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反应性乳化剂存在下半连续苯丙乳液共聚合表观动力学 总被引:1,自引:0,他引:1
研究了在反应性乳化剂SE-10N存在下,采用半连续滴加工艺进行苯丙乳液共聚合的表观动力学.首先利用间歇法研究了引发剂、乳化剂用量、单体总量和温度对聚合反应速率的影响,得到了相应的聚合反应速率方程为Rp =k[M]0.30[I]0.18[E]0.97,并计算得到聚合反应的表观活化能为90.8 kJ·mol-1.然后采用半连续滴加法,讨论了不同滴加速率对聚合表观速率Rp的影响,结果表明,随滴加速率Ra 的增加,反应速率Rp也增加,但增加的幅度逐渐减少,且聚合过程的状态不断远离饥饿态.要使该聚合过程的状态保持在稳定的饥饿态,单体滴加时间应控制在140 min 以上. 相似文献
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无机纳米粒子的引入可以使聚合物材料获得抗菌、导电和防紫外等诸多特性,但无机纳米粒子在聚合物基质中易团聚、引入量少,难以充分发挥其优点。细乳液聚合法基于其独特的成核方式--液滴成核,能够提高无机纳米粒子在聚合物基中的分散性和引入量,且复合材料的形貌易于控制,是目前制备特殊形貌有机/无机纳米复合材料的一种有效手段。本文介绍了有机/无机复合纳米材料的细乳液制备过程,综述了近年来不同无机纳米粒子与有机基质复合的研究进展,例如:纳米SiO2、纳米ZnO、金属纳米粒子、纳米氧化石墨烯等。最后就其发展现状提出了几点建议。 相似文献
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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。 相似文献
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用于纳米粒子合成的微乳液 总被引:17,自引:0,他引:17
微乳液作为纳米反应器的最大优点是可以实现纳米粒子尺寸控制。体系中水的含量、表面活性剂、助表面活性剂等都是控制粒子尺寸的可调因素,研究这些因素对所合成的纳米粒子尺寸以及产量的影响对于实际应用有重要的意义。本文评述了近年来相关的研究进展,对微乳液法在合成纳米粒子中的应用前景作了展望。 相似文献
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Dan Donescu Constantin Radovici Cristian Petcu Sever Serban Mihai Cosmin Corobea Marius Ghiurea 《Journal of Dispersion Science and Technology》2013,34(3):340-346
It was studied the polymerization of styrene (St) and of butyl acrylate (BuA) in nonionic microemulsions in the presence of a layered alumino silicates, montmorilonit (MMT) type. In time, the latexes separate in two distinct strata, MMT being distributed in the inferior strata where forms aggregates with on order of size bigger than the diameters of nanoparticles of latex. The solid products obtained are nanohybrids of intercalate type whose structural order increases direct proportional with the increase of hydrophobic character of the quaternary ammonium salts used for organophilization of MMT. The presence of nonionic surfactant, nonyl phenol with 25 mols of ethylene oxide, intercalated between the lamellar strata of MMT produces the decrease of thermal stability of hybrids and decreases the glass transition temperature of PSt which is more compatible than PBuA. 相似文献
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负载型ZnO/SiO2及ZnO-SiO2溶胶凝胶催化剂的表面结构研究 总被引:2,自引:0,他引:2
催化剂的表面结构不仅影响催化剂的催化活性, 而且还影响反应产物的选择性[1]. 制备催化剂的方法不同, 其表面结构及表面性质也不同[2~4]. 浸渍法简单实用, 有利于得到高分散、晶粒细小的高比表面催化剂, 而溶胶-凝胶法则由于其制备温度较低, 易于形成无定形的或介态的氧化物相[5]而可达到分子级的混合, 其活性组分能有效地嵌入网状结构中, 不易受外界的影响而聚集或长大, 因此对催化剂的稳定性更为有利[6,7]. 相似文献
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间氯苯胺的乳液聚合及聚合物链结构表征 总被引:2,自引:0,他引:2
聚苯胺以其良好的电化学稳定性和掺杂可逆性 ,成为一类优良的电活性聚合物 [1,2 ] ,但其溶解性差 ,限制了它的加工及应用 .用取代基对聚苯胺的结构进行修饰 ,可有效地提高其加工性能 [3,4 ] ,但有关含吸电子取代基的苯胺衍生物聚合的报道尚少 .Ranger等 [5]指出 ,含强吸电子取代基团的聚苯胺不易用化学氧化聚合方法制备 ,并提出被氧化单体中的 N7和 C4位置必须具有相近的电子自旋密度 ,才能进行“头 -尾”偶联 ,而含强吸电子取代基团的苯胺单体中这两个位置的反应能力是不等价的 ,但可采用与母体共聚的方法可制备含强吸电子取代基 (如— C… 相似文献
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ThemethodsofimProvingthestabilityofemulsifier-freeemulsionpolymerizationhavebeenreportedinliteraturet(a)choosingionizableinitiators,suchaspotassiumpersulfate'andazo-bis(isobutyramidinehydrochloride)';(b)copolymerizationwithhydrophiliccomonomers,whichinvolvestheionictypesuchascarboxylicmonomers',sulfoderivativesofvinylmonomers',andthenonionictypesuchasglycidylmethacrylate';(c)copolymerizationwithsurface-activemonomers,suchassulfodecylslyrylether';(d)addingorganicsolventstothesystem,suchasmethano… 相似文献
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溶胶—凝胶法制备NiO/SiO2催化剂研究 总被引:11,自引:0,他引:11
分别以正硅酸乙酯、硝酸镍为硅源和镍源,采用溶胶-凝胶法,经超临界流体干燥和普通干燥制备了NiO-A-SiO2、NiO-G-SiO2催化剂;以气凝胶和干凝胶为载体,采用浸渍法制备了NiO/A-SiO2、NiO/G-SiO2催化剂。并用XRD、TEM、BET、TPR等手段,研究了制备方法对催化剂织构、结构和Ni物种存在形态的影响,发现NiO-A-SiO2和NiO-G-SiO2催化剂上高度分散的NiO簇团与SiO2之间有较强的相互作用,其顺酐液相选择加氢转化率低于10%;NiO/G-SiO2催化剂上,以单一物种形态存在的NiO与SiO2相互作用弱,顺酐转化率为42%;NiO/A-SiO2催化剂上,以多种形态存在的微量NiO与SiO2间的相互作用较复杂,其顺酐液相选择加氢的转化率和丁二酸酐的选择性分别可达100%和98%。 相似文献
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《大分子反应工程》2018,12(3)
Cellulose nanocrystals (CNCs) are safe, “green,” hydrophilic nanoparticles. CNCs are added in situ during a semibatch 2‐ethyl hexyl acrylate (EHA)/n‐butyl acrylate (BA)/methyl methacrylate (MMA) emulsion polymerization. As EHA is a more hydrophobic monomer, manipulation of the monomer feed composition allows for the evaluation of the effect of hydrophobicity on CNC distribution in the nanocomposite and ultimately on adhesive properties. The adhesive properties (loop tack, peel strength, and shear strength) of three different EHA/BA/MMA latex formulations are shown to simultaneously improve with increasing CNC loading. However, the hydrophobicity of the EHA leads to a nonuniform distribution of CNCs in the latex films. Comparison of the in situ polymerized nanocomposites to their blended counterparts is also made. 相似文献
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Functional groups in a monomer molecule usually play an important role during polymerization by enhancing or decreasing the reaction rate due to the possible formation of side bonds. The situation becomes more complicated when polymerization takes place in the presence of graphene oxide since it also includes functional groups in its surface. Aiming to explore the role of functional groups on polymerization rate, the in situ bulk radical polymerization of hydroxyethyl acrylate (HEA) in the presence or not of graphene oxide was investigated. Differential scanning calorimetry was used to continuously record the reaction rate under both isothermal and non-isothermal conditions. Simple kinetic models and isoconversional analysis were used to estimate the variation of the overall activation energy with the monomer conversion. It was found that during isothermal experiments, the formation of both inter- and intra-chain hydrogen bonds between the monomer and polymer molecules results in slower polymerization of neat HEA with higher overall activation energy compared to that estimated in the presence of GO. The presence of GO results in a dissociation of hydrogen bonds between monomer and polymer molecules and, thus, to higher reaction rates. Isoconversional methods employed during non-isothermal experiments revealed that the presence of GO results in higher overall activation energy due to the reaction of more functional groups on the surface of GO with the hydroxyl and carbonyl groups of the monomer and polymer molecules, together with the reaction of primary initiator radicals with the surface hydroxyl groups in GO. 相似文献
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CdS quantum dots (QD) were capped with SiO2 via a microemulsion method for reducing the toxicity and imparting the biocompatibility of the CdS QD. The resulting CdS/SiO2 core/shell nanoparticles (NP) showed an improved water‐solubility and stability even in pH 4.0 acidic medium. Their fluorescence could be effectively enhanced in the presence of bovine serum albumin (BSA), due to the passivation effect of BSA on the surface of the NP. Furthermore, the concentration dependence of the fluorescence intensity obeys the Langmuir‐type binding isotherm. Thus a novel fluorescence enhancement method for the determination of BSA has been developed using the less‐toxic CdS/SiO2 core/shell NP as probes. Under optimal conditions, the linear range of calibration curve is 0.6–30 µg·mL?1, and the detection limit is 0.18 µg·mL?1. Compared with the water‐soluble CdS NP without SiO2 shell, the CdS/SiO2 core/shell NP exhibited slightly lower fluorescence response to BSA as well as other coexisting substances, such as heavy and transition metals, due to the inhibition of SiO2 shell. The proposed method was applied to the quantification of BSA in synthetic and serum samples with satisfactory results. 相似文献
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Cu/SiO2模型催化剂上甲醇部分氧化制氢反应研究 总被引:2,自引:1,他引:2
采用浸渍法,制备了不同组成的Cu/SiO2、Cu/Zn/SiO2催化剂,考察了Cu负载量及Cu/Zn比对甲醇部分氧化抽制氢(CH3OH|1/2O2→2H2 CO2)反应的影响,结果显示,当Cu的负载量为10%、Cu/Zn比为7:3时,催化剂活性最好。H2-TPR、XRD、XPS等表征结果表明,催化剂的制氢活性与Cu^0有关,而大量Cu^ 与Cu^2 的存在则不利于催化剂活性的提高。Zn助剂的引入,有利于分散Cu^0物种,提高催化剂的活性;但由于同时稳定了Cu^ 物种,导致Cu2O物种的大量生成,从而提高了催化剂的还原温度,抑制了Cu^0的氧化还原过程(Cu^2 →Cu^ →Cu^0或Cu^ →Cu^2 ),降低了催化剂的活性。因此,对于Cu/Zn/M催化剂,存在一个最佳的Cu/Zn比。 相似文献