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941.
Yun-Chang Zhang Lan Chen Hui Wang Ya-Ming Zhou Dan-Wei Zhang Zhan-Ting Li 《中国化学快报》2016,27(6):817-821
Two naphthalene(NP) and bipyridinium(BIPY~(2+)) alternately incorporated polymers P1 and P2 have been prepared through the formation of dynamic hydrazone bonds. The polymers formed NP–BIPY~(2+)donor–acceptor interaction-induced pleated secondary structure. Upon reducing the BIPY~(2+)units to radical cation BIPY+, intramolecular dimerization of the BIPY+units induced the backbones to afford another pleated secondary structure. Adding electron-rich macrocyclic polyether bis-1,5-dinaphtho[38]crown-10 or electron-deficient cyclobis(paraquat-p-phenylene) cyclophane did not break the first foldamer by complexing the BIPY2+or NP units of the polymers, whereas the di(radical cationic)ring of the second cyclophane could break the second foldamer by forming threading complexes with the BIPY+units of the polymers. 相似文献
942.
Covalent organic frameworks (COFs) represent an emerging class of porous crystalline materials and have recently shown interesting applications from catalysis to optoelectronic devices. In this review, by covering most of the reported work, we summarized the research progress of two-dimensional (2D) porphyrin- and phthalocyanine-based COFs, with highlighting the synthesis of these 2D COFs via various dynamic covalent reactions and emphasizing their potential applications in different areas. 相似文献
943.
Super-toughened poly(lactic acid) (PLA)/poly(ethylene-co-vinyl acetate) (EVA) blends were prepared via 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD) induced dynamic vulcanization and in situ interfacial compatibilization. The effects of AD on the morphology and properties of PLA/EVA blends were studied using a Brabender torque rheometer, gel content test, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and mechanical properties test. The torque and gel content demonstrated that EVA and PLA was successfully vulcanized in the presence of free radicals obtained by the decomposition of the 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (AD). Additionally, the gel content results indicated that, compared with PLA, EVA is more aggressive with free radicals. The SEM revealed that a relatively uniform phase morphology and good interfacial compatibilization were achieved in the dynamically vulcanized PLA/EVA/AD blends. The interfacial reaction and compatibilization between the component polymers resulted in the formation of super-toughened PLA/EVA blended materials. 相似文献
944.
Bruce W. Hermann Lesley M. Freed Michael Q. Thompson R. John Phillips Ken J. Klein W. Dale Snyder 《Journal of separation science》1990,13(5):361-365
Capillary gas chromatographic separations were performed with an electronic pressure control system developed to provide precise closed-loop control of inlet pressure through the use of a solid state micro-machined pressure sensor and electronically controlled proportional valve. The closed-loop control of the electronic system provided better precision than the open-loop control achieved by manual pressure regulation. Closed-loop control can perform pressure programming, which can be combined with temperature programming to optimize separations. The pressure sensor monitors the integrity of the flow system and singals the controller to reduce flow in the presence of a sudden loss of system pressure. 相似文献
945.
动态液相微萃取GC/MS-SIM方法检验毛发中的苯丙胺类毒品 总被引:2,自引:0,他引:2
建立了动态液相微萃取GC/MS-SIM方法检测毛发中4种苯丙胺类毒品的方法.毛发样品首先用1 mol/L NaOH溶液消解,然后用50μL氯仿涡旋提取1min,离心后用注射器直接抽取有机相,提取液进行GC/MS-SIM方法检测.毛发样品的测出限(S/N=3)分别为苯丙胺1 ng/mg,甲基苯丙胺、3、4-(亚甲二氧基)苯丙胺、3、4(亚甲二氧基)-甲基苯丙胺500 pg/mg.在毛发中添加上述4种苯丙胺毒品的质量分数为5 ng/mg时,5次测定的RSD分别为苯丙胺8.3%,甲基苯丙胺8.2%,3、4-(亚甲二氧基)苯丙胺2.0%,3、4(亚甲二氧基)2.7%.该方法可用于毛发中低含量苯丙胺类毒品的分析. 相似文献
946.
采用小角激光光散射(SALLS)并结合动态流变学方法,考察了气相法二氧化硅(SiO2)粒子的加入对聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混体系相行为的影响,得到了添加SiO2粒子前后的相图,发现SiO2粒子对基体相行为的影响与基体的组成有关.对PMMA/SAN(60/40)体系,加入SiO2粒子后相分离温度上升,但并未改变相分离机理,仍为亚稳单相分解过程(spinodal decomposition,SD);而对于PMMA/SAN(30/70)体系,加入SiO2粒子后却降低了体系的相分离温度.该现象可能是SiO2粒子和基体组分界面间组成与PMMA/SAN共混物基体组成的差异造成的. 相似文献
947.
948.
The mechanism of silica particle formation in monomer microemulsions is studied using dynamic light scattering (DLS), atomic
force microscopy, small-angle X-ray scattering (SAXS), and conductivity measurements. The hydrolysis of tetraethylorthosilicate
(TEOS) in methylmethacrylate (MMA) microemulsions (MMA = methylmethacrylate) is compared with the formation of SiO2 particles in heptane microemulsions. Stable microemulsions without cosurfactant were found for MMA, the nonionic surfactant
Marlophen NP10, and aqueous ammonia (0.75 wt%). In the one-phase region of the ternary phase diagram, the water/surfactant
ratio (R
w) could be varied from 6 to 18. The DLS and SAXS measurements show that reverse micelles form in these water-in-oil (w/o)
microemulsions. The minimum water-to-surfactant molar ratio required for micelle formation was determined. Particle formation
is achieved from the base-catalyzed hydrolysis of TEOS. According to atomic force microscopy measurements of particles isolated
from the emulsion, the particle size can be effectively tailored in between 20 and 60 nm by varying R
w from 2–6 in heptane w/o microemulsions. For MMA-based microemulsions, the particle diameter ranges from 25 to 50 nm, but
the polydispersity is higher. Tailoring of the particle size is not achieved with R
w, but adjusting the particle growth period produces particles between 10 and 70 nm. 相似文献
949.
A dynamic ultrasound-assisted extraction procedure utilizing diluted nitric acid was developed for the determination of copper,
iron, manganese and zinc in human hair taken from workers in permanent contact with a polluted environment. The extraction
unit of the dynamic ultrasound-assisted extraction system contains a minicolumn into which a specified amount of hair (5–50 mg)
is placed. Once inserted into the continuous manifold, trace metals were extracted at 3 mL min−1 with 3 mol L−1 nitric acid under the action of ultrasound for 2 min for zinc and 3 min for copper, iron and manganese determination, and
using an ultrasonic water-bath temperature of 70 °C for zinc and 80 °C for copper, iron and manganese determination. The system
permits the direct analysis of hair and yields concentrations with relative standard deviations of <3% (n = 11). The applicability of the procedure was verified by analysing human hair samples from workers exposed to welding fumes,
and its accuracy was assessed through comparison with a conventional sample dissolution procedure and the use of a certified
reference material (BCR 397, human hair). 相似文献
950.
采用动力学标度方法研究了磁控溅射沉积的非晶氮化铁薄膜的动力学生长机制, 结果表明, 具有连续类柱状岛形貌的非晶氮化铁薄膜具有标度不变的自仿射分形特点, 其粗糙度指数α=0.82±0.21, 生长指数β=0.44±0.07, 动力学标度指数1/z=0.54±0.07. 薄膜生长符合提出的热重新发射生长模型. 相似文献