单分散聚苯乙烯颗粒的制备及其胶体晶体微球的组装

采用无皂乳液聚合技术,以过硫酸钾(KPS)为引发剂、碳酸氢钠(NaHCO3)为缓冲剂、丙烯酸(AA)为共聚单体制备了表面含羧基的单分散聚苯乙烯(PS)颗粒。用悬浮液滴蒸发自组装技术制备了三维有序胶体晶体微球。采用傅立叶变换红外光谱(FT-IR)和扫描电子显微镜(SEM)对样品结构和形貌进行表征。结果表明,聚苯乙烯颗粒粒径分布均匀,单分散性好且具有良好的球形度,丙烯酸的共聚使颗粒带有羧基而实现功能化改性。离子强度、引发剂浓度和共聚单体浓度是影响聚苯乙烯颗粒尺寸大小的重要因素。胶体晶体呈规则球形,聚苯乙烯颗粒紧密排列,形成面心立方(fcc)结构,表面表现为六方紧密有序排列。     

SiO2胶体晶体的自组装结构及其带隙特征

光子晶体是一种具有光子带隙的新型功能材料.利用垂直沉积自组装法制成SiO2胶体晶体,并利用扫描电子显微镜和紫外分光度计对胶体晶体的显微形貌和光学特征进行了研究.结果表明,利用垂直沉积法自组装得到的SiO2胶体晶体具有面心立方结构;在可见光波段,胶体晶体在＜111＞面方向存在光子带隙.     

聚苯乙烯蓝色胶体晶体膜的制备工艺

本文以单分散的粒径为340±10nm的聚苯乙烯微球为原料,采用垂直自组装法制备了蓝色聚苯乙烯胶体晶体膜。研究了乳液浓度、干燥温度、组装容积等因素对聚苯乙烯胶体晶体膜的微观形貌和呈色性能的影响。结果表明:当乳液浓度较小时,微球呈现单层均匀分布,局部发生自组装,当乳液浓度达到0.1wt%时,微球呈现多层密排六方排列,宏观上呈现明亮的蓝色。当干燥温度为40℃时,该胶体晶体膜微观形貌为高质量的密排六方结构,呈现均匀明亮的蓝色。对比试验得出,在50mL的容器中,PS微球容易发生自组装且呈现明亮均匀的蓝色。同时发现,该胶体晶体膜在较低强度的光线下呈色比较微弱,蓝色饱和度较低,在强烈的光照下,呈现出绚丽的蓝色。     

二维胶体晶体成形及应用研究进展

综述了二维胶体晶体的结构特点及成形驱动力,介绍了LB(Langmuir-Blodgett)转移法、毛细组装法、电场沉积组装法、特殊装置组装法等二维胶体晶体成形方法的原理、成形过程及优缺点,同时概述了二维胶体晶体在微加工及微图案化、纳米传感器、纳米磁存储等领域的应用情况。     

单分散聚苯乙烯微球的制备及二维胶体晶体的自组装

以苯乙烯为原料、过硫酸钾为引发剂,采用无皂乳液聚合法成功地制备出具有良好球形度的单分散聚苯乙烯微球.研究了在聚苯乙烯微球合成过程中单体浓度、引发剂浓度、聚合时间对粒径及分布的影响.实验结果表明,适当改变单体浓度、引发剂浓度、聚合时间可以得到不同粒径的聚苯乙烯微球,且微球单分散性良好.采用自组装技术组装单分散聚苯乙烯微球,获得了二维有序聚苯乙烯胶体晶体.     

二氧化硅胶体球的制备、改性及其胶体晶体的组装

采用改进的St(O)ber法制备了单分散性较好、表面光滑的SiO2球形颗粒,将丁二酸化学键合于SiO2胶体球表面以提高其Zeta电势,再采用垂直沉积法在水溶液中制备出SiO2胶体晶体.通过X射线衍射仪、场发射扫描电子显微镜(SEM)和Zeta电位粒度仪对颗粒和胶体晶体的晶型、显微形貌、电学性能进行测试分析.结果表明:所...     

氘代聚苯乙烯胶体晶体的制备及光学性质研究

以水作为介质合成了高度单分散的氘代聚苯乙烯微球,并利用垂直沉积法制备了高质量的氘代聚苯乙烯胶体晶体.傅立叶变换红外光谱清楚地表明氘代苯乙烯单体发生了聚合反应;扫描电镜表面分析展示出胶体微球的高度有序排列,断面分析表明氘代聚苯乙烯胶体晶体为面心立方结构;光学透射谱显示出氘代聚苯乙烯胶体晶体的高次布拉格衍射特征,通过和理论计算的能带结构对比,进一步证实了氘代聚苯乙烯胶体晶体为面心立方结构;变角度光学透射谱测量显示,随着入射角的增大,(111)面的衍射峰蓝移,而(200)和(220)面的衍射峰发生红移.     

单分散SiO2胶体球制备及其胶体晶体组装

运用胶体化学法在乙醇介质中合成SiO2胶体球,将制得的样品在30℃下用双氧水浸泡处理48h.用扫描电子显微镜(SEM)、傅立叶红外光谱(FT-TR)、Zeta电位仪和标准氢氧化钠滴定法对其形貌、结构和表面电学性质进行分析.结果表明样品平均粒径为292nm,平均标准偏差小于5%;经双氧水浸泡处理后,SiO2胶体球表面羟基数目增多,在水溶液中的Zeta电位从-55.72mV提高到-63.26mV,表面电荷密度从0.19μC/cm2提高到0.28μC/cm2.通过垂直沉积法,在40℃和60%相对湿度条件下制备出有序性较好、密排结构的SiO2胶体晶体.在SEM下,观察到这种胶体晶体是面心立方(fcc)密排结构,其(111)晶面平行于基底.透射光谱表明,所制备的胶体晶体在(111)方向具有光子晶体的不完全带隙性质.     

聚苯乙烯-银胶体晶体的制备及自组装行为

利用冠醚可与银离子复合的特性,制备了聚苯乙烯-冠醚乳胶粒,采用原位还原的方法在乳胶粒表面引入银纳米颗粒,通过垂直沉降,乳胶粒子可自组装成紧密堆积具有面心立方的聚苯乙烯-银胶体晶体。结果表明:引入聚苯乙烯-银乳胶粒表面的银为胶粒总质量的6.7%,乳胶粒具有以银纳米颗粒为壳,聚苯乙烯为核的核壳结构,乳胶粒大小为260 nm,并具有很好的单分散性。由于Bragg散射,该胶体晶带隙位于580 nm,在可见光区域产生明显的光子带隙而呈现出亮丽的绿色。     

双基片垂直沉降法自组装二氧化硅胶体晶体

采用St(o)ber法制备了适于自组装的单分散性的SiO2球体颗粒,再采用双基片垂直沉积法在无水乙醇中制备出SiO2胶体晶体.通过X射线衍射仪和场发射扫描电子显微镜(SEM)对胶体晶体的晶型和显微形貌进行测试分析.结果表明:所得SiO2球体颗粒为无定形态,粒径为70～380nm,粒径随着氨水浓度的增大而增大;随着双基片间距增大,胶体晶体周期性排列越紧密有序,相同基片间距下,双尺寸胶体晶体更难以获得.     

Fabrication of polystyrene colloidal crystal film by electrophoretic deposition

Proper conditions for the formation of a colloidal crystal film by the electrophoretic deposition process were investigated in detail using monodisperse polystyrene (PS) colloidal spheres. Removal of the ionic contaminants and application of a pulsed current were effective in suppressing the electrolysis of water and obtaining a uniform film, but it was not possible to obtain colloidal crystals in which the particles were closely and periodically packed. Mixing EtOH at a high concentration with an aqueous PS suspension and withdrawing the substrate from the suspension at a moderate rate after the EPD process were found to be the key for the successful fabrication of colloidal crystal films. It was demonstrated that the formation of large area colloidal crystal films by the EPD technique was also possible. The advantage of the EPD process for scale up was successfully shown, taking into account the fast film fabrication rate.     

Measurement of polystyrene photodegradation rate using a quartz crystal microbalance

Polystyrene is a very popular polymer utilised in the manufacture of various consumer products. This polymer is very cheap; however, after its usage, the slowness of its photodegradation leads to environmental pollution. In this report, the author presents a technique to systematically measure the rate of photodegradation of a thin polystyrene film. The said film was made to coat a quartz crystal microbalance (QCM) sensor. In order to detect polymer degradation and the reduction in the molecular weight, the resonance frequency of the sensor was monitored for 24 h. Results revealed that QCM sensor irradiation with ultraviolet light with a wavelength of 365 nm and optical power of 1.5 mW caused a quite significant change in the polymer structure.     

PS微球的制备及三维胶晶模板的组装和应用

研究了PS微球合成中单体、引发剂和乳化剂浓度以及聚合温度对粒径及分布的影响。采用高速离心沉淀法、恒温加热蒸发诱导法和自然沉降法对单分散PS微球进行了组装,得PS胶体晶体模板,并以其为模板制备了锂离子筛前驱体Li4Mn5O12。用纳米粒度及ZETA电位分析仪、扫描电子显微镜(SEM)、饱和交换容量等表征了材料的粒径及分布、形貌、结构和离子交换性能。结果表明:通过控制反应条件可以在一定范围内制得粒径均一、单分散性好、表面规整光滑的PS微球;PS胶体晶体模板三维有序,排列规整;酸改性后的离子筛前驱体对Li+饱和交换容量为7.49mol/g锂离子筛。     

The near field properties of colloidal polystyrene microspheres on silicon

We have investigated the optical resonance and near field inside and under absorptive polystyrene (PS) microspheres on Si wafers. Near field flat plane images of PS microspheres were numerically simulated. Nanostructures were prepared on Si substrates using the regular two dimensional (2D) arrays by a single pulsed laser irradiation (KrF, lambda = 248 nm). Periodical PS nanoparticle, PS nanoflowers and Si nanobumps were fabricated by different laser fluence. Mechanisms for PS particle size reduction and Si nanobump formation by laser irradiation were discussed on the base of the theoretical calculations. Good agreement between theoretical calculations and experimental results has been observed.     

Influence of thermal treatment conditions on two-dimensional crystal growth of nanocrystal corundum abrasives

The effect of thermal treatment on mechanical property and microstructure evolution in two-dimension of nanocrystal corundum abrasives has been investigated. The abrasives with and without presence of bond were calcined at different thermal treatment temperatures. The results indicated that thermal treatment conditions had obvious influence on crystal size and mechanical strength of corundum abrasives. Crystal size increased with increasing of the calcining temperature, and crystal growth of sample with presence of bond was more remarkable than that without presence of bond. And it was found that 950 °C is the critical temperature of abnormal crystal growth of corundum abrasives in the heated treatment conditions. Beyond this critical temperature, crystal size evidently increased while strength and wear resistance of abrasive decreased. In this case, the degradation of the abrasive in microstructure and strength should be important considerations for the preparation of ceramic corundum abrasive grinding tool.     

On the parameters influencing the deposition of polystyrene colloidal crystals

Colloidal crystals of polystyrene particles of 1.0, 1.4 and 2.8 μm diameter have been prepared by vertical deposition. The influence of parameters such as temperature, particle size and concentration as well as dispersion medium has been studied. The size of domain and the crystalline structure of the particle arrays have been analyzed by optical microscopy. The quality of the crystals has been improved (minimizing cracks) by controlling sedimentation (density matching), evaporation (volatility of the medium) and drying (co-solvents).     

Design of two-dimensional polarization-selective diffractive optical elements with form-birefringent microstructures

We describe a design methodology for synthesizing polarization-sensitive diffractive optical elements based on two-dimensional form-birefringent microstructures. Our technique yields a single binary element capable of producing independent phase transformations for horizontally and vertically polarized illumination. We designed two elements for operation at 10.6 microm and fabricated them in silicon. Qualitative experimental results agree with design predictions.