OEt)2 support precursors with different particle architectures. They were fingerprinted based on a series of characterization and analytical methods. In a pairwise correlation analysis, none of structural features (such as particle size and pore volume) exhibited a clear correlation with ethylene polymerization performance. However, compound features created among different structural features reasonably reproduced the ethylene polymerization activity as well as 1-hexene incorporation efficiency, where a negative influence of pores with the size below 10 nm was dictated.

The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl4/MgCl2 Ziegler-Natta (Z-N) catalysts are determined by the structure and nature of active centers, which are mysterious and fairly controversial. In this work, the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene (PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity, active centers with different tacticity and propagation rate constant kp, fragmentation of the catalyst, crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature (60 °C) resulted higher activity, kp and lower [C*], and the isotactic active centers Ci* as the majority ones producing the highest isotactic polypropylene (iPP) components showed much higher kp when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles, and provide the solutions to the improvement of catalyst activity and isotacticity of PP.

In the field of Ziegler–Natta catalysis for olefin polymerization, carbon monoxide (CO) is used in the industrial practice to quench the reaction when it proceeds too fast, approaching critical levels for the plant safety. The quenching effect is explained as due to the reversible coordination of CO to the titanium active sites, but no direct evidence has been ever reported. In this work, we designed a series of experiments to monitor CO adsorption at variable temperatures on a model Ziegler–Natta catalyst by means of FT-IR spectroscopy. For the first time, we have been able to spectroscopically detect CO coordinated to alkylated Ti3+ sites and the Ti–acyl species formed upon the subsequent insertion of CO into the Ti3+–alkyl bond, both in the absence and in the presence of the olefin monomer. In perspective, this has important implications for the characterization of the active sites in industrial Ziegler–Natta catalysts, even under working conditions.

This paper presents the results of study of titanium–magnesium catalysts often used in polymerization processes, by photoluminescence spectroscopy (PL) in combination with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The interaction of dibutyl phthalate (DBP) with MgCl2was studied at DBPadded/Mg = 0–1 (mol/mol). The luminescence spectra with excitation at 278 nm and the excitation spectra for main emission bands were recorded. It was shown that DBP adsorbed on magnesium chloride, both in the form of donor–acceptor complexes (D+A–) and in the form of molecular complexes. At DBPadded/Mg +A–complexes occur predominantly; with an increase in DBPadded/Mg, the fraction of molecular complexes increases. Molecular complexes are destroyed during the treatment of the support by TiCl4. In this case, the structure of magnesium chloride is disordered and new coordination–unsaturated sites are formed. This work is a first attempt to apply PL spectroscopy in combination with DRIFTS spectroscopy to study titanium–magnesium Ziegler–Natta catalysts. The application of PL spectroscopy to such systems made it possible to detect interactions within and between donor molecules, which would be particularly challenging to achieve using other spectroscopic methods. Both spectroscopic methods provided crucial information about the existence of two types of complexes on the sample surface which is important for tuning the synthesis procedure of the titanium–magnesium catalysts for olefin polymerization.

1,9-decadiene/propylene copolymerization is assessed as a way for Ziegler-Natta catalysts to access long chain-branched polypropylene. A MgCl2/9,9-bis-(methoxymethyl)fluorine/TiCl4 catalyst with tr...

This study reported novel eco-friendly Ziegler-Natta catalysts containing bio-derived maleic rosinate tri-n-butyl and maleic rosinate tri-n-octyl as internal electron donors for propylene polymeriz...

Natta horizontalis Karsch, 1879 Natta horizontalis Karsch 1879: 362. Pochyta moschensis Caporiacco, 1947: 249, pl. 2, fig. 76 (D ♀), syn. n. For full reference list see World Spider Catalog (2021). Type material. Holotype of P. moschensis, female: TANZANIA: Moshi [Moschi in German], 3°20’S 37°20’E, Ran stream, leg. VI-VII.1906, leg. K. Kittenberger (HNHM). Remarks. The holotype of Pochyta moschensis is in good condition. There is no doubt that this specimen has been misidentified, and that in reality it is Natta horizontalis, common species in Africa. The first author knows N. horizontalis very well and redescribed it (Wesołowska 1993)., Published as part of Wesołowska, Wanda & Szűts, Tamás, 2021, A revision of the genus Pochyta Simon, with descriptions of new species (Araneae: Salticidae: Thiratoscirtina), pp. 1-41 in Zootaxa 5052 (1) on page 38, DOI: 10.11646/zootaxa.5052.1.1, http://zenodo.org/record/5565881, {"references":["Karsch, F. (1879) West-afrikanische Arachniden, gesammelt von Herrn Stabsarzt Dr. Falkenstein. Zeitschrift fur die Gesammten Naturwissenschaften, 52, 329 - 373.","Caporiacco, L. di (1947) Arachnida Africae Orientalis, a dominibus Kittenberger, Kovacs et Bornemisza lecta, in Museo Nationali Hungarico servata. Annales Historico-Naturales Musei Nationalis Hungarici, 40, 97 - 257.","World Spider Catalog (2021) World Spider Catalog. Version 22.5. Natural History Museum Bern. Available from: http: // wsc. nmbe. ch (accessed 17 May 2021) https: // doi. org / 10.24436 / 2","Wesolowska, W. (1993) Notes on the genus Natta Karsch, 1879 (Araneae, Salticidae). Genus, 4 (1), 17 - 32."]}

The scientific and technical advances in the field of polymer science has been abundant in recent years. Amongst the various polymeric materials available in market, synthesis of polyolefins has been in the forefront since decades. A major challenge in this domain remains in attaining stereoregular polyolefins especially polypropylene (PP) and significant efforts were carried out by synthesizing various internal donors (ID) aiding the catalysts involved in producing them. This short review gives an overview of i) various generations of Ziegler–Natta (ZN) catalyst systems ii) general classes of ID that has been demonstrated by the researchers over the past decades iii) their influence on PP isotacticity and polymer properties. The coordination modes of different donor classes on supported ZN system and comparative study especially between phthalate and diether ID classes were also addressed here. This review also presents the studies carried out on phthalate catalyst structure analysis, detailed comparison study on phthalate and diether IDs in terms of PP isotacticity, regioselectivity, hydrogen response, and also their cross combination study and competitive behavior. Further a brief description on other structurally varied IDs like malonates, maleates, silyl diol esters, bifunctional donors, multi ether donors demonstrated for isotactic PP were also presented. Studies conducted on compatibility of incorporation of two different classes of IDs on a single supported ZN system for the fundamental understanding of the catalyst behavior; and also on how mixed donor approach enables in tuning the catalyst for polymer properties were also presented. This review also provides an opportunity to the young minds and the basic researchers from academic point of view by and large to create new polymeric materials with useful properties or modify the existing materials for new applications by incorporating new IDs for further improvisation of the stereo regularity in obtaining the polymers. Graphic Abstract

Two series of polypropylene samples (PP) were prepared with two MgCl2/TiCl4-type catalysts with diisobutyl phthalate and 9,9-bis(methoxymethyl)fluorine as internal donors (named as cat1 and cat2), ...

MgCl2 supported Ziegler–Natta (Z–N) catalysts have emerged as the most exciting chemical process for polyolefin technology, which is responsible for the production of ∼150 million tons of polyolefin (polyethylene and polypropylene) per annum. However, fundamental chemistry of Z–N catalysts is not fully understood yet due to their multi-component nature as well as heterogeneous systems. Therefore, in this review, we have highlighted the chronological development of a heterogeneous Z–N catalyst and its polymerization (ethylene, propylene and 1-butene) process including termination steps. Then, we have discussed different structural and chemical aspects of the catalyst support, catalytically active sites, cocatalyst, internal/external electron donors and their different combinations. In the last two decades, density functional theory (DFT) has been employed in Z–N systems to strengthen the experimental work as well as to understand mechanistic aspects of Z–N systems. Future directions of Z–N catalysts have also been discussed.

The crystallization behavior of butene-ethylene random isotactic copolymers prepared with a Ziegler-Natta catalyst, in particular the surprising crystallization of form II of isotactic polybutene in samples with a high ethylene concentration, provides novel evidence of the long-debated blocky molecular structure of these "random" copolymers.

Advanced High Throughput Experimentation (HTE) methods were applied to quantify the regioselectivity and the so-called "hydrogen response" in propene polymerization of four Ziegler-Natta catalysts representative of the three latest industrial generations (i.e., modified with a dialkyl phthalate, 1,3-dimethoxypropane or dialkyl succinate Internal Donor), used in combination with AlEt3 and a library of eight alkoxysilane External Donors with large structural diversity. At odds with stereoselectivity, regioselectivity turned out to be only modestly impacted by the chemical structure of the electron donors used as surface modifiers. A clear and simple relationship between regioselectivity and "hydrogen response", and, therefore, polymer molecular weight modulation was highlighted.

Chain entanglement was very important for adjusting the processability and mechanical property of nascent ultrahigh molecular weight polyethylene (UHMWPE). So far, it is still a mystery to unravel ...

A new multidentate carbonate (3,3,3′,3′-tetramethyl-2,2′,3,3′-tetrahydro-1,1′-spirobiindane-5,5′,6,6′-tetracarbonate) is studied as a potential internal electron donor for Ziegler–Natta (Z–N) catal...

This paper introduces a high throughput experimentation method for fast and accurate evaluations of regioselectivity in Ziegler–Natta (ZN) propene polymerizations. With a simple protocol, the (very low) fraction of regio-irregular 2,1 monomeric units in the polymers can be quantitated by means of 13C NMR chain-end analyses on single H2-terminated polypropylene samples. The method, that was successfully validated for three representative ZN catalyst systems, also provides information on catalyst “dormancy” and propensity to undergo chain hydrogenolysis. This opens the door to the rapid and accurate implementation of quantitative structure–activity relationship (QSAR) databases of regioselectivity and “hydrogen response” in this important industrial catalysis.

Bromoalkyl-functionalized poly(olefin)s were synthesized by copolymerization of 4-(4-methylphenyl)-1-butene with 11-bromo-1-undecene using Ziegler–Natta polymerization. The resulting bromoalkyl-fun...

Propylene polymerization with two TiCl4/MgCl2 catalysts (Cat-1: Ti 0.1%; Cat-2: Ti 1.0%) showed different responses to (cyclo-C5H9)2Si(OCH3)2 (De) addition. Cat-1 was deactivated more than Cat-2 by De. Amount of three groups of active centers producing atactic, medium isotactic and isotactic polypropylene chains were all reduced by De addition, but those of Cat-1 were reduced more. Reactivity of the isospecific active centers (kpi) was enhanced by De, but kpi of Cat-2 was changed more sensitively than Cat-1. The lower stereoselectivity of Cat-1 than Cat-2 are attributable to weaker De adsorption on its surface Mg, and the more sparsely dispersed Ti species on Cat-1 is responsible for weak De adsorption.

This chapter presents fascinating insights into the research that earned its investigators Nobel Prizes in the field of organometallic chemistry: Karl Ziegler and Giulio Natta for olefin polymerization catalysts (1963), Ernst Otto Fischer and Geoffrey Wilkinson for sandwich compounds (1973), Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa for electrically conductive polymers (2000), William S. Knowles, Ryoji Noyori and K. Barry Sharpless for asymmetric catalysis (2001), Yves Chauvin, Robert H. Grubbs and Richard R. Schrock for olefin metathesis (2005), and Richard F. Heck, Eiichi Negishi and Akira Suzuki for Pd-catalyzed cross-coupling reactions (2010).

By combining the elementary reactions described in Chapter 6, transformations catalyzed by organometallic complexes can be constructed. This chapter introduces representative reaction systems catalyzed by organometallic complexes, and outlines the reactions occurring. Ziegler catalysts, prepared from tetrachlorotitanium (TiCl4) and alkylaluminium reagents (AlEt3 or AlEt2Cl), and Natta catalysts, prepared from crystalline TiCl3 and alkylaluminium, are very effective for olefin and propylene polymerization, respectively. This development was a paradigm shift, and Ziegler and Natta received the Nobel Prize in Chemistry in 1963 for their discoveries in the field of the chemistry and technology of high polymers. Transition metal complexes serve as catalysts and are used industrially, such as in olefin isomerization, olefin hydroformylation, the production of acetaldehyde by ethylene oxidation (the Wacker process) and the production of acetic acid from methanol and carbon monoxide (the Monsanto process). These catalytic systems successfully apply the elementary organometallic chemistry reactions described in this book and the basis of the catalytic action in these reactions is explained.

Developing donors for Ziegler‐Natta (ZN) catalysis to control the polymerization reaction and produce polymers with desirable properties has always been challenging due to the multi‐component nature of the catalytic systems. Here, we have developed a new synthetic protocol for making two external donors, D 1 (2,2,2‐trifluoroethyl myristate) and D 2 (2,2,2‐trifluoroethyl palmitate) that show self‐extinguishing properties, followed by a systematic DFT study to understand this peculiar property of these donors. D 1 and D 2 can undergo parallel reactions with aluminum and titanium species present in the system to produce ketones and aldehydes, which are poisons for ZN catalytic systems, thus explaining their self‐extinguishing nature. The non‐covalent interaction between the long alkyl chain of the donors with the surface plays a vital role in determining the donors' self‐extinguishing nature. There is a significant thermodynamic preference for the binding of the donor with the longer alkyl chain at the titanium center. The current work, therefore, provides interesting insights into how self‐extinguishing donors function in ZN catalytic systems.

The innovation of Ziegler-Natta (Z-N) catalysts opened a novel aspect of chemistry in terms of polyolefin formation. Significant progress of more than fifty years in catalytic olefin polymerization simplified polyolefin production by optimizing the reaction conditions and internal donors. In this review, we particularly emphasized on recent development on different internal donor based Z-N catalyst systems, the role of external electron donors and co-catalyst chemistry. Furthermore, the Ziegler-Natta catalyst system, polymerization reaction, and polymer process technologies gradually upgrading to produce different polyolefin products. In particular, polyolefin fibers, composites, foam, blends and polyolefin-based 3D-printing products targeted in this review for substantial benefits of both society and highly diversified industries.

International audience; Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler–Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of active sites of ZN catalysts in the absence of ethylene, referred to as dormant active sites, is elucidated from magnetic resonance experiments carried out on samples reacted with increasing amounts of BCl3 so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using electron paramagnetic resonance (EPR) and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by density functional theory (DFT) calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl2-supported Ziegler–Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene and enables us to propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations.

In this contribution, novel bio-derived rosin acid ester compounds have been developed and used as internal electron donors to prepare MgCl2 supported titanium catalysts for propylene polymerization. The results of the polymerization showed that tri-n-amyl maleate, triiso-amyl maleate and tri-n-heptyl maleate as internal electron donors in Ziegler-Natta catalysts all have high polymerization activity and stereoregularity. In particular, the Ziegler-Natta catalyst with tri-n-amyl maleate as the internal electron donor has the highest activity (up to 33.4 kgPP·gCat−1·h−1) for propylene polymerization and the isotacticity of polypropylene is as high as 96.8% determined by 13C NMR. Simultaneously, the obtained polypropylene with a relatively broad molecular weight distribution of 9.0 and melt flow rate of 160.3 g/10 min, which is beneficial to processing and has practical industrial application value when used as the basic material of melt blown cloth for medical mask.

This data article provides a dataset of the energetically accessible structures including the most stable structures of xMgCl2/yTiCl4 nanoplates (x = 6–19, y = 0–4). TiCl4-capped MgCl2 nanoplates are regarded as the building block of the Ziegler–Natta catalyst. The most stable structures were determined for MgCl2/TiCl4 nanoplates of different sizes and chemical compositions using a combination of the genetic algorithm and the DFT geometry optimization. The evolution in the genetic algorithm produced a number of meta-stable structures. A set of isomeric structures having similar energy to the most stable structure (termed energetically accessible structures) are provided as realistic models of MgCl2/TiCl4 nanoplates. These structures are useful for further investigation on the structural distribution of Ti species on MgCl2 regarding the Ziegler-Natta catalyst.

Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler-Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of “active sites” of ZN catalysts in the absence of ethylene, referred to as “dormant active sites”, is elucidated from magnetic resonance experiments, carried out on samples reacted with increasing amounts of BCl3 so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using EPR and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by DFT calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl2-supported Ziegler-Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene, and enables us propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations

The history of polymers in Italy certainly begins with Giulio Natta and the discovery of isotactic polypropylene [1,2], culminated in the delivery to Prof. Natta of the Nobel Prize for chemistry in 1963. Before those years, thanks to the development of the hydrocarbons and petrochemical sector by Montecatini (General Society for the Mining and Chemical Industry), the foundations for the development of macromolecular chemistry in Italy had been laid, but the real expansion occurred between 1958 and 1967 with a sector growth of 30% on an annual basis [3]. The research of Natta and his collaborators, on metal-organic catalysis applied to the polymerization reactions of -olefins and other unsaturated monomers, promoted the growth and consolidation, in Italy, of a network of industrial centers and academic institutes operating in the polymer science and technology sector, creating international skills. Since that period until today, Italy has kept pace with other countries and has certainly contributed to the development of the polymeric materials sector. Today, polymer science and technology in Italy represents a long-lasting and interdisciplinary field in which chemistry, physics, and engineering mix together to produce studies, which are considered among the best in the world. Several research groups coming from very different fields often collaborate in the design of the material, of the part, and of the processing technology to obtain innovative products with outstanding, new, and smart properties. Examples of the contributions of Italian research in the field are spread out in the top Journals and Conferences throughout the world. This Special Issue, which consists of 22 articles, including two review articles, aims at collecting an overview of Polymer Science and Technology in Italy, hoping that it can portray the state of the Polymeric Research in Italy and give the rest of the world a bright image of what is carried out in the field in our country.

Copolymerization of 1,3-butadiene with four 1-substituted 1,3-diene comonomers bearing amino and alkyoxy groups by a Ziegler–Natta iron(III) catalytic system to access in-chain functionalized syndiotactic 1,2-polybutadiene is reported herein. The polar comonomer content can be easily regulated by varying the comonomer loadings or polymerization conditions, affording functionalized syndiotactic 1,2-polybutadiene with different amounts of functionalities. The incorporation of a polar comonomer showed little influence on the 1,2-content and stereoregularity of the resulting polymers, giving a 1,2-structure as high as ∼85% and an rrrr pentad of 81.0%. Significantly improved surface properties of the polymers was obtained after incorporation of polar comonomer, as revealed from the remarkably decreased water contact angles.

Two MgCl2-supported Ziegler-Natta model catalysts were prepared by contacting activated MgCl2 with deficient or excess amount of TiCl4. Ethylene/1-hexene copolymerization with the catalysts was conducted under different 1-hexene feed, and active center concentration of the reaction system was determined by quench-labeling method using thiophene-2-carbonyl chloride as the quencher. The catalytic activity was only moderately enhanced (increment