China
Africa
Explore chapters and articles related to this topic
Photoresponsive Polymers
Published in Asit Baran Samui, Smart Polymers, 2022
Ion pair formation between the counter-ions is responsible for the formation of various states such as crystals, LCs, and liquids, through numerous interactions.49 Different functionalities can be attached to oppositely charged species so that the states and types of assembly of the ion pairs can be controlled to achieve the desired properties. By incorporating stimuli-responsive moieties in the ion pairs, the system can be controlled by applying an external stimulus. By incorporating azobenzene, various ion pairing assemblies can be realized due to different geometries and ratios of trans and cis forms. Photo-induced phase transitions via the isomerization of the azobenzene derivatives in the bulk phase are constrained because of the restriction of free volumes.50 Ion pair assemblies are formed due to non-covalent interactions, and the external conditions can be manipulated to achieve the required arrangement of the components. Azobenzene carboxylates as photo-responsive charged species can generate high crystalline assemblies and exhibit phase transitions.51 Azobenzene anions are coupled with bulky cations (tetrabutylammonium ion) to form ion pairs so that free volumes are available near the azobenzene moieties. Because of the formation of loosely connected ion pairs by non-covalent interactions, the azobenzene unit can easily undergo isomerization.
Kosmotropic Chromatography of Proteins
Published in Nelu Grinberg, Peter W. Carr, Advances in Chromatography Volume 57, 2020
Carlos Calleja-Amador, J. F. Ogilvie, Rigoberto Blanco
Several models have been proposed to explain the Hofmeister effect. One model is known as water-matching affinities and was proposed by Collins [43]. It establishes that two oppositely charged ions with similar strengths in their interaction with water can form ion pairs, which dominate the ion-specific interactions. Collins showed that many properties of aqueous ionic solutions are a function of the charge density of the ions [44–46]. An example of these is the strength of water–water interactions in bulk solution. Water–water interactions serve as a critical reference-energy level, and are comparable in strength with ion–water interactions [44].
Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
Ion pairs behave as single entities in determining conductivity, kinetic behavior, and osmotic properties. They do not conduct electricity, therefore it is possible to measure the amount of free ions present by conductivity measurements. Moreover, the dissociation constants of ion pairs are tabulated for many solvents. Generally, at low concentration, free ions are absent in solvents with dielectric constants ε lower than 15, whereas they are the main species in solvents with ε higher than 40 . A borderline behavior is found in between.
Effect of chemical dispersion on distribution of distillates cuts in various crude oil samples
Published in Petroleum Science and Technology, 2023
Imtiaz Ahmad, Waqas Ahmad, Syed Mohammad Sohail, Aftab Yasin
A number of interface-active materials, like surfactants (Zhang et al. 2015), lipids (Yanagisawa et al. 2013, Thiam, Bremond, and Bibette 2012), amphiphilic polymers (Li et al. 2012), or bi wetting nano- and microparticles (Binks et al. 2005, Binks and Murakami 2006) have been reported to create an energy barrier against droplet coalescence, stabilizing the emulsions when added to petroleum oils. The solvation of asphaltenes by the dispersants can be explained on the basis of the ion pair formation. Electrostatic interaction between the charged head groups of the surfactant molecules and the crude oil components is known as the ion pair formation. The solvation is further assisted by the interaction of the hydrophobic end of the dispersant (the tail of surfactant molecules) and crude oil components. Surfactants owing to a strong acid group (SO3-) are capable of interacting with asphaltene molecules, in crude oils (Ortega, Navarro, and García-Morales 2017).
Temperature and oxidation-sensitive dioleoylphosphatidylethanolamine liposome stabilized with poly(ethyleneimine)/(phenylthio)acetic acid ion pair
Published in Journal of Biomaterials Science, Polymer Edition, 2023
Fanyu Zhao, Garima Sharma, Jin-Chul Kim
In this study, a temperature and oxidation-sensitive DOPE liposome has been prepared by incorporating the ion pair of polyethyleneimine (PEI) and (phenythio)acetic acid (PTA) into the liposomal bilayer. The PEI electrostatically interacts with PTA to form an ion pair, and the ion pair can be self-assembled in an aqueous solution due to its amphiphilic property [19]. The amphiphilic ion pair would be able to act as a complementary molecule for the formation of DOPE liposomes because the phenyl group of PTA can be inserted into the lipid bilayer while the bulky PEI chains filling the space between the head groups of the phospholipid. It could be possible when the temperature is increased the ion pair may lose its amphiphilic property due to the hydration of the phenyl group of PTA molecule [20]. Thus, the ion pair would be desorbed from the liposomal membrane, causing the liposome to destabilize and release its payload. Moreover, under an oxidizing condition, the liposomes (DOPE/PEI/PTA) would be potentially destabilized due to the oxidation of DOPE and PTA. For DOPE, because of its unsaturated structure, it is readily oxidized by oxidants (references) which would affect the stability of formed liposomes [21]. For PTA, its sulfide group can be oxidized to the sulfoxide and the sulfone groups by oxidants, then change the polarity of PTA which might cause further the ion pair of PEI/PTA to lose its amphiphilicity [19]. Thus, detaching ion pair of PEI/PTA from the DOPE membrane, resulting in destabilization of liposomes and a triggered release (see Graphical abstract).
Screening of ionic liquids for gas separation using COSMO-RS and comparison between performances of ionic liquids and aqueous alkanolamine solutions
Published in Chemical Engineering Communications, 2020
Mohamed K. Hadj-Kali, Mamoun Althuluth, Salim Mokraoui, Irfan Wazeer, Emad Ali, Dominique Richon
In COSMO-RS, there are three approaches to represent ILs: (i) the meta-file approach, (ii) ion pair approach, and (iii) electro-neutral approach. The last approach describes the two ions as separate species in the liquid mixture and, is considered as the closest one to the real nature of ILs. Hence, this approach was adopted in this study to evaluate solubility of the most important components present in raw natural gas (CO2, CH4, C2H6, and C3H8) in eight selected ILs that have been previously investigated for its potential for separating CO2 from other natural gas components. Table 1 lists the references of experimental studies on binary (gas-IL) systems used in this work. The chemical structures of cations and anions forming the different ILs are provided as Supporting Material (Tables S2 and S3). The results of the screening were interpreted using σ-profile analysis of the involved species. The first step in the. COSMO-RS process is to generate a “.cosmo” file based on the optimized geometry of each involved species. In this study, we have used the “.cosmo” files provided in the COSMOthermX software database along with the BP_TZVP_C30_1401.ctd30 parameterization file generated using density functional theory and a triple zeta valence potential basis set.