Polymer-Surfactant Interactions and the Effect of Tail Size Variation on Micellization Process of Cationic ATAB Surfactants in Aqueous Medium

The interactions between oppositely charged surfactant-polymer systems have been studied using surface tension and conductivity measurements and the dependence of aggregation phenomenon over the polyelectrolyte concentration and chain length of cationic ATAB surfactants, cetyltrimethyl ammonium bromide (CTAB), tetradecyltrimethyl ammonium bromide (TTAB), and dodecyltrimethyl ammonium bromide (DTAB) have been investigated. It was observed that cationic surfactants induce cooperative binding with anionic polyelectrolyte at critical aggregation concentration (cac). The cac values of ATAB surfactants in the presence of anionic polyelectrolyte, sodium carboxy methyl cellulose (NaCMC), are considerably lower than their critical micelle concentration (cmc). After the complete complexation, free micelles are formed at the apparent critical micelle concentration (acmc), which is slightly higher in polyelectrolyte aqueous solution than in pure water. Among the cationic surfactants (i.e., CTAB, TTAB, and DTAB), DTAB was found to have least interaction with NaCMC. Surfactants with longer tail size strongly favor the interaction, indicating the dependence of aggregation phenomenon on the structure, morphology, and tail length of the surfactant.      

Evaluation of potential cationic probes for the detection of proline and betaine

Osmoregulants are the substances that help plants to tolerate environmental extremes such as salinity and drought. Proline and betaine are two of the most commonly studied osmoregulants. An indirect UV CE method has been developed for simultaneous determination of these osmoregulants. A variety of reported probes and compounds were examined as potential probes for the indirect detection of proline and betaine. Mobility and UV‐absorption properties highlighted sulfanilamide as a potential probe for indirect analysis of proline and betaine. Using 5 mM sulfanilamide at pH 2.2 with UV detection at 254 nm, proline and betaine were separated in less than 15 min. The LODs for proline and betaine were 11.6 and 28.3 μM, respectively. The developed method was successfully applied to quantification of these two osmoregulants in spinach and beetroot samples.     

Different Distributions of Counterions in the Surface Layer of Cationic Surfactant Solutions

We have separately determined the surface tension of pure aqueous solutions of cetyltrimethylammonium chloride and cetyltrimethylammonium bromide and their surface potentials by a Kelvin probe system. With the help of Gibbs equation, the surface excess has been determined through approximating the chemical activity of the surfactant by their dilute bulk concentration. In the following, the surface potential—surface excess isotherms were established. Those potential isotherms evidence that cetyltrimethylammonium chloride solution has a higher value compared to that of cetyltrimethylammonium bromide under equal surface excess. This phenomenon is supposed to be owed to the different distributions of chloride and bromide ions within the adsorption layer of the solutions, which can be attributed to the different properties of those two anions.     

淀粉接枝聚丙烯酰胺阳离子絮凝剂的合成及应用——推荐一个高分子化学综合实验

介绍一个综合化学实验。实验通过淀粉与丙烯酰胺的接枝聚合反应和阳离子化改性,合成了一种新型淀粉接枝聚丙烯酰胺阳离子高分子絮凝剂,进行了结构表征,以人工模拟染料废水和重金属离子废水为实验对象,探究了合成的聚丙烯酰胺、淀粉接枝聚丙烯酰胺和淀粉接枝聚丙烯酰胺阳离子絮凝剂在废水净化中的应用。本实验理论与实践相结合,有助于激发学生的学习兴趣,培养学生的学科交叉融合思维和分析解决问题的能力。     

碳量子点阳离子表面活性剂的多功能性

碳量子点以其多彩的荧光及廉价而丰富的制备原料引起人们的广泛兴趣。至今,已有大量关于碳量子点制备及其荧光性能直接利用的文献报道。若采用恰当的方法对碳量子点进行化学修饰,则可以将其转化为实用的精细化学品,从而拓展碳量子点的应用领域。本文报道了一种碳量子点阳离子表面活性剂的制备方法。首先,乙二胺四乙酸、二乙胺及双氧水的混合水溶液经水热处理,获得碳量子点(以OX-CQDs表示),再以氯代正构十二烷对其进行季铵化修饰,获得新型碳量子点阳离子表面活性剂(以OX-CQDs-C₁₂H₂₅表示)。OX-CQDs-C₁₂H₂₅具有良好的降低水的表面张力和减小水接触角的能力,水的界面张力能降低至26.7 mN∙m⁻¹,其性能超过了一些新型的Gemini型阳离子表面活性剂;季铵化的修饰也大大提高了OX-CQDs对大肠杆菌的抑菌能力,低至0.41 mg∙mL⁻¹的OX-CQDs-C₁₂H₂₅溶液其抑菌率接近100%。表面活性剂,抑菌性和荧光性能赋予了OX-CQDs-C₁₂H₂₅的多种功能性。     

Overview of cationic phthalocyanines for effective photoinactivation of pathogenic microorganisms

Phthalocyanine (Pc) dyes are photoactive compounds that can absorb and emit light in a large range of the UV–vis spectrum, with recognized potential for medical applications. Considering the low solubility of Pc macrocycles in water, it is important to use cationic symptoms on their skeleton to improve their amphiphilicity for biomedical applications. The use of suitable pyridinium groups on Pc is a good strategy to solve this drawback and make them more eff ;ective to photoinactivate microorganisms via a photodynamic inactivation (PDI) approach. This review focuses the synthesis of quaternized Pc dyes, their photophysical and photochemical properties, and their antimicrobial photoinactivation efficiency. This innovative study compares, for the first time, different cationic moieties on Pc taking into account the efficiency of singlet oxygen (¹O₂), quantum yield (Φ_Δ) generation, fluorescence quantum yield (Φ_F), (photo)stability, light irradiation type (visible/white and/or red light), maximized overlapped absorption effect of Pc (S- and/or Q-band) vs light system irradiation type, and water solubility (n-octanol/water partition coefficient, P_o/w), when these parameters are determined and provided in the multidisciplinary reports. This approach is also relevant to conjugate free-base (H₂Pc) and metalated phthalocyanines (MPc, M = Zn²⁺, Mg²⁺, In³⁺, Ga³⁺, Ge³⁺, Si⁴⁺, etc.) with aromatic or aliphatic substituents linked by N, O or S atoms on the peripheral or axial positions of the Pc structures, such as e.g. (methoxy, oxy, or thio)pyridinium, ammonium, or benzimidazolium units, etc. Here, the influence of the structural peripheral (α- and/or β-position of Pc) or axial substituents type, number and positive charge position that can affect the PDI process will be analysed. These aspects are important to design versatile molecules that can interact with pathogenic microorganisms of variable size, subcellular architecture, biochemical composition, and susceptibility to externally added chemical agents. This review highlights the important developments of several modifications of cationic Pc dyes for the PDI of microorganisms, such as pathogenic bacteria, fungi, and virus.     

Cationic and temperature-sensitive liposomes loaded with eugenol for the application to silk

Silk has been widely used in the clothing industry due to their soft and smooth features, good biocompatibility, good heat dissipation, warmth and ultraviolet resistance. The application of fragrance to silk can significantly improve the performance of silk. However, there are two key scientific problems that need to be solved: slowing down the release rate of fragrances and increasing the scent lasting time of silk. In this study, cationic and temperature-sensitive liposomes were designed and prepared to encapsulate eugenol. These fragrance-loaded liposomes significantly slowed down the release rate of the fragrance and controlled the release rate of the fragrance in a thermo-sensitive manner. The liposomes adhered to the silk through electrostatic adsorption interaction. The positive charge on the fragrance-loaded liposomes neutralized much negative charge on silk and thereby increasing the adhesion efficiency.     

Effect of reactive and non-reactive counterion micelles upon the alkaline degradation of indomethacin

In the present paper, kinetics of alkaline degradation of well known drug, indomethacin (2-[1-(4-chlorobenzoyl)-5-methoxy-2-methylindol-3-yl]acetic acid), was studied in presence of excess [NaOH]. The rate of hydrolysis of substrate was independent of the [indomethacin] though it increased linearly with increasing the hydroxide ion concentration with a positive slope, suggesting the following rate law: k_obs = k₁[OH⁻]. Cationic surfactants having non-reactive ions (cetyltrimethylammonium bromide, CTAB and cetyltrimethylammonium sulfate (CTA)₂SO₄) first increased the rate constants at lower concentrations and then decreased it at higher concentrations while in case of the surfactant with reactive counterions (cetyltrimethylammonium hydroxide, CTAOH) the rate increases sharply at lower concentrations of surfactant until it reaches to a plateau in contrast to the appearance of maxima in case of CTAB and (CTA)₂SO₄. Anionic surfactant, sodium dodecyl sulfate (SDS), inhibited the reaction rate at all concentrations used in the study. Pseudophase ion-exchange model was used for analyzing the effect of cationic micelles while the inhibition by SDS micelles was fitted using the Menger–Portnoy model. The effect of salts (NaCl, NaBr and (CH₃)₄NBr) was also seen on the hydrolysis of indomethacin and it was found that all salts inhibited the rate of reaction. The inhibition followed the trend NaCl < NaBr < (CH₃)₄NBr.     

十二烷基伯胺盐酸盐与十二烷基聚氧乙烯硫酸钠复配体系中的表面性质

研究了十二烷基胺盐酸盐(DAC)和十二烷基聚氧乙烯硫酸钠(AES)复配体系的表面性质与胶束化行为.发现该体系在广泛的复配比例区间和温度区间内保持了极为优异的表面活性,测定了该体系的临界胶束浓度(cmc)与其对应的表面张力(γcmc)的具体值,并研究了温度、pH值和离子强度等环境因素对相关体系的影响.