Special Issue "Catalytic Polymerization"

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Chemistry".

Deadline for manuscript submissions: closed (31 July 2019).

Special Issue Editors

Dr. Incoronata Tritto
Website
Guest Editor
Istituto di Scienze e Tecnologie Chimiche - SCITEC "G. Natta", Milano, Italy
Interests: olefin polymerization; homogeneous and heterogeneous catalytic systems; α–olefin and cyclic olefin homo- and copolymers; ROMP; stereochemistry; NMR analysis; block copolymers; nanostructured hybrid polymers; polymers from renewable sources
Dr. Laura Boggioni
Website
Guest Editor
Istituto di Scienze e Tecnologie Chimiche - SCITEC "G. Natta", Milano, Italy
Interests: olefin polymerization; homogeneous catalytic systems; α–olefin and cyclic olefin homo- and copolymers; microstructure analysis; polymers from renewable sources
Dr. Simona Losio
Website
Guest Editor
Istituto di Scienze e Tecnologie Chimiche - SCITEC "G. Natta", Milano, Italy
Interests: olefin polymerization; homogeneous catalytic systems; α–olefin homo- and copolymers; microstructural analysis; polymers from renewable sources

Special Issue Information

Dear Colleagues,

Olefin polymerization using transition–metal catalysts has revolutionized materials science and led to a family of materials whose low cost, processing versatility, and range of mechanical properties have made them essential for our everyday life and our modern infrastructure. Thus, the discovery of olefin polymerization using Ziegler–Natta catalysts is considered among the most important discoveries of the past century.

The scope of catalytic polymerization is progressing well beyond the frontiers of commodity polyolefins. Metal complexes are at the basis of a wide range of catalytic transformations. Advanced catalyst systems exist for catalytic carbon carbon bond formation by means of polyinsertion, metathesis, coupling reactions, and controlled radical polymerization and for ring-opening polymerization of lactide and epoxides. Catalytic processes produce polar polymers such as polyethers, polyesters, and polycarbonates.

In order to reflect the current state-of-the-art on the subject and to explore potential future developments, this Special Issue focuses on recent progress and modern trends in the field of catalytic polymerization: The development of new metal catalysts, new advancements in polymerization catalysis and in the synthesis of new polymeric materials, and new insights into the mechanism of catalytic polymerization. Both original articles and reviews are welcome.

Dr. Incoronata Tritto
Dr. Laura Boggioni
Dr. Simona Losio
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Homo- and copolymerization
  • Metal catalysts
  • Microstructure
  • Mechanism
  • Characterization
  • Olefins, Polar monomers, and non-olefinic monomers

Published Papers (12 papers)

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Research

Jump to: Review

Open AccessArticle
Synthesis of Ultrahigh Molecular Weight Polymers Containing Reactive Functionality with Low PDIs by Polymerizations of Long-Chain α-Olefins in the Presence of Their Nonconjugated Dienes by Cp*TiMe2(O-2,6-iPr2C6H3)–Borate Catalyst
Polymers 2020, 12(1), 3; https://doi.org/10.3390/polym12010003 - 18 Dec 2019
Viewed by 660
Abstract
Copolymerizations of 1-decene (DC) with 1,9-decadiene (DCD), 1-dodecene (DD) with 1,11-dodecadiene (DDD), and 1-tetradecene (TD) with 1,13-tetradecadiene (TDD), using Cp*TiMe2(O-2,6-iPr2C6H3) (1)–[Ph3C][B(C6F5)4] (borate) catalyst [...] Read more.
Copolymerizations of 1-decene (DC) with 1,9-decadiene (DCD), 1-dodecene (DD) with 1,11-dodecadiene (DDD), and 1-tetradecene (TD) with 1,13-tetradecadiene (TDD), using Cp*TiMe2(O-2,6-iPr2C6H3) (1)–[Ph3C][B(C6F5)4] (borate) catalyst in the presence of AliBu3/Al(n-C8H17)3 proceeded in a quasi-living manner in n-hexane at −30 to −50 °C, affording ultrahigh molecular weight (UHMW) copolymers containing terminal olefinic double bonds in the side chain with rather low PDI (Mw/Mn) values. In the DC/DCD copolymerization, the resultant copolymer prepared at −40 °C possessed UHMW (Mn = 1.40 × 106 after 45 min) with low PDI (Mw/Mn = 1.39); both the activity and the PDI value decreased at low polymerization temperature (Mn = 5.38 × 105, Mw/Mn = 1.18, after 120 min at −50 °C). UHMW poly(TD-co-TDD) was also obtained in the copolymerization at −30 °C (Mn = 9.12 × 105, Mw/Mn = 1.51, after 120 min), using this catalyst. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Mechanistic Insight into the Ring-Opening Polymerization of ε-Caprolactone and L-Lactide Using Ketiminate-Ligated Aluminum Catalysts
Polymers 2019, 11(9), 1530; https://doi.org/10.3390/polym11091530 - 19 Sep 2019
Cited by 3 | Viewed by 1014
Abstract
The reactivity and the reaction conditions of the ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LA) initiated by aluminum ketiminate complexes have been shown differently. Herein, we account for the observation by studying the mechanisms on the basis of [...] Read more.
The reactivity and the reaction conditions of the ring-opening polymerization of ε-caprolactone (ε-CL) and L-lactide (LA) initiated by aluminum ketiminate complexes have been shown differently. Herein, we account for the observation by studying the mechanisms on the basis of density functional theory (DFT) calculations. The calculations show that the ring-opening polymerization of ε-CL and LA are rate-determined by the benzoxide insertion and the C–O bond cleavage step, respectively. Theoretical computations suggest that the reaction temperature of L–LA polymerization should be higher than that of ε-CL one, in agreement with the experimental data. To provide a reasonable interpretation of the experimental results and to give an insight into the catalyst design, the influence of the electronic, steric, and thermal effects on the polymerization behaviors will be also discussed in this study. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Biodegradable Oligoesters of ε-Caprolactone and 5-Hydroxymethyl-2-Furancarboxylic Acid Synthesized by Immobilized Lipases
Polymers 2019, 11(9), 1402; https://doi.org/10.3390/polym11091402 - 26 Aug 2019
Cited by 7 | Viewed by 1114
Abstract
Following the latest developments, bio-based polyesters, obtained from renewable raw materials, mainly carbohydrates, can be competitive for the fossil-based equivalents in various industries. In particular, the furan containing monomers are valuable alternatives for the synthesis of various new biomaterials, applicable in food additive, [...] Read more.
Following the latest developments, bio-based polyesters, obtained from renewable raw materials, mainly carbohydrates, can be competitive for the fossil-based equivalents in various industries. In particular, the furan containing monomers are valuable alternatives for the synthesis of various new biomaterials, applicable in food additive, pharmaceutical and medical field. The utilization of lipases as biocatalysts for the synthesis of such polymeric compounds can overcome the disadvantages of high temperatures and metal catalysts, used by the chemical route. In this work, the enzymatic synthesis of new copolymers of ε-caprolactone and 5-hydroxymethyl-2-furancarboxylic acid has been investigated, using commercially available immobilized lipases from Candida antarctica B. The reactions were carried out in solvent-less systems, at temperatures up to 80 °C. The structural analysis by MALDI TOF-MS, NMR, and FT-IR spectroscopy confirmed the formation of cyclic and linear oligoesters, with maximal polymerization degree of 24 and narrow molecular weight distribution (dispersity about 1.1). The operational stability of the biocatalyst was explored during several reuses, while thermal analysis (TG and DSC) indicated a lower thermal stability and higher melting point of the new products, compared to the poly(ε-caprolactone) homopolymer. The presence of the heterocyclic structure in the polymeric chain has promoted both the lipase-catalyzed degradation and the microbial degradation. Although, poly(ε-caprolactone) is a valuable biocompatible polymer with important therapeutic applications, some drawbacks such as low hydrophilicity, low melting point, and relatively slow biodegradability impeded its extensive utilization. In this regard the newly synthesized furan-based oligoesters could represent a “green” improvement route. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Graphene Oxide and Oxidized Carbon Black as Catalyst for Crosslinking of Phenolic Resins
Polymers 2019, 11(8), 1330; https://doi.org/10.3390/polym11081330 - 10 Aug 2019
Cited by 2 | Viewed by 1189
Abstract
Influence of different graphite-based nanofillers on crosslinking reaction of resorcinol, as induced by hexa(methoxymethyl)melamine, is studied. Curing reactions leading from low molecular mass compounds to crosslinked insoluble networks are studied by indirect methods based on Differential Scanning Calorimetry. Reported results show a catalytic [...] Read more.
Influence of different graphite-based nanofillers on crosslinking reaction of resorcinol, as induced by hexa(methoxymethyl)melamine, is studied. Curing reactions leading from low molecular mass compounds to crosslinked insoluble networks are studied by indirect methods based on Differential Scanning Calorimetry. Reported results show a catalytic activity of graphene oxide (eGO) on this reaction, comparable to that one already described in the literature for curing of benzoxazine. For instance, for an eGO content of 2 wt %, the exothermic crosslinking DSC peak (upon heating at 10 °C/min) shifted 6 °C. More relevantly, oxidized carbon black (oCB) is much more effective as catalyst of the considered curing reaction. In fact, for an oCB content of 2 wt %, the crosslinking DSC peak can be shifted more than 30 °C and a nearly complete crosslinking is already achieved by thermal treatment at 120 °C. The possible origin of the higher catalytic activity of oCB with respect to eGO is discussed. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
A New Insight into the Comonomer Effect through NMR Analysis in Metallocene Catalysed Propene–co–1-Nonene Copolymers
Polymers 2019, 11(8), 1266; https://doi.org/10.3390/polym11081266 - 31 Jul 2019
Cited by 4 | Viewed by 896
Abstract
The “comonomer effect” is an intriguing kinetic phenomenon in olefin copolymerization that still remains without a detailed explanation. It typically relates to the rate of enhancement undergone in ethylene and propene catalytic polymerization just by adding small fractions of an alpha-olefin. The difficulty [...] Read more.
The “comonomer effect” is an intriguing kinetic phenomenon in olefin copolymerization that still remains without a detailed explanation. It typically relates to the rate of enhancement undergone in ethylene and propene catalytic polymerization just by adding small fractions of an alpha-olefin. The difficulty lies in the fact that changes caused by the presence of the comonomer in reaction parameters are so conspicuous that it is really difficult to pin down which of them is the primary cause and which ones are side factors with marginal contribution to the phenomenon. Recent investigations point to the modification of the catalyst active sites as the main driving factor. In this work, the comonomer effect in the metallocene copolymerization of propene and 1-nonene is analysed and correlated to the comonomer role in the termination of the chain-growing process. The associated termination mechanisms involved furnish most of chain-free active sites, in which the selective interaction of the comonomer was proposed to trigger the insertion of monomers. A thorough characterisation of chain-end groups by means of the 1H NMR technique allows for detailing of specific transfer processes, ascribed to comonomer insertions, as well as evidencing the influence of the growing chain’s microstructure over the different termination processes available. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Strong Interaction with Carbon Filler of Polymers Obtained by Pyrene Functionalized Hoveyda-Grubbs 2nd Generation Catalyst
Polymers 2019, 11(8), 1261; https://doi.org/10.3390/polym11081261 - 30 Jul 2019
Viewed by 961
Abstract
Hoveyda-Grubbs 2nd generation catalyst that has the alkylidene functionalized with pyrene (HG2pyrene) was synthesized and characterized. This catalyst can be bound to carbonaceous filler (graphite, graphene or carbon nanotubes) by π-stacking interaction, but, since the catalytic site become poorly accessible to [...] Read more.
Hoveyda-Grubbs 2nd generation catalyst that has the alkylidene functionalized with pyrene (HG2pyrene) was synthesized and characterized. This catalyst can be bound to carbonaceous filler (graphite, graphene or carbon nanotubes) by π-stacking interaction, but, since the catalytic site become poorly accessible to the incoming monomer, its activity in the ROMP (Ring Opening Metathesis Polymerization) is reduced. This is due to the fact that the above interaction also occurs with the aryl groups of NHC ligand of the ruthenium, as demonstrated by nuclear magnetic resonance and by fluorescence analysis of a solution of the catalyst with a molecule that simulated the structure of graphene. Very interesting results were obtained using HG2pyrene as a catalyst in the ROMP of 2-norbornene and 1,5-cyclooctadiene. The activity of this catalyst was the same as that obtained with the classical commercial HG2. Obviously, the polymers obtained with catalyst HG2pyrene have a pyrene as a chain end group. This group can give a strong π-stacking interaction with carbonaceous filler, producing a material that is able to promote the dispersion of other materials such as graphite in the polymer matrix. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Isoprene Polymerization: Catalytic Performance of Iminopyridine Vanadium(III) Chloride versus Vanadium(III) Chloride
Polymers 2019, 11(7), 1122; https://doi.org/10.3390/polym11071122 - 02 Jul 2019
Viewed by 924
Abstract
A series of vanadium complexes bearing iminopyridine bidentate ligands with various electronic and steric properties: V1 [CH2Ph], V2 [CMe2CH2CMe3], V3 [Ph] and V4 [2,6-iPr2Ph] were prepared and characterized by IR spectroscopy [...] Read more.
A series of vanadium complexes bearing iminopyridine bidentate ligands with various electronic and steric properties: V1 [CH2Ph], V2 [CMe2CH2CMe3], V3 [Ph] and V4 [2,6-iPr2Ph] were prepared and characterized by IR spectroscopy and microanalytical analysis. The catalytic capacity of all the complexes has been investigated for isoprene polymerization and was controlled by tuning the ligand structure with different N-alkyl and N-aryl groups. Activated by methylaluminoxane (MAO), the aryl-substituted complex V3 [Ph] exhibited high cis-1,4 selectivity (75%), and the resultant polymers had high molecular weights (Mn = 6.6 × 104) and narrow molecular weight distributions (PDI = 2.3). This catalyst showed high activity up to 734.4 kg polymer (mol V)−1 h−1 with excellent thermostability even stable at 70 °C. Compared to the traditional VCl3/MAO catalytic system, iminopyridine-supported V(III) catalysts displayed higher catalytic activities and changed the selectivity of monomer enchainment from trans-1,4 to cis-1,4. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Copolymerization of Norbornene and Styrene with Anilinonaphthoquinone-Ligated Nickel Complexes
Polymers 2019, 11(7), 1100; https://doi.org/10.3390/polym11071100 - 28 Jun 2019
Cited by 5 | Viewed by 1290
Abstract
Poly(norbornene-co-styrene)s were synthesized by the use of anilinonaphthoquinone-ligated nickel complexes [Ni(C10H5O2NAr)(Ph)(PPh3): 1a, Ar = C6H3-2,6-iPr; 1b, Ar = C6H2-2,4,6-Me; 1c, [...] Read more.
Poly(norbornene-co-styrene)s were synthesized by the use of anilinonaphthoquinone-ligated nickel complexes [Ni(C10H5O2NAr)(Ph)(PPh3): 1a, Ar = C6H3-2,6-iPr; 1b, Ar = C6H2-2,4,6-Me; 1c, Ar = C6H5] activated with modified methylaluminoxane (MMAO) or B(C6F5)3 in toluene. The effects of the cocatalysts were more significant than those of the nickel complexes, and MMAO gave higher activity than B(C6F5)3. The structural characterizations of the products indicated the formation of statistical norbornene copolymers. An increase of the styrene ratio in feed led to an increase in the incorporated styrene (S) content of the resulting copolymer. The molecular weight of the copolymer decreased with increasing the S ratio in feed at 70 °C. The copolymerization activity, using MMAO as a cocatalyst, decreased with lowering of the temperature from 70 to 0 °C, accompanied by an increase in the molecular weight of the copolymer. The S incorporation up to 59% with Mn of 78,000 was achieved by the 1b-B(C6F5)3 catalytic system. The glass transition temperatures of the norbornene (N)/S copolymers determined by differential scanning calorimetry, decreased from 329 to 128 °C according to the S content. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Catalyst Speciation during ansa-Zirconocene-Catalyzed Polymerization of 1-Hexene Studied by UV-vis Spectroscopy—Formation and Partial Re-Activation of Zr-Allyl Intermediates
Polymers 2019, 11(6), 936; https://doi.org/10.3390/polym11060936 - 29 May 2019
Cited by 2 | Viewed by 1605
Abstract
Catalyst speciation during polymerization of 1-hexene in benzene or toluene solutions of the catalyst precursor SBIZr(μ-Me)2AlMe2+ B(C6F5)4 (SBI = rac-dimethylsilyl-bis(1-indenyl)) at 23 °C is studied by following the accompanying UV-vis-spectral changes. These [...] Read more.
Catalyst speciation during polymerization of 1-hexene in benzene or toluene solutions of the catalyst precursor SBIZr(μ-Me)2AlMe2+ B(C6F5)4 (SBI = rac-dimethylsilyl-bis(1-indenyl)) at 23 °C is studied by following the accompanying UV-vis-spectral changes. These indicate that the onset of polymerization catalysis is associated with the concurrent formation of two distinct zirconocene species. One of these is proposed to consist of SBIZr-σ-polyhexenyl cations arising from SBIZr-Me+ (formed from SBIZr(μ-Me)2AlMe2+ by release of AlMe3) by repeated olefin insertions, while the other one is proposed to consist of SBIZr-η3-allyl cations of composition SBIZr-η3-(1-R-C3H4)+ (R = n-propyl), formed by σ-bond metathesis between SBIZr-Me+ and 1-hexene under release of methane. At later reaction stages, all zirconocene-σ–polymeryl cations appear to decay to yet another SBIZr-allyl species, i.e., to cations of the type SBIZr-η3-(x-R-(3-x)-pol-C3H3)+ (pol = i-polyhexenyl, x = 1 or 2). Renewed addition of excess 1-hexene is proposed to convert these sterically encumbered Zr-allyl cations back to catalytically active SBIZr-σ–polymeryl cations within a few seconds, presumably by initial 1-hexene insertion into the η1- isomer, followed by repeated additional insertions, while the initially formed, less crowded allyl cations, SBIZr-η3-(1-R-C3H4)+ appear to remain unchanged. Implications of these results with regard to the kinetics of zirconocene-catalyzed olefin polymerization are discussed. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessArticle
Ethylene-co-norbornene Copolymerization Using a Dual Catalyst System in the Presence of a Chain Transfer Agent
Polymers 2019, 11(3), 554; https://doi.org/10.3390/polym11030554 - 22 Mar 2019
Cited by 5 | Viewed by 1653
Abstract
Ethylene-co-norbornene copolymers were synthesized by a dual catalyst system at three concentrations of norbornene in the feed and variable amounts of ZnEt2, as a possible chain transfer agent. The dual catalyst system consists of two ansa-metallocenes, isopropyliden(η5- [...] Read more.
Ethylene-co-norbornene copolymers were synthesized by a dual catalyst system at three concentrations of norbornene in the feed and variable amounts of ZnEt2, as a possible chain transfer agent. The dual catalyst system consists of two ansa-metallocenes, isopropyliden(η5-cyclopentadienyl)(η5-indenyl)zirconium dichloride (1) and isopropyliden(η5-3-methylcyclopentadienyl)(η5-fluorenyl)zirconium dichloride (2), activated with dimethylanilinium tetrakis(pentafluorophenyl)borate, in presence of TIBA. Values of norbornene content, molecular mass, glass transition temperature, and reactivity ratios r11 and r21 of copolymers prepared in the presence of 1+2 are intermediate between those of reference copolymers. The study of tensile and elastic properties of ethylene-co-norbornene copolymers (poly(E-co-N)s) gave evidence that copolymers were obtained in part through transfer of polymer chains between different transition metal sites. Mechanical properties are clearly different from those expected from a blend of the parent samples and reveal that copolymers obtained in the presence of 1+2 and ZnEt2 consist of a reactor blend of segmented chains produced by exchange from 2 to 1 and 1 to 2 acting as the ideal compatibilizer of chains produced by the chain transfer from 1 to 1, and from 2 to 2. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Open AccessEditor’s ChoiceArticle
Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae
Polymers 2019, 11(2), 358; https://doi.org/10.3390/polym11020358 - 19 Feb 2019
Cited by 7 | Viewed by 1887
Abstract
The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity [...] Read more.
The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity of ethylene polymerization was only 25% of that of propylene, and the polymerization rate (Rp) quickly decayed with time (tp) in the former system, in contrast to stable Rp in the latter. The ethylene system showed a very low [C*]/[Ti] ratio (<0.6%), in contrast to a much higher [C*]/[Ti] ratio (1.5%–4.9%) in propylene polymerization. The two systems showed noticeably different morphologies of the nascent polymer/catalyst particles, with the PP/catalyst particles being more compact and homogeneous than the PE/catalyst particles. The different kinetic behaviors of the two systems were explained by faster and more sufficient catalyst fragmentation in propylene polymerization than the ethylene system. The smaller lamellar thickness (<20 nm) in nascent polypropylene compared with the size of nanopores (15–25 nm) in the catalyst was considered the key factor for efficient catalyst fragmentation in propylene polymerization, as the PP lamellae may grow inside the nanopores and break up the catalyst particles. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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Review

Jump to: Research

Open AccessReview
Development of Large-Scale Stopped-Flow Technique and its Application in Elucidation of Initial Ziegler–Natta Olefin Polymerization Kinetics
Polymers 2019, 11(6), 1012; https://doi.org/10.3390/polym11061012 - 07 Jun 2019
Cited by 5 | Viewed by 1434
Abstract
The stopped-flow (SF) technique has been extensively applied to study Ziegler–Natta (ZN) olefin polymerization kinetics within an extremely short period (typically <0.2 s) for understanding the nature of the active sites as well as the polymerization mechanisms through microstructure analyses of obtained polymers. [...] Read more.
The stopped-flow (SF) technique has been extensively applied to study Ziegler–Natta (ZN) olefin polymerization kinetics within an extremely short period (typically <0.2 s) for understanding the nature of the active sites as well as the polymerization mechanisms through microstructure analyses of obtained polymers. In spite of its great applicability, a small amount of polymer that is yielded in a short-time polymerization has been a major bottleneck for polymer characterizations. In order to overcome this limitation, a large-scale SF (LSF) system has been developed, which offers stable and scalable polymerization over an expanded time range from a few tens milliseconds to several seconds. The scalability of the LSF technique has been further improved by introducing a new quenching protocol. With these advantages, the LSF technique has been effectively applied to address several unknown issues in ZN catalysis, such as the role of physical and chemical transformations of a catalyst on the initial polymerization kinetics, and regiochemistry of ZN propylene polymerization. Here, we review the development of the LSF technique and recent efforts for understanding heterogeneous ZN olefin polymerization catalysis with this new system. Full article
(This article belongs to the Special Issue Catalytic Polymerization)
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