Pickering乳液聚合制备核-壳结构PS-SiO2复合微球

用二氯二甲基硅烷对纳米SiO2粒子进行疏水改性,当其表面Zeta电位由-54.8 mV变成-25.8 mV时,SiO2粒子就能在苯乙烯-水界面自组装,形成稳定的Pickering乳液,即以胶体粒子为乳化剂的乳液.利用Pickering乳液聚合制备了以聚苯乙烯(PS)为核、纳米SiO2为壳的PS-SiO2复合微球.用FT-IR、XPS、SEM、偏光显微镜等对复合微球进行了表征.结果表明:复合微球由聚苯乙烯和纳米二氧化硅粒子组成,二氧化硅粒子以单层、六方密排的方式分布在聚苯乙烯微球表面.     

软颗粒在液-液界面吸附及界面催化

正Pickering乳液是由吸附在水油两相界面上的颗粒稳定的乳状液,而这些颗粒的界面脱附往往需要很高的热力学脱附能,使得Pickering乳液具有良好的稳定性~1。相比于传统的表面活性剂稳定的乳液,颗粒在液液界面的存在不仅有效阻止了乳滴间的聚结合并,还赋予了乳液环境响应性,如pH、温度~2。因此,Pickering乳液被广泛应用于医药、催化、材料、能源、食品等领域~(3–5)。诸多颗粒被证明可以作为Pickering乳液的乳化剂,如二氧化硅纳米球、聚苯乙烯微球、碳酸钙颗粒等。除此以外,软颗粒稳定的Pickering乳液越来越引起了研究者的兴趣,而最具代表性的便是微凝胶粒子(microgel) ~6和蛋白质颗粒。     

Pickering乳滴模板法制备超粒子结构有机/无机杂化微球

Pickering乳滴模板法制备有机/无机杂化的核壳微球越来越引起人们的关注,主要因为该方法制备出的微球具有以无机粒子为壳层的超粒子结构(supracolloidal structure),能够赋予微球独特的功能.胶体粒子在乳滴表面自组装形成有序的球面胶体壳,得到稳定Pickering乳液,固定乳滴表面的胶体粒子来制备核壳结构的微球或者以胶体粒子为壳层的微胶囊(colloidosome).本文综述了我们课题组以Pickering乳滴模板法制备超粒子结构有机/无机杂化微胶囊包括实心微球方面的工作.我们选择具有不同性能、种类的胶体粒子以及具有不同性质和功能的核材料,采用Pickering乳滴模板法,对吸附在乳滴表面的胶体粒子用不同的固定方法制备具有不同结构和性能的微球和微胶囊,利用基于多重Pickering乳液的聚合技术制备双纳米复合的超粒子结构多核聚合物微球.     

以单分散P(DC-TMPTA)聚合物微球为Pickering乳液稳定剂制备石蜡乳液和石蜡微球

以三羟甲基丙烷三丙烯酸酯(TMPTA)和1-十二烯(DC)为单体,不使用任何乳化剂或分散稳定剂,通过沉淀聚合制备了高度单分散P(DC-TMPTA)的聚合物微球颗粒.以此聚合物微粒为Pickering稳定剂,不添加任何化学助剂,以乙醇-水混合介质在70℃下通过恒速振荡制得了单分散石蜡Pickering乳液.将该体系迅速降温至石蜡熔点之下,制得了窄分布的固体石蜡微球.研究了连续相水含量、振荡频率及稳定粒子尺寸对Pickering乳液及石蜡微球的影响,优化了石蜡乳液和微球的制备条件.利用扫描电子显微镜对石蜡微球的表面和内部形貌进行了表征,结果表明P(DC-TMPTA)微球全部聚集在石蜡液滴和固化后的石蜡微球表面.基于石蜡微球和聚合物稳定粒子的尺寸,计算了不同条件下石蜡微球表面聚合物粒子的数量.通过聚合物粒子在石蜡-乙醇和水混合溶液界面的三相接触角以及石蜡-乙醇和水混合溶液界面张力的测定,计算了聚合物粒子在石蜡-乙醇和水混合溶液界面吸附能,为解释该体系Pickering乳液的稳定性提供了理论支持.     

纳米粒子稳定乳液及其在纳米结构合成中的应用*

本文在介绍常规乳状液、微乳液和固体稳定乳液的基础上,着重综述了纳米粒子稳定乳液的特点及其在纳米结构合成中的应用进展,并对目前该研究领域亟待解决的问题进行了分析。纳米粒子稳定乳液具有独特的油、水、固三相环境和水油、水固、油固三个相界面,分散相液滴尺寸可以在微米、亚微米乃至纳米尺度调节,因而可以作为合成组成、结构和性能极为丰富多样的纳米结构的介质。纳米粒子对乳液稳定作用的机理,以及纳米粒子稳定乳液中化学反应的特殊规律还有待深入研究。本文在介绍固体稳定乳液的基础上,着重综述了纳米粒子稳定乳液的特点及其在纳米结构合成中的应用进展,并对目前该研究领域亟待解决的问题进行了分析。纳米粒子稳定乳液具有独特的油、水、固三相环境和水油、水固、油固三个相界面,分散相液滴尺寸可以在微米、亚微米乃至纳米尺度调节,因而可以作为合成组成、结构和性能极为丰富多样的纳米结构的介质。纳米粒子对乳液稳定作用的机理,以及纳米粒子稳定乳液中化学反应的特殊规律还有待深入研究。     

双球状双亲纳米SiO_2粒子的合成

以纳米SiO_2粒子为原料,六甲基二硅氮杂烷(HMDS)和γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)分别作为亲油改性剂和亲水改性剂,采用溶胶-凝胶法制备了亲油和亲水纳米SiO_2粒子.通过亲油SiO_2和亲水SiO_2粒子表面化学键的偶合,将亲油粒子和亲水粒子偶联,制备了粒径为30 nm的双球状双亲纳米SiO_2粒子.以双球状双亲纳米SiO_2粒子作为稳定剂,制备了环己烷/水Pickering乳液,证明了双球状纳米SiO_2粒子具有较好的双亲性能.     

肉桂酸改性透明质酸颗粒乳化剂的制备及性能

将具有紫外吸收性能的单体肉桂酸(CA)引入天然大分子透明质酸(HA)中,制得疏水性改性HA(HA-CA),然后在二甲亚砜与水的混合溶剂中自组装制备HA-CA胶体粒子,并以之为颗粒乳化剂稳定油水界面制备Pickering乳液。通过紫外、核磁、纳米粒度仪、透射电镜、光学显微镜等方法对HA-CA、HA-CA胶体粒子及其所稳定的乳液进行表征。结果表明,HA-CA可以在选择性溶剂中自组装形成粒径约为95nm的球形胶体粒子;所得的HA-CA胶体粒子可以有效地稳定油/水界面,制备水包油(O/W)型的Pickering乳液,且所得乳液具有良好的耐盐性和细胞相容性;此外该胶体粒子可稳定多种油/水体系,具有一定普适性。     

表面活性剂-纳米粒子协同稳定Pickering乳液的双相反转实验设计

本实验以表面活性剂原位改性纳米粒子协同稳定Pickering乳液为研究对象,通过对乳液的双相反转行为研究,探究表面活性剂分子在纳米粒子表面的吸附模式,加深学生对胶体与界面化学领域相关原理的理解,培养学生综合实验能力和分析推理能力。     

改性海藻酸钠活化SiO2纳米粒子稳定载药Pickering乳液及释药性

以胆固醇疏水改性两亲性海藻酸钠衍生物表面,活化SiO2纳米粒子,再制得负载氯氟氰菊酯的O/W型Pickering乳液.通过傅里叶变换红外光谱(FTIR),氢核磁共振波谱(1H NMR)、荧光光谱、动态光散射、光学显微镜和释药实验分别对海藻酸钠衍生物和Pickering乳液的性能进行了表征.结果表明,胆固醇基接枝到了海藻酸钠分子链上,改性后的海藻酸钠临界聚集浓度由1.26 mg/L降为0.28 mg/L,表现出了良好的两亲性.将海藻酸钠衍生物(CSAD)和表面活性剂十六烷基三甲基溴化铵(CTAB)吸附于SiO2纳米粒子表面,得到活化SiO2纳米粒子,其Zeta电位分别为-30.7和16.4 mV,粒径分别增大到583.3和438.4 nm.由CSAD活化SiO2粒子制备的乳液释药速率更缓慢.CSAD的交联作用使吸附于油水界面的活化SiO2粒子形成了比较稳定的网络结构或界面膜.     

细乳液聚合制备载有CdTe的交联聚苯乙烯荧光微球

利用改进的正相细乳液聚合法, 对疏水的CdTe纳米晶进行包覆, 得到了纳米级的交联聚苯乙烯荧光微球. 研究发现, 较高的引发剂浓度和较高的交联度有利于抑制相分离的发生和荧光的保持. 进而将3-甲基丙烯酰氧基丙基三甲氧基硅烷作为共聚单体, 得到了表面硅羟基功能化的聚苯乙烯荧光微球, 改善了微球在水相中的分散性, 并将此类荧光功能微球成功用于细胞成像.     

加料方式对CuO/ZnO/Al2O3系催化剂前驱体性质的影响

用XRD、TG-DTG、TPR技术研究了不同加料方式对CuO/ZnO/Al2O3系催化剂前驱体物相组成及其结晶情况的影响，用加压微反装置考察了催化剂合成甲醇反应活性。结果表明, 加料方式对Cu2+形成的中间化合物的物相组成及结晶度影响显著,对Zn2+及Al3+的沉淀物相的影响很小。不同加料方式对催化剂前驱体物相组成及催化剂性能的影响主要是形成的初始前驱体中Cu的物相及结晶度不同。正加法主要形成Cu2(OH)3NO3,并流法主要形成无定形Cu2CO3(OH)2,后者与Zn5(CO3)2(OH)6相互作用转化为(Cu,Zn)2CO3(OH)2和（Cu,Zn）5(CO3)2(OH)6，由它们分解形成的CuO-ZnO固溶体是合成甲醇反应的活性相。并流法能最大程度的形成CuO-ZnO固溶体，有利于CuO粒子的细化，其催化活性较好。     

不同载体负载的Cu2(OH)3CI催化剂对甲醇氧化羰基化的催化性能

采用浆液浸渍法制备了小同载体负载的Cu2(OH)3Cl催化剂,考察了催化剂对甲醇氧化羰基化合成碳酸二甲酯(DMC)反应的催化性能.结果表明,各载体负载的Cu2(OH)3Cl催化剂活性均高于传统的负载CuCl2催化剂;以比表面积较大的活性炭(AC)为载体的催化剂活性最高.以Cu2(OH)3Cl/AC(w(Cu)=18.71%)为催化剂时,甲醇转化率、DMC选择性和DMC时宅收率可分别达到6.93%,67.3%和139.1mg/(g·h);其催化性能比较稳定,反应60h后其催化活性略有下降.通过CO程序升温脱附、X射线衍射、X射线光电子能谱和扫描电镜等技术对催化剂进行了表征.结果表明,在反应过程中催化剂的活性物种Cu2(OH)3Cl的晶粒逐渐团聚、长大,并且转化为CuCl2和CuO;同时,新鲜催化剂中唯一的CuⅡ物种部分转化为CuⅠ物种.     

In situ formed Mg(OH)2 nanoparticles as pH-switchable stabilizers for emulsions

Different from traditional methods for preparing pH-switchable Pickering emulsifiers, a simple and straightforward approach is established on the basis of a reversible process between in situ formation and dissolution of Mg(OH)(2) nanoparticles (MHp). It was found that when pH value was above 9.5, emulsions of liquid paraffin-in-water can be stabilized by the resulting surface-active particles. Below this pH, emulsions demulsify, resulting in a reversible Pickering emulsifier. Based on the strongly pH-dependent precipitation of metal hydroxide nanoparticles, this procedure offers a new way to design pH-switchable emulsifiers without aid of any other organic matters.     

Novel Janus Cu2(OH)2CO3/CuS microspheres prepared via a Pickering emulsion route

Janus Cu2(OH)2CO3/CuS microspheres were prepared via a Pickering emulsion route for the first time. By treating the Janus Cu2(OH)2CO3/CuS microspheres with dilute hydrochloric acid, ringent Cu2(OH)2CO3/CuS core/shell microspheres and ringent CuS shells were obtained. The hatch size of the ringent CuS shells increased with the increase of the hydrophobicity of the precursor Cu2(OH)2CO3 microspheres. Scanning electron microscopy, X-ray diffraction, energy dispersion spectra, and particle size analysis were used to characterize the products thus formed.     

Pickering emulsions stabilized by surface-modified Fe3O4 nanoparticles

Unmodified Fe(3)O(4) nanoparticles do not stabilize Pickering emulsions of a polar oil like butyl butyrate. In order to obtain stable emulsions, the Fe(3)O(4) nanoparticles were modified by either carboxylic acid (RCOOH) or silane coupling agents (RSi(OC(2)H(5))(3)) to increase their hydrophobicity. The influence of such surface modification on the stability of the resultant Pickering emulsions was investigated in detail for both a non-polar oil (dodecane) and butyl butyrate in mixtures with water. The stability of dodecane-in-water emulsions in the presence of carboxylic acid-coated particles decreases as the length of the alkyl group (R) and the coating extent increase. However, such particles are incapable of stabilizing butyl butyrate-water emulsions even when the carboxylic acid length is decreased to two. However, the silane-coated Fe(3)O(4) nanoparticles can stabilize butyl butyrate-in-water emulsions, and they also increase the stability of dodecane-in-water emulsions. Thermal gravimetric analysis indicates that the molar quantity of silane reagent is much higher than that of carboxylic acid on nanoparticle surfaces after modification, raising their hydrophobicity and enabling enhanced stability of the resultant polar oil-water emulsions.     

Study of emulsion polymerization stabilized by amphiphilic polymer nanoparticles

Submicron-sized polystyrene (PS) microspheres with a relatively narrow particle size distribution can be easily produced through emulsion polymerization induced by γ-ray at room temperature using a new type of amphiphilic cross-linked poly(stearyl methacrylate-co-acrylamide-co-acrylic acid) particles as stabilizer. The properties of these amphiphilic particles were described, including morphology, size, ζ potential, and contact angles. The effect of the pH value and the content of amphiphilic particles on the formation and stability of emulsions were also investigated. Meanwhile, the obtained PS microspheres were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. In addition, through observing the morphology and size of emulsion droplets at different times under an optical microscope, we found it is interesting that Pickering emulsions formed initially disappeared gradually, which is different from the common Pickering emulsions stabilized by inorganic particles. Thus, the mechanism was further discussed.     

贯通孔道网络结构大孔Al2O3催化材料的制备

采用模板法制备了具有贯通孔道网络结构的大孔Al2O3催化材料. 为确保模板材料的体积分数低于74%时Al2O3孔道的贯通, 设计并实现了模板聚苯乙烯(PS)微球先胶凝再与催化材料Al2O3纳米颗粒复合的制备路线. 通过PS微球悬浮液的流变性表征凝胶状态的形成. 实验结果表明, 加入适当浓度的硝酸铝溶液后PS微球悬浮液出现了由溶胶向凝胶的转变. 通过扫描电镜对大孔Al2O3催化材料的孔道结构进行表征, 结果表明, 与有序大孔材料相比大孔催化材料中孔配位数有所降低, 骨架厚度提高且具有贯通的孔道网络结构. 大孔结构抗压强度实验表明, 随着模板PS微球质量分数的降低, 机械强度明显提高.     

Fabrication of macroporous foam and microspheres of polystyrene by Pickering emulsion polymerization

Poly(styrene-co-methacrylic acid) (PS-co-MAA) particles were synthesized via surfactant-free emulsion polymerization and then used as particulate emulsifiers for preparation of Pickering emulsions. Our results showed that adjusting the solution pH can tune the wettability of PS-co-MAA particles to stabilize either water-in-oil (W/O) or oil-in-water (O/W) Pickering emulsions. Stable W/O emulsions were obtained with PS-co-MAA particles at low pH values due to their better affinity to the dispersed oil phase. In contrast, increasing the pH value significantly changed the stabilizing behavior of the PS-co-MAA particles, leading to the phase inversion and formation of stable O/W emulsions. We found that the oil/water ratio had a significant influence on pH value of the phase inversion. It decreased with decreasing the oil/water ratio, and no phase inversion occurred when the styrene volume fraction reduced to 10 %. Additionally, macroporous polystyrene (PS) foam and PS microspheres were obtained via polymerization of Pickering high internal phase emulsion (Pickering HIPE) and O/W Pickering emulsion, respectively.     

A Study on Kinetics of the Bronze Powder-Corrosion Development

HCl acid was applied to the surface of the self-prepared Cu-Sn-Pb alloy, and the methods of IR-REF, IR-PAS, XRD, SPM, SEM, TEM and pH were employed to study the forming process and the developing speed of the bronze powder-corrosion Cu_2(OH)_3Cl (PC). It is found that the corrosion develops fast in acid environment at room temperature; the corrosion Cu_2(OH)_3Cl with valence Cu~(2+) forms from alloy through the intermediate corrosion CuCl with valence Cu~+; PC is contagious, which can pollute the fresh bronze alloy from the corroded sample by air; when CuCl is oxidized to produce Cu_2(OH)_3Cl, Cu~(2+) cation forms at the same time, and both the oxidizing reactions have zero-order reaction with respect to O_2 in the air; the P1 formation reaction has first-order reaction with respect to Cull; in enormous distilled water Cu_2(OH)_3Cl forms from CuCl through the intermediate product Cu_2O.All the results above are discussed in the present article, and the mechanism of PC formation is studied further. The r     

Synthesis, Characterization, and Photocatalytic Activity of Bi_2O_3

A series of Bi2O3 were prepared by a facile hydrothermal method using NaOH and ammonia as the mineralizers. The products were characterized by XRD, IR, UV-vis diffuse reflectance spectra, and photodegradation of Rhodamine B dye. Simply using NaOH to supply a strong base condition, single phase α-Bi2O3 was formed. When changing the amount of NaOH and ammonia, mixed phases of α-Bi2O3, （BiO）4CO3（OH）2 and Bi2O2CO3 were obtained. All samples were found to show photocatalytic activities towards the degradation of Rhodamine B dye under UV light irradiation, in which mixed phase samples showed higher activities than single phase α-Bi2O3 possibly owing to the synergistic effect of the mixed phases.