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超声催化反应的研究现状和发展趋势 总被引:25,自引:0,他引:25
综述了近几十年来超声在催化反应领域中的研究成果,包括超声在均相和多相催化反应中的应用,探讨了超声在催化反应领域中的发展趋势。 相似文献
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作为生物高分子降解材料,聚乳酸具有良好的生物相容性和生物降解性,已经广泛应用于包装材料、农用薄膜等环境领域和药物控制释放体系、医用缝合线、组织工程支架等医学领域。丙交酯开环聚合是制备聚乳酸的理想之选,其催化体系目前以金属催化剂为主,但金属离子在聚合物中的痕量残留和细胞毒性限制了聚乳酸在生物医学及微电子领域的应用,而有机催化剂能够克服这些缺点,是目前聚乳酸合成领域的研究热点。本文从不同的活化机理角度,阐述了近年来有机催化剂在合成聚乳酸中的研究进展,总结了各种催化体系在活性、结构可控性及选择性方面的特点,同时展望有机催化剂在开环聚合反应中所面临的机遇与挑战。 相似文献
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因为环糊精的生物相容性和多功能性,通过改性以及各种剂型的设计,能够扩展其在医药领域的应用。本文介绍了环糊精及其衍生物在药物控制释放体系中的作用机理及特点,并结合本课题组的研究工作,综述了近年来环糊精在该领域中的应用研究进展。 相似文献
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综述国内外固相微萃取技术在法庭科学领域中毒物、毒品和微量物证(炸药残留物、助燃剂残留物、人体气味)样品前处理及分析中的应用,以及在火场助燃剂残留物及人体气味鉴别方面的应用;对固相微萃取技术在法庭科学领域中的发展方向进行了展望。可以对法庭科学领域毒物毒品、微量物的相关研究和侦查办案提供参考。 相似文献
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8—羟基喹啉的高分子化及其应用展望 总被引:8,自引:0,他引:8
综述了8-羟基喹啉的各种高分子化方法,介绍了其在分析,环境,材料等领域中的应用情况,并展望了其在有机电致发光领域和导电聚合物等领域中的应用前景,提出了一些与之相关的值得深入研究的问题。 相似文献
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N. E. Silina A. G. Morozov E. E. Gornostaeva L. A. Smirnova S. D. Zaytsev 《Polymer Science Series B》2017,59(5):551-559
The block copolymers of chitosan with D,L-lactide are synthesized under UV irradiation of the homogeneous solution of the corresponding homopolymers with the yield of the main product being 96 wt %. The polyblock structure of copolymer chains, in which the size of polylactide blocks is varied in the range of (2.9–22.0) × 103 depending on the synthesis conditions, is demonstrated. The incorporation of polylactide blocks into the structure of chitosan leads to development of the material structure close to the structure of polylactide. The films of the block copolymers containing 16 wt % polylactide and having a molecular mass of its blocks of 22.0 × 103 have increased values of breaking stress (47 MPa) and ultimate strain (20%) compared to chitosan (24 MPa and 1.9%, respectively). The obtained block copolymers possess bactericidal properties. 相似文献
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X-ray imaging functionalization of biodegradable polyesters is a great demand and challenge in biomedical applications.In this work,a strategy of in-chain functionalization through the combination of ring opening copolymerization and oxime "Click" postfunctionalization was developed towards X-ray opaque polylactide copolymers.A functionalized cyclic carbonate was first synthesized and used as comonomer of polylactide copolymers,which were subjected to postfunctionalization of oxime "Click" reaction towards iodinated polylactide copolymers.The chemical structure and physical properties of the target products were traced and confirmed.In vitro cytotoxicity evaluation with 3T3-Swiss albino by Alamar blue demonstrated a low cytotoxicity.The X-ray radiopacity was analyzed by Micro-CT and quantified by Hounsfield Units value,which could be tailorable by the feedstock.It is a promising X-ray visible implantable biomaterial in biomedical applications. 相似文献
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Screening of metal catalysts influence on the synthesis,structure, properties,and biodegradation of PLA‐PBA triblock copolymers obtained in melt
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Anna Kundys Andrzej Plichta Zbigniew Florjańczyk Anita Frydrych Konrad Żurawski 《Journal of polymer science. Part A, Polymer chemistry》2015,53(12):1444-1456
The synthesis of ABA type triblock copolymers comprising poly(1,4‐butylene adipate) macroinitiator and polylactide segments is described in this article. Acetylacetonates of various low‐toxic metals: Li, Mg, Ca, Zn, Fe, and Zr are used as catalysts. The course of polymerization, microstructure, thermal properties, and biodegradation of the copolymers obtained are analyzed based on the electronegativity of the metal used. The macroinitiator is completely incorporated into the major products, however, linear and cyclic lactide homopolymers and copolymers are present because of moisture presence and transesterification processes. The efficiency of side reactions depends on the catalyst used. The highest molar mass of copolymer is obtained with a Zr‐based catalyst. The efficacy of polylactide racemization is higher for catalysts comprising the metal of lower electronegativity. Under thermal degradation conditions the polylactide segment degrades before the macroinitiator one. The copolymers studied undergo faster biodegradation than polylactide and they can decompose in compost within 16 weeks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1444–1456 相似文献
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In this study, the adsorption of amphiphilic poly(ethylene oxide)-block-polylactide (mPEO-PLA) copolymers from a selective solvent onto a polylactide surface was studied as a method of polylactide surface modification and its effect on nonspecific protein adsorption was evaluated. A series of well defined mPEO-PLA copolymers was prepared to investigate the effect of copolymer composition on the resulting PEO chain density and on the surface resistance to protein adsorption. The copolymers contained PEO blocks with molecular weights ranging between 5600 and 23,800 and with 16-47 wt% of PLA. The adsorption of both the copolymers and bovine serum albumin was quantified by attenuated total reflection FTIR spectroscopy (ATR-FTIR). In addition to the adsorbed copolymer amount, its actual composition was determined. The PEO chain density on the surface was found to decrease with the molecular weight of the PEO block and to increase with the molecular weight of the PLA block. The adsorbed copolymers displayed the ability to reduce protein adsorption. The maximum reduction within the tested series (by 80%) was achieved with the copolymer containing PEO of MW 5600 and a PLA block of the same MW. 相似文献
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A series of novel biodegradable polymers, graft copolymers of D,L-lactide on gelatin, were designed and synthesized to overcome the shortcomings of gelatin and polylactide(PLA) biomaterials. The copolymers were characterized by nitrogen analysis, IR, 1H-NMR and thermal analysis. The amphiphilic properties of these copolymers were also investigated. 相似文献
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ABA block copolymers of polylactide and poly(ethylene glycol) as amphiphilic bioabsorbable polymers were synthesized by the ring-opening
polymerization of dl- lactide onto poly(ethylene glycol) (PEG 2000 or PEG 6000) and their structures were characterized on the basis of proton
NMR. Biodegradable nanocapsules of an aqueous insulin solution were prepared from the block copolymers and polylactide by
an improved interfacial coacervation technique. The results showed that the diameters of the nanocapsules were mainly dependent
on the ratio of the two chains in the block polymers. The size of the nanocapsules decreased with an increase in the amount
of surfactant used. More insulin solution resulted in an enlargement of the nanocapsules in diameter. In an optimum condition,
biodegradable nanocapsules could be achieved with a size around 250 nm with a narrow distribution. The encapsulation percentages
of insulin were larger in the nanocapsules from the PEG 2000 copolymers than in those from the PEG 6000 analogs and changed
with the ratios of the blocks in the block copolymers.
Received: 17 July 2000 Accepted: 24 November 2000 相似文献
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Anionic polymerization of isoprene initiated by an alkyl lithium containing a silyl ether protected hydroxyl functionality followed by termination with ethylene oxide gave α,ω‐functionalized polyisoprene with narrow molecular weight distribution and prescribed molecular weight in high yield. Deprotection resulted in α,ω‐hydroxyl polyisoprene (HO‐PI‐OH) that was reacted with triethylaluminium to form the corresponding aluminium alkoxide macroinitiator. The macroinitiator was used for the controlled polymerization of lactide to yield polylactide‐block‐polyisoprene‐block‐polylactide triblock copolymers with narrow molecular weight distributions and free of homopolymer (HO‐PI‐OH) contamination. Microphase separation in these novel triblock copolymers was confirmed by SAXS and DSC. 相似文献
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T. S. Demina K. N. Bardakova E. A. Svidchenko N. V. Minaev G. I. Pudovkina M. M. Novikov D. V. Butnaru N. M. Surin T. A. Akopova V. N. Bagratashvili A. N. Zelenetskii P. S. Timashev 《High Energy Chemistry》2016,50(5):389-394
The graft copolymers of chitosan and oligo(D,L-lactide) obtained by solid-phase synthesis have been used as the basis of photosensitive compositions for the fabrication of three-dimensional microstructures by laser-induced stereolithography. The electronic absorption spectra of the copolymers are close to the sum of the spectra of native chitosan and polylactide, which has been chosen as a model of grafted oligolactide chains. The fundamental absorption bands of the copolymers lie in a range to 500 nm, and their contribution to the absorption intensity of a photosensitive composition based on the copolymers at second harmonic laser frequency is insignificant. Depending on the macromolecular characteristics of the copolymers, the three-dimensional crosslinking of photosensitive compositions on their basis in the course of microstructuring occurs with different efficiency. 相似文献
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Alexandre Richez Joel Belleney Laurent Bouteiller Sandrine Pensec 《Journal of polymer science. Part A, Polymer chemistry》2006,44(23):6782-6789
Formation of a stereocomplex from polylactide copolymers can be tuned by changing the size and the chain topology of the second block in the copolymer. In particular, the use of a dendritic instead of linear architecture is expected to destabilize the cocrystallisation of polylactide blocks. With this idea in mind, dendritic‐linear block copolymers were synthesized by ring‐opening polymerization (ROP) of lactides using benzyl alcohol dendrons of generation 1–3 as macroinitiators and stannous octoate as catalyst. Polymers with controlled and narrow molar mass distribution were obtained. The MALDI‐TOF mass spectra of these dendritic‐linear block copolymers show well‐resolved signals. Remarkably, 10% or less of odd‐membered polymers are present, indicating that ester‐exchange reactions which occur classically parallel to the polymerization process, were in these conditions, very limited. Thermal analysis of polyenantiomers of generation 1–3 and the corresponding blends were examined. The blend of a pair of enantiomeric dendritic‐linear block copolymers exhibit a higher melting temperature than each copolymer, characteristic for the formation of a stereocomplex. Melting temperatures are strongly dependent on the dendron generation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6782–6789, 2006 相似文献
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In this study, biodegradable shape‐memory polymers—polylactide‐co‐poly(glycolide‐co‐caprolactone) multiblock (PLAGC) copolymers—were synthesized by the coupling reaction of both macrodiols of polylactide (PLLA‐diol) and poly(glycolide‐co‐caprolactone) (PGC‐diol) in the presence of 1,6‐hexanediisocyanate as coupling agent. The copolymers formed were found to be thermoplastic and easily soluble in common solvents. The compositions of the copolymers were determined by 1H‐NMR and the influences of segment lengths and contents of both macrodiols on the properties of the PLAGC copolymers were investigated. It was found that the copolymers had adjustable mechanical properties which depended on contents and segment lengths of both macrodiols. The copolymers showed such good shape‐memory properties that the strain fixity rate (Rf) and the strain recovery rate (Rr) exceed 90%. By means of adjusting the compositions of the copolymers, PLAGC copolymers with transition temperatures around 45°C could be obtained. The degradation rate determination showed that the PLAGC copolymers have fast degradation rates, the mechanical strengths of the PLAGC copolymers would be completely lost within 1–2 months depending on molecular weights and contents of the both segments of PLLA and PGC. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献