原子转移自由基聚合反应(atom transfer radical polymerization,ATRP)是纤维素及其衍生物进行修饰改性的一种有效途径。通过ATRP对纤维素及其衍生物进行改性,可以得到不包含相应均聚物的纯接枝产物,且接枝链的长度及分子量分布均可控...原子转移自由基聚合反应(atom transfer radical polymerization,ATRP)是纤维素及其衍生物进行修饰改性的一种有效途径。通过ATRP对纤维素及其衍生物进行改性,可以得到不包含相应均聚物的纯接枝产物,且接枝链的长度及分子量分布均可控。通过ATRP不仅可对纤维素进行本体改性,还可对其进行表面改性。原子转移自由基聚合方法在纤维素及其衍生物改性方面的应用Ⅰ″一文介绍了通过ATRP对纤维素及其衍生物进行本体改性的研究进展。本文概述了通过ATRP对纤维素及其衍生物进行表面改性的研究进展。展开更多
A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood（pine wood（PW））, hardwoods（...A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood（pine wood（PW））, hardwoods（poplar wood, catalpa bungi, and Chinese parasol）, and agricultural wastes（rice straw, wheat straw, and corn stover（CS）） were exploited. Results showed that the best pretreatment effect was in PW with 54.3% and 31.7% dissolution and extraction ratios, respectively. The crystal form of cellulose in PW extract transformed from I to II, and the contended cellulose ratio and glucose conversion ratio reached 85.1% and 85.4%, respectively. CS after steam explosion achieved a similar pretreating effect as PW, with its cellulose hydrolysis ratio reaching as high as 91.5% after IL pretreatment.展开更多
In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose （EC） was constructed, combining the host-guest interaction of β-cyclodextrin （β-CD） group and trans-isomer of azobenzene...In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose （EC） was constructed, combining the host-guest interaction of β-cyclodextrin （β-CD） group and trans-isomer of azobenzene （tAzo） group. To link β-CD to the hydrophobic section, renewable EC was used as macroinitiator to initiate the polymerization of ε-caprolactone （ε-CL） to form biocompatible and biodegradable comb copolymer EC-g-PCL, and β-CD was attached to the end of PCL side chain via click reaction. Meanwhile, hydrophilic PEG-tAzo was obtained by N,N＇-dicyclohexylcarbodiimide （DCC） coupling. Then, the structures of the products were characterized by nuclear magnetic resonance （NMR） and gel permeation chromatography （GPC）. Subsequently, with the formation of inclusion complexes by β-CD and tAzo groups, the obtained EC-g-PCL-β-CD/PEG-tAzo supramolecular system self-assembled in water with hydrophobic EC-g-PCL-β-CD as core and hydrophilic PEG-tAzo as shell. Furthermore, dynamic light scattering （DLS） and transmission electron microscopy （TEM） were utilized to investigate the particle size and size distribution, while NMR and UV-Vis spectra were applied to explore the UV-Visible light stimuli-responsiveness of the micelles.展开更多
A constitutive model is constructed to consider the resin matrix post-yield softening and progressive hardening behaviors. A user-defined material mechanical behavior （UMAT） subroutine is created, then the non-linea...A constitutive model is constructed to consider the resin matrix post-yield softening and progressive hardening behaviors. A user-defined material mechanical behavior （UMAT） subroutine is created, then the non-linear three-dimensional finite element analysis on the tensile processes of multi-fiber composites is conducted. The approximate 45° shear bands emanating from the matrix crack tip are found, being coincided with the experimental observations. The shear stress on the adjacent intact fiber/matrix interface is strongly influenced by the shear band and thus the stress concentration factor （SCF） changes obviously in the adjacent fibers. The distinct stress redistribution in the adjacent intact fibers implies the significant effect of the shear bands on the progressive fiber fracture initiation. As the inter-fiber spacing increases, the peak value of the SCF in the adjacent intact fiber decreases, whereas the overload zone becomes wider. The research has provided a helpful tool to evaluate the failure of fiber composites and optimize the composite performance through the proper selection of resin matrix properties and fiber volume fraction.展开更多
Quaternized cellulose( QC) derivatives were synthesized by reacting cellulose with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride( CHPTAC) in an aqueous solution of Na OH-urea. The chemical structures and physic...Quaternized cellulose( QC) derivatives were synthesized by reacting cellulose with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride( CHPTAC) in an aqueous solution of Na OH-urea. The chemical structures and physical properties of the obtained QC derivatives were characterized using nitrogen content analysis,Fourier transform infrared spectroscopy( FT-IR),~1H-nuclear magnetic resonance(1H-NMR),X-ray diffraction( XRD),and thermal gravity analysis( TGA). The FT-IR and ~1H-NMR results confirmed the successful introduction of cationic quaternary ammonium groups into the main chain of cellulose. A series of QC derivatives with the degree of substitution( DS) values ranging from 0. 33 to 0. 80 were derived by adjusting the molar ratio of CHPTAC to anhydroglucose unit( AGU) of cellulose,concentration of cellulose in the Na OH-urea solution,as well as reaction temperature and time. According to the DS values of the QC derivatives,the optimized synthetic conditions were as follows: 25℃ reaction temperature,3% cellulose in Na OH-urea solution,the molar ratio of etherification agent to glycosidic cellulose of 15∶ 1,and 12 h reaction time. The TGA and XRD results revealed that the crystalline structure was destroyed during etherification,and the thermal stability of the QC derivatives was lower than that of cellulose.展开更多
文摘原子转移自由基聚合反应(atom transfer radical polymerization,ATRP)是纤维素及其衍生物进行修饰改性的一种有效途径。通过ATRP对纤维素及其衍生物进行改性,可以得到不包含相应均聚物的纯接枝产物,且接枝链的长度及分子量分布均可控。通过ATRP不仅可对纤维素进行本体改性,还可对其进行表面改性。原子转移自由基聚合方法在纤维素及其衍生物改性方面的应用Ⅰ″一文介绍了通过ATRP对纤维素及其衍生物进行本体改性的研究进展。本文概述了通过ATRP对纤维素及其衍生物进行表面改性的研究进展。
基金supported by the National Natural Science Foundation of China(No.21006118)the National High Technology Research and Development Program of China(863Project,Nos.2012AA101807 and 2012AA022301)
文摘A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood（pine wood（PW））, hardwoods（poplar wood, catalpa bungi, and Chinese parasol）, and agricultural wastes（rice straw, wheat straw, and corn stover（CS）） were exploited. Results showed that the best pretreatment effect was in PW with 54.3% and 31.7% dissolution and extraction ratios, respectively. The crystal form of cellulose in PW extract transformed from I to II, and the contended cellulose ratio and glucose conversion ratio reached 85.1% and 85.4%, respectively. CS after steam explosion achieved a similar pretreating effect as PW, with its cellulose hydrolysis ratio reaching as high as 91.5% after IL pretreatment.
基金financially supported by the National Natural Science Foundation of China(Nos.21174076 and 21374053)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120002110015)
文摘In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose （EC） was constructed, combining the host-guest interaction of β-cyclodextrin （β-CD） group and trans-isomer of azobenzene （tAzo） group. To link β-CD to the hydrophobic section, renewable EC was used as macroinitiator to initiate the polymerization of ε-caprolactone （ε-CL） to form biocompatible and biodegradable comb copolymer EC-g-PCL, and β-CD was attached to the end of PCL side chain via click reaction. Meanwhile, hydrophilic PEG-tAzo was obtained by N,N＇-dicyclohexylcarbodiimide （DCC） coupling. Then, the structures of the products were characterized by nuclear magnetic resonance （NMR） and gel permeation chromatography （GPC）. Subsequently, with the formation of inclusion complexes by β-CD and tAzo groups, the obtained EC-g-PCL-β-CD/PEG-tAzo supramolecular system self-assembled in water with hydrophobic EC-g-PCL-β-CD as core and hydrophilic PEG-tAzo as shell. Furthermore, dynamic light scattering （DLS） and transmission electron microscopy （TEM） were utilized to investigate the particle size and size distribution, while NMR and UV-Vis spectra were applied to explore the UV-Visible light stimuli-responsiveness of the micelles.
基金financially supported by the National Key Basic Research Program of China(No.2010CB631102)the National Natural Science Foundation of China(Nos.51173100 and 51373090)the Natural Science Foundation of Shandong Province(No.JQ201016)
文摘A constitutive model is constructed to consider the resin matrix post-yield softening and progressive hardening behaviors. A user-defined material mechanical behavior （UMAT） subroutine is created, then the non-linear three-dimensional finite element analysis on the tensile processes of multi-fiber composites is conducted. The approximate 45° shear bands emanating from the matrix crack tip are found, being coincided with the experimental observations. The shear stress on the adjacent intact fiber/matrix interface is strongly influenced by the shear band and thus the stress concentration factor （SCF） changes obviously in the adjacent fibers. The distinct stress redistribution in the adjacent intact fibers implies the significant effect of the shear bands on the progressive fiber fracture initiation. As the inter-fiber spacing increases, the peak value of the SCF in the adjacent intact fiber decreases, whereas the overload zone becomes wider. The research has provided a helpful tool to evaluate the failure of fiber composites and optimize the composite performance through the proper selection of resin matrix properties and fiber volume fraction.
基金financially supported by grants from the National Natural Science Foundation of China(No.31500493)the Liaoning Educational Common Scientific Research Project(No.L2015044)+1 种基金the Liaoning Natural Science Foundation(No.2015020576)the Open Foundation of the Key Lab of Pulp and Paper Science & Technology,and Ministry of Education(Shandong Province),Qilu University of Technology(No.08031338)
文摘Quaternized cellulose( QC) derivatives were synthesized by reacting cellulose with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride( CHPTAC) in an aqueous solution of Na OH-urea. The chemical structures and physical properties of the obtained QC derivatives were characterized using nitrogen content analysis,Fourier transform infrared spectroscopy( FT-IR),~1H-nuclear magnetic resonance(1H-NMR),X-ray diffraction( XRD),and thermal gravity analysis( TGA). The FT-IR and ~1H-NMR results confirmed the successful introduction of cationic quaternary ammonium groups into the main chain of cellulose. A series of QC derivatives with the degree of substitution( DS) values ranging from 0. 33 to 0. 80 were derived by adjusting the molar ratio of CHPTAC to anhydroglucose unit( AGU) of cellulose,concentration of cellulose in the Na OH-urea solution,as well as reaction temperature and time. According to the DS values of the QC derivatives,the optimized synthetic conditions were as follows: 25℃ reaction temperature,3% cellulose in Na OH-urea solution,the molar ratio of etherification agent to glycosidic cellulose of 15∶ 1,and 12 h reaction time. The TGA and XRD results revealed that the crystalline structure was destroyed during etherification,and the thermal stability of the QC derivatives was lower than that of cellulose.
