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1.
Shuhong Mao Boyuan Hua Na Wang Xiaojie HU Zhijiang Ge Yanqing Li Sha Liu Fuping Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(2):287-292
BACKGROUND: The improved efficiency of steroid biotransformation using the biphasic system is generally attributed to the positive effect on the solubility of substrate in aqueous media. A promising alternative for the application of organic solvents in biphasic systems is the use of ionic liquids (ILs). This study aims to investigate the applicability of the biphasic ILs/water system for 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by Aspergillus ochraceus. RESULTS: Of the seven ILs tested, [C3mim][PF6] exhibited the best biocompatibility, with markedly improved biotransformation efficiency. In the [C3mim][PF6]‐based biphasic system, substrate conversion reached 90% under the condition in which buffer pH, volume ratio of buffer to ILs, cell concentration, and substrate concentration were 4.8, 10/1, 165 g L?1 and 20 g L?1, respectively. This is more efficient than that of the monophasic aqueous system. The effects of the cations and anions of these ILs on the 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus is also discussed. CONCLUSION: The above results showed that IL/water biphasic system improved the efficiency of 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus, thus suggesting the potential industrial application of ILs‐based biphasic systems for steroid biotransformation. © 2012 Society of Chemical Industry 相似文献
2.
Antonia P. de los Ríos Francisco J. Hernández‐Fernández Manuel Rubio Demetrio Gómez Gloria Víllora 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(2):190-195
Five different ionic liquids, based on dialkylimidazolium cations associated with perfluorinated and bis{(trifluoromethyl)sulfonyl}imide anions, were used to investigate the scope and limitations of these new solvents as media for penicillin G acylase‐catalyzed reactions. Deactivation of the native enzyme in ionic liquids (ILs) and in organic solvents (toluene, dichloromethane and 2‐propanol) at low water content and 40 °C was investigated using the hydrolysis of penicillin G as activity test. Native penicillin G acylase shows greater stability in IL media than in organic solvents. For example, a half‐life time of 23 h was obtained in 1‐ethyl‐3‐methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [emim+][Tf2N?], which was about 2000‐fold higher than that in 2‐propanol. An enhancement of the PGA stability was observed by the presence of substrate in ionic liquids based on tetrafluoroborate and hexafluorophosphate anions, achieving the highest increase of the half‐life time in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim+][PF6?]), which was about 9‐fold higher than the half‐life time in the absence of substrate. Copyright © 2007 Society of Chemical Industry 相似文献
3.
Influence of ionic liquid composition on the stability of polyvinyl chloride‐based ionic liquid inclusion membranes in aqueous solution
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Francisca Tomás‐Alonso Aurora M. Rubio Alfonso Giménez Antonia P. de los Ríos Maria J. Salar‐García Victor M. Ortiz‐Martínez Francisco J. Hernández‐Fernández 《American Institute of Chemical Engineers》2017,63(2):770-780
Membrane technology has gained significant importance with the incorporation of ionic liquids into their structure. This work shows the influence of ionic liquid composition on the stability of PVC‐based polymer ionic liquid inclusion membranes (PILIMs) in aqueous solution. Among the ILs investigated, those membranes which contain between 20 and 30%w/w of the least soluble, [OMIM+][PF6?] and [OMIM+][Ntf2?], exhibit losses of IL lower than 10%. For both ILs, the amount immobilized was maximum for the membranes with 30%w/w of IL (0.0838 and 0.0832 g, respectively). On the contrary, the ionic liquid loss increases as its solubility in water increase, reaching 99.52% when PILIMs are prepared with 70%w/w of [OMIM+][BF4?]. The results demonstrate that the stability of PILIMs depends on the solubility of the IL in the surrounding phase and the specific interaction between the IL and the polymeric support for PVC‐to‐IL ratios higher than 30%w/w. © 2016 American Institute of Chemical Engineers AIChE J, 63: 770–780, 2017 相似文献
4.
Well‐defined polystyrenes with an α‐hydrogen atom and an ω‐chlorine atom end groups and narrow polydispersity (Mn = 2500–4200, Mw/Mn = 1.29–1.48) have been synthesized by a free radical polymerization process using a 1,1,2,2‐tetraphenyl‐1,2‐ethanediol (TPED)/FeCl3/PPh3 initiation system. The end groups were monitored by 1H nuclear magnetic resonance spectroscopy. When the polymerization of styrenes in bulk carried out at 120°C and the ratio of [St]0 : [TPED]0 : [FeCl3]0 : [PPh3]0 was 200 : 1 : 4 : 12, the polymerization exhibited some living/controlled radical polymerization characteristics. The polymerization mechanism was proposed proceeding via a reverse atom transfer radical polymerization (ATRP). Because the polymers obtained were end‐functionalized by chlorine atoms, they were used as macroinitiators to proceed chain extension polymerization in the presence of CuCl/2,2′‐bipyridine catalyst system via a conventional ATRP process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1607–1613, 2000 相似文献
5.
Haixia Shan Zaijun Li Ming Li Guoxia Ren Yinjun Fang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(6):886-891
BACKGROUND: Enzymes may exhibit enhanced activity, stability and selectivity in ionic liquids, depending on the properties of the liquid. The physical–chemical properties of ionic liquids, however, may be modified by altering the anion or cation in the ionic liquid. This feature is a key factor for realizing successful reactions. In this work, a new ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [i‐C4mim][PF6]), was synthesized and investigated as a novel medium for the transesterification reaction of 2‐phenylethanol with vinyl acetate catalyzed by pseudomonas capaci lipase. As contrasts, the reaction was also carried out in two reference solvents; the isomeric ionic liquid [i‐C4mim][PF6], 1‐butyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [C4mim][PF6]), and hexanes. RESULTS: As reaction medium, [i‐C4mim][PF6] was best among the three solvents. The initial reaction rate, the equilibrium conversion of 2‐phenylethanol and the half‐lifetime of the lipase in [i‐C4mim][PF6] medium were about 1.5, 1.2 and 3‐fold that obtained in [C4mim][PF6] medium, respectively. The lipase in [i‐C4mim][PF6] medium was recycled 10 times without substantial diminution in activity. CONCLUSION: The ionic liquid [i‐C4mim][PF6] has good biocompatibility, and can be used widely as green media in various biocatalysis reactions to improve the activity and stability of enzymes. Besides hydrophobicity and nucleophilicity, the spatial configuration of ionic liquids is also considered a key factor effecting the behaviour of the enzyme in ionic liquids. Copyright © 2008 Society of Chemical Industry 相似文献
6.
Multilayer wall microcapsules efficiently loaded with a lubricant (ionic liquid [BMIm]PF6) are successfully synthesized via a combination of interfacial and in situ polymerization reactions based on lignin nanoparticle–stabilized Pickering emulsion templates. The resulting microcapsules are spherical in shape, with an ideal structure of a rough outer surface and a smooth inner surface. The mean diameter and wall thickness of the resultant microcapsules are 52 ± 18 µm and 3–6 µm. The core fraction is ≈71.29 wt%. Compared with the pure epoxy resin, the friction coefficient of self‐lubricating composites decreases by 83.6% (from 0.55 to 0.09) and the wear rate decreases by 218 times (from 76.8 × 10?14 to 0.352 × 10?14 m3 N?1 m?1) by incorporating 20 wt% of the resultant microcapsules into the epoxy resin. It is demonstrated that [BMIm]PF6, a more efficient lubricant, release from the microcapsules during the friction process produced a boundary lubricating film. The bipolar property of [BMIm]PF6 makes the lubricating film firmer, which can efficiently prevent direct contact between the resin matrix and counterface. Furthermore, the rough poly(urea‐formaldehyde) outer surface of multilayer microcapsules brings in an improved interface property between the microcapsules and resin matrix. 相似文献
7.
The low absorption of cyclopentadienyl‐Fe‐cumene hexafluorophosphate (I‐261) above 300 nm limits its utilization of longer wavelength emission from light sources. We report here the synthesis and photoactivity of a carbazole‐bound ferrocenium salt, cyclopentadienyl‐Fe‐carbazole hexafluorophosphate ([Cp‐Fe‐carbazole]+PF6?), which efficiently absorbs radiation between 300 and 400 nm. Its photoactivity is higher than that of I‐261 as a cationic photoinitiator. When the photosensitizer benzoyl peroxide (BPO) is employed, [Cp‐Fe‐carbazole]+PF6? can obviously be sensitized. Two other ferrocenium salts with amine groups, cyclopentadienyl‐Fe‐aniline hexafluorophosphate ([Cp‐Fe‐aniline]+PF6?) and cyclopentadienyl‐Fe‐p‐methylaniline hexafluorophosphate ([Cp‐Fe‐p‐methylaniline]+PF6?) were also studied. As photoinitiators, they perform poorly and can not be sensitized by BPO. Copyright © 2005 Society of Chemical Industry 相似文献
8.
Hongxia Guo Shaocheng Yu Tongtong Liu Quan‐Fu An Xiaoyan Ren Zhenping Qin Yucang Liang 《大分子材料与工程》2019,304(12)
The manipulation of surface wettability has been regarded as an efficient strategy to improve the membrane performances. Herein, the counterion‐switched reversibly hydrophilic and hydrophobic surface of TiO2‐loaded polyelectrolyte membrane are prepared by layer‐by‐layer assembly of poly(sodium 4‐styrene sulfonate) (PSS) and poly(diallydimethyl‐ammoniumchloride (PDDA) containing TiO2@PDDA nanoparticles (NPs) on the hydrolyzed polyacrylonitrile (PAN) substrate membrane. The obtained polyelectrolyte multilayer (PEM) membranes [PEM‐TiO2]4.5+X? (X? = Cl?, PFO? [perfluorooctanoate] etc.) show different hydrophilicity and hydrophobicity with various counterions. The integration of TiO2 NPs obviously improves the wettability and nanofiltration (NF) performance of PEM membrane for (non)aqueous system of dyes (crystal violet, eriochrome black T) with a high recyclability. The highly hydrophilic [PEM‐TiO2]4.5+Cl? (water contact angle [WCA]: 13.2 ± 1.8°) and hydrophobic [PEM‐TiO2]4.5+PFO? (WCA: 115.4 ± 2.3°) can be reversibly switched via counterion exchange between Cl? and PFO?, verifying the surface with a reversible hydrophilic–hydrophobic transformation. For such membranes, the morphology, wettability, and NF performance rely on the loading of TiO2@PDDA NPs and surface counterion. Meanwhile, the motion and interaction of water or ethanol in the hydrophilic or hydrophobic membrane are revealed by low‐field nuclear magnetic resonance. This work provides a facile and rapid approach to fabricate smart and tunable wetting surface for potential utilization in (non)aqueous NF separation. 相似文献
9.
UNIFAC model for ionic liquid‐CO (H2) systems: An experimental and modeling study on gas solubility
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Zhigang Lei Chengna Dai Qian Yang Jiqin Zhu Biaohua Chen 《American Institute of Chemical Engineers》2014,60(12):4222-4231
The universal quasichemical functional‐group activity coefficients (UNIFAC) model for ionic liquids (ILs) has become notably popular because of its simplicity and availability via modern process simulation softwares. In this work, new group binary interaction parameters (αmn and αnm) between CO (H2) and IL groups were obtained by correlating the solubility data in pure ILs at high temperatures (above 273.2 K) collected from the literature. the solubility of CO in [BMIM]+[BF4]?, [OMIM]+[BF4]?, [OMIM]+[Tf2N]?, and their mixtures, as well as that of H2 in [EMIM]+[BF4]?, [BMIM]+[BF4]?, [OMIM]+[Tf2N]?, and their mixtures, at temperatures from 243.2 to 333.2 K and pressures up to 6.0 MPa were measured. The UNIFAC model was observed to well predict the solubility in pure and mixed ILs at both high (above 273.2 K) and low (below 273.2 K) temperatures. Moreover, the selectivity of CO (or H2) to CO2 in ILs increases with decreasing temperature, indicating that low temperatures favor for gas separation. © 2014 American Institute of Chemical Engineers AIChE J 60: 4222–4231, 2014 相似文献
10.
Norbert Moszner Frank Zeuner Thomas Vlkel Urs Karl Fischer Volker Rheinberger 《应用聚合物科学杂志》1999,72(13):1775-1782
1,3‐Bis[(1‐alkoxycarbonyl‐2‐vinylcyclopropane‐1‐yl)carboxy]benzenes 1 [RO: CH3O (a), C2H5O (b)] were synthesized by the esterification of the corresponding 1‐alkoxycarbonyl‐2‐vinylcyclopropane‐1‐carboxylic acids with resorcinol. The structure of the new vinylcyclopropanes was confirmed by elemental analysis and infrared (IR), 1H nuclear magnetic resonance (1H‐NMR), and 13C nuclear magnetic resonance (13C‐NMR) spectroscopy. The radical polymerization of difunctional 2‐vinyl‐cyclopropanes in bulk with 2,2′‐azoisobutyronitrile (AIBN) results in hard, transparent, crosslinked polymers. During the bulk polymerization of the crystalline bis[(1‐methoxycarbonyl‐2‐vinylcyclopropane‐1‐yl)carboxy]benzene 1a, an expansion in volume of about 1% took place. The radical solution polymerization of 1a resulted in a soluble polymer with pendant 2‐vinylcyclopropane groups. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1775–1782, 1999 相似文献
11.
Min Zhang Huanfeng Jiang PierreH. Dixneuf 《Advanced Synthesis \u0026amp; Catalysis》2009,351(10):1488-1494
The regioselective synthesis of β,γ‐unsaturated ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)pentamethylcyclopentadieneruthenium hexafluorophosphate [Cp*Ru(NCMe)3+ PF6−] and para‐toluenesulfonic acid catalysts. These allyl ketones undergo direct regioselective hydroarylation/Friedel–Crafts reaction to introduce an electron‐rich aryl group at the γ‐position in the presence of ligand‐free silver triflate (AgOTf) catalyst. Both catalytic reactions take place with atom economy and provide an alternative to the synthesis of a variety of allyl ketones and γ‐arylated ketones. 相似文献
12.
Yun Zhang Xirong Huang Yuezhong Li 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1230-1235
BACKGROUND: [bmim][PF6] is a hydrophobic ionic liquid which could be considered as an environmentally friendly solvent for biocatalysis. In pure [bmim][PF6], however, alcohol dehydrogenase from yeast (YADH) has no catalytic activity. The aim of the present work was (1) to quantitatively study the negative effect of [bmim][PF6] on the catalytic activity of YADH and the related mechanism and (2) to made an attempt to lessen the negative effect of [bmim][PF6] on YADH by microemulsifying [bmim][PF6]. RESULTS: The activity of YADH in the homogeneous solution formed by H2O, CH3CH2OH and [bmim][PF6] decreased rapidly with the increase of the molar fraction of [bmim][PF6]. The inhibitory effect of [bmim][PF6] on YADH was probably caused by the competition of the imidazole group of [bmim][PF6] with the coenzyme NAD+ for the binding sites on YADH. In a water‐in‐[bmim][PF6] microemulsion, YADH was catalytically active due to the formation of the interfacial membrane of the nonionic surfactant TritonX‐100, which separated YADH from [bmim][PF6] and avoided the direct inactivation of [bmim][PF6] on YADH. Under optimal conditions, the activity of YADH was as high as 51 µmol L?1 min?1. CONCLUSION: [bmim][PF6] was an inhibitor of YADH and its negative effect on YADH could be lessened by its microemulsification. Copyright © 2008 Society of Chemical Industry 相似文献
13.
Optimization of Enzymatic Synthesis of Tricaprylin in Ionic Liquids by Response Surface Methodology 总被引:1,自引:0,他引:1
Qiuyue Pan Liping Yang Xianghe Meng 《Journal of the American Oil Chemists' Society》2013,90(4):501-509
Ten 1,3‐dialkylimidazolium‐based ionic liquids (ILs) have been investigated as media for the enzymatic synthesis of tricaprylin, in comparison with the conventional organic solvent hexane. The results suggested that the esterification activity of Novozym 435 was higher than Lypozyme RM IM in all the ILs assayed. Novozym 435 showed higher catalytic activity in ILs with anions Tf2N? and PF6? than in BF4? and hexane. FTIR analysis of the secondary structure of the lipase indicated that a smaller decrease of the α‐helix was observed in [C4MIM] Tf2N and [C4MIM] PF6 than [C4MIM] BF4 and hexane, indicating that the anions of ILs might be a key factor for the activity of lipase in ILs. Process parameters (amount of lipase, caprylic acid/glycerol molar ratio, temperature and their interactive effects) were optimized in 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([C4MIM]PF6) using Novozym 435 by response surface methodology. When the reactions were performed with the lipase amount of 6.1 % substrate mass at a caprylic acid/glycerol molar ratio of 4.5:1 and 66.7 °C, a higher yield was reached up to 92.4 %. 相似文献
14.
Sergey A Chesnokov Marya Yu Zakharina Alexander S Shaplov Yuriy V Chechet Elena I Lozinskaya Olga A Mel'nik Yakov S Vygodskii Gleb A Abakumov 《Polymer International》2008,57(3):538-545
BACKGROUND: The fast development of practical applications of photopolymerizable compositions (PPCs) leads to a growing demand for the elaboration of novel monomers and simultaneously for the investigation of three‐dimensional polymerization mechanisms including the possible influence of initiator, additives, etc. The aim of the current study is to explore and clarify the role of ionic liquids (ILs) as environmentally friendly catalytic additives in the photopolymerization of poly(ethylene glycol dimethacrylate)s. RESULTS: The photopolymerization of triethylene glycol dimethacrylate (TEGDM) and poly(ethylene glycol‐400 dimethacrylate) (PEGDM) in the presence of various ILs both imidazolium‐based, i.e. [1‐methyl‐3‐alkylim]+ (CF3SO2)2N? (im = imidazolium; alkyl = C2H5, C4H9, C14H29), and phosphonium‐based, i.e. [P+ (C6H13)3(C14H29)]X? (X? = PF6?, BF4?, (CF3SO2)2N?, Cl?), as catalytic additives was investigated. The influence of the concentration of the ionic salts as well as the nature of the ILs upon the photopolymerization was studied in detail. It was found that imidazolium ILs accelerate TEGDM photopolymerization and suppress the polymerization of PEGDM. In contrast, polymerization of PEGDM with extra small amounts of phosphonium ionic solvents proceeded at a high rate and offered access to new polymers and the utilization of low‐reactivity monomers in PPCs. CONCLUSION: The most striking advantage is that the use of certain ILs permits the control of polymerization rate to achieve maximum oligomer conversion. Copyright © 2007 Society of Chemical Industry 相似文献
15.
Rapid living free‐radical polymerization of methyl acrylate under 60Co γ‐ray irradiation in the presence of benzyl 1H‐imidazole‐1‐carbodithioate at room temperature is reported. The results showed that the polymerization is a fast living process, and that the molecular weight of the polymer is as high as 39 600 g mol?1 at 68 % conversion with Mw/Mn = 1.09 within 68 min. The polymerization rate was markedly influenced by the structures of thiocarbonylthio compounds. Copyright © 2004 Society of Chemical Industry 相似文献
16.
Xiongfa Yang Qian Shao Qing Fang Linlin Yang Cheng Cao Zhaohui Ren Lianbin Wu Guoqiao Lai Gaorong Han 《Polymer International》2014,63(2):347-351
Rare earth solid super acids SO42?/TiO2/Ln3+ have been successfully developed to synthesize vinyl end‐capped polydimethylsiloxane by ring opening polymerization of octamethylcyclotetrasiloxane (D4) end‐capped with 1,1,3,3‐tetramethyl‐1,3‐divinyldisiloxane. The features of ring opening polymerization reactions have been investigated in detail. The preferable conditions for the ring opening polymerization of D4 are as follows: [Nd3+] = 0.07 mol L?1 and [SO42?] = 1.85 mol L?1 in the immersing solution; the amount of SO42?/TiO2/Nd3+ calcined at 500 °C was 5 wt% of the amount of D4; polymerization at 80 °C for 1 h. The average molecular weights of the products obtained using various rare earth catalysts were in order Nd > La > Sm > Gd, which shows that the light rare earths were more favorable for higher molecular weight products than the heavy ones. According to the polymerization features, a cationic equilibrium reaction mechanism is proposed. © 2013 Society of Chemical Industry 相似文献
17.
Katsuhiko Takenaka Satomi Kawamoto Masamitsu Miya Hiroki Takeshita Tomoo Shiomi 《Polymer International》2010,59(7):891-895
The presence of a bulky substituent at the 2‐position of 1,3‐butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free‐radical polymerization of 2‐triethoxysilyl‐1,3‐butadiene ( 1 ) was carried out under various conditions, and its polymerization behavior was compared with that of 2‐triethoxymethyl‐ and other silyl‐substituted butadienes. A sticky polymer of high 1,4‐structure ( ) was obtained in moderate yield by 2,2′‐azobisisobutyronitrile (AIBN)‐initiated polymerization. A smaller amount of Diels–Alder dimer was formed compared with the case of other silyl‐substituted butadienes. The rate of polymerization (Rp) was found to be Rp = k[AIBN]0.5[ 1 ]1.2, and the overall activation energy for polymerization was determined to be 117 kJ mol?1. The monomer reactivity ratios in copolymerization with styrene were r 1 = 2.65 and rst = 0.26. The glass transition temperature of the polymer of 1 was found to be ?78 °C. Free‐radical polymerization of 1 proceeded smoothly to give the corresponding 1,4‐polydiene. The 1,4‐E content of the polymer was less compared with that of poly(2‐triethoxymethyl‐1,3‐butadiene) and poly(2‐triisopropoxysilyl‐1,3‐butadiene) prepared under similar conditions. Copyright © 2010 Society of Chemical Industry 相似文献
18.
The free‐radical polymerization behavior of 1‐vinyl,2‐pyrrolidone (NVP) was studied at low conversions, using capillary dilatometry. The aqueous media were kept at neutral pH and the studies were conducted isothermally, at 40 or 45°C. The azo‐type initiators used were 4,4′‐azobis‐4‐cyanopentanoic acid (ACPA), 2,2′‐azobisisobutyronitrile (AZBN), and 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane dihydrochloride] (ABDH). The monomer concentration and initiator concentration ranges were 1.17–2.34 mol L−1 and 1–8 mmol L−1, respectively. The rates of polymerization (Rp) and orders of reaction with respect to NVP and the initiator were evaluated and the kinetic equations were found to be Rp ∝ [NVP] [ACPA]1.2; Rp ∝ [NVP] [AZBN]1.1; and Rp ∝ [NVP]2.2 [ABDH]1.1. The polymers obtained were characterized by their viscosity numbers and correlation of the viscosity average molecular weights made with the type and amount of the azo initiator. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 239–246, 2000 相似文献
19.
The copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propane sulfonate (AMPS) was synthesized through the free radical dispersion polymerization in an aqueous solution of ammonium sulfate and in the presence of poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonate) as stabilizer. The average particle size of the copolymer ranged from 1 to 4 μm, and the molecular weight was from 2.0 × 106 to 7.0 × 106 g mol?1. By analyzing apparent viscosity and particle size, the swelling property of the dispersion copolymer was studied. When the dispersion was diluted with salt water in which the ammonium sulfate concentration kept equal with that of the original dispersion, particle size and particle size distribution of the diluted dispersion changed a little, compared with that of the original dispersion. While diluted with deionized water, particle size and particle size distribution could expand several times. The effects of varying concentrations of the stabilizer, the monomer, the salt and the initiator on particle size, and molecular weight of the copolymer were investigated, respectively. The reaction conditions for preparing stable dispersion were concentrations of 20–28% of the salt, 6–14% of monomers, and 1.8–2.7% of the stabilizer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2379–2385, 2006 相似文献
20.
Effect of ionic liquids on the structural,thermal, and in vitro degradation properties of poly(ε‐caprolactone) synthesized in the presence of Candida antarctica lipase B
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The study provides detailed information on the differences in the structural, thermal and degradation properties of poly(ε‐caprolactone) synthesized in two different ionic liquids, 1‐butyl‐3‐methylimidazolium hexafluorophosphate [bmim][PF6] and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [bmim][NTf2], regarding its further usage in the pharmaceutical field. The polymer structure confirms the presence of both linear polymer chains with end‐functional hydroxyl groups allowing covalent coupling of the therapeutic agents, and cyclic macromolecules, both affecting the degree of crystallinity of polymer. The highest macrocyclic content (64%) after 7 days of polymerization at 80 °C was observed for [bmim][NTf2]. For [bmim][PF6], the macrocyclic content value was not dependent on the reaction time and remained at a similar level (10–14% at 80 °C). The results of degradation test revealed that hydrolytic degradation of ester bonds is more pronounced for PCLs synthesized in [bmim][NTf2], due to their lower degree of crystallinity compared with PCLs obtained in [bmim][PF6]. A high purity, low polydispersity index of the obtained polymers and high yield of the process (ca., 90%) indicate that ionic liquids seem to be promising solvents for the synthesis of biomedical polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43728. 相似文献