APPLIED CATALYSIS A-GENERAL
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2017
·
IF 4.339
Zhixiong Luo,Somboon Chaemchuen,Kui Zhou,Andres Alvarado Gonzalez,Francis Verpoort
A series of metal organic frameworks (MOFs) MDABCO (M = Co, Ni, Cu, Zn; DABCO = 1,4-diazabicyclo[2.2.2]octane) are utilized as catalysts for the bulk ring-opening polymerization of l -lactide. The catalytic activity varies in the order CuDABCO, NiDABCO < ZnDABCO, CoDABCO. By adding lactic acid, we unexpectedly observed enhanced catalytic activity. The combined use of lactic acid and ZnDABCO during polymerization results in a highly active polymerization system, along with the gradual change of MOFs structure caused by an increased acid concentration. Compared to related homogeneous fragments, such as zinc nitrate and 1,4-diazabicyclo[2.2.2]octane, ZnDABCO is found to afford highly isotactic polylactide, which would be ascribed to the unique structural properties of MOFs.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
Crystals
·
2020
·Vol. 10
·期 9
·781
·
IF 2.404
Qintong Huang,Rui Li,Guangying Fu,Jiuxing Jiang
ZSM-5 zeolites are commonly used as a heterogeneous catalyst for reactions. Four ZSM-5 catalysts (with various crystallite sizes and a similar ratio of Si/Al) and their ball-milling/surface-poisoning derivates were used to convert L-lactic acid to L, L-lactide. The reaction products were analyzed by three independent analytical methods (i.e., Proton nuclear magnetic resonance (1H NMR), high-pressure liquid chromatography (HPLC), and chiral gas chromatography (GC)) for determining the L, L-lactide yield and L-lactic acid conversion. A clear size effect, i.e., smaller catalysts providing better performance, was observed. Further ball-milling/surface-poisoning experiments suggested that the size effect of the ZSM-5 catalysts originated from the diffusion-controlled nature of the reaction under the investigated conditions.Keywords:ZSM-5 zeolites;L,L-lactide;size effect;diffusion control
研究领域:
催化化学
·
材料科学
✓ 已验证
DOI
高影响因子
Chemistry Africa-A Journal of the Tunisian Chemical Society
·
2021
·Vol. 5
·期 1
·79-87
·
IF 0
Naz Farah,Ciprian Matteo,Luo Zhixiong,Yan Shilin,Iqbal Shahzad Zafar,Zhu Meifang,Chaemchuen Somboon,Verpoort Francis
The synthesis and use of MOF-derived Co/NCF (N-doped carbon framework) material as a heterogeneous catalyst for copolymers synthesis via ring-opening polymerization (ROP) are reported for the first time. The Co/NCF material is applied for the copolymerization of L -lactides (LA) and ε-caprolactone (ε-CL) as monomers via ROP in bulk without any solvent or co-catalyst. The as-prepared catalyst is characterized using XRD, TPD, XPS, SEM, and TEM analytical techniques. At the same time, 1 H and 13 C-NMR spectroscopy were used to analyze the microstructure of the copolymer confirming the random copolymer structure. The average r values calculated from the heterodiad analysis of the 1 H NMR, data were r LA = 0.96 and r CL = 0.93 and L value calculated from the triads analysis of 13 C NMR, data were L LA = 3.17 and L CL = 2.79, respectively. It has been observed that the melting temperature and glass transition temperature of the copolymer increases with higher LA content. The XRD and DSC analyses also confirmed that the as-synthesized copolymer possesses two phases corresponding to the polylactide and polycaprolactone, respectively. Additionally, the activity of Co/NCF is also compared with other Co-based heterogeneous catalysts to demonstrate its ability. Graphic Abstract
研究领域:
材料科学
·
催化化学
✓ 已验证
DOI
Polymers
·
2022
·Vol. 14
·期 12
·2317
·
IF 4.967
Juliene Oliveira Campos de França,Deborah da Silva Valadares,Mateus Freitas Paiva,Sílvia Cláudia Loureiro Dias,José Alves Dias
Poly(lactic acid) (PLA) is an important polymer that is based on renewable biomass resources. Because of environmental issues, more renewable sources for polymers synthesis have been sought for industrial purposes. In this sense, cheaper monomers should be used to facilitate better utilization of less valuable chemicals and therefore granting more sustainable processes. Some points are raised about the need to study the total degradability of any PLA, which may require specific composting conditions (e.g., temperature, type of microorganism, adequate humidity and aerobic environment). Polymerization processes to produce PLA are presented with an emphasis on D,L-lactic acid (or rac-lactide) as the reactant monomer. The syntheses involving homogeneous and heterogeneous catalytic processes to produce poly(D,L-Lactic acid) (PDLLA) are also addressed. Additionally, the production of blends, copolymers, and composites with PDLLA are also presented exemplifying different preparation methods. Some general applications of these materials mostly dedicated to the biomedical area over the last 10–15 years will be pointed out.Keywords:poly(lactic acid)-PLA;polymerization based on D,L-lactic acid;D,L-lactide;stereo polymerization of D,L-lactic acid;blends of PLA;poly(DL-lactide-co-polymer);composites of PDLLA
研究领域:
高分子化学
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生物材料学
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环境科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
International Journal of Polymeric Materials and Polymeric Biomaterials
·
2016
·
IF 1.667
Zhaosheng Hou,Hao Zhang,Wenqiang Qu,Zhen Xu,Zheng Han
In the study, a new approach for synthesizing biomedical segmented polyurethanes (SPUs) based on polyethylene glycol (PEG, Mn = 800), poly(ε-caprolactone-co-D,L-lactide) (PCLA) and aliphatic diurethane diisocyanates with a long uniform hard segment was developed. By the chain extension of a mixture of PEG diol and PCLA diol with diurethane diisocyanates based on inexpensive 1,6-hexanediisocyanate, three SPUs (SPU-I, SPU-II, and SPU-III) with different contents of hydrophilic segments (PEG) and hard segments were obtained. The chemical structures of diurethane diisocyanates, PCLA and SPUs were confirmed by 1H NMR, 13C NMR, FT-IR, HR-TOF-MS, and GPC. The SPU films exhibited similar thermostability, indicating that the hard segment content marginally affects on the thermostability. From the results of differential scanning calorimetry, two glass transition temperatures were observed, suggesting the microphase separation of soft and hard segments. The SPU films exhibited satisfactory mechanical properties with ultimate stress of 17.4–22.3 MPa and strain at break of 890–1060%, and the initial modulus increased with the increasing content of hard segments. In vitro degradation studies indicated that the time of SPU films to become fragments was 22–33 days, and the degradation rate increased with the increasing content of hydrophilic segments in SPU. Hence, the degradation time of SPU films could be controlled by adjusting the PEG content in SPU, which made them good candidates for further biomedical applications. Studies of in vitro drug release were conducted using vitamin B1 as model drugs. Drug-loaded films exhibited a high initial release rate and matrix-controlled release for more than two weeks, thereby demonstrating a promising material for a long-acting controlled release system. Cytotoxicity test of film extracts and cell attachment on the film surface were conducted using L929 mouse fibroblasts, and the results indicated that the SPU films possess excellent cytocompatibility and cell adhesive ability.
研究领域:
生物医学材料
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高分子化学
·
药物释放系统
✓ 已验证
产品关联
DOI
高影响因子
Journal of Macromolecular Science Part A-Pure and Applied Chemistry
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2013
·
IF 0.807
Shi-Ping Zhan,Xing Huang,Qi-Cheng Zhao,Li Chen,Wei-Min Hou,Song Zhang,Jin-Jun Deng
Dispersion polymerization of lactides and lactones has been studied and has received a great deal of attention used to prepare biodegradable polymers in supercritical carbon dioxide (ScCO2). The triblock copolymers of poly(ϵ-caprolactone) PCL-polydimethylsiloxane (PDMS)-poly(ϵ-caprolactone) PCL by the feed ratio of 1:2:1 and 1:3:1, respectively were synthesized to be used as the stabilizers in the dispersion polymerization of L-lactide. The fine poly(L-lactide) (PLLA) powders were obtained at the concentrations of 3% to 5%w/w (stabilizer/monomer). The results demonstrated that the triblock copolymers were the effective stabilizers for the dispersion polymerization of L-lactide. It was also found that the cooling process had a significant effect on the particle size of the fine powders. In order to obtain the best PLLA powders, it would be necessary to use the cooling process with stirring.
研究领域:
高分子科学
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化学工程
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材料科学
·
绿色化学
✓ 已验证
DOI
高影响因子
COLLOIDS AND SURFACES B-BIOINTERFACES
·
2021
·
IF 5.268
Yujie Chen,Zihao Jia,Muhammad Shafiq,Xianrui Xie,Xianghao Xiao,Rita Castro,João Rodrigues,Jinglei Wu,Guangdong Zhou,Xiumei Mo
Electrospun nanofibers emulate extracellular matrix (ECM) morphology and architecture; however, small pore size and tightly-packed fibers impede their translation in tissue engineering. Here we exploited in situ gas foaming to afford three-dimensional (3D) poly(L-lactide-co-ε-caprolactone)/silk fibroin (PLCL/SF) scaffolds, which exhibited nanotopographic cues and a multilayered structure. The addition of SF improved the hydrophilicity and biocompatibility of 3D PLCL scaffolds. Three-dimensional scaffolds exhibited larger pore size (38.75 ± 9.78 μm 2 ) and high porosity (87.1% ± 1.5%) than that of their 2D counterparts. 3D scaffolds also improved the deposition of ECM components and neo-vessel regeneration as well as exhibited more numbers of CD163 + /CCR7 + cells after 2 weeks implantation in a subcutaneous model. Collectively, 3D PLCL/SF scaffolds have broad implications for regenerative medicine and tissue engineering applications.
研究领域:
生物材料学
·
组织工程学
·
再生医学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
EUROPEAN POLYMER JOURNAL
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2018
·
IF 3.741
Wu Xiaomeng,Chen Xiaoyu,Fan Zhongyong
The macroinitiator of poly(1,3-trimethylene carbonate- ran -glycolide) (P(TMC- ran -GA)) copolymers terminated with hydroxyl groups were synthesized by ring-opening polymerization (ROP) at 120 °C for 12 h. Then, the novel block copolymers consisting of P(TMC- ran -GA) segments bonding with L -lactide ( L LA) and glycolide (GA) random copolymerization segments were prepared. The poly(TMC/GA- block - L LA/GA)) block copolymers were synthesized by ROP in bulk at 130 °C with high M n ¯ (above 2.0 × 10 5 Da). Such kind of block copolymers composed of P(TMC- ran -GA) and P( L LA- ran -GA) segments show good mechanical properties and adjustable degradation rate. The molecular structures of block copolymers were characterized by GPC, FTIR, and 1 H NMR. Chain microstructure analysis was performed in detail with 13 C NMR spectroscopy. The effect of GA units content on thermal behaviors, mechanical properties as well as biodegradability of copolymers was investigated by DSC, XRD, stress-strain measurements and enzymatic degradation tested in comparison with corresponding block copolymers P(TMC- block - L LA/GA). The results shown that amorphous P(TMC- ran -GA) segments significantly improve the flexibility of block copolymers. The incorporation of GA units strongly decreases the crystallization ability of L LA segment within copolymers due to more random L LA-GA sequence and shorter average L LA block length. Meanwhile, the tensile strength of material and flexibility are significantly improved with the raising GA units content. The enzymatic degradation rate is also accelerated with the increase GA unit content. Thus, the biodegradable block copolymers with unique molecular structure and modifiable properties are promising new materials for biomedical applications.
研究领域:
生物材料学
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高分子化学
·
生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
POLYMERS FOR ADVANCED TECHNOLOGIES
·
2018
·Vol. 29
·期 6
·1684-1696
·
IF 2.137
Xiaoyu Chen,Xiaomeng Wu,Zhongyong Fan,Qinghua Zhao,Qing Liu
The macroinitiator of poly(1,3-trimethylene carbonate) (PTMC) with number-average molecular weight ( ) of 9.6 × 10 3 g mol −1 was synthesized by ring-opening polymerization at 120°C. Then, the novel terpolymer P(TMC- b -( L LA- ran -GA)) consisting of PTMC homopolymer segment attached with various monomer molar ratios of L -lactide ( L LA) and glycolide (GA) random copolymerization block was prepared with about 5.0 × 10 4 g mol −1 by ring-opening polymerization in bulk at 140°C. The tailored molecular structures of P(TMC- b -( L LA- ran -GA)) were characterized by 1 H nuclear magnetic resonance, 13 C NMR, FTIR, and gel permeation chromatography, and chain microstructure analysis was performed in detail with 13 C NMR spectroscopy. The effect of GA units on the thermal and crystallization behaviors, mechanical properties, as well as biodegradability of terpolymers was investigated by differential scanning calorimetry, wide-angle X-ray diffraction, stress-strain measurements, and in vitro tests in comparison with corresponding poly(trimethylene carbonate- block - L -lactide) copolymer P(TMC- b - L LA). The results show that amorphous PTMC segments have a significant effect on condensed state behavior of the terpolymers, and the incorporation of GA units strongly decreases the crystallinity and crystallization ability of L LA segment within terpolymers because of more random L LA-GA sequence and shorter average L LA block length. Meanwhile, the toughness of materials is greatly improved, and in vitro degradation is also accelerated. Peripheral vascular stents were 3D printed for the first time and met the requirements for application. The results show totally biodegradable terpolymers with unique molecular structure, and modifiable properties are promising new biomaterials with advanced performance for biomedical application.
研究领域:
生物材料学
·
高分子化学
·
医学工程
✓ 已验证
DOI
高影响因子
MACROMOLECULES
·
2019
·
IF 5.997
Na Zhao,Chuanli Ren,Yong Shen,Shaofeng Liu,Zhibo Li
Degradable long-chain aliphatic polyesters are promising alternatives to polyolefins. The ring-opening polymerization (ROP) of ω-pentadecalactone (PDL) enables the synthesis of aliphatic polyesters with melting temperature close to low-density polyethylene (LDPE). However, this ROP reaction is of great challenge because of low ring strain of the PDL monomer. The occurrence of intra- and intermolecular transesterification reactions during ROP made it difficult to prepare well-defined block copolyesters for advanced properties. In this context, cyclic trimeric phosphazene base (CTPB) in combination with benzyl alcohol (BnOH) was proved to be an efficient initiator system for ROP of PDL, showing an excellent polymerization rate (TOF up to 600 h–1) at 80 °C. Well-defined diblock copolyesters, i.e., PPDL-b-PLLA, can be easily synthesized by sequential addition of PDL and l-lactide (L-LA). In contrast, sequential addition of PDL and ε-caprolactone (CL) or δ-valerolactone (VL) only led to the random copolyesters under the same conditions. On the other hand, CTPB is an inherent tribasic superbase and can be partially neutralized to decrease its basicity for better control over active lactones such as CL and VL. Hence, we introduced 0.33–1.0 equiv of benzoic acid (PhCOOH) relative to CTPB and demonstrated that it can diminish the transesterification during ROP of CL or VL. Based on this strategy, PPDL-b-PCL or PPDL-b-PVL diblock copolyesters were successfully prepared by sequential addition of monomers of CL or VL after ROP of PDL. The block copolyester structures were confirmed by the 13C NMR spectroscopy and DSC characterizations.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULES
·
2012
·
IF 5.167
Yang Wang,Wei Zhao,Xinli Liu,Dongmei Cui,Eugene Y.-X. Chen
A simple, inexpensive, and convenient catalyst system consisting of supporting ligand-free MgnBu2 in combination with an alcohol, isopropanol (iPrOH), benzyl methanol (PhCH2OH), diphenylmethanol (Ph2CHOH), or triphenylmethanol (Ph3COH), generates a convenient catalyst system to promote the polymerization of l-LA. In particular, the binary system MgnBu2/Ph2CHOH demonstrates an unprecedentedly high activity in the presence of a large excess amount of Ph2CHOH with the [OH]0/[Mg]0 ratio varying from 2 to 500, producing up to 500 polylactide (PLA) chains per Mg center and thus showing a typical nature of immortal polymerization. The molecular weights of the obtained PLAs with a broad range of monomer-to-metal ratios ([l-LA]0/[Mg]0 = 200–5000) are rather accurately controlled by the Ph2CHOH loading, relative to [Mg]0, while the molecular weight distributions remain nearly constant with polydispersity index (PDI) = 1.08–1.18. Moreover, the active polymerization intermediate has been isolated from the stoichiometric reaction between MgnBu2 and Ph2CHOH and structurally characterized as a tetranuclear complex, Mg4(Ph2CHO)8(THF)2 (1). Complex 1 remains the tetranuclear structure in solution or in the presence of excess Ph2CHOH as determined by 2D DOSY. On the basis of structural information about the active intermediates and polymerization kinetics, a coordination–insertion polymerization mechanism is proposed.
研究领域:
化学
·
高分子科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）