排序方式: 共有23条查询结果,搜索用时 312 毫秒
11.
本文综述了“双亲性”嵌段共聚物在选择性溶剂中胶束行为和胶束形貌的主要影响因素,包括溶液温度、选择性溶剂种类、嵌段长度、链段结晶、链段与溶剂间氢键作用以及共聚物浓度对胶束最终形貌产生影响的因素;系统介绍了对嵌段共聚物胶束形貌进行调控的实验方法;在此同时介绍了对环境刺激如温度和pH变化等具有响应性能的“双亲性”嵌段共聚物在选择性溶剂中胶束行为研究的最新进展;最后提出了该研究领域目前存在的问题和今后的可能发展方向。 相似文献
12.
Zhang P Qian J An Q Du B Liu X Zhao Q 《Langmuir : the ACS journal of surfaces and colloids》2008,24(5):2110-2117
Two sulfonated poly(sulphone) sodium salts (SPSF) with different molecular weights and ionic exchange capacities in a N,N-dimethyl formamide/water (DMF-H2O) mixed solvent with various DMF contents were selected as a model system for investigating the influences of solvent composition, solution properties, and charge density of polyelectrolytes on the layer-by-layer (LbL) self-assembly of water-insoluble polyelectrolytes. Poly(dimethyldiallylammonium chloride) (PDDA) in aqueous solution was used as the counterpart. The PDDA/SPSF multilayer films grew nearly linearly with the layer numbers regardless of the volume fraction of DMF, phiDMF, in the SPSF solutions. The total absorption amount of the PDDA/SPSF multilayer films was strongly dependent on the charge density of the SPSF molecules and the phiDMF value of the SPSF solutions. Minimum values of absorption amount were observed at phiDMF = 0.6 to approximately 0.7. The surface hydrophobicity and roughness of the multilayer films can be tuned by varying phiDMF. These observations were rationalized in terms of the chain dimension and the ionization degree of the SPSF molecules as a function of phiDMF, which was characterized by the intrinsic viscosity ([eta]SPSF) and conductivity (LSPSF) of the SPSF solutions. The results indicate that the molecular structures of the DMF-H2O mixed solvent strongly affect the solution properties of SPSF, which in turn determine the growth behavior and physical properties of the PDDA/SPSF multilayer films. 相似文献
13.
Kashimoto K Yoon J Hou B Chen CH Lin B Aratono M Takiue T Schlossman ML 《Physical review letters》2008,101(7):076102
The results of x-ray reflectivity studies of two oil/water (liquid/liquid) interfaces are inconsistent with recent predictions of the presence of a vaporlike depletion region at hydrophobic/aqueous interfaces. One of the oils, perfluorohexane, is a fluorocarbon whose superhydrophobic interface with water provides a stringent test for the presence of a depletion layer. The other oil, heptane, is a hydrocarbon and, therefore, is more relevant to the study of biomolecular hydrophobicity. These results are consistent with the subangstrom proximity of water to soft hydrophobic materials. 相似文献
14.
Effects of laterally heterogeneous slip on the resonance properties of quartz crystals immersed in liquids 总被引:1,自引:0,他引:1
Du B Goubaidoulline I Johannsmann D 《Langmuir : the ACS journal of surfaces and colloids》2004,20(24):10617-10624
A formalism is presented which predicts the influence of laterally heterogeneous slip (for instance, induced by nanoscopic air bubbles) on the shift of the resonance frequency and bandwidth of quartz crystal resonators immersed in liquids. The lateral heterogeneities are decomposed into their Fourier components. The distribution of slip lengths provides a boundary condition, giving rise to a small, secondary flow field. The mean stress exerted by this secondary field induces a shift in resonance frequency and bandwidth. If the slip length is much smaller than the penetration depth of the shear waves and smaller than the lateral correlation length, one finds that the effects of the heterogeneities scale as n(3/2), with n being the overtone order. The frequency, f, and half-band-half-width, Gamma, decrease by the same amount. These calculations match experimental results obtained with a gold-coated resonator in contact with various hydrophilic liquids. 相似文献
15.
16.
For a thin viscoelastic film deposited on a quartz crystal microbalance in a liquid environment, the change in dissipation induced by the presence of a film is proportional to the film's elastic compliance, Jf'. This surprising result is a consequence of the fact that the film is "clamped" by a viscous fluid. 相似文献
17.
Hu Z Huang H Zhang F Du B He T 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3271-3277
The molecular chain and lamellar crystal orientation in ultrathin films (thickness < 100 nm) of poly-(di-n-hexylsilane) (PDHS) on silicon wafer substrates have been investigated by using transmission electronic microscopy, wide-angle X-ray diffraction, atomic force microscopy, and UV absorption spectroscopy. PDHS showed a film thickness-dependent molecular chain and lamellar crystal orientation. Lamellar crystals grew preferentially in flat-on orientation in the monolayer ultrathin films of PDHS, i.e., the silicon backbones were oriented along the surface-normal direction. By contrast, the orientation of lamellar crystals was preferentially edge-on in ultrathin films thicker than ca. 13 nm, i.e., the silicon backbones were oriented parallel to the substrate surface. We interpret the different orientations of molecular chain and lamellar crystal as due to the reduction of the entropy of the polymer chain near the substrate surface and the particularity of the crystallographic (001) plane of flat-on lamellae, respectively. A remarkable influence of the orientations of the silicon backbone on the UV absorption of these PDHS ultrathin films was observed due to the one-dimensional nature of sigma-electrons delocalized along the silicon backbone. With the silicon backbones perpendicular or parallel to the surface of the substrate, the UV absorbance increased or decreased with an increase of the angle between the incident UV beam direction and direction normal to the thin film, respectively. 相似文献
18.
Guo L Nie J Du B Peng Z Tesche B Kleinermanns K 《Journal of colloid and interface science》2008,319(1):175-181
Silver nanoparticles (Ag NPs) stabilized by a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), have been synthesized by the reduction of silver ions with NaBH(4) in aqueous solutions. The obtained Ag NPs are very stable at room temperature due to the extended coil conformation of the PNIPAM chain at temperatures below its volume phase transition temperature ( approximately 32 degrees C). At higher temperatures (such as 45 degrees C) above the phase transition of PNIPAM, only minute aggregation between Ag NPs was observed, showing that the collapsed PNIPAM chains still retain the ability to stabilize Ag NPs. The PNIPAM-stabilized Ag NPs were then characterized as a function of the thermal phase transition of PNIPAM by UV-vis spectroscopy, dynamic light scattering, transmission electron microscopy, and cyclic voltammeter. Consistent results were obtained showing that the phase transition of PNIPAM has some effect on the optical properties of Ag NPs. Switchable electrochemical response of the PNIPAM-stabilized Ag NPs triggered by temperature change was observed. 相似文献
19.
Jia Gao Kun An Chao Lv Jingjing Nie Junting Xu Binyang Du 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2318-2328
A series of linear symmetrical ABCBA pentablock terpolymers, poly(tert-butyl acrylate)-b-polystyrene-b-poly(ethylene oxide)-b-polystyrene-b-poly(tert-butyl acrylate) with constant lengths of PS and PEO blocks but different degree of polymerization x of PtBA block, namely PtBAx-b-PS130-b-PEO90-b-PS130-b-PtBAx (x = 40, 75, 100, 165, and 200), were found to form various vesicular nanostructures in dilute aqueous solution as observed by conventional transition electron microscopy (TEM), cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy (SEM). Genus vesicles with nanometer sizes and various genus values (g), including individual spherical vesicles, tubular vesicles (g = 0), toroidal vesicles (g = 1) and the vesicles with even larger g values (g > 1) were observed, respectively. The g value of genus vesicles formed by PtBAx-b-PS130-b-PEO90-b-PS130-b-PtBAx pentablock terpolymers decreased with the increasing length of PtBA block. The formation mechanism of genus vesicles was preliminarily discussed by the combination of membrane bending energy, the area-difference-elasticity and the edge effect. 相似文献
20.