The aqueous cationic system sodium undecenoate-dodecyltrimethylammonium bromide at low concentration

The aqueous sodium undecenoate (SUD) –dodecyltrimethylammonium bromide (DTAB) catanionic system was studied at low concentration. The system did not precipitate, even at a 1:1 SUD:DTAB proportion, but showed the formation of a coacervate in a range of surfactant mixture compositions. Micelles have a preferential composition of 0.37 mole fraction of SUD. This behavior is attributed to the presence of the double bond at the distal extreme of the SUD molecule, which can form hydrogen bonds with water. Consequently, the –CH=CH₂ group is situated at the interface between the hydrocarbon micelle core and water, reducing the interfacial free energy. Structural computations demonstrate that the mentioned SUD proportion produces complete coverage of the micelle surface by the double bonds.     

Polyphosphates as inorganic polyelectrolytes interacting with oppositely charged ions,polymers and deposited on surfaces: fundamentals and applications

Polyphosphates are important but neglected polyelectrolytes that play a major role in biology and in surface science for the stabilization of colloids against flocculation and for the preservation of food. They are also known as “Calgon” ® and intensively used as additives in washing powders. This review aims to review recent developments in which linear polyphosphates are used for the design of new functional coatings using sol–gel processes and layer-by-layer deposition methods. All these methods rely on the high charge density of polyphosphates as inorganic polyelectrolytes, therefore the structure and properties of these molecules are also reviewed. New perspectives will also been given for the design of stimuli responsive coatings at the tiny frontier between biology and materials science.     

Dynamic mechanical and morphological studies of homopolymer/block copolymer blends

A triblock copolymer of styrene-butadiene-styrene (SBS) was blended with a high and a low molecular weight polybutadiene [designated as PB(H) and PB(L), respectively]. Electron micrographs of these blends show that PB(L) was solubilized into the butadiene domains of the SBS, while PB(H) was present in a separate phase. Dynamic mechanical data of the SBS&PB(L) blends indicate the presence of an intermediate loss peak between those of the glass transitions of the styrene and butadiene blocks in SBS, which can be attributed to the slippage of untrapped entanglements of PB(L) chains. Similar data for blends containing PB(H) also show an intermediate loss peak, which is, however, due to crystallization and melting of the polycisbutadiene chains. The peak due to the primary glass transition of the butadiene phase was shifted to lower temperatures upon incorporation of PB(L) as a result of plasticization effect of PB(L). The same transition for PB(H) blends is split into a doublet because of the presence of the homopolymer in a separate phase. Dynamic mechanical data for cross-linked blends were also taken for comparison.     

High compact melamine-formaldehyde microPCMs containing n-octadecane fabricated by a two-step coacervation method

Microcapsules containing n-octadecane were successfully fabricated by an in-situ polymerization process with melamine-formaldehyde (MF) prepolymer and a hydrolyzed copolymer of styrene and maleic anhydride (SMA) as shell materials. To achieve a long service time of microcapsules containing phase change materials (microPCMs), the compactness of shells was improved by adding the MF prepolymer twice. The mechanism of this method was a two-step coacervation (TSC) under the help of hydrolyzed SMA compared to a one-step coacervation (OSC). To understand the influence of both coacervations, properties of shells were investigated in terms of morphologies, density, thickness, and stability by means of scanning electron microscopy (SEM), transmission electron microscopy, and thermal gravimetric analysis (TGA). The data of shells thickness were achieved from the cross-section SEM images. It shows that the average thickness of shells from two kinds of process are 0.1 μm. The density and stability in water of shells fabricated by TSC are both higher than that of shells by OSC. TGA curves show the expected microPCMs of TSC losing weight from 200 to 400 °C. The release curves, relationship between time and logarithmic residual weight of core, show there are two decrease-linear steps after curve regression. It can be concluded from all these results that the TSC method may be a promising method leading to a compact shell structure for various application.     

基于壳聚糖-溴化氰改性褐藻酸钠凝集作用的日本血吸虫安培免疫传感器

研制了一种基于壳聚糖和溴化氰改性褐藻酸钠凝集作用的日本血吸虫安培免疫传感器.褐藻酸钠-抗体复合物通过静电吸附作用被凝集到含石墨-石蜡-壳聚糖组分的电极表面,然后与抗原和酶标抗原进行竞争反应,以邻氨基酚(o-AP)为电子媒介,通过测定酶催化下双氧水对其氧化的电流大小来间接测定抗原的浓度.研究表明这种免疫传感器具有很低的非特异吸附性能,而且在经过简单的处理后可以重复使用,其重现性和灵敏度良好.传感器对日本血吸虫抗原的响应在0.64～40μg/mL之间呈线性关系.检测限为0.64μg/mL.将电极应用于兔血清中日本血吸虫抗原的测定,取得了满意结果.     

原位凝聚法制备聚电解质微胶囊——模板中掺杂聚电解质量对微胶囊结构与性能的影响

通过在CaCO3制备过程中加入不同浓度聚苯乙烯磺酸钠(PSS)的方法来控制掺杂进CaCO3粒子中的PSS含量,得到了PSS掺杂量为4%～11%,尺寸均匀的CaCO3球形微粒.在微粒表面仅吸附一层聚烯丙基胺盐酸盐(PAH)后,用乙二胺四乙酸二钠(EDTA)使碳酸钙溶解;释放出的PSS与PAH原位凝聚制备得到了分散良好且完整的聚电解质复合物微胶囊.在所研究的范围内,模板微粒中PSS的含量对微胶囊的形态结构和性能没有明显影响.与传统的层层组装微胶囊相比,聚电解质复合物微胶囊有较好的热稳定性,但在高盐浓度下尺寸收缩程度较大.由于和层层组装微胶囊相比缺乏结合紧密的有序结构,原位凝聚法制备的微胶囊囊壁的截留分子量较大.     

壳聚糖纳米粒子的制备

利用对离子复合凝聚法,以EDTA为对离子,戊二醛为交联剂,壳聚糖(CS)为原料制备了CS纳米粒子。用动力学光散射分析(DLS)、透射电子显微镜(TEM)、FTIR对合成的CS纳米粒子进行了表征。表征结果表明,采用该方法合成的CS纳米粒子约为70nm,CS和EDTA通过电荷吸引凝聚成纳米粒子。     

Xanthan gum-gelatin complexes

Gelatin (G) and xanthan gum (X) formed complexes either on bringing their blends to pH 2.3 or carrying out the electrode process in aqueous blends of X and G at pHs from 9 to 11. X carboxylic groups and G peptide moieties were involved in the interactions between the partners. Also non-coulombic interactions with involvement of NH and OH groups, as well as hydrophobic interactions were involved, as proved by FTIR and thermal analyses, respectively. The reaction yield declined with increase of concentration of G in the blends. Simultaneously, the thermal stability of the complexes slightly increased with increase in G content in the blend. The latter increased with its concentration in the reaction mixture. Slow formation by electrosynthesis provided more an organised matrix.     

Phase separation: Bridging polymer physics and biology

Significant parallels exist between the phase separation behavior of polymers in solution and the types of biomolecular condensates, or ‘membraneless organelles,’ that are of increasing interest in living systems. Liquid–liquid phase separation allows for compartmentalization and the sequestration of materials and can be harnessed as a sensitive strategy for responding to small changes in the environment. Here, I review many of the parallels and synergies between ongoing efforts to study and take advantage of phase separation in living versus synthetic materials.     

A fast assay of water hardness ions based on alkaline earth metal induced coacervation (HALC)

In this work, a rapid assay of water hardness is presented based on the formation of a coacervate phase made up of multilamellar vesicles and close bilayers produced upon the reaction of alkaline earth metals with a carboxylate anionic surfactant in the presence of a co-surfactant (methanol). The procedure exploits the light scattering abilities of the coacervate phase which can be logarithmically linked to total hardness as CaCO₃ equivalents via spectrophotometric detection at 350 nm. The method, abbreviated as HALC, stemming from hardness by alkaline earth metal coacervation, is straightforwardly applicable overcoming the requirement for regulation of the experimental parameters involved in the determination procedure. In total, 28 water samples with various matrix compositions and hardness contents were analyzed with satisfactory accuracy as evidenced by comparison of the results with EDTA complexometric titration. The method is free from interferences from environmentally significant metal cations and inorganic anions affording detection limits as low as 13.5 mg L⁻¹ CaCO₃ with the aid of a correction factor, which is determined by the non-linear absorbance properties of the solution mixture, and satisfactory reproducibility (RSD = 4.21-8.08%).