The Experts below are selected from a list of 17724 Experts worldwide ranked by ideXlab platform
Meidong Lang - One of the best experts on this subject based on the ideXlab platform.
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synthesis and self assembly of ph responsive amphiphilic poly e Caprolactone block poly acrylic acid copolymer
2012Co-Authors: Yan Zhang, Meidong LangAbstract:The pH-responsive amphiphilic poly(e-Caprolactone)-block-poly(acrylic acid) (PCL-b-PAA) copolymer was prepared by selective hydrolysis of one novel poly(e-Caprolactone)-block-poly(methoxymethyl acrylate) (PCL-b-PMOMA) block copolymer, which was synthesized by combining ring-opening polymerization (ROP) of e-Caprolactone (e-CL) and atom transfer radical polymerization (ATRP) of methoxymethyl acrylate (MOMA). Selective hydrolysis of the hemiketal ester groups on the PMOMA block gave 100% deprotection without the cleavage of the PCL block. The self-assembly behavior of PCL-b-PAA was investigated by fluorescence spectroscopy, DLS and TEM. The spherical micelles were formed with the hydrophobic PCL block as the core and the hydrophilic PAA as the shell by a co-solvent evaporation method. Moreover, the size and size distribution of the micelles varied with pH value and ionic strength in aqueous solution. The cytotoxicity of the PCL-b-PAA was lower, which was confirmed by MTT assay.
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fine tuning micellar core forming block of poly ethylene glycol block poly e Caprolactone amphiphilic copolymers based on chemical modification for the solubilization and delivery of doxorubicin
2011Co-Authors: Jinliang Yan, Yan Xiao, Yan Zhang, Min Chen, Zhanzhan Liu, Yan Zhou, Wensong Tan, Meidong LangAbstract:This study aimed to optimize poly(ethylene glycol)-b-poly(e-Caprolactone) (PEG-b-PCL)-based amphiphilic block copolymers for achieving a better micellar drug delivery system (DDS) with improved solubilization and delivery of doxorubicin (DOX). First, the Flory-Huggins interaction parameters between DOX and the core-forming segments [i.e., poly(e-Caprolactone) (PCL) and poly[(e-Caprolactone-co-γ-(carbamic acid benzyl ester)-e-Caprolactone] (P(CL-co-CABCL))] was calculated to assess the drug-polymer compatibility. The results indicated a better compatibility between DOX and P(CL-co-CABCL) than that between DOX and PCL, motivating the synthesis of monomethoxy-poly(ethylene glycol)-b-poly[(e-Caprolactone-co-γ-(carbamic acid benzyl ester)-e-Caprolactone] (mPEG-b-P(CL-co-CABCL)) block copolymer. Second, two novel block copolymers of mPEG-b-P(CL-co-CABCL) with different compositions were prepared via ring-opening polymerization of CL and CABCL using mPEG as a macroinitiator and characterized by (1)H NMR, FT-IR, GPC, WAXD, and DSC techniques. It was found that the introduction of CABCL decreased the crystallinity of mPEG-b-PCL copolymer. Micellar formation of the copolymers in aqueous solution was investigated with fluorescence spectroscopy, DLS and TEM. mPEG-b-P(CL-co-CABCL) copolymers had a lower critical micelle concentration (CMC) than mPEG-b-PCL and subsequently led to an improved stability of prepared micelles. Furthermore, both higher loading capacity and slower in vitro release of DOX were observed for micelles of copolymers with increased content of CABCL, attributed to both improved drug-core compatibility and favorable amorphous core structure. Meanwhile, DOX-loaded micelles facilitated better uptake of DOX by HepG2 cells and were mainly retained in the cytosol, whereas free DOX accumulated more in the nuclei. However, possibly because of the slower intracellular release of DOX, DOX-loaded micelles were less potent in inhibiting cell proliferation than free DOX in vitro. Taken together, the introduction of CABCL in the core-forming block of mPEG-b-PCL resulted in micelles with superior properties, which hold great promise for drug delivery applications.
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fine tuning micellar core forming block of poly ethylene glycol block poly e Caprolactone amphiphilic copolymers based on chemical modification for the solubilization and delivery of doxorubicin
2011Co-Authors: Mi Che, Zhanzha Liu, Ya Xiao, Ya Zhang, Ya Zhou, Meidong LangAbstract:This study aimed to optimize poly(ethylene glycol)-b-poly(e-Caprolactone) (PEG-b-PCL)-based amphiphilic block copolymers for achieving a better micellar drug delivery system (DDS) with improved solubilization and delivery of doxorubicin (DOX). First, the Flory–Huggins interaction parameters between DOX and the core-forming segments [i.e., poly(e-Caprolactone) (PCL) and poly[(e-Caprolactone-co-γ-(carbamic acid benzyl ester)-e-Caprolactone] (P(CL-co-CABCL))] was calculated to assess the drug–polymer compatibility. The results indicated a better compatibility between DOX and P(CL-co-CABCL) than that between DOX and PCL, motivating the synthesis of monomethoxy-poly(ethylene glycol)-b-poly[(e-Caprolactone-co-γ-(carbamic acid benzyl ester)-e-Caprolactone] (mPEG-b-P(CL-co-CABCL)) block copolymer. Second, two novel block copolymers of mPEG-b-P(CL-co-CABCL) with different compositions were prepared via ring-opening polymerization of CL and CABCL using mPEG as a macroinitiator and characterized by 1H NMR, FT-IR, GP...
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novel poly e Caprolactone s bearing amino groups synthesis characterization and biotinylation
2010Co-Authors: Jinliang Yan, Yi Zhang, Yan Xiao, Yan Zhang, Meidong LangAbstract:Abstract A novel functional e-Caprolactone monomer containing protected amino groups, γ-(carbamic acid benzyl ester)-e-Caprolactone (γCABeCL), was successfully synthesized. A series of copolymers [poly(CL- co -CABCL)] were prepared by ring-opening polymerization of e-Caprolactone (CL) and γCABeCL in bulk using tin (II)-2-ethylhexanoate [Sn(Oct) 2 ] as catalyst. The morphology of the copolymers changed from semi-crystalline to amorphous with increasing γCABeCL monomer content. They were further converted into deprotected copolymers [poly(CL- co -ACL)] with free amino groups by hydrogenolysis in the presence of Pd/C. After deprotection, the free amino groups on the copolymer were further modified with biotin. The monomer and the corresponding copolymers were characterized by 1 H NMR, 13 C NMR, FT-IR, mass, GPC and DSC analysis. The obtained data have confirmed the desired monomer and copolymer structures.
Bert F Sels - One of the best experts on this subject based on the ideXlab platform.
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selective nickel catalyzed conversion of model and lignin derived phenolic compounds to cyclohexanone based polymer building blocks
2015Co-Authors: Wouter Schutyser, Sander Van Den Bosch, Jan Dijkmans, Stuart Turner, Maria Meledina, Gustaaf Van Tendeloo, Damien P Debecker, Bert F SelsAbstract:Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Lignin is converted into novel polymer building blocks through four steps: catalytic hydroprocessing of softwood to form 4-alkylguaiacols, their conversion into 4-alkylcyclohexanols, followed by dehydrogenation to form cyclohexanones, and Baeyer–Villiger oxidation to give Caprolactones. The formation of alkylated cyclohexanols is one of the most difficult steps in the series. A liquid-phase process in the presence of nickel on CeO2 or ZrO2 catalysts is demonstrated herein to give the highest cyclohexanol yields. The catalytic reaction with 4-alkylguaiacols follows two parallel pathways with comparable rates: 1) ring hydrogenation with the formation of the corresponding alkylated 2-methoxycyclohexanol, and 2) demethoxylation to form 4-alkylphenol. Although subsequent phenol to cyclohexanol conversion is fast, the rate is limited for the removal of the methoxy group from 2-methoxycyclohexanol. Overall, this last reaction is the rate-limiting step and requires a sufficient temperature (>250 °C) to overcome the energy barrier. Substrate reactivity (with respect to the type of alkyl chain) and details of the catalyst properties (nickel loading and nickel particle size) on the reaction rates are reported in detail for the Ni/CeO2 catalyst. The best Ni/CeO2 catalyst reaches 4-alkylcyclohexanol yields over 80 %, is even able to convert real softwood-derived guaiacol mixtures and can be reused in subsequent experiments. A proof of principle of the projected cascade conversion of lignocellulose feedstock entirely into Caprolactone is demonstrated by using Cu/ZrO2 for the dehydrogenation step to produce the resultant cyclohexanones (≈80 %) and tin-containing beta zeolite to form 4-alkyl-e-Caprolactones in high yields, according to a Baeyer–Villiger-type oxidation with H2O2.
Robert Jerome - One of the best experts on this subject based on the ideXlab platform.
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synthesis of pcl clay masterbatches in supercritical carbon dioxide
2008Co-Authors: Laetitia Urbanczyk, Robert Jerome, Christine Jerome, Michael Alexandre, Cedric Calberg, Fabrice Stassin, Christophe DetrembleurAbstract:Abstract Pre-exfoliated nanoclays were prepared through a masterbatch process using supercritical carbon dioxide as solvent and poly(ɛ-Caprolactone) as organic matrix. In situ polymerization of ɛ-Caprolactone in the presence of large amount of clay was conducted to obtain these easily dispersible nanoclays, collected as a dry and fine powder after reaction. Dispersion of these pre-exfoliated nanoclays in chlorinated polyethylene was also investigated. All the results confirm the specific advantages of supercritical CO2 towards conventional solvents for filler modification.
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combination of ring opening polymerization and click chemistry toward functionalization and grafting of poly e Caprolactone
2007Co-Authors: Raphael Riva, Robert Jerome, Stephanie Schmeits, Christine Jerome, Philippe LecomteAbstract:A straightforward strategy is proposed for the derivatization of poly(e-Caprolactone) (PCL). First, statistical copolymerization of α-chloro-e-Caprolactone (αCleCL) with e-Caprolactone (eCL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendent chlorides were converted into azides by reaction with sodium azide. Finally, duly substituted terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, thus a “click” reaction. According to this strategy, pendent hydroxyl and acrylate groups and atom transfer radical polymerization (ATRP) initiators were successfully attached to PCL. Similarly, amphiphilic graft copolymers were prepared by cycloaddition of an alkyne end-capped poly(ethylene oxide) (PEO) onto the azide substituents of the copolyester. The dependence of the grafting yield on the experimental conditions of the “click” reaction, i.e., temperature, solvent, and catalyst, was investigated. This strategy is very versatile be...
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new prospects for the grafting of functional groups onto aliphatic polyesters ring opening polymerization of α or γ substituted e Caprolactone followed by chemical derivatization of the substituents
2006Co-Authors: Philippe Lecomte, Raphael Riva, Stephanie Schmeits, Jutta Rieger, Kathy Van Butsele, Christine Jerome, Robert JeromeAbstract:Recent progress in the synthesis of aliphatic polyesters, substituted by pendent functional groups, has been reviewed. Two main strategies have to be distinguished. The first route consists of the ring-opening polymerization of e-Caprolactone substituted by various functional groups, protected if needed, in α- or γ-position. In a second strategy, the functional groups are grafted onto preformed polyesters chains in α-position of the carbonyl groups. α-chloro-e-Caprolactone is quite an interesting monomer because, after polymerization, the activated chloride can be easily derivatized by atom transfer radical addition and click chemistry, respectively. Similarly, γ-acrylic-e-Caprolactone is precursor of (co)polyesters well-suited to derivatization of the pendent double bonds by Michael addition.
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dual living free radical and ring opening polymerizations from a double headed initiator
1998Co-Authors: Craig J Hawker, Mikael Trollsas, David Mecerreyes, Georges Moineau, Eva Malmstrom, James L Hedrick, Philippe Dubois, Robert JeromeAbstract:The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled free radical procedures, either nitroxide mediated or atom transfer radical polymerization (ATRP), with the living ring opening polymerization of e-Caprolactone, and vice versa, is demonstrated by the synthesis of a variety of well-defined block copolymers. For example, from a hydroxy-functionalized alkoxyamine, either the living ring opening polymerization of e-Caprolactone, or the “living” free radical polymerization of styrene can be performed leading to narrow polydispersity polymeric initiators. These polymeric initiators can then be used to initiate the living polymerization of the other monomer system without the need for intermediate steps. In a similar way, hydroxy-functionalized ATRP initiators can be used as bifunctional initiators for the polymerization of both e-Caprolactone and a variety of...
Philippe Dubois - One of the best experts on this subject based on the ideXlab platform.
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synthesis and supramolecular organization of amphiphilic diblock copolymers combining poly n n dimethylamino 2 ethyl methacrylate and poly e Caprolactone
2007Co-Authors: Francois Bougard, Philippe Dubois, Melanie Jeusette, Laetitia Mespouille, Roberto LazzaroniAbstract:Well-defined poly(e-Caprolactone) (PCL)/poly(N,N-dimethylamino-2-ethyl methacrylate (PDMAEMA) diblock copolymers were synthesized, and their self-assembly was investigated as micelles both in aqueous solutions and in thin solid deposits. The synthetic approach combines controlled ring opening polymerization (ROP) of e-Caprolactone (CL) and atom transfer radical polymerization (ATRP) of N,N-dimethylamino-2-ethyl methacrylate (DMAEMA). Diblock copolymers were prepared by ROP of CL initiated by (Al(OiPr)3), followed by quantitative reaction of the PCL hydroxy end-groups with bromoisobutyryl bromide. The α-isopropyloxy ω-2-bromoisobutyrate poly(e-Caprolactone) (PCL-Br) obtained was used as a macroinitiator for the ATRP of DMAEMA. The molecular characterization of those diblock copolymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self-assembly of the copolymers into micellar aggregates in aqueous media was followed with dynamic light scattering (DLS), as a funct...
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functionalization of carbon nanotubes by atomic nitrogen formed in a microwave plasma ar n2 and subsequent poly e Caprolactone grafting
2007Co-Authors: Benoit Ruelle, Michael Alexandre, Sophie Peeterbroeck, Rachel Gouttebaron, Thomas Godfroid, Fabien Monteverde, J P Dauchot, M Hecq, Philippe DuboisAbstract:Multi-walled carbon nanotubes (MWNTs) are placed under atomic nitrogen flow formed through an Ar + N2 microwave plasma in order to functionalize covalently their side walls with nitrogen-containing groups. The MWNT surface analyzed by X-ray photoelectron spectroscopy shows the presence of amides, oximes and mainly amine and nitrile functions grafted in this way. In order to highlight the actual location of the amine functions grafted on MWNTs, they were considered as initiation species in ring-opening polymerization of e-Caprolactone using triethylaluminium as activator. The so-generated poly(e-Caprolactone) chains remain grafted on the MWNTs via amide bonds and form polyester islets along the nanotubes surface. TEM images of these MWNT surfaces grafted with poly(e-Caprolactone) show a good amino-sidewall distribution. This work demonstrates the side-wall amino-functionalization of carbon nanotubes readily achieved by microwave plasma with the possibility to reach within a short time period very high contents in nitrogen-based functions (∼10 at.%).
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mechanisms and kinetics of thermal degradation of poly e Caprolactone
2001Co-Authors: Olivier Persenaire, Michael Alexandre, And Philippe Degee, Philippe DuboisAbstract:Thermogravimetric analysis (TGA) simultaneously coupled with mass spectrometry (MS) and Fourier transform infrared spectrometry (FTIR) was developed as an original technique to study the thermal modification/degradation of poly(e-Caprolactone) (PCL) through in depth analysis of the evolved gas. Perfectly well-defined PCL samples with controlled end groups, predictable molecular weight, and narrow molecular weight distribution were synthesized by living “coordination−insertion” ring-opening polymerization of e-Caprolactone initiated by aluminum triisopropoxide. TGA analyses carried out on purified PCL samples, deprived from any residual catalyst or monomer, highlighted a two-step thermal degradation. Evolved gas analysis by both MS and FTIR showed that the first process implies a statistical rupture of the polyester chains via ester pyrolysis reaction. The produced gases were identified as H2O, CO2, and 5-hexenoic acid. The second step leads to the formation of e-Caprolactone (cyclic monomer) as result of ...
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dual living free radical and ring opening polymerizations from a double headed initiator
1998Co-Authors: Craig J Hawker, Mikael Trollsas, David Mecerreyes, Georges Moineau, Eva Malmstrom, James L Hedrick, Philippe Dubois, Robert JeromeAbstract:The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled free radical procedures, either nitroxide mediated or atom transfer radical polymerization (ATRP), with the living ring opening polymerization of e-Caprolactone, and vice versa, is demonstrated by the synthesis of a variety of well-defined block copolymers. For example, from a hydroxy-functionalized alkoxyamine, either the living ring opening polymerization of e-Caprolactone, or the “living” free radical polymerization of styrene can be performed leading to narrow polydispersity polymeric initiators. These polymeric initiators can then be used to initiate the living polymerization of the other monomer system without the need for intermediate steps. In a similar way, hydroxy-functionalized ATRP initiators can be used as bifunctional initiators for the polymerization of both e-Caprolactone and a variety of...
Steven M Howdle - One of the best experts on this subject based on the ideXlab platform.
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kinetics of enzymatic ring opening polymerization of e Caprolactone in supercritical carbon dioxide
2006Co-Authors: Kristofer J Thurecht, Andreas Heise, Matthijs Degeus, Silvia Villarroya, Jiaxiang Zhou, Mark F Wyatt, Steven M HowdleAbstract:The kinetics of enzymatic ring-opening polymerization (eROP) of e-Caprolactone in supercritical carbon dioxide (scCO2) was investigated using a new, high-pressure sampling autoclave. The polymerization was performed using Candida antarctica lipase B (CALB) as catalyst and was found to be approximately first order with respect to monomer up to 80% conversion. For the first time we have been able to present kinetic results on the eROP of Caprolactone in scCO2. These results show that high molecular weight polymer could be obtained (up to 50 kDa) with polydispersities in the range of 2. The relatively poor molecular weight control was attributed to the large degree of enzyme-catalyzed transesterification that forms both cyclic species (intramolecular transesterification) and linear polymer (intermolecular transesterification). This effect has also been observed for eROP of e-Caprolactone in conventional solvents. The formation of cyclic oligomers of poly(Caprolactone) (PCL) was investigated as a function of ...
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kinetics of enzymatic ring opening polymerization of e Caprolactone in supercritical carbon dioxide
2006Co-Authors: Kristofer J Thurecht, Andreas Heise, Matthijs Degeus, Silvia Villarroya, Jiaxiang Zhou, Mark F Wyatt, Steven M HowdleAbstract:The kinetics of enzymatic ring-opening polymerization (eROP) of e-Caprolactone in supercritical carbon dioxide (scCO2) was investigated using a new, high-pressure sampling autoclave. The polymerization was performed using Candida antarctica lipase B (CALB) as catalyst and was found to be approximately first order with respect to monomer up to 80% conversion. For the first time we have been able to present kinetic results on the eROP of Caprolactone in scCO2. These results show that high molecular weight polymer could be obtained (up to 50 kDa) with polydispersities in the range of 2. The relatively poor molecular weight control was attributed to the large degree of enzyme-catalyzed transesterification that forms both cyclic species (intramolecular transesterification) and linear polymer (intermolecular transesterification). This effect has also been observed for eROP of e-Caprolactone in conventional solvents. The formation of cyclic oligomers of poly(Caprolactone) (PCL) was investigated as a function of conversion, and comparisons were made to similar studies undertaken in conventional solvents.
