可分散性纳米二氧化硅

河南王屋纳米科技有限责任公司采用液相原位表面修饰技术，开发出可分散性纳米二氧化硅（特种白炭黑）粉体系列产品，在甲苯、二氯乙烷、增塑剂、胶粘剂、密封剂、涂料、油墨、树脂等中许多有机介质具有良好的分散性及分散稳定性，外观呈现类真溶液状态。可分散性纳米二氧化硅微粒分为DNS和RNS系列，其中DNS系列为饱合有机碳链或聚合物修饰的二氧化硅；     

几丁聚糖纳米颗粒的动态光散射研究

利用离子凝胶法制备几丁聚糖纳米颗粒,并用动态光散射测量所得颗粒的粒径分布与界面电位。研究结果发现,随着CS/TPP比值的减小,几丁聚糖纳米颗粒的粒径由单峰分布转变为双峰分布,说明三聚磷酸钠含量的增加会使几丁聚糖纳米颗粒之间产生聚集效应。界面电位值随着CS/TPP比值的减小而逐渐下降,原因是三聚磷酸钠浓度的增加使几丁聚糖纳米颗粒表面上更多的NH3+离子与三聚磷酸根离子反应中和的缘故。     

PVP调控制备单分散性的二氧化硅纳米粒子

通过一种简便的PVP调控法,制备了不同粒径的单分散性的二氧化硅纳米粒子(Si O2NPs)。利用PVP加入量的不同,所制备的Si O2NPs粒径分别约为150 nm、400 nm和600 nm,并且所得产物都有很好的单分散性和良好的水分散性,其中粒径150 nm的Si O2NPs是非常合适的药物载体,具有在癌症化疗领域的应用潜力。通过傅立叶变换红外光谱和热重分析可知,这种Si O2NPs是由PVP和Si O2共同构成的纳米复合材料,PVP含量约为总质量的12.9 wt%。     

光纤后向动态光散射测量纳米颗粒的浓度适用范围研究

常用的动态光散射法在测量高浓度纳米颗粒时需要充分稀释样品,避免多次散射效应,以得到准确的测量结果。基于单模光纤后向动态光散射原理发展了一套光纤后向动态光散射测量装置,利用单根单模光纤同时发射激光与接收散射光来抑制多次散射,无须稀释样品,实现了高浓度纳米颗粒粒度的直接测量。为确定该测量方法的浓度适用范围,开展了理论与实验研究。首先,理论分析了不同粒径的颗粒散射平均自由程与体积浓度的关系,并根据该装置的散射区域特性计算了理论测量浓度上限。其次,利用该装置对不同粒径纳米颗粒多种体积浓度的样品进行了颗粒粒度测量。理论与实验结果表明,随着粒径的增加,测量浓度的上限降低,二者趋势一致,但在颗粒大于300 nm后实验结果与理论分析结果的偏差逐渐增大,实验浓度略低于理论浓度1%～2%(体积)。     

动态光散射研究温度对SBS胶束动力学行为的影响

动态光散射研究了温度对ＳＢＳ胶束动力学行为的影响。结果发现,随温度升高胶束的散射光强度下降和单分子的散射光强度增加,表明胶束逐渐解缔合成单分子,并存在一个临界胶束温度（ＣＭＴ）;当温度大于ＣＭＴ,胶束全部解缔合成单分子。     

纳米粒子光散射探针在药物分析中的应用

综述了近年来纳米粒子作为共振光散射探针在药物分析中的研究进展,展望了纳米粒子共振光散射探针应用于药物分析的未来发展方向。     

基于动态光散射的溶菌酶水力学直径研究

采用Zeta电位和粒度分析仪测量了溶菌酶的水力学直径,研究了pH值、离子强度和脲浓度对其大小的影响.随着 pH值增加,溶菌酶的水力学直径呈” W”形分布;在极端的碱性条件下,溶菌酶水力学直径随离子强度的增加而显著变大;中性pH值时,水力学直径随离子强度的增加变化不大.脲对溶菌酶具有双重作用,随着溶液中脲浓度的增加,溶菌酶的水力学直径先减小后增大.结果表明,动态光散射技术可以很好地应用于研究蛋白质分子的均一性和稳定性,同时也可以通过水力学直径来表征pH值、离子强度和脲对溶菌酶的影响.     

粒子分散性对环氧树脂/纳米SiO2材料性能的影响

通过原位分散聚合法制得了环氧树脂／纳米SiO2复合材料。采用超声波和偶联剂改善了纳米SiO2在基体中的分散性，利用拉伸实验、冲击实验、扫描电子显微镜、热重法等方法研究了粒子分散性对复合材料结构和性能的影响。结果表明：超声波和偶联剂都能使纳米SiO2均匀地分散在环氧树脂基体中，有效地增加复合材料的力学强度及韧性，并能提高材料的耐热性。对于提高纳米SiO2在环氧树脂中的分散均匀性，超声波的作用优于偶联剂。     

Microgelation of unsaturated polyester resins by static and dynamic light scattering

The microgelation phenomenon during the curing of unsaturated polyester resin was investigated by both static and dynamic light scattering before gelation. The results of static light scattering revealed that the polymer molecular weight increased with degree of curing. The second virial coefficient, A₂, decreased slowly in the initial stage of curing and decreased dramatically at a conversion around α ∼ 8.7%, indicating a drastic decrease of compatibility between the polyesters and styrene. Two modes of the size distribution of the microgel particles during curing were observed by dynamic light scattering. The small particles consist of primary unsaturated polyester molecules. The large ones consist of microgel particles formed by linking adjacent polyester molecules. The sizes of the microgel particles increased in the initial stage of curing, then decreased slightly at a conversion of α ∼ 8.7%, which was due to the intramolecular crosslink reaction of the microgel particles. The experimental results revealed that the compatibility between polyesters and the styrene monomer became worse as the intramolecular crosslinking reaction inside the microgel particles caused a tight packing of the micro-gel molecules. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 871–878, 1998     

Real-time dynamic light scattering on gelation and vitrification

The time-resolved dynamic light scattering has been employed to investigate gelation of divinylbenzene (DVB; branched chains) and vitrification of styrene (St; linear chains) during radical polymerization in bulk. The intensity correlation function (ICF) was obtained every 30 s during polymerization process. The DVB system exhibited a power law behavior in ICF characteristic of gelation threshold, which was followed by vitrification. In the case of St, two relaxation modes appeared before vitrification, which were assigned to be the cooperative and the slow relaxation modes.     

Distribution analyses of multi-modal dynamic light scattering data

A method of data analysis for dynamic light scattering is proposed to evaluate the weight fraction, w(R_h), of a small amount of large aggregates in a dilute solution, where R_h is the hydrodynamic radius. We examined the time-correlation function of scattering intensity for model multi-modal systems, i.e., mixtures of latex solutions having different particle sizes and of polystyrene standard solutions having different molecular weights, by properly taking into account the unknown fractions, w(R_h), and scattering intensities of individual components. We derived an equation to evaluate the weight fractions of the components. The validity of this method was verified by successfully reconstructing the observed correlation functions having fast and slow modes. As a demonstration, the fraction of aggregates in a thermosensitive polymer solution in water was evaluated as a function of temperature.     

Dissolution and enzymatic hydrolysis of casein micelles studied by dynamic light scattering

The effects of temperature, ionic strength, and enzymatic hydrolysis on the average hydrodynamic radius (R _h) of casein micelles in phosphate buffer were studied by using dynamic light scattering. The results showed that the average R _h value of casein micelles decreased irreversibly during the heating, decreased with the increase of ionic strength in lower ionic strength solution (less than 0.05 mol/L), but opposite in higher ionic strength solution (above 0.1 mol/L). The R _h value of casein increased rapidly during the process of enzymatic hydrolysis, and the structural model of casein micelles in the enzymatic hydrolysis process was also proposed, i.e. the casein micelle changed from compact sphere into unfolded and regularly flocky peptides. Translated from The Chinese Journal of Process Engineering, 2006, 6(4), 615–618 [译自: 过程工程学报]     

大豆分离蛋白及其与丙烯酸接枝产物在不同pH值水相中的动态光散射研究

利用动态光散射技术,研究了大豆分离蛋白及其与丙烯酸接枝共聚物在水相体系中对pH值的响应性。结果发现,大豆分离蛋白和接枝产物对水相pH值都具有很高的响应性。大豆分离蛋白平均流体力学半径在等电点附近(pH=4~5)达到最大值。接枝率为27.5%的丙烯酸的接枝共聚物的平均流体力学半径在pH为2~3范围内最大。随着接枝率增加,丙烯酸的接枝共聚物在水相体系中的溶解性能越好。对接枝产物不同pH值水溶液进行研究具有很大的理论指导意义。     

激光衍射光散射法在聚氯乙烯树脂粒度分析中的应用

主要介绍激光衍射光散射法在聚氯乙烯树脂粒度分析中的应用。并与筛分法对照,比较了两种方法测得样品的平均粒径,分布宽度,三目集中率,同时论述了颗粒形态与加工性能之间的关系。     

Viscoelastic characterization of moderately concentrated polystyrene solutions by dynamic light scattering

The dynamic light scattering measurements were performed for moderately concentrated entangled solutions of atactic polystyrene in benzene (BZ) at 25.0 °C, in cyclohexane (CH) at 34.5 °C (Θ), and in diethyl malonate (DEM) at 35.0 °C (Θ) to characterize their viscoelastic properties. The results have shown that while the mutual diffusion coefficient D increases in the BZ solutions and decreases in the CH and DEM solutions with increasing polymer mass concentration c, the friction coefficient ζ for the three solutions increases with c showing the same power-law behavior irrespective of the weight-average molecular weight M_w and solvent quality. It has been found that the instantaneous longitudinal modulus L₀ for the CH and DEM solutions increases in proportion to c², obeying the familiar relation for the plateau value (4/3)G_N of the longitudinal stress relaxation modulus, but the L₀ values for these solutions are somewhat smaller than the values predicted from the relation. The terminal relaxation time τ_m for the two Θ solvent systems has been found to follow the power-law τ_m∝c^2.7, showing good correspondence to the relation established by rheological measurements.     

Microgelation of unsaturated polyester resins in the presence of poly(vinyl acetate) by static and dynamic light scattering

The partially cured unsaturated polyester (UPE)/styrene resins with various degrees of conversion lower than gel conversion blended with PVAc and 2‐fluorotoluene solvent were investigated using both static and dynamic light scattering (SLS and DLS). The solvent (i.e., 2‐fluorotoluene) is isorefractive with PVAc; thus, one sees only primary and partially cured UPEs in light‐scattering experiments. DLS was used to follow the variations of primary UPE and UPE microgel particle sizes, and SLS was used to follow the variations of UPE molecular weight, second virial coefficient (A₂), anisosymmetry (ρ_v), and differential index refraction (dn/dC) with degree of UPE conversion and PVAc concentration. The experimental data showed that, at a fixed degree of UPE/styrene conversion, increasing PVAc concentration in the UPE/styrene system caused decreases in dn/dC, A₂, ρ_v, and particle sizes of UPE microgels. These results suggest that mixing PVAc into UPE/styrene resins causes an increase in the compactness of UPE coils and favors intramolecular UPE/styrene cyclization in the early stage of curing. Thus A₂, ρ_v, and particle sizes of microgels decreased with increasing PVAc concentration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1439–1449, 2001     

Determination of polystyrene-carbon dioxide-decahydronaphthalene solution properties by high pressure dynamic light scattering

The diffusion coefficients of polystyrene (PS) in decahydronaphthalene (DHN) and in solutions of carbon dioxide (CO₂) and DHN were measured for dilute PS solutions over a range of temperatures and CO₂-DHN ratios using high pressure dynamic light scattering. Infinite dilution diffusion coefficients (D₀) of PS and dynamic second virial coefficients (k_D) were determined for essentially monodisperse 308 kDa PS. At a system pressure of 20.7 MPa, PS diffusion coefficients increased by a factor of 2.5, and the activation energy of diffusion decreased by approximately 16% when DHN was “expanded” with 44 mol% CO₂. However, the hydrodynamic radius of PS at a given temperature was not particularly sensitive to the CO₂ concentration. Solvent quality, as measured by k_D, decreased at higher CO₂ concentrations. The addition of CO₂ to polymer solutions may offer a way to “tune” the properties of the solution to facilitate the heterogeneous catalytic hydrogenation of polymers.     

Characterization of magnetic nanoparticle by dynamic light scattering

Here we provide a complete review on the use of dynamic light scattering (DLS) to study the size distribution and colloidal stability of magnetic nanoparticles (MNPs). The mathematical analysis involved in obtaining size information from the correlation function and the calculation of Z-average are introduced. Contributions from various variables, such as surface coating, size differences, and concentration of particles, are elaborated within the context of measurement data. Comparison with other sizing techniques, such as transmission electron microscopy and dark-field microscopy, revealed both the advantages and disadvantages of DLS in measuring the size of magnetic nanoparticles. The self-assembly process of MNP with anisotropic structure can also be monitored effectively by DLS.