Benzo-12-crown-4 modified<i>N</i>-heterocyclic carbene for organocatalyst: Synthesis, characterization and degradation of block copolymers of ϵ-caprolactone with<i>L</i>-lactide

Wang, Yan; Niu, Jin; Jiang, Lijuan; Niu, Yun‐Xia; Zhang, Lifang

doi:10.1080/10601325.2016.1166004

Cited by 5 publications

(6 citation statements)

References 29 publications

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“…P(LA- stat -CL)s have thus attracted a great deal of attention in the biomedical and pharmaceutical fields − and as compatibilizers for PLA/PCL blends . The precision synthesis of P(LA- stat -CL) copolymers is still particularly challenging whether organometallic or organic − catalysts are used. This is due to the highly differing reactivity of the two monomers during ring-opening copolymerization (ROcP).…”

Section: Introductionmentioning

confidence: 99%

“…This is due to the highly differing reactivity of the two monomers during ring-opening copolymerization (ROcP). LA is typically incorporated first, although CL gives faster rates than LA in homopolymerization reactions. − ,− ,− Aluminum-based catalysts are most efficient for the statistical and controlled ROcP of LA and CL, ,− although less toxic catalysts based on zinc and molybdenum have also been successfully employed for this purpose.…”

Section: Introductionmentioning

confidence: 99%

“…LA is typically incorporated first, although CL gives faster rates than LA in homopolymerization reactions. [21][22][23][24][25][27][28][29][31][32][33][34][35][36][37] Aluminum-based catalysts are most efficient for the statistical and controlled ROcP of LA and CL, 35,[38][39][40] thought less toxic catalysts based on zinc 41 and molybdenum 42 have also been successfully employed for this purpose.Organic catalysis for polymerization is a fast developing field in polymer chemistry, offering a number of advantages over metal-catalysis, such as more sustainable processes, reduced toxicity and cost, and easier catalyst synthesis, purification, handling andstorage. 43,44 In this regard, the organocatalyzed ring-opening polymerization (OROP) of LA and CL has been particularly…”

mentioning

confidence: 99%

“…[44][45][46][47][48][49][50] Attempts to design P(LA-stat-CL) copolymers by OROcP, however, have met with limited success. [21][22][23][24][25][26][27][28][29] Basic-type organocatalysts, such as phosphazenes, 22 N-heterocyclic carbenes, 23,27 1,5,7-triazabicyclo[4.4.0]dec-5-ene guanidine 21 and thiourea-amine 28 only enable incorporation of LA in the polymer chain, and P(LA-stat-CL) copolymer synthesis cannot be achieved in this way. In contrast, a few Brønsted acid-type catalysts have been shown to perform the statistical OROcP of LA and CL.…”

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confidence: 99%

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Bulk Organocatalytic Synthetic Access to Statistical Copolyesters from l-Lactide and ε-Caprolactone Using Benzoic Acid

et al. 2019

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The development of synthetic strategies to produce statistical copolymers based on L-lactide (L-LA) and ε-caprolactone (CL), denoted as P(LA-stat-CL), remains highly challenging in polymer chemistry. This is due to the differing reactivity of the two monomers during their ring-opening copolymerization (ROcP). Yet, P(LA-stat-CL) materials are highly sought-after as they combine the properties of both polylactide PLA and poly(ε-caprolactone) (PCL). Here, benzoic acid (BA), a naturally occurring, cheap, readily recyclable and thermally stable weak acid, is shown to trigger the organocatalyzed ring-opening copolymerization (OROcP) of L-LA and CL under solvent-free conditions at 155 °C, in presence of various alcohols as initiators, with good control over molar masses and dispersities (1.11 <Đ< 1.35) of the resulting copolyesters. Various compositions can be achieved, and the formation of statistical compounds is shown through characterization by 1 H, 13 C and DOSY-NMR spectroscopies and by DSC, as well as through the determination of reactivity ratios (r LA = 0.86, r CL = 0.86), using the visualization of the sum of squared residuals space method. Furthermore, this BA-OROcP process can be exploited to access metal-free PLAb-P(LA-stat-CL)-b-PLA triblock copolymers, using a diol as initiator. Finally, residual traces of BA remaining in P(LA-stat-CL) copolymers (< 0.125 mol%) do not show any cytotoxicity towards hepatocyte-like HepaRG cells, demonstrating the safety of this organic catalyst.As biodegradable, nontoxic and biocompatible polymers, polylactide (PLA) and poly(εcaprolactone) (PCL) can be attractive biosourced surrogates for petroleum-based polymers. 1-4 Both PLA and PCL have been intensively investigated in applications ranging from pharmaceutics to packaging and electronics. 4-7 Yet, both PLA and PCL show some limitations in these applications.For instance, PLA is brittle, exhibits a poor elasticity, 8 a low thermal stability and a modest permeability to drugs. PCL has higher thermal stability and elasticity than PLA, with a glass transition temperature (T g ) around -60 °C vs. 45 -65 °C for PLA, 9,3,10 but suffers from poor mechanical properties. PCL has also a higher permeability to drugs 11 and a half time in vivo of 1year, 12 vs. a few weeks for PLA. 13 As a result, statistical copolymers of lactide (LA) and caprolactone (CL), i.e. P(LA-stat-CL) aliphatic copolyesters, are highly sought-after materials as they combine the strengths and minimize the weaknesses of both homopolymers. P(LA-stat-CL)s have thus attracted a great deal of attention in the biomedical and pharmaceutical fields, 14-18 and as compatibilizers for PLA/PCL blends. 19 The precision synthesis of P(LA-stat-CL) copolymers is still particularly challenging whether organometallic 20 or organic 21-30 catalysts are used. This is due to the highly differing reactivity of the two monomers during ring-opening copolymerization (ROcP). LA is typically incorporated first, although CL gives faster rates than LA in homopolymerization reactions. [21][...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Bulk Organocatalytic Synthetic Access to Statistical Copolyesters from l-Lactide and ε-Caprolactone Using Benzoic Acid

et al. 2019

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“…Synthesis of statistical copolymers based on L-LA and CL, P(LA- stat -CL), remains very challenging, whatever the catalysts employed to this end. ,− This is due to the highly differing reactivity of the two monomers during RO c P. LA is typically incorporated first, although CL gives faster rates than LA in homopolymerization reactions. Recently, some of us have reported the ROP of L-LA and CL catalyzed by benzoic acid (BA) in bulk at 155 °C.…”

Section: Introductionmentioning

confidence: 99%

Benzoic Acid as an Efficient Organocatalyst for the Statistical Ring-Opening Copolymerization of ε-Caprolactone and L-Lactide: A Computational Investigation

et al. 2019

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Statistical copolymers of l-lactide (L-LA) and ε-caprolactone (CL) are of major interest as a result of the desired combination of properties they exhibit for high-added-value applications, including in the biomedical field and in microelectronics. However, the high difference of reactivity between the two monomers makes difficult their statistical insertion in copolymer chains. Here, the ring-opening polymerization and copolymerization (ROP and ROcP, respectively) of L-LA and CL mediated by benzoic acid (BA) are investigated by means of density functional theory (DFT). It is first evidenced that the mechanism involves a hydrogen-bonding dual activation, where the acidic proton of BA activates the carbonyl moiety of the monomer, while the conjugated base of BA activates the alcohol initiator. In accordance with experimental findings, DFT calculations have then revealed a kinetically favored energetic profile for the BA-organocatalyzed ROP of CL compared to L-LA. In addition, energetic profiles of the BA-mediated ROcP of CL and L-LA does not show any preference of the insertion between CL and L-LA, irrespective of the type of growing species. Even though the caproyl unit insertion is kinetically favored by the primary nature of the growing chain end alcohol, this is eventually mitigated by the stabilizing effect of the ester moieties of the lactidyl unit, which is thermodynamically favored. As one effect compensates for the other, the dual activation mechanism involved in this organocatalytic pathway using BA as a weak organic acid is shown to be crucial to achieve truly statistical copolymers based on L-LA and CL.

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Synthesis, structure and catalysis/applications of N-heterocyclic carbene based on macrocycles

Yang

Liu

Wang

et al. 2017

J Incl Phenom Macrocycl Chem

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Benzo-12-crown-4 modifiedN-heterocyclic carbene for organocatalyst: Synthesis, characterization and degradation of block copolymers of ϵ-caprolactone withL-lactide

Cited by 5 publications

References 29 publications

Bulk Organocatalytic Synthetic Access to Statistical Copolyesters from l-Lactide and ε-Caprolactone Using Benzoic Acid

Bulk Organocatalytic Synthetic Access to Statistical Copolyesters from l-Lactide and ε-Caprolactone Using Benzoic Acid

Benzoic Acid as an Efficient Organocatalyst for the Statistical Ring-Opening Copolymerization of ε-Caprolactone and L-Lactide: A Computational Investigation

Synthesis, structure and catalysis/applications of N-heterocyclic carbene based on macrocycles

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