Ring‐opening polymerization of lactide, <i>ε</i>‐caprolactone and their copolymerization catalyzed by <i>β</i>‐diketiminate zinc complexes

Keram, Maryam; Ma, Haiyan

doi:10.1002/aoc.3893

Cited by 27 publications

(25 citation statements)

References 71 publications

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“…In contrast, previous results showed that, although the active PLL did initiate CL in a sequential copolymerization, the resulting copolymer had more of a random/statistical distribution of monomers than would be expected for a block copolymer microstructure . This was attributed to the occurrence of transesterification reactions caused by the CL‐derived hydroxyl end‐groups generated during the second‐step copolymerization, as also observed by other workers …”

Section: Resultsmentioning

confidence: 64%

“…In other previous studies, a P(CL‐ b ‐LL) block copolymer was prepared via a two‐step polymerization in which PCL was generated as a prepolymer in the first step. Reversal of the monomer addition using a PLL prepolymer as the propagating species gave a more random structure which was attributed to increased transesterification during copolymerization . Other researchers have also attempted to synthesize P(LL‐ b ‐CL) using PLL as a propagating species, employing either rare earth metal based initiators or specially designed, sterically hindered tin(IV) initiators .…”

Section: Introductionmentioning

confidence: 99%

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Physical and thermal properties of l‐lactide/ϵ‐caprolactone copolymers: the role of microstructural design

Phetsuk

Molloy

Nalampang

et al. 2019

Polymer International

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Understanding the underlying role of microstructural design in polymers allows for the manipulation and control of properties for a wide range of specific applications. As such, this work focuses on the study of microstructure–property relationships in l‐lactide/ϵ‐caprolactone (LL/CL) copolymers. One‐step and two‐step bulk ring‐opening polymerization (ROP) procedures were employed to synthesize LL/CL copolymers of various compositions and chain microstructures. In the one‐step procedure, LL and CL were simultaneously copolymerized to yield P(LL‐stat‐CL) statistical copolymers. In the two‐step procedure, poly(l‐lactide) (PLL) and poly(ϵ‐caprolactone) (PCL) prepolymers were synthesized in the first step before CL and LL respectively were added in the second step to yield P[LL‐b‐(CL‐stat‐LL)‐b‐LL] and P[CL‐b‐(LL‐stat‐CL)‐b‐CL] block copolymers as the final products. The findings reveal that, in addition to the copolymerization procedure employed, the length and type of the prepolymer play important roles in determining the chain microstructure and thereby the overall properties of the final copolymer. Moreover, control over the degree of crystallinity and the type of crystalline domains, which is controlled during the polymer chemistry process, heavily influences the physical and mechanical properties of the final polymer. In summary, this work describes an interesting approach to the microstructural design of biodegradable copolymers of LL and CL for potential use in biomedical applications. © 2019 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Physical and thermal properties of l‐lactide/ϵ‐caprolactone copolymers: the role of microstructural design

Phetsuk

Molloy

Nalampang

et al. 2019

Polymer International

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“…在本组之前的工作中, 我们合成了一系列基于非对称 β-二亚胺配体的锌硅氨基络合物, 对外消旋丙交酯和 ε-己内酯聚合表现出较高的催化活性, 并可催化两种单体共聚主要得到两嵌段共聚物 [72] . 在此基础上, 本文进一步设计合成了相应的非对称 β-二亚氨基镁络合物, 系统研究了配体其中一个 N-芳基为 2,6-二异丙基苯基、同时在另一个 N-芳基上引入具有较小位阻效应的供电子或吸电子基团时, 该类取代基因素对镁络合物催化外消旋丙交酯、ε-己内酯开环聚合及 L-丙交酯和 ε-己内酯共聚性能的影响.…”

Section: β-二亚胺配体因其合成简单很容易通过改变苯胺上的取代基以调整金属周围的空间位阻和电子性质故广泛用于与不同的金unclassified

“…(见图 1)主要参照文献方法合成 [37,72] ; 镁硅氨基络合物 1～7 的合成路线如图 1 [72] , 这一点与对称取代 β-二亚氨基锌、镁络合物中的规律一致 [48,49] . 镁金属中心与配体骨架中 [49,50,56] , 说明在固体 Figure 2 The molecular structure of complex 1 [68] .…”

Section: 镁络合物的合成非对称 β-二亚胺配体 Hl 1～7unclassified

Non-symmetric β-Diketiminate Magnesium Complexes as Initiators for Ring-Opening Polymerization/Copolymerization of Lactide, ε-Caprolactone

布美热木·克力木¹,

Keram²

2018

Acta Chim. Sinica

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Magnesium silylamido complexes 1～7 bearing non-symmetric β-diketiminate ligands were synthesized via the reactions of corresponding proligands HL 1～7 with one equivalent of Mg[N(SiMe 3 ) 2 ] 2 at 80 ℃ in toluene. All complexes were characterized by 1 H NMR, 13 C NMR and elemental analysis. The monomeric nature of complexes 1 and 5 in the solid state was further confirmed by X-ray diffraction studies. In both complexes, the metal center is tri-coordinated by the β-diketiminate ligand and one silylamido group. The very close bond lengths of two Mg-N bonds as well as close C-N distances of the chelate ring indicate significant delocalization. The apparent deviation of the magnesium center from the ligand backbone plane suggests a certain η n -coordination nature of the ligand to the metal center. These magnesium silylamido complexes showed good catalytic activities for the ring-opening polymerization of rac-lactide under ambient conditions, and could polymerize 300 equivalents of rac-lactide to high molecular weight polymers within short time in THF. The solvent effect played a critical role during the polymerization process. All complexes showed higher catalytic activity in THF than in toluene. Taking complex 2 as an example, a monomer conversion of 96% could be achieved within 10 min in THF, whereas a conversion of 80% could only be achieved within extended polymerization time of 210 min in toluene (Table 1, Entries 6 and 9, [LA] 0 /[Mg] 0 ＝100). Upon the addition of isopropanol, the activities of magnesium silylamido complexes 1～7 increased significantly. For instance, when the polymerization runs were carried in THF in the presence of isopropanol, the reaction time could be reduced to 10～20 min even with a high molar ratio of [LA] 0 /[Mg] 0 ＝300. Moreover, the type and location of the substituent(s) on the N-aryl group of the β-diketiminate ligand exerts a significant influence on the catalytic activity of the corresponding complex toward the polymerization of rac-lactide. In the absence of excess isopropanol, the introduction of sterically demanding substituent to the ortho-position of N-aryl ring leads to a decrease of the polymerization activity; but the influence of electron-withdrawing group is different in different solvents (toluene or THF). These magnesium complexes could produce heterotactic polymers in THF (P r ＝0.64～0.80) and atactic polymers in toluene (P r ＝0.45～0.58). Magnesium complexes 1～7 also displayed high catalytic activities for the ring-opening polymerization (ROP) of ε-caprolactone, among them complexes bearing β-diketiminate ligand with bulky ortho-substituted N-aryl rings showed higher activities. Generally, the ROPs of ε-caprolactone initiated by these magnesium silylamido complexes were not well-controlled, giving moderately distributed polymers (M w /M n ＝1.37～1.67). Additionally, diblock copolymers of L-lactide and ε-caprolactone were obtained by using 2 as the initiator via both sequential feeding of two monomers (in either order) and the one-pot method. The formation of ...

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“…Many metal complexes have been explored for catalytic (co)polymerization of lactide, such as tin, [9][10][11] lanthanum, [12,13] aluminum, [14,15] zinc [16][17][18][19] and zirconium. [20][21][22][23] It is well known that stannous octoate Sn(Oct) 2 is the most popular catalyst in polymerization of lactide for its high efficiency.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and properties of polylactide terpolymers P(LLA‐TMC‐GA) catalyzed by zirconium (IV) acetylacetonate

Chen

Lei

et al. 2017

Applied Organom Chemis

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A series of L‐lactide (LLA), 1,3‐trimethylene carbonate (TMC) and glycolide (GA) terpolymers (LTG) of different monomer molar ratios were synthesized by using ring‐opening copolymerization. An effective and low‐toxic zirconium (IV) acetylacetonate Zr(Acac)4 was used as catalyst. The viscosity‐average molecular weights (Mη) of obtained polymers were all above 2.2×104 g/mol. The chemical structure and viscosity of terpolymers were confirmed by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance (1HNMR), 13C nuclear magnetic resonance (13CNMR) and an Ubbelohde viscometer. The thermal and mechanical properties were investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) and stress‐strain measurements. Results suggested that all terpolymers were amorphous and showed good thermal stability. Also it was found that elongation increased with the decreasing of LLA unit. More importantly, terpolymers displayed shape memory property when deformation temperatures were 14‐15 °C above Tg.

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Ring‐opening polymerization of lactide, ε‐caprolactone and their copolymerization catalyzed by β‐diketiminate zinc complexes

Cited by 27 publications

References 71 publications

Physical and thermal properties of l‐lactide/ϵ‐caprolactone copolymers: the role of microstructural design

Physical and thermal properties of l‐lactide/ϵ‐caprolactone copolymers: the role of microstructural design

Non-symmetric β-Diketiminate Magnesium Complexes as Initiators for Ring-Opening Polymerization/Copolymerization of Lactide, ε-Caprolactone

Synthesis and properties of polylactide terpolymers P(LLA‐TMC‐GA) catalyzed by zirconium (IV) acetylacetonate

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