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Catalysts for the Ring Opening Polymerization
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Catalysts for the Ring Opening Polymerization

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalysis in Organic and Polymer Chemistry".

Deadline for manuscript submissions: closed (5 October 2023) | Viewed by 9545

Special Issue Editor

Dr. Ruaraidh McIntosh

E-Mail Website
Guest Editor
Inst Chem Sci, Heriot Watt University, Edinburgh, Midlothian, Scotland, UK
Interests: polymers; ring-opening polymerization; catalytic polymerisation; catalysts design; catalytic mechanism

Special Issue Information

Dear Colleagues,

Plastics are increasingly associated with negative impacts on the environment. Widespread public concern over this issue primarily arises from the volume and persistence of waste generated by single-use plastics. Furthermore, the reliance on fossil fuels to produce these materials raises ongoing concerns.

The development of more sustainable materials that degrade more readily has led to an increase in research into ring-opening polymerization reactions, typically of heteroatom-containing cyclic monomers. In this Special Issue, we aim to highlight the broad spectrum of chemistries incorporating ring-opening polymerization reactions with a particular focus on the development of catalysts, both homogeneous and heterogeneous, for these reactions.

Dr. Ruaraidh McIntosh
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 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

  • polymers
  • ring-opening polymerization
  • catalytic polymerisation
  • catalysts design
  • catalytic mechanism

Published Papers (5 papers)

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Research

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14 pages, 3284 KiB  
Article
DFT Investigations on the Ring-Opening Polymerization of Trimethylene Carbonate Catalysed by Heterocyclic Nitrogen Bases
by Michael Lalanne-Tisné, Audrey Favrelle-Huret, Wim Thielemans, João P. Prates Ramalho and Philippe Zinck
Catalysts 2022, 12(10), 1280; https://doi.org/10.3390/catal12101280 - 20 Oct 2022
Cited by 1 | Viewed by 1443
Abstract
Organocatalysts for polymerization have known a huge interest over the last two decades. Among them, heterocyclic nitrogen bases are widely used to catalyse the ring-opening polymerization (ROP) of heterocycles such as cyclic carbonates. We have investigated the ring-opening polymerization of trimethylene carbonate (TMC) [...] Read more.
Organocatalysts for polymerization have known a huge interest over the last two decades. Among them, heterocyclic nitrogen bases are widely used to catalyse the ring-opening polymerization (ROP) of heterocycles such as cyclic carbonates. We have investigated the ring-opening polymerization of trimethylene carbonate (TMC) catalysed by DMAP (4-dimethylaminopyridine) and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) as case studies in the presence of methanol as co-initiator by Density Functional Theory (DFT). A dual mechanism based on H-bond activation of the carbonyl moieties of the monomer and a basic activation of the alcohol co-initiator has been shown to occur more preferentially than a direct nucleophilic attack of the carbonate monomer by the heterocyclic nitrogen catalyst. The rate-determining step of the mechanism is the ring opening of the TMC molecule, which is slightly higher than the nucleophilic attack of the TMC carbonyl by the activated alcohol. The calculations also indicate TBD as a more efficient catalyst than DMAP. The higher energy barrier found for DMAP vs. TBD, 23.7 vs. 11.3 kcal·mol−1, is corroborated experimentally showing a higher reactivity for the latter. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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24 pages, 4710 KiB  
Article
Mono(imidazolin-2-iminato) Hafnium Complexes: Synthesis and Application in the Ring-Opening Polymerization of ε-Caprolactone and rac-Lactide
by Maxim Khononov, Heng Liu, Natalia Fridman, Matthias Tamm and Moris S. Eisen
Catalysts 2022, 12(10), 1201; https://doi.org/10.3390/catal12101201 - 09 Oct 2022
Cited by 1 | Viewed by 1759
Abstract
Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, [...] Read more.
Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, the Hf-N bond can be regarded as a double bond with similar electronic properties. The main difference among the monomeric complexes is the cone angle of the ligand, which induces varying steric hindrances around the metal center. When the monomeric complex of mono(bis(diisopropylphenyl)imidazolin-2-iminato) hafnium tribenzyl was reacted with three equivalents (equiv) of iPrOH, the benzyl groups were easily replaced, forming the corresponding tri-isopropoxide complex. However, when BnOH was used, dimeric complexes were obtained. When five equivalents of the corresponding alcohols (BnOH, iPrOH) were reacted with the monomeric complex, different dimeric complexes were obtained. Regardless of the high oxophilicity of the hafnium complexes, all complexes were active catalysts for the ring-opening polymerization (ROP) of ε-caprolactone. Dimeric complexes 5 and 6 were found to be the most active catalysts, enabling polymerization to occur in a living, immortal fashion, as well as the copolymerization of ε-caprolactone with rac-lactide, producing block copolymer PCL-b-LAC. The introduction of imidazolin-2-iminato ligands enables the tailoring of the oxophilicity of the complexes, allowing them to be active in catalytic processes with oxygen-containing substrates. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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11 pages, 1884 KiB  
Article
The Contribution of Commercial Metal Amides to the Chemical Recycling of Waste Polyesters
by Federica Santulli, Marina Lamberti, Andrea Annunziata, Rita Chiara Lastra and Mina Mazzeo
Catalysts 2022, 12(10), 1193; https://doi.org/10.3390/catal12101193 - 08 Oct 2022
Cited by 4 | Viewed by 1756
Abstract
Simple and commercially available metal amides are investigated as catalysts for the chemical depolymerization of polyesters of commercial interest such as polylactide (PLA) and polyethylene terephthalate (PET) via alcoholysis. In the alcoholysis reactions performed with methanol or ethanol at room temperature, Zn, Mg, [...] Read more.
Simple and commercially available metal amides are investigated as catalysts for the chemical depolymerization of polyesters of commercial interest such as polylactide (PLA) and polyethylene terephthalate (PET) via alcoholysis. In the alcoholysis reactions performed with methanol or ethanol at room temperature, Zn, Mg, and Y amides showed the highest activities, while the amides of group 4 metals were revealed as poor catalysts. During the ethanolysis of PLA at higher temperatures and the glycolysis of PET, the good activity of the Zn amide was preserved, while for Mg and Y amides, a significant decrease was observed. The reaction temperature had an opposite effect on the performance of group 4 amides, with the Zr amide revealed to be the best catalyst in the PET glycolysis, reaching activities comparable to the best ones reported in the literature for metal catalysts (78% BHET yield within one hour at 180 °C). These studies represent new opportunities for the sustainable recycling of plastics, which are currently being used on a large scale, and provide significant contributions to the design of a circular economy model in the plastic industry. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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23 pages, 6712 KiB  
Article
Ring Opening Polymerization of Lactides and Lactones by Multimetallic Titanium Complexes Derived from the Acids Ph2C(X)CO2H (X = OH, NH2)
by Xin Zhang, Timothy J. Prior, Kai Chen, Orlando Santoro and Carl Redshaw
Catalysts 2022, 12(9), 935; https://doi.org/10.3390/catal12090935 - 24 Aug 2022
Cited by 3 | Viewed by 1764
Abstract
The reactions of the titanium alkoxide [Ti(OR)4] (R = Me, nPr, iPr, tBu) with the acids 2,2′-Ph2C(X)(CO2H), where X = OH and NH2, i.e., benzilic acid (2,2′-diphenylglycolic acid, L1H2 [...] Read more.
The reactions of the titanium alkoxide [Ti(OR)4] (R = Me, nPr, iPr, tBu) with the acids 2,2′-Ph2C(X)(CO2H), where X = OH and NH2, i.e., benzilic acid (2,2′-diphenylglycolic acid, L1H2), and 2,2′-diphenylglycine (L2H3), have been investigated. The variation of the reaction stoichiometry allows for the isolation of mono-, bi-, tri or tetra-metallic products, the structures of which have been determined by X-ray crystallography. The ability of the resulting complexes to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and r-lactide (r-LA) has been investigated. In the case of ε-CL, all catalysts except that derived from [Ti(OnPr)4] and L2H3, i.e., 7, exhibited an induction period of between 60 and 285 min, with 7 exhibiting the best performance (>99% conversion within 6 min). The PCL products are moderate- to high-molecular weight polymers. For r-LA, systems 1, 3, 4 and 7 afforded conversions of ca. 90% or more, with 4 exhibiting the fastest kinetics. The molecular weights for the PLA are somewhat higher than those of the PCL, with both cyclic and linear PLA products (end groups of OR/OH) identified. Comparative studies versus the [Ti(OR)4] starting materials were conducted, and although high conversions were achieved, the control was poor. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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Review

Jump to: Research

24 pages, 10051 KiB  
Review
A Review on the Synthesis of Polypeptoids
by Zhifeng Qiu, Min Zhang, Di Liu, Xiran Shen, Wencheng Zhou, Wenqi Liu, Jianwei Lu and Li Guo
Catalysts 2023, 13(2), 280; https://doi.org/10.3390/catal13020280 - 27 Jan 2023
Cited by 7 | Viewed by 2058
Abstract
Polyeptoids are a promising class of polypeptide mimetic biopolymers based on N-substituted glycine backbones. Because of the high designability of their side chains, polypeptoids have a wide range of applications in surface antifouling, biosensing, drug delivery, and stimuli-responsive materials. To better control [...] Read more.
Polyeptoids are a promising class of polypeptide mimetic biopolymers based on N-substituted glycine backbones. Because of the high designability of their side chains, polypeptoids have a wide range of applications in surface antifouling, biosensing, drug delivery, and stimuli-responsive materials. To better control the structures and properties of polypeptoids, it is necessary to understand different methods for polypeptoid synthesis. This review paper summarized and discussed the main synthesis methods of polypeptoids: the solid-phase submonomer synthesis method, ring-opening polymerization method and Ugi reaction method. Full article
(This article belongs to the Special Issue Catalysts for the Ring Opening Polymerization)
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