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991.
Zhi Huai SI Guo Chang WANG* He Xian LI Jia Long YUAN Bing Lin HE State Key Laboratory of Functional Polymer Materials for Adsorption Separation Institute of Polymer Chemistry Nankai University Tianjin 《中国化学快报》2003,14(1)
The aggregation of amphiphilic block copolymers is a crucial phenomenon that controls various applications, and has been extensively treated in the literature1-3. Pyrene is a widely used fluorescence probe for the relative intensities of the vibrational fine structure (five bands) of its fluorescence spectra have been found to be sensitive to the polarity of its environment, the so-called Ham effect4. We report the studies of the aggregation properties of a PS-b-PAA copolymer using pyrene … 相似文献
992.
在不同实验条件下,用微波等离子体化学气相沉积设备在硬质合金(WC+6%Co)衬底上沉积了 具有不同结构特征的金刚石薄膜.用Raman谱表征薄膜的品质和应力,用压痕实验表征薄膜的 附着性能,考察了薄膜中sp2杂化碳含量、形核密度、薄膜厚度对薄膜附着性能 的影响.结 果表明:sp2杂化碳的缓冲作用使薄膜中sp2杂化碳的含量对薄膜中 残余应力有较大的影 响,从而使薄膜压痕开裂直径统计性地随sp2杂化碳含量的增加而减小;仅仅依 靠超声遗 留的金刚石晶籽提高形核密度并不能有效改变薄膜与硬质合金基体之间的化学结合状况,从 而不能有效提高薄膜在衬底上的附着性能;在薄膜较薄时,晶粒之间没有压应力的存在,开 裂直径并不明显随厚度增加而增加,只有当薄膜厚度增加到一定值,晶粒之间才有较强压应 力存在,开裂直径随厚度的增加而较为迅速地增加.
关键词:
金刚石薄膜
附着性能
2杂化碳')" href="#">sp2杂化碳
成核密度
薄膜厚度 相似文献
993.
Xiaodong Hou Qiaobo Li Yong He Lin Jia Yang Li Yingdan Zhu Amin Cao 《Journal of Polymer Science.Polymer Physics》2009,47(14):1393-1405
Spontaneous stereocomplex aggregation of diblock poly(styrene)‐b‐poly(L ‐lactide) PS‐b‐PLLA/poly(D ‐lactide) PDLA pairs has been investigated under ambient temperature in tetrahydrofuran solution. First, diblock PS260‐b‐PLLA165 and PS260‐b‐PDLA162 bearing similar lengths of respective PLLA and PDLA blocks were synthesized through controlled atom‐transfer radical polymerization of styrene, and a subsequent living ring‐opening polymerization of optically pure lactides, and their structures were further characterized by nuclear magnetic resonance spectroscopy (NMR) and gel‐permeation chromatography (GPC). Subsequently, new enantiomeric poly(D ‐lactide) stabilized core‐shell fluorescent CdSe quantum dots (CdSe/PDLA QD) were designed and prepared as sensitive fluorescence labels to shed new lights on the spontaneous stereocomplex aggregation in THF, which was mediated by stereocomplexation of the PLLA and PDLA chains. Upon simply mixing two individual THF solution of diblock PS260‐b‐PLLA165 and HO‐PDLA30‐SH, spontaneous stereocomplex aggregation was studied, and the aggregated uniform spherical particles were observed by scanning electronic microscopy (SEM) to exhibit average particle diameters of 2.0 μm. Finally, utilizing the prepared CdSe/PDLA QDs as new fluorescent labels, morphologies of the spontaneous aggregates by new diblock PS260‐b‐PLLA165/HO‐PDLA30‐SH pair were for the first time directly visualized by a confocal laser scanning fluorescence microscopy (CLSFM). These results might suggest alternative ways to simply prepare functional fluorescent particles with tunable diameter sizes and would be helpful to understand the mechanism of stereocomplex particle aggregation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1393–1405, 2009 相似文献
994.
Yanping Wang Li Zhou Guoming Sun Jie Xue Zhifeng Jia Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2008,46(12):1114-1120
Poly(ethylene glycol) (PEG) can form either the inclusion complex with α‐cyclodextrins (α‐CDs) through host–guest interactions or the interpolymer complex with poly(acrylic acid) (PAA) through hydrogen‐bonding interaction. Mixing α‐CD, PEG, and PAA ternary components in an aqueous solution, the competition between host–guest and hydrogen‐bonding interactions occurs. Increasing feed ratio of α‐CD:EG:AA from 0:1:1 to 0.2:1:1 (molar ratio), various interesting supramolecular polymer systems, such as hydrogen‐bonding complex, dynamic polyrotaxane, crystalline inclusion complex, and thermoresponsive hydrogel, are successively obtained. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1114–1120, 2008 相似文献
995.
996.
The bilinear finite element approximation for the Poisson equation has an asymptotic error expansion on the anisotropic rectangular meshes. Extrapolation can be obtained based on this expansion and the postprocessing interpolation. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007 相似文献
997.
用第一性原理的密度泛函理论计算了PbTe(001)表面的几何结构和电子结构.计算结果表明:PbTe(001)表面不发生重构,但表面几层原子表现出明显的振荡弛豫现象,其中第一、第二层间距减小4.5%,第二、第三层间距增加2.0%,并且表面层原子出现褶皱.表面带隙在X 点,带隙变宽,在基本带隙中不引入新的表面态,而导带底和价带顶附近等多处出现新的表 面共振态;弛豫后费米面处态密度很低,所以表面结构很稳定.
关键词:
密度泛函理论
表面几何结构
表面电子结构
PbTe 相似文献
998.
999.
1000.
In this paper, an electromechanical coupled nonlinear dynamic equation of a microbeam under an electrostatic force is presented.
Using the nonlinear dynamic equations and perturbation method, we investigated nonlinear free vibrations, forced responses
far from and near to natural frequency, respectively. Nonlinear natural frequencies and vibrating amplitudes of the electromechanical
coupled microbeam are dependent on the mechanical and electric parameters. Compared with linear forced responses, the obvious
shift of the mean dynamic response occurs. Under certain condition, the jump phenomenon will occur. The studies can be used
to design parameters of the microbeam and remove undesirable dynamic behavior such as jump phenomenon, etc. 相似文献