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Journal articles on the topic 'Catalyst chain growth polymerization'

Author: Grafiati

Published: 4 June 2021

Last updated: 8 February 2022

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1

Yokozawa, Tsutomu, Isao Adachi, Ryo Miyakoshi, and Akihiro Yokoyama. "Catalyst-Transfer Condensation Polymerization for the Synthesis of Well-Defined Polythiophene with Hydrophilic Side Chain and of Diblock Copolythiophene with Hydrophilic and Hydrophobic Side Chains." High Performance Polymers 19, no. 5-6 (October 2007): 684–99. http://dx.doi.org/10.1177/0954008307081212.

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Chain-growth condensation polymerization of 2-bromo-5-chloromagnesio-3-[2-(2-metho-xyethoxy)ethoxy]methylthiophene (2) with Ni catalysts was studied, and the block copolymer of poly2 and poly(3-hexylthiophene) was synthesized by this polymerization method. The polymerization of 2 depended on the ligands of the Ni catalyst, and poly2 with the lowest polydispersity was obtained when 1,2-bis(diphenylphosphino)ethane (dppe) was used as the ligand. The linear relationships between the conversion of 2 and Mn of the polymer and between the feed ratio of 2 to the Ni catalyst and Mn of the polymer indicate that this polymerization proceeds in a chain-growth polymerization manner via a catalyst-transfer condensation polymerization mechanism. The block copolymerization of 2 and 2-bromo-5-chloromagnesio-3-hexylthiophene (1) was then carried out in four ways by changing the order of polymerization of the two monomers and the catalysts. It turned out that the block copolymer was obtained without the formation of the homopolymers by the polymerization of 1 with Ni(dppe)Cl2 or Ni(dppp)Cl2 (dppp = 1,2-bis(diphenylphosphino)propane), followed by the postpolymerization of 2. Of the two catalysts, Ni(dppe)Cl2 resulted in narrower polydispersity of the block copolymer.

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2

Schoeneberger, Elsa M., and Gerrit A. Luinstra. "Investigations on the Ethylene Polymerization with Bisarylimine Pyridine Iron (BIP) Catalysts." Catalysts 11, no. 3 (March 23, 2021): 407. http://dx.doi.org/10.3390/catal11030407.

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The kinetics and terminations of ethylene polymerization, mediated by five bisarylimine pyridine (BIP) iron dichloride precatalysts, and activated by large amounts of methyl aluminoxane (MAO) was studied. Narrow distributed paraffins from initially formed aluminum polymeryls and broader distributed 1-polyolefins and (bimodal) mixtures, thereof, were obtained after acidic workup. The main pathway of olefin formation is beta-hydrogen transfer to ethylene. The rate of polymerization in the initial phase is inversely proportional to the co-catalyst concentration for all pre-catalysts; a first-order dependence was found on ethylene and catalyst concentrations. The inhibition by aluminum alkyls is released to some extent in a second phase, which arises after the original methyl groups are transformed into n-alkyl entities and the aluminum polymeryls partly precipitate in the toluene medium. The catalysis is interpretable in a mechanism, wherein, the relative rate of chain shuttling, beta-hydrogen transfer and insertion of ethylene are determining the outcome. Beta-hydrogen transfer enables catalyst mobility, which leads to a (degenerate) chain growth of already precipitated aluminum alkyls. Stronger Lewis acidic centers of the single site catalysts, and those with smaller ligands, are more prone to yield 1-olefins and to undergo a faster reversible alkyl exchange between aluminum and iron.

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3

Balcar, Hynek, Jan Sedláček, Jan Svoboda, Naděžda Žilková, Jiří Rathouský, and Jiří Vohlídal. "Hybrid Catalysts for Acetylenes Polymerization Prepared by Anchoring [Rh(cod)Cl]2 on MCM-41, MCM-48 and SBA-15 Mesoporous Molecular Sieves - The Effect of Support Structure on Catalytic Activity in Polymerization of Phenylacetylene and 4-Ethynyl-N-{4-[(trimethylsilyl)ethynyl]benzylidene}aniline." Collection of Czechoslovak Chemical Communications 68, no. 10 (2003): 1861–76. http://dx.doi.org/10.1135/cccc20031861.

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Hybrid catalysts for polymerization of acetylenes were prepared by anchoring, via (3-aminopropyl)trimethoxysilane linker, the [Rh(cod)Cl]2 complex on siliceous mesoporous molecular sieves differing in the pore size and architecture (MCM-41, MCM-48 and SBA-15). In comparison with [Rh(cod)Cl]2 used as homogeneous catalyst, all hybrid catalysts exhibited comparable or even higher catalytic activity in the polymerization of phenylacetylene and 4-ethynyl-N-{4-[(trimethylsilyl)ethynyl]benzylidene}aniline. The initial polymerization rate increased with increasing accessibility of mesoporous surface of catalysts in the order: MCM-41 < MCM-48 < SBA-15. Molecular weights of the prepared polymers increased in reverse order suggesting suppression of the chain growth termination reactions by space limitations in the pores. No effect of catalyst support on the microstructure of formed polymers was found.

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4

Gegenhuber, Thomas, Alexander M. Schenzel, Anja S. Goldmann, Per B. Zetterlund, and Christopher Barner-Kowollik. "A facile route to segmented copolymers by fusing ambient temperature step-growth and RAFT polymerization." Chemical Communications 53, no. 77 (2017): 10648–51. http://dx.doi.org/10.1039/c7cc06347d.

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We introduce the facile synthesis of segmented copolymers via a catalyst-free Diels–Alder (DA) reaction at ambient temperature via step-growth polymerization and subsequent reversible addition fragmentation chain transfer (RAFT) polymerization.

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5

Echevskaya, L. G., M. A. Matsko, and V. A. Zakharov. "Kinetic Studies of Chain-Transfer Reactions in Polymerization of Hexene-1 over Highly Active Supported Titanium-Magnesium Catalysts." Kataliz v promyshlennosti 19, no. 2 (March 15, 2019): 104–13. http://dx.doi.org/10.18412/1816-0387-2019-2-104-113.

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The influence of concentrations of the monomer, triethylaluminum, and hydrogen on the molecular mass of polyhexene obtained by polymerization of hexene-1 over a supported titanium-magnesium catalyst was studied. Ratios of rate constants of the transfer of polymer chain with the monomer, triethylaluminum (AlEt3) and hydrogen to the rate constant of the chain-growth were calculated.The data obtained allowed the contribution of individual reactions of chain transfer to molecular mass of the polymer to be estimated at various polymerization conditions and the polymerization conditions to be chosen deliberately in order to synthesize polyhexene with the required molecular mass. The discovered inhomogeneity of the centers active to the chain transfer with hydrogen in the presence of the AlEt3 co-catalyst caused changes in the polymer polydispersion upon changes in the hydrogen concentration in the reaction medium. Curves of the polyhexene molecular mass distribution in polyhexene samples with different polydispersion were analyzed using their resolution into Flory components.

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6

German, Ian, Wissem Kelhifi, Sébastien Norsic, Christophe Boisson, and Franck D'Agosto. "Telechelic Polyethylene from Catalyzed Chain-Growth Polymerization." Angewandte Chemie International Edition 52, no. 12 (February 13, 2013): 3438–41. http://dx.doi.org/10.1002/anie.201208756.

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7

Park, Kyung Lee, Jun Won Baek, Seung Hyun Moon, Sung Moon Bae, Jong Chul Lee, Junseong Lee, Myong Sun Jeong, and Bun Yeoul Lee. "Preparation of Pyridylamido Hafnium Complexes for Coordinative Chain Transfer Polymerization." Polymers 12, no. 5 (May 11, 2020): 1100. http://dx.doi.org/10.3390/polym12051100.

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The pyridylamido hafnium complex (I) discovered at Dow is a flagship catalyst among postmetallocenes, which are used in the polyolefin industry for PO-chain growth from a chain transfer agent, dialkylzinc. In the present work, with the aim to block a possible deactivation process in prototype compound I, the corresponding derivatives were prepared. A series of pyridylamido Hf complexes were prepared by replacing the 2,6-diisopropylphenylamido part in I with various 2,6-R2C6H3N-moieties (R = cycloheptyl, cyclohexyl, cyclopentyl, 3-pentyl, ethyl, or Ph) or by replacing 2-iPrC6H4C(H)- in I with the simple PhC(H)-moiety. The isopropyl substituent in the 2-iPrC6H4C(H)-moiety influences not only the geometry of the structures (revealed by X-ray crystallography), but also catalytic performance. In the complexes bearing the 2-iPrC6H4C(H)-moiety, the chelation framework forms a plane; however, this framework is distorted in the complexes containing the PhC(H)-moiety. The ability to incorporate α-olefin decreased upon replacing 2-iPrC6H4C(H)-with the PhC(H)-moiety. The complexes carrying the 2,6-di(cycloheptyl)phenylamido or 2,6-di(cyclohexyl)phenylamido moiety (replacing the 2,6-diisopropylphenylamido part in I) showed somewhat higher activity with greater longevity than did prototype catalyst I.

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8

Balasubramanian, Arumugam, Ting-Chia Ku, Hong-Pin Shih, Alishetty Suman, Huang-Jyun Lin, Ting-Wen Shih, and Chien-Chung Han. "Chain-growth cationic polymerization of 2-halogenated thiophenes promoted by Brønsted acids." Polym. Chem. 5, no. 20 (2014): 5928–41. http://dx.doi.org/10.1039/c4py00521j.

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9

Tkachov, Roman, Volodymyr Senkovskyy, Tetyana Beryozkina, Kseniya Boyko, Vasiliy Bakulev, Albena Lederer, Karin Sahre, Brigitte Voit, and Anton Kiriy. "Palladium-Catalyzed Chain-Growth Polycondensation of AB-type Monomers: High Catalyst Turnover and Polymerization Rates." Angewandte Chemie International Edition 53, no. 9 (February 12, 2014): 2402–7. http://dx.doi.org/10.1002/anie.201310045.

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10

Tkachov, Roman, Volodymyr Senkovskyy, Tetyana Beryozkina, Kseniya Boyko, Vasiliy Bakulev, Albena Lederer, Karin Sahre, Brigitte Voit, and Anton Kiriy. "Palladium-Catalyzed Chain-Growth Polycondensation of AB-type Monomers: High Catalyst Turnover and Polymerization Rates." Angewandte Chemie 126, no. 9 (February 12, 2014): 2434–39. http://dx.doi.org/10.1002/ange.201310045.

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11

Shi, Xiaochao, Masayoshi Nishiura, and Zhaomin Hou. "Simultaneous Chain-Growth and Step-Growth Polymerization of Methoxystyrenes by Rare-Earth Catalysts." Angewandte Chemie 128, no. 47 (October 24, 2016): 15032–37. http://dx.doi.org/10.1002/ange.201609065.

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12

Shi, Xiaochao, Masayoshi Nishiura, and Zhaomin Hou. "Simultaneous Chain-Growth and Step-Growth Polymerization of Methoxystyrenes by Rare-Earth Catalysts." Angewandte Chemie International Edition 55, no. 47 (October 24, 2016): 14812–17. http://dx.doi.org/10.1002/anie.201609065.

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13

Pal, Deep Sankar, Haridas Kar, and Suhrit Ghosh. "Controllable supramolecular polymerization via a chain-growth mechanism." Chemical Communications 54, no. 8 (2018): 928–31. http://dx.doi.org/10.1039/c7cc08302e.

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A naphthalene-diimide appended carboxylic acid either spontaneously self-assembles (P) by an open-chain H-bonding or can be arrested in an intra-molecularly H-bonded monomeric state (M) depending on the sample preparation method. Living supramoleular polymerization of M can be initiated by a seed, generated from P.

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14

Miyakoshi, Ryo, Akihiro Yokoyama, and Tsutomu Yokozawa. "Catalyst-Transfer Polycondensation. Mechanism of Ni-Catalyzed Chain-Growth Polymerization Leading to Well-Defined Poly(3-hexylthiophene)." Journal of the American Chemical Society 127, no. 49 (December 2005): 17542–47. http://dx.doi.org/10.1021/ja0556880.

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15

Wu, Shupeng, Yuequan Sun, Li Huang, Jianwei Wang, Yihan Zhou, Yanhou Geng, and Fosong Wang. "Grignard Metathesis Chain-Growth Polymerization for Poly(bithienylmethylene)s: Ni Catalyst Can Transfer across the Nonconjugated Monomer." Macromolecules 43, no. 10 (May 25, 2010): 4438–40. http://dx.doi.org/10.1021/ma100537d.

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16

Tobisch, Sven. "Mechanistic insight into the selective trans-1,4-polymerization of butadiene by terpyridine–iron(II) complexes — A computational study." Canadian Journal of Chemistry 87, no. 10 (October 2009): 1392–405. http://dx.doi.org/10.1139/v09-101.

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The density functional theory (DFT) method has been employed to unravel mechanistic intricacies of the 1,4-polymerization of 1,3-butadiene mediated by the [(η3-RC3H4)FeII(C15H11N3)(η2-C4H6)]+ terpyridine–iron(II) active catalyst species. The π-allyl-insertion mechanism is operative for chain growth, whilst the alternative σ-allyl-insertion mechanism has been explicitly demonstrated as being inoperable. This study elucidates the mechanism of cis–trans regulation and unveils the factors that govern the observed high trans-1,4 stereoselectivity, in particular, the discriminative role of allylic isomerization. An atactic trans-1,4-polydiene is expected from polymerization of a terminally monosubstituted butadiene, the experimental results of which have not been reported thus far.

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17

Xu, Yu Qing, Yong Ke, Xiao Yong Hu, Jin Cui, Zhi Yuan Lin, and Ming Jun He. "Research of Atom Transfer Radical Polymerization of Methyl Polypropylene." Materials Science Forum 852 (April 2016): 720–25. http://dx.doi.org/10.4028/www.scientific.net/msf.852.720.

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The methyl polypropylene was prepared bsaed on toluene as solvent, cuprous bromide (CuBr) / copper bromide (CuBr2)/tris (2-dimethylaminoethyl) amine (Me6TREN) as catalyst, azo dimethoxyisoquinolin heptanenitrile (V-70) as radical additive, 2-bromoisobutyrate (EtBiB) as initiator. The polymerization reaction was initiated by using the ultimate atomic radical polymerization (UATRPSM), whose chain reaction was manifested in linear first-order kinetics. In this study, the conversion of monomers, polymer dispersion coefficient and the relative molecular weight with monomer conversion rate changes were studied by gas chromatography (GC) and gel permeation chromatography (GPC). The results show that the final monomer conversion was 87%; with increasing monomer conversion, polymer dispersion coefficient (PDI) decreases and reaches the optimum value 1.19, while the relative molecular weight of the linear growth, and prove the reaction was precise control.

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18

Ali, Amjad, Nadeem Muhammad, Shahid Hussain, Muhammad Imran Jamil, Azim Uddin, Tariq Aziz, Muhammad Khurram Tufail, et al. "Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure." Polymers 13, no. 2 (January 15, 2021): 268. http://dx.doi.org/10.3390/polym13020268.

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The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (kp) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher kp 1007 kp (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and kp value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via β-H transfer have been investigated by 1H NMR analysis.

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19

van Meurs, Martin, George J. P. Britovsek, Vernon C. Gibson, and Steven A. Cohen. "Polyethylene Chain Growth on Zinc Catalyzed by Olefin Polymerization Catalysts: A Comparative Investigation of Highly Active Catalyst Systems across the Transition Series." Journal of the American Chemical Society 127, no. 27 (July 2005): 9913–23. http://dx.doi.org/10.1021/ja050100a.

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20

Basko, Malgorzata. "Activated monomer mechanism in the cationic polymerization of L,L-lactide." Pure and Applied Chemistry 84, no. 10 (May 22, 2012): 2081–88. http://dx.doi.org/10.1351/pac-con-11-10-19.

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Cationic polymerization of L,L-lactide (LA) in the presence of trifluoromethanesulfonic acid (TfA) has been studied. It was found that propagation proceeds mainly according to the activated monomer (AM) mechanism. Hydroxyl groups required for this type of propagation are formed as a result of the ring opening of protonated lactide. Thus, part of the acid (acting as an initiator) is consumed for the generation of hydroxyl groups, and part (acting as a catalyst) is involved in the protonation of monomer molecules forming secondary oxonium ions which are then able to react with the hydroxyl groups. A dual role of the protic acid is reflected in the kinetic results and in the dependence of experimental degree of polymerization on theoretical values. The structure of active species responsible for polymer chain growth was determined by phosphorus ion-trapping method. The evidence that in the cationic ring-opening polymerization (ROP) of LA initiated by protic acids, both hydroxyl groups and secondary oxonium ions are present throughout the polymerization (as required for polymerization proceeding by the AM mechanism) was found on the basis of changes of the averaged proton chemical shift in 1H NMR spectra of LA polymerizing mixture.

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21

Bautista, Michael V., Anthony J. Varni, Josué Ayuso-Carrillo, Chia-Hua Tsai, and Kevin J. T. Noonan. "Chain-Growth Polymerization of Benzotriazole Using Suzuki–Miyaura Cross-Coupling and Dialkylbiarylphosphine Palladium Catalysts." ACS Macro Letters 9, no. 9 (August 28, 2020): 1357–62. http://dx.doi.org/10.1021/acsmacrolett.0c00580.

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22

Ghosh, Goutam, Pradip Dey, and Suhrit Ghosh. "Controlled supramolecular polymerization of π-systems." Chemical Communications 56, no. 50 (2020): 6757–69. http://dx.doi.org/10.1039/d0cc02787a.

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Externally-initiated controlled supramolecular polymerization of the kinetically trapped aggregated state in a chain growth mechanism can produce well-defined living supramolecular polymers and copolymers.

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23

Nishimori, Kana, and Makoto Ouchi. "AB-alternating copolymers via chain-growth polymerization: synthesis, characterization, self-assembly, and functions." Chemical Communications 56, no. 24 (2020): 3473–83. http://dx.doi.org/10.1039/d0cc00275e.

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In this review, four topics on alternating copolymers synthesized via chain-growth polymerization are reviewed: (1) how to control the alternating sequence; (2) sequence analysis; (3) self-assembly; and (4) functions.

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24

Nishikawa, Tsuyoshi, and Makoto Ouchi. "An Alkenyl Boronate as a Monomer for Radical Polymerizations: Boron as a Guide for Chain Growth and as a Replaceable Side Chain for Post‐Polymerization Transformation." Angewandte Chemie International Edition 58, no. 36 (September 2, 2019): 12435–39. http://dx.doi.org/10.1002/anie.201905135.

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25

Imbrogno, Jennifer, Robert C. Ferrier, Bill K. Wheatle, Michael J. Rose, and Nathaniel A. Lynd. "Decoupling Catalysis and Chain-Growth Functions of Mono(μ-alkoxo)bis(alkylaluminums) in Epoxide Polymerization: Emergence of the N–Al Adduct Catalyst." ACS Catalysis 8, no. 9 (August 9, 2018): 8796–803. http://dx.doi.org/10.1021/acscatal.8b02446.

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26

Hai, Zijuan, Zhou Lu, Shuaikang Li, Zhong-Yan Cao, and Shengyu Dai. "The synergistic effect of rigid and flexible substituents on insertion polymerization with α-diimine nickel and palladium catalysts." Polymer Chemistry 12, no. 32 (2021): 4643–53. http://dx.doi.org/10.1039/d1py00812a.

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27

Chen, Mao, Shihong Deng, Yuwei Gu, Jun Lin, Michelle J. MacLeod, and Jeremiah A. Johnson. "Logic-Controlled Radical Polymerization with Heat and Light: Multiple-Stimuli Switching of Polymer Chain Growth via a Recyclable, Thermally Responsive Gel Photoredox Catalyst." Journal of the American Chemical Society 139, no. 6 (February 2, 2017): 2257–66. http://dx.doi.org/10.1021/jacs.6b10345.

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28

Tomov, Atanas K., Vernon C. Gibson, George J. P. Britovsek, Richard J. Long, Martin van Meurs, David J. Jones, Kilian P. Tellmann, and Juan J. Chirinos. "Distinguishing Chain Growth Mechanisms in Metal-catalyzed Olefin Oligomerization and Polymerization Systems: C2H4/C2D4Co-oligomerization/Polymerization Experiments Using Chromium, Iron, and Cobalt Catalysts." Organometallics 28, no. 24 (December 28, 2009): 7033–40. http://dx.doi.org/10.1021/om900792x.

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29

Braendle, Andreas, Carina Vidovič, Nadia Mösch-Zanetti, Markus Niederberger, and Walter Caseri. "Synthesis of High Molar Mass Poly(phenylene methylene) Catalyzed by Tungsten(II) Compounds." Polymers 10, no. 8 (August 7, 2018): 881. http://dx.doi.org/10.3390/polym10080881.

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Poly(phenylene methylene)s (PPMs) with high molar masses were isolated by polymerization of benzyl chloride catalyzed with tungsten(II) compounds and subsequent fractionation. Four different tungsten(II) catalysts were successfully exploited for the polymerization, for which a strict temperature profile was developed. The PPMs possessed roughly a trimodal molar mass distribution. Simple fractionation by phase separation of 2-butanone solutions allowed to effectively segregate the products primarily into PPM of low molar mass (Mn = 1600 g mol−1) and high molar mass (Mn = 167,900 g mol−1); the latter can be obtained in large quantities up to 50 g. The evolution of the trimodal distribution and the monomer conversion was monitored by gel permeation chromatography (GPC) and 1H NMR spectroscopy, respectively, over the course of the polymerization. The results revealed that polymerization proceeded via a chain-growth mechanism. This study illustrates a new approach to synthesize PPM with hitherto unknown high molar masses which opens the possibility to explore new applications, e.g., for temperature-resistant coatings, fluorescent coatings, barrier materials or optical materials.

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Гиззатова, Э. Р., А. С. Исмагилова, and С. Л. Подвальный. "SEARCH FOR UNCERTAINTY REGIONS OF KINETIC CONSTANTS IN MODELING PROCESSES OF NON-BREAK POLYMERIZATION OF DIENES." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 1 (April 19, 2021): 7–13. http://dx.doi.org/10.36622/vstu.2021.17.1.001.

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Рассматриваются процессы полимеризации на катализаторах Циглера-Натта. Исследован вопрос о механизме процессов как необходимом наборе элементарных стадий кинетической схемы. Приведена общая схема допустимых стадий процесса, включающая стадии инициирования, роста цепи, передач цепи и обрыва цепи. Указано, что часть элементарных реакций может быть убрана из кинетической схемы за счет способа приготовления самого катализатора, а часть - на основании получаемых кинетических зависимостей. Но гипотеза о наличии или отсутствии элементарных стадий может быть доказана не только экспериментальным, но и вычислительным путем. Приводимые в работе табличные данные свидетельствуют о практически нулевом значении константы скорости элементарной стадии материального обрыва цепи - дезактивации активных центров, что, в свою очередь, вызывает оптимизацию кинетической схемы. Тогда рассматриваемые процессы могут быть отнесены к типу безобрывной полимеризации. Составление кинетической и математической моделей для исследуемых процессов позволяет поставить прямые и обратные кинетические задачи. Решение последних может быть получено методом многократного решения прямых кинетических задач и сравнения расчетных значений молекулярных характеристик с их экспериментальными аналогами. Однако целесообразнее проводить предварительный этап нахождения областей локальных минимумов по оптимизируемым значениям констант путем построения базисной поверхности и при поиске допустимых наборов значений констант скоростей оперировать найденными областями минимумов This paper considers the processes of polymerization on Ziegler-Natta catalysts. The question of the mechanism of the processes as a necessary set of elementary stages of the kinetic scheme is investigated. A general scheme of the permissible stages of the process is given, including the stages of initiation, chain growth, chain transfers and chain termination. It is indicated that part of the elementary reactions can be removed from the kinetic scheme due to the method of preparation of the catalyst itself, and part on the basis of the obtained kinetic dependences. However, the hypothesis about the presence or absence of elementary stages can be proved not only experimentally but also computationally. The tabular data presented in the work indicate a practically zero value of the rate constant of the elementary stage of material chain termination - deactivation of active centers, which, in turn, leads to optimization of the kinetic scheme. Then the processes under consideration can be attributed to the type of non-break polymerization. Compilation of kinetic and mathematical models for the processes under study makes it possible to pose direct and inverse kinetic problems. The solution of the latter can be obtained by the method of multiple solution of direct kinetic problems and comparison of the calculated values of molecular characteristics with their experimental counterparts. However, it is more expedient to carry out the preliminary stage of finding the regions of local minima by the optimized values of the constants by constructing the base surface. When searching for admissible sets of values of the rate constants, operate with the found areas of minima

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31

Svejda, Steven A., Lynda K. Johnson, and Maurice Brookhart. "Low-Temperature Spectroscopic Observation of Chain Growth and Migratory Insertion Barriers in (α-Diimine)Ni(II) Olefin Polymerization Catalysts." Journal of the American Chemical Society 121, no. 45 (November 1999): 10634–35. http://dx.doi.org/10.1021/ja991931h.

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32

Jitonnom, Jitrayut, and Wijitra Meelua. "Cationic ring-opening polymerization of cyclic carbonates and lactones by group 4 metallocenes: A theoretical study on mechanism and ring-strain effects." Journal of Theoretical and Computational Chemistry 16, no. 01 (February 2017): 1750003. http://dx.doi.org/10.1142/s0219633617500031.

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Group 4 metallocene-mediated cationic ring-opening polymerizations of a series of lactones and cyclic carbonates, with different ring sizes ([Formula: see text]–8) have been theoretically studied. Using the “naked cation” approach in combination with density functional theory, the activated chain-end mechanism and the influence of transition metals, solvent and monomer ring size on the polymerizability were explored in detail. The results showed that the cationic metallocene–monomer complex, [catalyst][monomer][Formula: see text], is formed, generating cationic (carbocation ion) species responsible for polymer chain growth. We found that poor polymerizability of five-membered lactone and six-membered ring carbonate depends not only on the nature of the monomer ring size but also the relative stability of the complex, which was found to correlate well with the ring strain. Subsequently, several propagation steps take place through an SN2 reaction which involves ring opening of an active monomer, via alkyl–oxygen bond cleavage. Based on the computed activation energies of all metallocene systems, the first propagation was found to be the rate-determining step of the overall propagation and the hafnocene was found to be most active with the energy barrier of 17.6[Formula: see text]kcal/mol, followed by zirconocene (18.6[Formula: see text]kcal/mol) and titanocene (19.5[Formula: see text]kcal/mol), respectively. The mechanistic study may be applicable to the cationic ROP of lactides and other related monomers.

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Lin, Si-Ting, Chung-Chi Wang, Chi-Jung Chang, Yasuyuki Nakamura, Kun-Yi Andrew Lin, and Chih-Feng Huang. "Progress in the Preparation of Functional and (Bio)Degradable Polymers via Living Polymerizations." International Journal of Molecular Sciences 21, no. 24 (December 16, 2020): 9581. http://dx.doi.org/10.3390/ijms21249581.

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This review presents the latest developments in (bio)degradable approaches and functional aliphatic polyesters and polycarbonates prepared by typical ring-opening polymerization (ROP) of lactones and trimethylene carbonates. It also considers several recent innovative synthetic methods including radical ring-opening polymerization (RROP), atom transfer radical polyaddition (ATRPA), and simultaneous chain- and step-growth radical polymerization (SCSRP) that produce aliphatic polyesters. With regard to (bio)degradable approaches, we have summarized several representative cleavable linkages that make it possible to obtain cleavable polymers. In the section on functional aliphatic polyesters, we explore the syntheses of specific functional lactones, which can be performed by ring-opening copolymerization of typical lactone/lactide monomers. Last but not the least, in the recent innovative methods section, three interesting synthetic methodologies, RROP, ATRPA, and SCSRP are discussed in detail with regard to their reaction mechanisms and polymer functionalities.

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Cai, Zhengguo, Zhongliang Shen, Xiaoyuan Zhou, and Richard F. Jordan. "Enhancement of Chain Growth and Chain Transfer Rates in Ethylene Polymerization by (Phosphine-sulfonate)PdMe Catalysts by Binding of B(C6F5)3 to the Sulfonate Group." ACS Catalysis 2, no. 6 (May 15, 2012): 1187–95. http://dx.doi.org/10.1021/cs300147c.

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STEFANINI, Simonetta, Stefano CAVALLO, Benedetta MONTAGNINI, and Emilia CHIANCONE. "Incorporation of iron by the unusual dodecameric ferritin from Listeria innocua." Biochemical Journal 338, no. 1 (February 8, 1999): 71–75. http://dx.doi.org/10.1042/bj3380071.

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The polypeptide chain that assembles into the unusual dodecameric shell of Listeria innocua apoferritin lacks the ferroxidase centre characteristic of H-type mammalian chains, but is able to catalyse both Fe(II) oxidation and nucleation of the iron core. A cluster of five carboxylate residues, which correspond in part to the site of iron core nucleation typical of L-type mammalian ferritins, has been proposed to be involved in both functions. The features of the iron uptake kinetics and of Fe(II) autoxidation in the presence of citrate followed spectrophotometrically confirm this assignment. In Listeria the kinetics of iron uptake is hyperbolic at low Fe(II)-to-dodecamer ratios and becomes sigmoidal when iron exceeds 150 Fe(II) atoms per dodecamer, namely when a fast crystal growth phase follows a slow initial nucleation step. Iron autoxidation in the presence of citrate displays a similar behaviour. Thus the time course is sigmoidal at low citrate-to-Fe ratios at which Fe(III) polymerization is predominant, but is hyperbolic at ligand concentrations high enough to prevent polymerization. The marked inhibitory effect of Tb(III) on the kinetics of iron incorporation confirms that carboxylates provide the iron ligands in L. innocua apoferritin. Iron uptake followed in steady-state fluorescence experiments allows one to distinguish Fe(II) binding and oxidation from the subsequent movement of Fe(III) into the apoferritin cavity as in mammalian ferritins despite the different localization of the tryptophan residues.

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Yokoyama, Akihiro, Hirofumi Suzuki, Yasuhiro Kubota, Kazuei Ohuchi, Hideyuki Higashimura, and Tsutomu Yokozawa. "Chain-Growth Polymerization for the Synthesis of Polyfluorene via Suzuki−Miyaura Coupling Reaction from an Externally Added Initiator Unit." Journal of the American Chemical Society 129, no. 23 (June 2007): 7236–37. http://dx.doi.org/10.1021/ja070313v.

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Sugiyama, Yu-ki, Rei Kato, Tetsuya Sakurada, and Sentaro Okamoto. "Chain-Growth Cycloaddition Polymerization via a Catalytic Alkyne [2 + 2 + 2] Cyclotrimerization Reaction and Its Application to One-Shot Spontaneous Block Copolymerization." Journal of the American Chemical Society 133, no. 25 (June 29, 2011): 9712–15. http://dx.doi.org/10.1021/ja203584c.

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38

Panagiotopoulos, Christos, Athanasios Porfyris, Dimitrios Korres, and Stamatina Vouyiouka. "Solid-State Polymerization as a Vitrimerization Tool Starting from Available Thermoplastics: The Effect of Reaction Temperature." Materials 14, no. 1 (December 22, 2020): 9. http://dx.doi.org/10.3390/ma14010009.

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In the current work, solid-state polymerization (SSP) was studied for the synthesis of poly(butylene terephthalate), PBT-based vitrimers. A two-step process was followed; the first step involved alcoholysis reactions and the incorporation of glycerol in the polymer chains. The second step comprised transesterification reactions in the solid state (SSP) in the presence of zinc(II) catalyst resulting in the formation of a dynamic crosslinked network with glycerol moieties serving as the crosslinkers. The optimum SSP conditions were found to be 3 h at 180 °C under N2 flow (0.5 L/min) to reach high vitrimer insolubility (up to 75%) and melt strength (2.1 times reduction in the melt flow rate) while increasing the crosslinker concentration (from 3.5 to 7 wt.%) improved further the properties. Glass transition temperature (Tg) was almost tripled in vitrimers compared to initial thermoplastic, reaching a maximum of 97 °C, whereas the melting point (Tm) was slightly decreased, due to loss of symmetry perfection under the influence of the crosslinks. Moreover, the effect of the dynamic crosslinked structure on PBT crystallization behavior was investigated in detail by studying the kinetics of non-isothermal crystallization. The calculated effective activation energy using the Kissinger model and the nucleating activity revealed that the higher crosslinker content impeded and slowed down vitrimers melt crystallization, also inducing an alteration in the crystallization mechanism towards sporadic heterogeneous growth.

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Men, Xiao, Fan Wang, Guo-Qiang Chen, Hai-Bo Zhang, and Mo Xian. "Biosynthesis of Natural Rubber: Current State and Perspectives." International Journal of Molecular Sciences 20, no. 1 (December 22, 2018): 50. http://dx.doi.org/10.3390/ijms20010050.

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Natural rubber is a kind of indispensable biopolymers with great use and strategic importance in human society. However, its production relies almost exclusively on rubber-producing plants Hevea brasiliensis, which have high requirements for growth conditions, and the mechanism of natural rubber biosynthesis remains largely unknown. In the past two decades, details of the rubber chain polymerization and proteins involved in natural rubber biosynthesis have been investigated intensively. Meanwhile, omics and other advanced biotechnologies bring new insight into rubber production and development of new rubber-producing plants. This review summarizes the achievements of the past two decades in understanding the biosynthesis of natural rubber, especially the massive information obtained from the omics analyses. Possibilities of natural rubber biosynthesis in vitro or in genetically engineered microorganisms are also discussed.

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40

Гиззатова, Э. Р., С. Л. Подвальный, and С. И. Спивак. "SEARCH FOR KINETIC CONSTANTS IN MODELING THE PROCESSES OF POLYCENTERS NON-BREAK POLYMERIZATION OF DIENES." ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, no. 5() (November 18, 2020): 13–18. http://dx.doi.org/10.36622/vstu.2020.16.5.002.

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Приводится методика решения обратной кинетической задачи поиска констант скоростей полимеризационного процесса для кинетически неоднородных каталитических систем Циглера-Натта. Неоднородность катализаторов рассматривается как существование нескольких типов активных центров, параллельно друг другу ведущих процессы роста и обрыва полимерных цепей. Кинетическая схема процесса исключает материальный обрыв цепи, что влечет передачу активности с одного центра на другой. Наблюдаемое условие постоянства концентрации активных центров является уравнением материального баланса полимеризационной системы. Оно соблюдается в математической модели, описывающей процесс в виде автономной системы, содержащей бесконечное число обыкновенных дифференциальных уравнений первого порядка по мономеру, преобразованной методом моментов к конечному виду. Отмечено, что статистические моменты, присутствующие в системе дифференциальных уравнений, являются начальными моментами молекулярно-массового распределения. На их основе даны аналитические зависимости для искомых средних молекулярных масс образующихся полимеров на каждом типе активных центров и всего полимерного образца. Расчетный эксперимент проведен для процесса полимеризации изопрена на 4-центровой ванадийсодержащей каталитической системе с целью получения решения обратной кинетической задачи. Найден совокупный набор констант скоростей элементарных стадий процесса. Показаны графические иллюстрации сравнений расчетов и экспериментов по значениям средних молекулярных масс по каждому типу активных центров и всего полимера в целом We present a technique for solving the inverse kinetic problem of finding the rate constants of the polymerization process for kinetically inhomogeneous catalytic systems of the Ziegler-Natta. We consider inhomogeneity of catalysts as the existence of several types of active centers, parallel to each other leading processes of growth and termination of polymer chains. The kinetic scheme of the process excludes material breaking of the chain, which entails the transfer of activity from one center to another. The observed condition for the constancy of the concentration of active centers is the material balance equation for the polymerization system. It is observed in a mathematical model that describes the process in the form of an autonomous system containing an infinite number of ordinary differential equations of the first order in monomer, transformed by the method of moments to a finite form. We note that the statistical moments present in the system of differential equations are the initial moments of the molecular weight distribution. On their basis, we give analytical dependences for the desired average molecular weights of the resulting polymers on each type of active centers and the entire polymer sample. We carried out a computational experiment for the process of isoprene polymerization on a 4-center vanadium-containing catalytic system in order to obtain a solution to the inverse kinetic problem. We found a cumulative set of rate constants for elementary stages of the process. We show graphical illustrations of comparisons of calculations and experiments on the values of the average molecular weights for each type of active site and the entire polymer as a whole

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Terrak, Mohammed, and Martine Nguyen-Distèche. "Kinetic Characterization of the Monofunctional Glycosyltransferase from Staphylococcus aureus." Journal of Bacteriology 188, no. 7 (April 1, 2006): 2528–32. http://dx.doi.org/10.1128/jb.188.7.2528-2532.2006.

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ABSTRACT The glycosyltransferase (GT) module of class A penicillin-binding proteins (PBPs) and monofunctional GTs (MGTs) belong to the GT51 family in the sequence-based classification of GTs. They both possess five conserved motifs and use lipid II precursor (undecaprenyl-pyrophosphate-N-acetylglucosaminyl-N-acetylmuramoyl- pentapeptide) to synthesize the glycan chain of the bacterial wall peptidoglycan. MGTs appear to be dispensable for growth of some bacteria in vitro. However, new evidence shows that they may be essential for the infection process and development of pathogenic bacteria in their hosts. Only a small number of class A PBPs have been characterized so far, and no kinetic data are available on MGTs. In this study, we present the principal enzymatic properties of the Staphylococcus aureus MGT. The enzyme catalyzes glycan chain polymerization with an efficiency of ∼5,800 M−1 s−1 and has a pH optimum of 7.5, and its activity requires metal ions with a maximum observed in the presence of Mn2+. The properties of S. aureus MGT are distinct from those of S. aureus PBP2 and Escherichia coli MGT, but they are similar to those of E. coli PBP1b. We examined the role of the conserved Glu100 of S. aureus MGT (equivalent to the proposed catalytic Glu233 of E. coli PBP1b) by site-directed mutagenesis. The Glu100Gln mutation results in a drastic loss of GT activity. This shows that Glu100 is also critical for catalysis in S. aureus MGT and confirms that the conserved glutamate of the first motif EDXXFXX(H/N)X(G/A) is likely the key catalytic residue in the GT51 active site.

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42

Ölscher, Franz, Inigo Göttker-Schnetmann, Vincent Monteil, and Stefan Mecking. "Role of Radical Species in Salicylaldiminato Ni(II) Mediated Polymer Chain Growth: A Case Study for the Migratory Insertion Polymerization of Ethylene in the Presence of Methyl Methacrylate." Journal of the American Chemical Society 137, no. 46 (November 16, 2015): 14819–28. http://dx.doi.org/10.1021/jacs.5b08612.

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43

Yokozawa, Tsutomu, and Yoshihiro Ohta. "Transformation of Step-Growth Polymerization into Living Chain-Growth Polymerization." Chemical Reviews 116, no. 4 (November 10, 2015): 1950–68. http://dx.doi.org/10.1021/acs.chemrev.5b00393.

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44

Yuan, Jingsong, Wenqi Wang, Zefeng Zhou, and Jia Niu. "Cascade Reactions in Chain-Growth Polymerization." Macromolecules 53, no. 14 (June 26, 2020): 5655–73. http://dx.doi.org/10.1021/acs.macromol.0c00417.

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45

Yokoyama, Akihiro, and Tsutomu Yokozawa. "Converting Step-Growth to Chain-Growth Condensation Polymerization." Macromolecules 40, no. 12 (June 2007): 4093–101. http://dx.doi.org/10.1021/ma061357b.

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46

Goto, Atsushi, Norihiro Hirai, Tsutomu Wakada, Koji Nagasawa, Yoshinobu Tsujii, and Takeshi Fukuda. "Living Radical Polymerization with Nitrogen Catalyst: Reversible Chain Transfer Catalyzed Polymerization withN-Iodosuccinimide." Macromolecules 41, no. 17 (September 9, 2008): 6261–64. http://dx.doi.org/10.1021/ma801323u.

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47

Colombani, Daniel. "Chain-growth control in free radical polymerization." Progress in Polymer Science 22, no. 8 (January 1997): 1649–720. http://dx.doi.org/10.1016/s0079-6700(97)00022-1.

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German, Ian, Wissem Kelhifi, Sébastien Norsic, Christophe Boisson, and Franck D'Agosto. "Telechelic Polyethylene from Catalyzed Chain-Growth Polymerization." Angewandte Chemie 125, no. 12 (February 13, 2013): 3522–25. http://dx.doi.org/10.1002/ange.201208756.

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Huang, Li, Shupeng Wu, Yao Qu, Yanhou Geng, and Fosong Wang. "Grignard Metathesis Chain-Growth Polymerization for Polyfluorenes." Macromolecules 41, no. 22 (November 25, 2008): 8944–47. http://dx.doi.org/10.1021/ma801538q.

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50

Höcker, Hartwig. "Metathesis polymerization — stepwise or chain growth reaction?" Journal of Molecular Catalysis 65, no. 1-2 (March 1991): 95–99. http://dx.doi.org/10.1016/0304-5102(91)85086-h.

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