Monolayers, insoluble polymer

Most of the studies of insoluble polymer Langmuir monolayers have been devoted to neutral polymers, and less effort have been devoted to polymer monolayers of polyelectrolytes. 

Kawaguchi s group [82,83] have pointed out that polymer monolayers of poly(n-alkyl 4- vinylpiridinium) chains show a gas - liquid phase transition at surface pressures below 1 N.m 1. As already mentioned, this behavior is different to that of polymer monolayers of neutral and insoluble polymers. 

Modification of the solid surface. The surface can be completely coated by monolayers of low surface energy compounds on which oil drops having higher surface tension will not spread, or covered with narrow ring coatings of insoluble polymers of low surface energy, such as fluorocarbon derivatives, which surround the oil drop. 

It is the increase in surface viscosity produced by adsorbed films (insoluble and Gibbs monolayers, adsorbed polymers, etc.) that leads to the production of persistent foams, helps stabilize emulsions, and explains the role of spread monolayers in dampening surface waves, among other important interfacial phenomena. 

On the other hand, the electrodes attaching electroactive polymer films and polymer CMEs having ionic, electronically conductive, or redox property have been widely studied. Electronically conducting polymers, which are usually more conductive than redox polymers, can be doped to increase their intrinsic conductivity. Such films are now popular because they are technically easier to modify by applying polymer onto an electrode compared to covalent monolayer formation. Polymer films generally adhere satisfactorily to electrodes simply by forces of chemisorption or by being insoluble in the contacting solvent. 

Isotherms of perfluoropolyethers with chain lengths of approximately one hundred atoms with various hydrophilic head groups have been reported [14]. As in the case of polybutadiene the water insoluble polymer backbone does not form a monolayer by itself. Hydrophilic head groups, however, make the polymer surface active, and isotherms of an expanded type can be recorded, (see Fig. 2). 

Poloxamers suppress the formation of foam by forming an insoluble monolayer, thus the antifoaming action of poloxamers depends on the cloud point, above which the polymer becomes insoluble. For the poloxamer to... 

Monolayers are best formed from water-insoluble molecules. This is expressed well by the title of Gaines s classic book Insoluble Monolayers at Liquid-Gas Interfaces [104]. Carboxylic acids (7-13 in Table 1, for example), sulfates, quaternary ammonium salts, alcohols, amides, and nitriles with carbon chains of 12 or longer meet this requirement well. Similarly, well-behaved monolayers have been formed from naturally occurring phospholipids (14-17 in Table 1, for example), as well as from their synthetic analogs (18,19 in Table 1, for example). More recently, polymerizable surfactants (1-4, 20, 21 in Table 1, for example) [55, 68, 72, 121], preformed polymers [68, 70, 72,122-127], liquid crystalline polymers [128], buckyballs [129, 130], gramicidin [131], and even silica beads [132] have been demonstrated to undergo monolayer formation on aqueous solutions. 

Micellar aggregates are considered in chapter 3 and a critical concentration is defined on the basis of a change in the shape of the size distribution of aggregates. This is followed by the examination, via a second order perturbation theory, of the phase behavior of a sterically stabilized non-aqueous colloidal dispersion containing free polymer molecules. This chapter is also concerned with the thermodynamic stability of microemulsions, which is treated via a new thermodynamic formalism. In addition, a molecular thermodynamics approach is suggested, which can predict the structural and compositional characteristics of microemulsions. Thermodynamic approaches similar to that used for microemulsions are applied to the phase transition in monolayers of insoluble surfactants and to lamellar liquid crystals. 

The use of insoluble, highly cross-linked anisotropic networks created by the polymerisation of photoreactive monomers, eliminates the problem of crystallisation, at least for organic materials, since polymer networks are macromole-cular structures incapable of crystallising, see Chapter 6. Furthermore, the fabrication of multilayer devices would be facilitated by the use of a cross-linked stable HTL next to the anode on the solid substrate surface, onto which subsequent layers can be deposited by vapour deposition. Multilayer OLEDs are intrinsically more stable than monolayer devices due to a better balance of charge-carriers and concentration of the charged species away from the electrodes. The synthesis and cross-linking of a suitable aromatic triarylamine derivative with a polymerisable oxetane group at each end of the molecule for use as a HTL has been reported recently, ... 

Another spreading method, often applied when insoluble monolayers of soluble components (polymers) are to be made. Involves a rod that is placed on the bottom of the container emd that has its roughened tapered top Just penetrating the upper phase, as shown in fig. 3.3b. The rod should consist of material that is preferentially wetted by the lower phase, so that it remains covered with a film of the lower liquid. The tip of the syringe is placed on the top of the rod and the solution is spread in the direction of the cUTOws, shown in fig. 3b. In this way Trumlt, who invented this method, successfully spread protein molecules from an aqueous solution on em air-water interface. ... 

Insoluble amphiphilic compounds will also form films on water surfaces and these may be tightly packed, as in condensed films, or more loosely packed, as in expanded and gaseous films. We have seen that polymers and proteins may also form insoluble monolayers. 

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