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11.
12.
Synthesis and characterization of thermally crosslinked polyimide with second-order nonlinear optical chromophore 总被引:2,自引:0,他引:2
Incomparisonwithinorganicnonlinearoptic(NLO)materials,organicpolymericNLOmaterialshavemanyadvantages,suchasliablemoleculardesignandoptimization,largernonresonanceNLOcoefficiency,lowerdielectricconstant,goodworkingability,opticaltransparencyandresistancea… 相似文献
13.
Kai Li Harald D. H. Stver 《Journal of polymer science. Part A, Polymer chemistry》1993,31(10):2473-2479
Narrow disperse microparticles are formed by dispersion polymerization of commercial divinylbenzene in acetonitrile or ethanol solution in the presence of 2,2′-azobis(2-methylpropionitrile) initiator and polyvinylpyrrolidone stabilizer. The particles have average diameters between 1 and 9 μm depending on monomer concentration, solvent, and temperature. While the smaller particles are relatively smooth, surface texture increases with diameter to give popcorn shapes at 9 μm diameter. High crosslinker concentration is shown to be essential for particle formation. © 1993 John Wiley & Sons, Inc. 相似文献
14.
15.
采用阴离子配位聚合方法, 合成了二氧化碳、1,2-环氧丁烷与ε-己内酯的三元共聚物: 聚[碳酸(亚丁酯-co-ε-己内酯)酯](PBCL). 并采用复相乳液(W/O/W)溶剂挥发法制备了包裹抗菌药物甲磺酸帕珠沙星的可降解微球. 对聚合物进行了FTIR, 1H NMR, 13C NMR, DSC, TGA和WAXD等表征, 以及降解性能和载药微球特性的研究. 结果表明, PBCL热稳定性及降解性能优于聚碳酸亚丁酯(PBC). 所得PBCL微球球形规整、表面光滑. 大部分微球粒径在0.5~1 μm的范围内, 载药量和包封率分别达到38.21%和87.9%. 微球的体外释药性能研究在pH 7.4的磷酸缓冲溶液中进行, 释放21 d后, PBCL微球的累积释药量为84.74%, PBC微球的释药量仅为17.29%. 药物的体外释放行为符合Higuchi方程. PBCL载药微球具有长效缓释作用. 相似文献
16.
作为细胞微载体的明胶基缓释微球的制备 总被引:7,自引:0,他引:7
用改良的乳化冷凝法制备载牛血清蛋白(BSA)的大粒径明胶微球. 结果表明, 明胶水溶液的质量分数为25%、水相与油相体积比3∶20、搅拌速度300 r/min、交联剂用0.1 mL质量分数为25%的戊二醛、 表面活性剂用0.1 g span-80为制备平均直径约250 μm明胶微球的理想条件. 所制备微球的后处理方法不同, 则明胶微球的表面形貌也不同, 细胞粘附率不同. 空白明胶微球在体外可以完全降解, 载BSA的明胶微球对BSA具有良好的缓释性, 释放时间可长达30 d. 显微镜观察成纤维细胞在明胶微载体上生长良好. 相似文献
17.
An investigation of heparinase immobilization 总被引:1,自引:0,他引:1
Bernstein Howard Yang Victor C. Langer Robert 《Applied biochemistry and biotechnology》1987,16(1):129-143
A systematic investigation of the parameters that affect the efficiency of immobilizing heparinase onto cyanogen bromide activated
crosslinked 8% agarose beads was conducted. Two experimental measures, the “fraction bound” and the “fraction retained,” were
used to monitor the coupling efficiency. The fraction bound is the portion of the total initial enzyme that is bound to the
agarose gel. The fraction retained is the fraction of bound enzyme that is active. The product of the two measures indicates
the coupling efficiency. The activity of the immobilized heparinase was measured under conditions free of both internal and
external mass transfer limitations, and thus, the fraction retained represents the true immobilized enzyme activity.
Increasing the degree of activation of the beads results in an increase in the fraction bound, the fraction retained, and
consequently, the coupling efficiency. As the ratio of enzyme solution to gel volume increases from 1.5 to 2.2, the fraction
bound remains constant but the fraction retained decreases (heparinase concentration; 0.15 mg/mL and degree of activation;
9.5 μmol of cyanate esters/g of gel). At volume ratios greater than 2.2, both the fraction bound and the fraction retained
decline continuously. Changing the heparinase concentration in the coupling solution changes the coupling efficiency in a
manner similar to that of the volume ratio change.
When heparin is added during the coupling process, the fraction bound declines as the heparin concentration increases, whereas
the fraction retained increases up to a heparin concentration of 12 mg/mL and decreases thereafter. When arginine, lysine,
and glycine are used to block the unreacted cyanate ester groups after the coupling process, the immobilized heparinase shows
different pH optima of 6.5, 6.9, and 7.2, respectively. Based upon these findings, a protocol to optimize heparinase immobilization
is developed. 相似文献
18.
Shu-ning Li Xin-lin Yang Wen-qiang Huang 《高分子科学》2007,(6):555-563
Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine)(poly(EGDMA-co-4-VPy))microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate(EGDMA)and 4-vinylpyridine (4-VPy)with 2,2'-azobisisobutyronitrile(AIBN)as initiator in neat acetonitrile.The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm,which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles.The catalytic properties of the pyridyl- functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction. 相似文献
19.
Crosslinked copolymers with single Li~+-ionic conductivity were prepared from oligo (oxyethylene) methacrylate (MEO_n), methacryloyl alkylsulfonic acid lithium (SAMLi), and oligo (oxyethylene) dimethacrylate (DMEO_n). Li~+-ionic conductivity of the copolymer is improved by crosslinking and presented as a function of polymerization degree (n) in MEO_n, comonomeric salt concentration (O/Li), and crosslinking degree. The crosslinked copolymer P (0.7 MEO_(14)-0.3DMEO_(14)-SHMLi) without other small molecular additives exhibits an optimum Li~+-ionic conductivity of 1.2×10~(-6) S/cm at 25℃. Dc polarization test in the cell composed of Li/copolymer/Li shows a constant dc ionic conductivity which closes gradually to the ac one with decreasing dc polarization potential. 相似文献
20.
R. M. Masegosa M. A. Llorente M. G. Prolongo I. Hernández-Fuentes A. Horta 《Colloid and polymer science》1984,262(11):862-866
Measurements of preferential sorption,(
3), determined by refractometry, and swelling equilibrium,
3
–1, of PMMA networks have been carried out in the cosolvent mixture MeCN+BuOH at 25 and 49 C. With an intermediate mixture composition,
3
–1 passes through a maximum at both temperatures. At 25 C MeCN is preferentially adsorbed by the network over most of the composition range, but a small inversion is detected. At 49 C MeCN is preferentially adsorbed over all the composition range.The behavior of the system crosslinked PMMA/MeCN + BuOH is compared with the results obtained for solutions of linear PMMA in mixtures formed by the same two solvents, MeCN and BuOH. 相似文献