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The persistence length and the overlap concentration(c~*) of poly(ethylene oxide)(PEO) and hydroxyethylcellulose(HEC) with similar molecular weight in 1×TBE buffer were studied by laser light scattering and viscometry.Their effect on DNA separation was investigated by capillary electrophoresis.It was determined that the persistence length of HEC was at least 5 times higher than that of PEO.Therefore,the c~* of HEC was smaller than that of PEO by a factor of ca.2.5.It was also found that the c~* values de... 相似文献
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美国斯坦福大学化学系教授Richard N.Zare于1997年提出[1]:“由化学家来构造生命”是21世纪最伟大的挑战之一,即“用化学的方法去得到能自我复制、自我组装,甚至有进化可能性的系统”是当今对化学家最严峻的挑战之一。为什么研究生命体系要寄希望于化学家呢?因为一则生命体系由 相似文献
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在苯乙烯(St)-二乙烯苯(DVB)自由基聚合的凝胶化反应过程中,定时取样,得到凝胶化点前后及直至反应终点的一系列溶胶样品,利用光散射技术研究了溶胶相的重均分子量Mw、尺寸均方旋转半径Rg的变化过程,建立了Mw、Rg和反应时间t的标度关系,并在此基础上提出一神新的准确求取凝胶化时间tgel的方法. 相似文献
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<正>The effects of heating rate on the aggregate behavior of poly(ethylene oxide)-b-poly(N-isopropylacrylamide) in aqueous solutions were investigated in detail by laser light scattering and TEM.By employing two separate heating protocols,step-by-step heating at5 K/step and one-step jump,to heat the sample from 15℃to the selected temperature, we found that the heating rate only showed significant effect on the aggregates above the cloud point.The aggregate formed by step-by-step heating exhibited a much larger size and a broader size distribution than those formed by one-step jump heating.Moreover,neither of the aggregates were ideal micellar structures as indicated by the size and the R_g/R_h values.On the contrary,at temperatures below the cloud point where the block copolymer formed core-shelled micelles,the heating rate showed negligible effect on the size and size distribution of the micelles.Since the system underwent a phase separation above the cloud point,the heating rate effect could be reasonably explained by the phase separation mechanisms:the nucleation-and-growth mechanism in the metastable region and the spinodal decomposition mechanism in the unstable region. 相似文献
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The dependence of the scattered intensity on angles was measured by SAXS for a series of samples taken during the span process of the gelation of styrene with divinylbenzene. Based on these data. we obtained the fractal dimensions and their evolution for both sols and gels successfully. 相似文献
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动、静态光散射在线跟踪DPPC/PA脂质体的聚集和融合过程 总被引:1,自引:0,他引:1
结合动、静激光光散射在线跟踪了经低温培养的二棕榈酰基磷脂酰胆碱/棕榈酸(摩尔比为1:2)脂质体在25-41℃温度范围内的聚集和融合过程.在升温过程中,脂质体的尺寸和相对分子质量明显增大,表明有聚集或融合发生.另外,尺寸分布出现角度依赖性,证明囊泡结构遭到破坏.而在接下来的降温过程中,粒径和相对分子质量继续增大,没有回到初始状态.根据光散射结果,我们认为脂质体富集脂肪酸分子的区域随温度升高会发生黏合而形成聚集,该聚集体形态类似反六方柱状相.融合发生的比例较小.降温过程中的变化表明囊泡是动力学稳定态,一旦聚集发生,会自发继续进行聚集或融合. 相似文献