Fluoroalkyl end-capped

Scandium triflate-catalyzed aldol reactions of silyl enol ethers with aldehyde were successfully carried out in micellar systems and encapsulating systems. While the reactions proceeded sluggishly in water alone, strong enhancement of the reactivity was observed in the presence of a small amount of a surfactant. The effect of surfactant was attributed to the stabiMzation of enol silyl ether by it. Versatile carbon-carbon bondforming reactions proceeded in water without using any organic solvents. Cross-linked Sc-containing dendrimers were also found to be effective and the catalyst can be readily recycled without any appreciable loss of catalytic activity.Aldol reaction of 1-phenyl-l-(trimethylsilyloxy) ethylene and benzaldehyde was also conducted in a gel medium of fluoroalkyl end-capped 2-acrylamido-2-methylpropanesulfonic acid polymer. A nanostmctured, polymer-supported Sc(III) catalyst (NP-Sc) functions in water at ambient temperature and can be efficiently recycled. It also affords stereoselectivities different from isotropic solution and solid-state scandium catalysts in Mukaiyama aldol and Mannich-type reactions. 

Poly(Ai-acryloylmorphobne) pAOM RAFT polymerization [3(X), 466-468] Well soluble in water is probably 1(X) °C 36 < Tip < 80°C thermosensitive fluoroalkyl-end-capped pAOM homo- and co-oUgomers [469,470] Tacticity [223]... 

FIGURE 4.1 Schematic model for the formation of fluoroalkyl end-capped oligomeric aggregates with the aggregation of end-capped fluoroalkyl groups. 

In this chapter, we would like to review the recent development of preparation and applications of fluoropolymer nanocomposites by the use of fluoroalkyl end-capped oligomers as key intermediates. 

SCHEME 4.2 Synthesis of two fluoroalkyl end-capped acrylic acid oligomer by using fluoroalkanoyl peroxide. 

PREPARATION AND THERMAL STABILITY OF FLUOROALKYL END-CAPPED OLIGOMERS/SILICA NANOCOMPOSITES... 

Fluoroalkyl end-capped A-(l,l-dimethyl-3-oxobutyl)acrylamide oligomer/silica nanocomposites [Rp—(DOBAA) —Rp/Si02l were prepared by the sol-gel reactions of the corresponding oligomer with tetraethoxysilane (TEOS) under alkaline conditions (see Scheme 4.5) [43 5]. 

SCHEME 4.5 Preparation of fluoroalkyl end-capped A -(l,l-dimethyl-3-oxobutylacrylamide) oligomers [Rp—(DOBAA) —Rpl/silica nanocomposites. 

Fluoroalkyl end-capped acrylic acid oligomer [Rp—(CH2CHCOOH) —Rp/Si02l [Rp—(ACA) —Rp]/silica nanocomposites decompose completely at 800°C to afford the weight loss in proportion to the content of Rp—(ACA) —Rp oligomer in composites due to the nonformation of ammonium hexafluorosihcate during the calcination... 

Fluoroalkyl end-capped acrylic acid oligomer [Rp—(ACA) —Rp] can also react with (TEOS) and silica nanoparticles in the presence of low molecular weight aromatic compounds [Ar—H] such as cetylpyridinium chloride (CPC) and bisphe-nol AF under alkaline conditions to afford Rp—(ACA) —Rp/Si02 nanocomposites-encapsulated Ar—H in excellent to moderate isolated yields (see Scheme 4.7) [49],... 

These fluorinated silica nanocomposites-encapsulated Ar—H can exhibit no weight loss behavior corresponding to the contents of Ar—H even after calcination at 800°C, although fluoroalkyl end-capped acrylic acid oligomer in the nanocomposites decomposed completely under similar conditions [49]. 

Novel cross-linked fluoroalkyl end-capped trimethoxyvinylsilane oligomeric nanoparticles [Rp—(VM-Si02) —Rp]-encapsulated l,l -bi(2-naphthol) (BINOL) were prepared by the sol-gel reaction of fluoroalkyl end-capped trimethoxyvinylsilane oligomer in the presence of BINOL under alkaline conditions (see Scheme 4.8) [50],... 

SCHEME 4.8 Preparation of fluoroalkyl end-capped trunethoxyvinylsilane oligomeric nanoparticles [Rp—(VM-Si02) —RpJ ncapsulated l,l -bi(2-naphthol) (BINOL). 

PREPARATION AND PROPERTIES OF FLUOROALKYL END-CAPPED OLIGOMERS/TITANIUM OXIDE NANOCOMPOSTTES... 

It is well-known that anatase transforms irreversibly to rutile at elevated temperatures [70]. Normally, the phase transformation temperature in air from anatase to rutile titanium oxide is between 600°C and 750°C [71]. From an applicable viewpoint of anatase titanium oxide into a variety of fields, it is deeply desirable to develop thermally stable anatase titanium oxide composites without the phase transformation to mtile under such higher temperature conditions. We have very recently found that fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposites [Rp—(VM—Si02) —RF/0 -TiO2] can keep completely its... 

Polyaniline (PAn)/inorganic composites have been considered as new class of materials due to their improved properties compared with those of pure conducting polymers and inorganic materials [73-77]. For example, the combination of electrical conductivity of PAn and UV sensitivity of anatase Ti02 are expected to find applications in electrochromic devices, nonlinear optical system, and photochemical devises [73], From this point of view, it is in particular interest to prepare fluoroalkyl end-capped oligomers/PAn/titanium oxide nanocomposites. In fact, fluoroalkyl end-capped acrylic acid oligomer [Rp—(ACA) —Rp]/, 2-methacryloyloxyethane sulfonic acid oligomer [Rp—(MES) —Rp]/, 2-acrylamido-2-methylpropanesulfonic acid... 

SCHEME 4.11 Preparation of fluoroalkyl end-capped oligomers/PAn nanocomposites. 

Fluoroalkyl end-capped oligomeric aggregates can be applicable to the encapsulation of metal flne particles such as gold nanoparticles [98-101], magnetic nanoparticles [102], palladium nanoparticles [103], zinc oxide nanoparticles [104], copper nanoparticles [105,106], and silver nanoparticles [107] to afford the colloidal stable fluorinated oligomeric nanocomposites-encapsulated these metal nanoparticles. In these nanocomposites, especially, encapsulated gold nanoparticles into these fluorinated oligomeric nanocomposite cores can afford the extremely red-shifted plasmon... 

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