Hydrophobic entities, groups

Scheme 6.2 Schematic representation of hydrogelators, which self assemble preferentially in one dimension. Lighterregions correspond to hydrophihc groups and darter areas to hydrophobic entities (AA amino acids). Chemical stmctures of hydrogelators 8a-d are based on 1,3,5-cyclohexyltricaib-oxamide. Reproduced with permission from Ref. [23], copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim...

HASE thickeners are polyacrylate dispersions that contain a higher amoimt of carboxyUc acids, predominantly acryUc acid or methacryUc acid. Upon neutralisation during the paint manufacturing they sweU and thicken the paint. Due to additional hydrophobic functional groups attached to the polymer backbone, they can interact with the hydrophobic part of surfactants and the hydrophobic entities of other thickener molecules forming a kind of micellar strucmre in the water phase. In addition, they can interact with hydro-phobic domains on the surface of emulsion polymer binders. This extensive hydrophobic interactions improve efficiency of the HASE thickener and helps the coating formulation... 

In highly diluted solutions the surfactants are monodispersed and are enriched by hydrophil-hydrophobe-oriented adsorption at the surface. If a certain concentration which is characteristic for each surfactant is exceeded, the surfactant molecules congregate to micelles. The inside of a micelle consists of hydrophobic groups whereas its surface consists of hydrophilic groups. Micelles are dynamic entities that are in equilibrium with their surrounded concentration. If the solution is diluted and remains under the characteristic concentration, micelles dissociate to single molecules. The concentration at which micelle formation starts is called critical micelle concentration (cmc). Its value is characteristic for each surfactant and depends on several parameters [189-191] ... 

Micelles are the simplest possible structures. These are spherical entities in which the hydrophobic groups are directed towards the interior. Micelle formation occurs preferentially when the head groups are larger than the hydrophobic groups, as in fatty acids. 

Another way for covalent immobilisation is to synthesise indicator chemistry with polymerizable entities such as methacrylate groups (Figure 4). These groups can then be copolymerized with monomers such as hydrophobic methyl methacrylate or hydrophilic acryl amide to give sensor copolymers. In order to obtain self-plasticized materials, methacrylate monomers with long alkyl chains (hexyl or dodecyl methacrylate) can be used. Thus, sensor copolymers are obtained which have a Tg below room temperature. Similarly, ionophores and ionic additives (quaternary ammonium ions and borates) can be derivatised to give methacrylate derivatives. 

Figure 1 Schematic structures of micelle and liposome, their formation and loading with a contrast agent, (a) A micelle is formed spontaneously in aqueous media from an amphiphilic compound (1) that consists of distinct hydrophilic (2) and hydrophobic (3) moieties. Hydrophobic moieties form the micelle core (4). Contrast agent (asterisk gamma- or MR-active metal-loaded chelating group, or heavy element, such as iodine or bromine) can be directly coupled to the hydrophobic moiety within the micelle core (5), or incorporated into the micelle as an individual monomeric (6) or polymeric (7) amphiphilic unit, (b) A liposome can be prepared from individual phospholipid molecules (1) that consists of a bilayered membrane (2) and internal aqueous compartment (3). Contrast agent (asterisk) can be entrapped in the inner water space of the liposome as a soluble entity (4) or incorporated into the liposome membrane as a part of monomeric (5) or polymeric (6) amphiphilic unit (similar to that in case of micelle). Additionally, liposomes can be sterically protected by amphiphilic derivatization with PEG or PEG-like polymer (7) [1].

Water, being a polar solvent, can interact with the anion [NO3] but the long alkane chains (Cjo) of the cation are hydrophobic hence, there is little interaction of water with the cahon, and thus the anion entity is favored by the (IL + water) mixtures. When one alkyl chain (Cjg) was changed by the benzyl group and the other one by the longer alkane chain (C12-C14) as the substituents at the cation, the decrease of solubility was reported. These new substituents had strong influence on packing effects in the liquid phase. 

Considering the van der Waals interaction between nonpolar groups and hydration effects of these groups as an integral entity, i.e., the hydrophobic interaction, one can state that upon increasing temperature... 

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