Cationic Modification

Crown-ethers are macrocyclic polyethers capable of forming host-guest complexes, especially with inorganic and organic cations. Modification of the crown-ether by the introduction of four carboxylic groups makes it possible to use this class of compounds as chiral selectors in CE. ... 

The differential thermal analysis, thermogravimetric analysis, and x-ray results establish that the cationic modifications are stable under the outgassing conditions used in the sorption measurements. 

The reducibility of nickel and copper cations in Nb- and Al-containing MCM-41 It is known that transition metal cations, which occupy extra lattice positions in zeolites, are reduced while activated under vacuum or in an inert gas flow [20], The same occurs while applying mesoporous matrices for metal cations. The species formed during the auto reduction depend on the nature of a matrix, the conditions of cation modification, and activation They can be identified by H2-TPR, ESR, and NO/FTIR measurements. 

Because of the unusual behavior of Na-mordenite in the reactions of benzene hydrogenations, it seemed of interest to study other cation modifications of mordenite in this reaction. The data obtained with a number of cation forms are summed up in Table II. 

Schneider, N.S. and Rivin, D., 2004. Interaction of dimethyl methylphosphonate with Nafion in acid and cation modifications. Polymer, 45, pp. 6309-6320. 

B9 Modifi- cation Modifications of a piece of pre-developed software shall be performed compliant with the requirements of lEC 62138 (clause 6.9). GOTO. .. IEC62138, 6.9... 

This chapter focuses on the use of nanotechnology in the development of cellulose and chitin nanoctystals and their novel biomedical applications. It consists of four main sections. The first section is a brief introduction. The second section focuses on cellulose nanocrystals (CNCs) and their preparation procedure, physical properties, and surface modifications. Cationic modification of CNCs is also presented to produce positively charged CNCs. Various bioapplications of CNCs in bionanocomposites, drug delivery, and biosensors are discussed as well. The third section focuses on chitin nanoctystals (CHNCs). Except for a short introduction on chitin and its structure, the methods of isolation and characterization of chitin are discussed and the surface modifications and properties of CHNCs are summarized. The applications of CHNCs as reinforcing fillers in nanocomposites and several biomedical applications are discussed. The fourth section is a summary and perspective highlighting the future directions on the application of these natural nanoctystals in various key industries related to biomedicine. 

Cationic modification can introduce positive charges on the surface of CNCs, which could reverse the surface charge and lead to stable aqueous suspensions of cationic CNCs. Such a surface cationization procedure was conducted by grafting epoxypropyltrimethylammonium chloride (EPTMAC)... 

Studies on CNCs are relatively new and there are limited studies on cationic modification of CNCs. In the following, a number of biomedical applications of CNCs are discussed. Given the recent interest on cationic modification of CNCs, there have not been any specific bioapplications reported for cationic CNCs. However, the applications of CNCs in enzyme immobilization can be extended to cationic CNCs as well. 

Cationic nanocarriers are prepared from natural or synthetic polymers. The most widely used cationic polymers have been reported as PEI, PLL, poly-methacrylates (PMA), chitosan and cationic modifications of other polymers such as cyclodextrin, gelatin and imidazole-containing polymers. ... 

Figure 1.20 Schematic of the nitroxyl-based organic cation modification of montmorillonite surface and generation of PS nanocomposite. Reproduced from Ref [44] with permission from American Chemical Society.

Petzold G, Schwarz S, Buchhammer HM, Lunkwitz K (1997) A very effective method for the cationic modification of cellulose. Die Angew Makromol Chem 253 1... 

As shown for the pure Na+ cation modifications of A, X and Y zeolites, the catalytic activity decreases with increasing framework Si/Al ratio, i.e., with the decrease in the amount of cations of a given type, cf.. Figure 4. 

Mann, J. P, A. McCluskey, and R. Atkin. 2009. Activity and Thermal Stability of Lysozyme in Alkylammonium Formate Ionic Liquids-Intluence of Cation Modification. Green Chemistry 11 (6) 785-792. 

Further, ILs dedicated to very specific extractions have been synthesized and called task specific ionic liquids (TSILs). Elimination of the use of additional extractant or ligand from the organic phase can be pointed out as a consequence of imidazolium cation modification with other compounds. However, according to Abbot et al. (2011), the term TSIL should be changed into functionalised ILs, as now most of ILs are designed and synthesised for a dedicated application. 

The effect of 3d-cation modification on the properties of cordierite-like catalysts... 

---