Surfactant surface-grafted

Direct hydrothermal synthesis. Prepared using titanium isopropoxide (triethanolaminato) and TEOS as the sources of Ti and Si, respectively, and the Gemini-type surfactant 18-12-18 or cetyl-benzyl dimethylammonium chloride (CBDAC) as a template. In the grafting method, silicious MCM-48 first prepared and then the dry surface grafted with titanium isopropoxide... 

In the next section, therefore, we review recent studies of simpler cases, i.e., homopoly(macromonomers), star- and comb-shaped polymers, followed by some interesting properties of the graft copolymers to be used as polymeric surfactants, surface modifiers, and compatibilizers for blends. 

An elegant example of the analysis of colloid surfaces containing covalently attached hydrophilic species has been provided by Brindley et al who studied the surface chemistry of polystyrene colloids with surface grafted polyethylene glycol groups [39]. These colloids were prepared by surfactant-free copolymerization of styrene with PEG using potassium persulphate as an initiator. The XPS analysis of these microparticles is shown in Fig. 11. 

Several laboratories have developed the methods of mesoporous silica surface functionalization with simultaneous removal of the surfactant and grafting of organic functionalities without prior calcination. A convenient and highly controllable approach to the surface functionalization of mesoporous silica[221] employs an alcoholic solution of... 

Electrospun polystyrene (PS) (Rojas et al. 2009) and PCL (Zoppe et al. 2009) micro or nanofibers reinforced with cellulose nanocrystals were obtained by electrospinning. Nonionic surfactant sorbitan monostearate was used to improve the dispersion of the particles in the hydrophobic PS matrix while surface grafting of long chains was used in the case of PCL. 

A second class of substrates corresponds to surfaces which are smooth but on which molecules with a long tail (such as surfactants) are grafted, forming a layer that the liquid crystal can penetrate (Fig. 4b). The influence of the substrate on the liquid crystal at a microscopic level can then be separated into two parts the effect of the surface underlying the surfactant layer and the effect of the chains forming the layer. It seems that the latter always dominates the liquid crystal adopts the orientation of the chains... 

Concerning the PHB and PHBV nanocomposites with CNC production, the non-hydrosoluble system can be performed through two routes in order to obtain non-flocculated dispersions coating the surface of CNCs with surfactant and, grafting of hydrophobic chains onto the surface of CNCs [21]. 

Most polymeric surfaces are hydrophobic in nature. In order to improve adhesion (adhesion with other surfaces, adhesion with paints or heparin for biomedical appUcations), this trait must be modified [31]. The most common method of doing this is by oxidation of the surface, which can be carried out by either corona discharge, flame treatment, plasma polymerization at the surface, grafting reactions, or blending the polymer with reactive surfactants that enrich at polymer interfaces. It has been shown that benzophenone xmder ultraviolet irradiation can abstract hydrogen from a polymer surface ... 

Tethering may be a reversible or an irreversible process. Irreversible grafting is typically accomplished by chemical bonding. The number of grafted chains is controlled by the number of grafting sites and their functionality, and then ultimately by the extent of the chemical reaction. The reaction kinetics may reflect the potential barrier confronting reactive chains which try to penetrate the tethered layer. Reversible grafting is accomplished via the self-assembly of polymeric surfactants and end-functionalized polymers [59]. In this case, the surface density and all other characteristic dimensions of the structure are controlled by thermodynamic equilibrium, albeit with possible kinetic effects. In this instance, the equilibrium condition involves the penalties due to the deformation of tethered chains. 

Ti-MCM-48 (surface area = 1000-1450 m2/g, pore volume = 0.8-1.1 cm3/g, pore diameter = 2.4-2.7 nm) was synthesized by hydrothermal and postsynthetic grafting techniques from cationic alkylammonium surfactants (22,25,323). 

The mesoporous materials reported above are usually prepared from relatively expensive surfactants. Some of them have poor hydrothermal stability. Furthermore, the MCM-41 host structure has a one-dimensional pore system with consequent pore blockage and diffusion limitations. Shan et al. (52) reported the synthesis of a three-dimensional and randomly connected mesoporous titano-silicate (Ti-TUD-1, mesopore wall thickness = 2.5-4 nm, surface area — 700-1000 m2/g, tunable pore size —4.5-5.7 nm) from triethanolamine (TEA). Ti-TUD-1 showed higher activity (about 5.6 times) for cyclohexene epoxidation than the framework-substituted Ti-MCM-41. Its activity was similar to that of the Ti-grafted MCM-41 (52). 

Y. Sela, Y. Magdassi, and N. Garti Polymeric Surfactants Based on PolysUoxanes-Graft-Poly(Oxyethylene) for Stabilization of Multiple Emulsions. Colloids Surfaces 83, 143 (1993). 

Y. Sela, S. Magdassi, and N. Garti Newly Designed Polysiloxane-Graft-Poly (Oxyethylene) Copolymeric Surfactants Preparation, Surface Activity and Emulsification Properties. Colloid Polym. Sci. 272, 684 (1994). 

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