POLYMER TESTING
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2015
·
IF 2.24
Xinchao Bian,Lidong Feng,Gao Li,Zhiming Chen,Xuesi Chen
An analytical method has been developed to quantitatively determine the residual lactide monomer in polylactide (PLA) using an internal standard method of gas chromatography (GC). The experimental results showed that diphenyl ether (DPE) was an appropriate internal standard for quantitative analysis of residual lactide in PLA. PLA and DPE were dissolved in dichloromethane and precipitated in hexane . At the same time, the residual lactide in PLA and DPE as an internal standard were extracted to hexane from the polymer solution . The resulting solution could be directly injected into a GC system. Therefore, the residual lactide was determined quantitatively using an internal standard method of GC. This method is practical for measuring the residual lactide content in PLA. When the lactide content is 5.0%, the relative standard deviation ( RSD ) of the measurements is 1.7%, while RSD is 6.9% at the low level of 0.4%, which indicates that the method is sufficiently precise.
研究领域:
分析化学
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材料科学
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DOI
高影响因子
JOURNAL OF POLYMER RESEARCH
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2015
·Vol. 22
·期 5
·1-7
·
IF 1.92
Teng Lijing,Xu Xiaohong,Nie Wangyan,Zhou Yifeng,Song Linyong,Chen Pengpeng
Star-shaped polylactide (PLLA) is a potential candidate in many biomedical applications owing to its short degradation time; however, non-bioresorbable polyols have been used in most syntheses of star-shaped polylactide and these are a potential hazard. In this work, reaction of natural xylitol with l -lactide (LLA) was used to synthesize a star-shaped polyester via ring-opening polymerization. The chemical structures of the prepared star-shaped PLLA were characterized by means of 1 H NMR and gel permeation chromatography (GPC). The crystallization behaviors of the polymers were examined by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD curves of all the star-shaped PLLA based on various xylitol molar fractions were similar, but the crystallinity decreased with the increase of the xylitol molar fraction. These polymers were amorphous when the molar fraction of xylitol was higher than 6 %, whereas they were semicrystalline when the molar ratio of xylitol fell below 6 %. Finally, the degradation of the star-shaped PLLA was studied in phosphate buffer solution (pH 7.4) at 37 °C, which indicated that the degradation rate of polymers increased with the increase of xylitol molar fraction.
研究领域:
材料科学
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生物医学工程
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DOI
高影响因子
Journal of Applied Biomaterials & Functional Materials
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2016
·
IF 0.934
Junyan Yao,Shijie Zhang,Wudan Li,Yujie Li
BackgroundThe amorphous poly(lactic acid-co-lysine) (PLL) with hydrophilic reactive groups was synthesized by the condensing copolymerization and the blending miscibility of poly(L-lactic acid) (PLLA) and PLL was investigated.MethodsThe miscibility of PLLA and PLL was evaluated by analyzing the thermal properties, crystallization behaviors, crystal morphologies and mechanical properties of the PLLA/PLL blends.ResultsThe results indicated that amorphous PLL changed the crystallization behaviors and thermal properties of PLLA, decreasing the crystallinity of PLLA in the blends. The amorphous PLL molecule chains in PLLA/PLL blends were able to enter into the lamellars of PLLA spherulites and affect the crystallization behaviors of PLLA, resulting in imperfect, spherulite structures of PLLA. The formation of hydrogen bonds between PLLA molecular chains and PLL molecular chains enabled partial compatibility in this blend system.ConclusionsThe existence of PLL improved the hydrophility of PLLA/PLL blends, led to a higher content of PLL in the PLLA/PLL blend system, and better hydrophilic properties of the blend system. The PLL was partially miscible with the PLLA, and the PLLA/PLL blend with 10 wt% PLL had improved tensile properties.
研究领域:
材料科学
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高分子化学
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产品关联
DOI
PubMed
高影响因子
APPLIED ORGANOMETALLIC CHEMISTRY
·
2016
·Vol. 31
·期 9
·e3688
·
IF 2.452
Baolong Wang,Jianing Zhang,Huanqin Zhao,He Huang,Junpei Zheng,Liying Wang,Junmin Sun,Yongfeng Zhang,Zhenzhu Cao
Monomeric bis(isopropoxy) titanium complexes LTi(O i Pr) 2 (L = ─ OC 6 H 2 –4-R 1 –6-R 2 –2-CH 2 N[(CH 2 ) 2 N(R 3 ) 2 ]CH 2 –4-R 4 –6-R 5 -C 6 H 2 O ─ , R 1 = R 2 = t Bu, R 3 = Et, R 4 = R 5 = Cl, (L 1 )Ti(O i Pr) 2 ; R 1 = R 2 = Me, R 3 = Et, R 4 = R 5 = Me, (L 2 )Ti(O i Pr) 2 ; R 1 = R 2 = t Bu, R 3 = Et, R 4 = OMe, R 5 = t Bu, (L 3 )Ti(O i Pr) 2 ; R 1 = R 4 = OMe, R 3 = Et, R 2 = R 5 = t Bu, (L 4 )Ti(O i Pr) 2 ; R 1 = R 2 = t Bu, R 3 = Me, R 4 = OMe, R 5 = t Bu, (L 5 )Ti(O i Pr) 2 ) supported by amine bis(phenolate) ligands were synthesized and characterized using NMR spectroscopy and elemental analysis. The solid-state structure of (L 3 )Ti(O i Pr) 2 was determined using single-crystal X-ray diffraction. (L 1 –5 )Ti(O i Pr) 2 were all found to initiate the ring-opening polymerization of l -lactide and rac -lactide in a controlled manner at 110–160°C. As shown by kinetic studies, (L 1 )Ti(O i Pr) 2 polymerized l -lactide faster than did (L 2 –5 )Ti(O i Pr) 2 . In addition, good number-average molecular weight and narrow polydispersity index (1.00–1.71) of polymers were also obtained. The microstructure of the polymers and a possible mechanism of coordination–insertion of polymerization were evidenced by MALDI-TOF and 1 H NMR spectra of the polylactides.
研究领域:
有机化学
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高分子化学
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DOI
高影响因子
Fermentation-Basel
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2020
·Vol. 7
·期 1
·3
·
IF 0
Stefania Costa,Daniela Summa,Bruno Semeraro,Federico Zappaterra,Irene Rugiero,Elena Tamburini
Lactic acid (LA) obtained by fermentation of carbohydrates is well-known and widely used in the food sector. This process is as an alternative to the chemical synthesis and ensures several advantages especially in terms of environmental sustainability. In particularly, the opportunity to use agro-food residues as fermentable raw materials could improve the overall process sustainability, without considering the indisputable advantages in terms of waste reduction and residual biomass valorization, in a bio- and circular economy perspective. This research deals with the study and development of the fermentation processes of various waste biomasses from the agro-food industries, including milk whey (MW), ricotta cheese whey (RCW), pear processing residues (PPR), potato pomace (PP), tomato pomace (PT), in order to obtain an experimental protocol applicable to the production of LA.Lactobacillus caseiDSM 20011 (ATCC 393), a homofermentative L(+)-LA producing bacterium has been used, starting from small-scale tests to verify of the microorganism to grow in complex medium with different carbon sources and the possible presence of potentially toxic substances for microbial growth. Yields from 27.0 ± 0.3% to 46.0 ± 0.7% have been obtained. Then, a scaling-up was performed in a 1 L batch fermenter, using a mixed medium of RCW and PPR in different ratio. The best LA yield was 78.3% with a volumetric productivity of 1.12 g/L·h in less than 60 h.Keywords:lactic acid;PLA;Lactobacillus casei;agri-food waste;circular economy
研究领域:
生物技术
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环境科学
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发酵工程
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DOI
APPLIED CATALYSIS A-GENERAL
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2021
·
IF 5.706
Somboon Chaemchuen,Qingping Dai,Jichao Wang,Chenyang Zhu,Nikom Klomkliang,Ye Yuan,Chen Cheng,Mirella Elkadi,Zhixiong Luo,Francis Verpoort
A catalyst series of zeolitic imidazole frameworks (ZIFs) with a sodalite (SOD) structure was explored as an effective heterogeneous catalyst for l -lactide polymerization into biodegradable polylactides (PLAs). The catalyst series of ZIF-8, ZIF-67, and bimetallic ZnCo-ZIF was synthesized under the green method (room temperature synthesis), which contained a variance in the metal species/contents. The chemical and physical properties of catalysts were characterized by several techniques to illustrate the relation between catalyst properties and catalytic performance. The results indicated that the metals in the ZIF structure revealed an influencing role in catalytic activities, kinetic rates, and properties of polymer products under bulk ring-opening polymerization of l -lactide. Moreover, the best performing ZIF showed potential as a heterogeneous catalyst since it could be reused at least four times without significant loss of catalytic activity.
研究领域:
材料科学
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催化化学
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DOI
高影响因子
ANALYST
·
2014
·Vol. 140
·期 3
·797-802
·
IF 3.906
Chong Sun,Daoying Wang,Muhan Zhang,Yanxiu Ni,Xiaohui Shen,Youchao Song,Zhiming Geng,Weimin Xu,Fang Liu,Chun Mao
The development of advanced nanomaterials for the highly efficient electrical detection of biological species has attracted great attention. Here, novel polypyrrole-Pluronic F127 nanoparticles (PPy-F127 NPs) with conducting and biocompatibility properties were synthesized and used to construct a L-lactic acid biosensor that could be applied in biochemical assays. The PPy-F127 NPs were characterized by transmission electron microscopy (TEM), elemental analysis and UV-vis spectroscopy. Lactate oxidase (LOx) structure variation on the PPy-F127 NPs was investigated by circular dichroism (CD). The cyclic voltammetric results indicated that LOx immobilized on the PPy-F127 NPs exhibited direct electron transfer reaction with a formal potential value (E0′) of 0.154 V vs. SCE. Moreover, the biosensor had good electrocatalytic activity toward L-lactic acid with a wide linear range (0.015–37.5 mM) and a low detection limit of 0.0088 mM. The regression equation was I (μA) = 0.02353c (mM) + 1.4135 (R2 = 0.9939). The L-lactic acid biosensor had a good anti-interference property towards uric acid (UA), ascorbic acid (AA), glucose and cysteine. The idea and method provide a promising platform for the rapid development of biosensors that can be used in the detection of biological species.
研究领域:
生物化学
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材料科学
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分析化学
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产品关联
DOI
PubMed
高影响因子
BIORESOURCE TECHNOLOGY
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2023
·
IF 11.4
Chunying Si,Sheng Wang,Zhen Chen,Guoming Hu,Xuanying Zhao,Ping Sun,Quanxing Zhang,Wei Jiang
The utilization of wasted Poly(lactic acid) (PLA) as low-cost carbon sources in solid-phase denitrification is hindered by its low biodegradability, which can be attributed to its high molecular weight . This study presents a new approach by blending high-molecular-weight PLA with a small amount of ʟ-lactide (PLA/LA x ) to treat nitrate-contaminated wastewater. The addition of ʟ-lactide enhanced the release of carbon from high-molecular-weight PLA. An impressive denitrification efficiency of 96.7% was achieved, accompanied by extremely low levels of accumulated NO 2 - - N (0.1 mg/L) and NH 4 + - N (0.4 mg/L). The quantity of ʟ-lactide used significantly impacted the bacterial community structure. A high abundance of the phyla Bacteroidota and Chloroflexi associated with polymer degradation was observed. The most dominant denitrifier was the genus unclassified_f__Rhodocyclaceae belonged to the phylum Proteobacteria . This study demonstrates that blending PLA with just 5 wt% lactide can transform it into a highly effective solid-phase carbon source to eliminate nitrates.
研究领域:
环境工程
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微生物学
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污水处理
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产品关联
DOI
PubMed
高影响因子
CHINESE JOURNAL OF CHEMISTRY
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2021
·Vol. 39
·期 9
·2403-2409
·
IF 6
Xiao Jiang,Na Zhao,Zhibo Li
Main observation and conclusion Substantial progresses have been made toward the development of metal-free catalysts for stereoselective ring-opening polymerization (ROP) of rac -lactide. Yet the discovery of organic catalysts effective at ambient temperature remains a major challenge. Here, the bifunctional H-bonding catalyst SQ-1 containing a basic tertiary amine and squaramide motif proved to be good candidate for the stereoselective ROP of rac -lactide at room temperature, yielding stereoregular polylactide with controlled molecular weights (up to 21.1 kg/mol) and high tacticity ( P i ESC up to 0.88). Furthermore, binary H-bonding catalytic system consisting of squaramides (SQ-2 to SQ-6) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) could efficiently promote the ROP of rac -lactide at room temperature within short reaction time. Among them, the most bulky squaramide SQ-2 exhibited the best steroselectivity towards the ROP of rac -lactide without transesterification side reactions during the polymerization process. The resulting polylactides were proved to have controlled molecular weights as high as 22.2 kg/mol and narrow distributions (1.10—1.24).
研究领域:
高分子化学
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有机化学
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产品关联
DOI
高影响因子
POLYMER TESTING
·
2020
·
IF 3.275
Lidong Feng,Sheng Xiang,Yanlong Liu,Xinchao Bian,Gao Li,Xuesi Chen
An analytical method was developed to quantitatively determine residual monomers, namely, lactide (LA) and ε -caprolactone (CL), in poly(lactide- co - ε -caprolactone) (PLCL) using an internal-standard method of gas chromatography (GC). PLCL and diphenyl ether (DPE) as an internal standard were initially dissolved in dichloromethane (DCM), and then PLCL was precipitated in cyclohexane. The residual LA and CL monomers in PLCL, as well as DPE, were extracted into cyclohexane from the polymer solution. The resulting solution was directly injected into a GC system. This method was practical for measuring the residual LA and CL contents in PLCL. The relative standard deviation ( RSD ) ( n = 5) denoting the repeatability of this method was less than 5.6% and 4.3% for the LA and CL measurements, respectively, indicating that the method was sufficiently precise. The recovery rate of standard addition was 96.5%–101.5% and 98.4%–104.2% for the determination of LA and CL in PLCL, respectively. The RSD of the recovery of standard addition ( n = 5) was not more than 2.0%, indicating that the method was sufficiently accurate.
研究领域:
分析化学
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高分子材料科学
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医学材料
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产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2022
·
IF 4.326
Yunlong Xu,Linlin Yang,Chunying Si,Shuoqi Zhang,Quanxing Zhang,Guixiang Zeng,Wei Jiang
Sn-beta zeolite is a promising catalyst for the direct synthesis of lactide from lactic acid; here, we clarify the relationship between its local structure and activity through the interplay of experiments and DFT calculations. The open sites (HO-Sn-(OSi)3 with adjacent Si–OH) play a key role in the high activity of Sn-beta zeolite, where the reaction rate significantly decreases from 0.2258 mmol min–1 gcat–1 to 0.0724 mmol min–1 gcat–1 if the open sites were masked with Na+. Density functional theory (DFT) calculations show that the decrease in reaction rate comes from the weaker interaction between substrate and the open Sn site by Na+ exchange, which leads to the significant increase in the Gibbs energy barrier from 34.0 kcal/mol to 57.2 kcal/mol (rate-determining step). Other activities of heteroatom M-beta zeolites (where M = Ti, Zr, Hf) were also investigated, where the open sites were found to be crucial for the high activity in the direct synthesis of lactide as well. The information provided by this work is valuable for precise design of efficient catalysts for the one-step synthesis of lactide.
研究领域:
催化化学
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材料科学
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产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2022
·
IF 4.326
Jiashu Liu,Shengnan Zhao,Song Song,Haifeng Cong,Wei Luo,Tong Ding,Ye Tian,Xingang Li
One-step lactide (LD) synthesis from lactic acid (LA) is a promising method for an economically viable polylactic acid (PLA) industry. However, this synthesis is based on a highly water-sensitive esterification reaction, and few studies focus on developing an efficient method to improve its activity by water removal from the reaction environment. Herein, we report a new strategy coupling salt-promoted toluene–water phase separation with heteroazeotropic distillation to enhance water removal to realize highly efficient LD synthesis. Different kinds of chloride salts (LiCl, NaCl, CsCl, MgCl2, and CaCl2) were selected to study their influence on the reaction. The highest yield of LD (84.7%) was obtained when CaCl2 was added, much higher than that of the salt-free reaction (72.3%). Hydrated Ca2+ cations with relatively large charge number and small radius can efficiently reduce the solubility of water in toluene due to their strong electrostatic force to attract more water molecules. Mechanism studies demonstrate that the increased yield of LD after adding CaCl2 was attributed to its significant inhibition of LD hydrolysis resulting from the deep water removal from the toluene solvent.
研究领域:
化学工程
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高分子化学
·
绿色化学
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产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）