Thiourea binding with carboxylic acid promoted cationic ring-opening polymerization

Li, Xiaopei; Zhang, Qiguo; Li, Zhenjiang; Wang, Xin; Liu, Jingjing; Cui, Saide; Xu, Songquan; Zhao, Changzhi; Chen, Cheng; Guo, Kai

doi:10.1016/j.polymer.2015.12.057

Cited by 22 publications

(9 citation statements)

References 56 publications

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“…Below, in Scheme , this kind of activation of trifluoroacetic acid with a derivative of thiourea is shown, as presented by Zhang and Guo et al, from where we copied this picture …”

Section: External Activation With Hydrogen Bonding and Other Activati...mentioning

confidence: 93%

“…Below, in Scheme 23, this kind of activation of trifluoroacetic acid with a derivative of thiourea is shown, as presented by Zhang and Guo et al, from where we copied this picture. 111 The authors suggested "massive success" and observed an increase of the rates of polymerization: three times for δVL and ca. 30% for CL.…”

Section: External Activation With Hydrogen Bonding and Other Activati...mentioning

confidence: 99%

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Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Penczek

Pretula

2021

ACS Macro Lett.

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The origin of the activated monomer mechanism (AMM) in cationic ring-opening polymerization (CROP) is described first. Then, conditions leading to the active chain end (ACE) mechanism and AMM are compared, as well as methods allowing to distinguish between these two mechanisms. These methods are based on the “ion trapping” of the active ionic species using highly basic phosphines or by comparing ACE and AMM kinetics of polymerization. The major factors deciding on the actual mechanism include: basicity of the monomers, ring strain, and the presence of the protic additives in the reaction system. These factors are tabulated for major cyclic ethers and cyclic esters. The historically evolved subsequent steps of AMM in the polymerization of cyclic esters are described: from the first experiments with trialkyloxonium salts, precursors of protonic acids, and added alcohols, via HCl as catalyst, and then CF3S(O)2OH (polymerizing lactides) to the most popular derivatives of phosphoric acid, like diphenyl phosphate. Conditions allowing to synthesize poly(ε-caprolactone) (PCL), according to AMM-CROP, with molar mass up to 105 g·mol–1, are described as well as methods to polymerize CL with a protic initiator and acidic catalyst in one molecule. Then various methods enhancing the activity of the polymerizing systems are compared, based predominantly on hydrogen bonding, either to the polymer active end group (usually the hydroxyl group) or to the acid anion. Finally, kinetic equations for ACE and AMM are compared, and it is shown that the majority of the AMM-CROP systems, mostly studied for CL and lactides, proceed as living/controlled polymerizations. Since polymer end groups are hydroxyl groups, then, as it was shown in several papers, any initiator with one or many hydroxyl groups provides macromolecules with the corresponding architecture. The papers on synthetic methods are not discussed in detail.

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“…Below, in Scheme , this kind of activation of trifluoroacetic acid with a derivative of thiourea is shown, as presented by Zhang and Guo et al, from where we copied this picture …”

Section: External Activation With Hydrogen Bonding and Other Activati...mentioning

confidence: 93%

Section: External Activation With Hydrogen Bonding and Other Activati...mentioning

confidence: 99%

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Penczek

Pretula

2021

ACS Macro Lett.

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“…In addition, Im-TEPB bearing a noncoordinating and bulky borate anion was used as the XB catalyst to ensure sufficient interaction with a soft Lewis basic moiety of Schreiner’s thiourea ( STU ) (Scheme ). Im-TEPB could be easily obtained from Im-TfO in 93% yield by the anion metathesis reaction with an excess amount of NaB(C 6 F 5 ) 4 . When polymerization was performed at 0 °C in dichloromethane using STU / Im-TEPB cocatalysis in the dark, the monomer was consumed very slowly to reach the conversion of 58% after 67 h but no polymer was detected in the GPC analysis (Table , entry 1).…”

Section: Results and Discissionmentioning

confidence: 99%

Application of Thiourea/Halogen Bond Donor Cocatalysis in Metal-Free Cationic Polymerization of Isobutyl Vinyl Ether and Styrene Derivatives

2022

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Cationic polymerization of isobutyl vinyl ether (IBVE) was investigated using Schreiner's thiourea (STU) combined with Im-TEPB bearing a 2-iodoimidazolium cation and a noncoordinating borate anion. Both the CF 3 CO 2 H adduct and the HCl adduct of IBVE had the ability to initiate polymerization, but the number-averaged molecular weight was rather low compared with the theoretical value and the molecular weight distribution was fairly broad (M w /M n > 2.6). On the other hand, fast cationic polymerization of p-methoxystyrene (pMOS, 50 equiv relative to pMOS•HCl) proceeded using STU/Im-TEPB cocatalysts, giving rise to poly(pMOS) with M n = 4580 and M w /M n = 1.38. STU/Im-TfO exhibited decreased activity due to the coordination of a trifluoromethanesulfonate counteranion with the NH group of STU, which was supported by the NMR spectrum, DFT calculation, and UV−vis titration experiment. The molecular weight of poly(pMOS) could be roughly regulated by STU/Im-TEPB cocatalysis between M n = 2400 and M n = 7500 by the monomer feed ratio with keeping the molecular weight distribution below 1.41, although these values were lower than the theoretical ones probably due to the unignorable chain-transfer reaction. The polymerization kinetics revealed that the monomer consumption rate depends on the concentration of Im-TEPB rather than STU, which reveals the catalytic function of STU/Im-TEPB.

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“…The acid used here must capable of protonating the bases and highly active in the ring-opening polymerizations. On the basis of our previous experience in acid-catalyzed ROPs, − we choose TfOH and MSA as acidic catalysts and protonating agents. The protonation of HMCP is reversible, and HMCP is stable in the protonation and deprotonation process (Figures S2 and S3).…”

Section: Resultsmentioning

confidence: 99%

Dual Switching in Both RAFT and ROP for Generation of Asymmetric A²A¹B¹B² Type Tetrablock Quaterpolymers

Dong

Zhu

et al. 2017

Macromolecules

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In reversible addition–fragmentation chain transfer (RAFT) polymerization, monomers are divided into “more-activated” monomers (type-A1 monomer) and “less-activated” monomers (type-A2 monomer). In ring-opening polymerization (ROP), monomers are considered to fall into electrophilically polymerizable monomers (lactones and carbonates, type-B1 monomer) and nucleophilically polymerizable monomers (lactides and carbonates, type-B2 monomer). Developing a strategy to copolymerize the four kinds of monomers for formation of asymmetric A2A1B1B2 type tetrablock quaterpolymers by one-pot sequential ROP and RAFT polymerization is a challenge. Herein, we designed and synthesized a molecule, 2-hydroxyethyl 2-(methyl(pyridin-4-yl)carbamothioylthio)propanoate, which functioned as a trifunctional initiator, to initiate ROPs and to modulate RAFT polymerizations sequentially in one-pot. We proposed a dual “acid/base switch” strategy in both RAFT polymerizations and ROPs for one-pot generation of asymmetric A2A1B1B2 type tetrablock quaterpolymers. A series of di-, tri-, and tetrablock copolymers were synthesized and showed predicted molar mass and narrow dispersities, manifesting that the ROPs and RAFT polymerizations proceeded independently in controlled manners. The dual “acid/base switch” strategy paved a new avenue to combine RAFT polymerizations and ROPs for synthesis of designed copolymers with advanced functionalities and architectures.

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Thiourea binding with carboxylic acid promoted cationic ring-opening polymerization

Cited by 22 publications

References 56 publications

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Application of Thiourea/Halogen Bond Donor Cocatalysis in Metal-Free Cationic Polymerization of Isobutyl Vinyl Ether and Styrene Derivatives

Dual Switching in Both RAFT and ROP for Generation of Asymmetric A²A¹B¹B² Type Tetrablock Quaterpolymers

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Thiourea binding with carboxylic acid promoted cationic ring-opening polymerization

Cited by 22 publications

References 56 publications

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Activated Monomer Mechanism (AMM) in Cationic Ring-Opening Polymerization. The Origin of the AMM and Further Development in Polymerization of Cyclic Esters

Application of Thiourea/Halogen Bond Donor Cocatalysis in Metal-Free Cationic Polymerization of Isobutyl Vinyl Ether and Styrene Derivatives

Dual Switching in Both RAFT and ROP for Generation of Asymmetric A2A1B1B2 Type Tetrablock Quaterpolymers

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Dual Switching in Both RAFT and ROP for Generation of Asymmetric A²A¹B¹B² Type Tetrablock Quaterpolymers