Polymer structure, cationic surfactant

Fontell K, Khan A, Lindstrom B, Maciejewska D, Puangngern S (1991) Phase-Equilibria and Structures in Ternary-Systems of a Cationic Surfactant (C16tabr or (C16ta)2so4), Alcohol, and Water. Colloid Polym Sci 269 727-742 Israelachvili JN, Mitchell DJ, Ninham BW (1977) Theory of Self-Assembly of Lipid Bilayers and Vesicles. Biochim Biophys Acta 470 185-201... 

The formation and equilibrium structure of polymer layered silicate nanocomposites, in particular with organically modified layered silicates, has been shown to be a strong function of the nature of the polymer (polar or apolar), the charge carrying capacity of the layered silicate, as well as the chain length and structure of the cationic surfactant. However, both the polymer/silicate compatibility and hybrid equilibrium structure for these nanocomposites are observed to be independent of polymer molecular weight. The experimental results have been summarized by Vaia et al. and a lattice based mean field theory has been developed to explain these results [26]. 

In this paper, the results on solution and Interfaclal properties of a cationic celluloslcs polymer with hydrophobic groups are presented. Interaction of such polymers with added surfactants can be even more complex than that of "unmodified" polymers. In the past we have reported the results of Interactions of unmodified cationic polymer with various surfactants Investigated using such techniques as surface tension, preclpltatlon-redlssolutlon, viscosity, solubilization, fluorescence, electroklnetlc measurements, SANS,etc.(15-17). Briefly, these results showed that as the concentration of the surfactant Is Increased at constant polymer level significant binding of the surfactant to the polymer occurred leading to marked Increases In the surface activity and viscosity. These systems were able to solubilize water Insoluble materials at surfactant concentrations well below the CMC of polymer-free surfactant solutions. Excess surfactant beyond that required to form stoichiometric complex was found to solubilize this Insoluble complex and Information on the structure of these solubilized systems has been presented. 

The relation between the extent of solubilization and the structures of solubi-lizate and surfactant-polymer complex is not completely clear. Aromatic hydrocarbons appear to be more highly solubilized than aliphatic hydrocarbons by complexes of anionic surfactants and hydrophilic polymers with no proton-donating groups, such as polyvinylpyrrolidone, but the nature of the forces involved is not clear. Some cationic surfactant-polymer complexes are broken by the solubilization of aromatic hydrocarbons. It has been suggested that structural compatibility between solubilizate and polymer may be a factor and that the function of the surfactant is to increase the hydrophilic character of the polymer and to promote contact between polymer and solubilizate (Saito, 1967). 

Recently, we have synthesized microporous carbons [6] and Pt particles supported on microporous carbon [7] by carbonization of cationic surfactant-anionic resorcinol/formaldehyde (RF) composites. The porous structure produced by decomposition of the surfactant plays an important role for the gasification of the RF polymer at higher temperatures. However, the average pore size of the microporous carbons obtained with this method is smaller than... 

Amiel et al. [85, 86] investigated the formation of ternary complexes of a water soluble epichlorohydrin-linked f-CD polymer, cationic surfactant dodecyltrimethy-lammonium bromide (DTAB), and a polyanion sodium salt dextran sulfate (NaDxS) by viscometry and small angle neutron scattering. They proposed a structure of polyion complexes between NaDxS and the supramolecular polycation formed from fi-CD polymer and DTAB. More recently, Amiel et al. [87] have characterized in detail the supramolecular polycation. 

All authors conclude that carbons with adjusted pore size distribution in the entire range of the nanopores can be obtained, depending the synthesis conditions and cationic surfactants used as templates. Despite this, it is an effective pathway to obtain porous carbons, even though the pore formation mechanism is not well understood. Hence, different mechanisms are used to explain its effect emerged, such as liquid crystal templating mechanism, cooperative self-assembly, electrostatic interaction between cationic surfactant molecules and the anionic RF polymer chain and micelles as nanoreactors to produce RF nanoparticles [51, 70]. In these cases, the simple mold effect from the globular form and the RF polymerization around it is insufficient to explain the structuring of the material by the template, where spherical closed pores would be expected. 

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