Carbon silane functionalization

Zhou, Z., Wang, S., Lu, L., Zhang, Y, and Zhang, Y. 2007. Isothermal crystallization kinetics of pol5q)ropylene with silane functionalized multi-walled carbon nanotubes. 

In its simplest terms, the titanate function (1) mechanism may be classed as proton-reactive through solvolysis (monoalkoxy) or coordination (neoalkoxy) without the need of water of condensation, while the silane function (1) mechanism may be classed as hydroxyl-reactive through a silanol-sUoxane mechanism requiring water of condensation. The silane s silanol-siloxane water of condensation mechanism limits its reactions to temperatures below 100 °C, thereby reducing the possibility of in situ reaction in the thermoplastic or elastomer melt above 100 °C as is possible with titanates. In addition, a variety of particulate fillers such as carbonates, sulfates, nitrides, nitrates, carbon, boron and metal powders used in thermoplastics, thermosets, and cross-linked elastomers do not have surface silane-reactive hydroxyl groups, while almost all three-dimensional particulates and species have surface protons, thereby apparently making titanates universally more reactive. 

Ma, P.C., Kim, J.-K., Tang, B.Z., 2007. Effects of silane functionalization on the properties of carbon nanotube/epoxy nanocomposites. Composites Science and Technology 67, 2965-2972. 

As is well known to all, chemical functionalization disrupts the extended n conjugation of CNTs and consequently reduces the electrical conductivity of functionalized CNTs. Silane-functionalized CNT/epoxy nanocomposites exhibited lower electrical conductivity than did untreated CNT composites at the same content of CNTs. In 2005, Cho and co-workers observed that the electrical conductivity of the surface-functionalized MWNT composites was lower than that of the untreated MWNT composites with the identical content of CNTs. This is attributed to the increased defects in the lattice stmaure of carbon-carbon bonds on the surface of CNTs due to the acid treatment. Generally, the severe functionalization of CNTs can sigrtificantly lower the conductivity of the composites. However, several researchers have foimd that the fimaionalization of CNTs could improve the electrical conductivity of the composites. In 2005, Tambutri and co-workers reported that the functionalization of SWNTs with -COOH and -OH groups enhanced the conductivity of composites compared to untreated SWNTs. 

Although there have been few reports on the chemistry of transient silanethiones,113 some stable examples have been successfully isolated by thermodynamic stabilization. In 1989, Corriu et al. reported the first synthesis of an isolable silanethione 31a (mp 170-171°C) by the reactions of the pentacoordinated functionalized silane 30a with elemental sulfur or carbon disulfide (Scheme 8).17... 

As an example of the selective reactivity of borazirconocene alkenes, their hydrolysis was examined [1]. The carbon—zirconium bond is more reactive than the carbon—boron bond towards various electrophiles, and so hydrolysis can be expected to occur with preferential cleavage of the former bond. Since hydrolysis of alkenylzirconocenes is known to proceed with retention of configuration [4,127—129], a direct utility of 45 is the preparation of (Z)-1-alkenylboronates 57 (Scheme 7.17) [12]. Though the gem-dimetalloalkenes can be isolated, in the present case it is not necessary. The desired (Z)-l-alkenylboronates can be obtained in a one-pot procedure by hydrozirconation followed by hydrolysis with excess H20. The reaction sequence is operationally simple and is compatible with various functional groups such as halides, acetals, silanes, and silyloxy protecting groups [12]. 

Silyltitanation of 1,3-dienes with Cp2Ti(SiMe2Ph) selectively affords 4-silylated r 3-allyl-titanocenes, which can further react with carbonyl compounds, C02, or a proton source [26]. Hydrotitanation of acyclic and cyclic 1,3-dienes functionalized at C-2 with a silyloxy group has been achieved [27]. The complexes formed undergo highly stereoselective addition with aldehydes to produce, after basic work-up, anti diastereomeric (3-hydroxy enol silanes. These compounds have proved to be versatile building blocks for stereocontrolled polypropionate synthesis. Thus, the combination of allyltitanation and Mukayiama aldol or tandem aldol-Tishchenko reactions provides a short access to five- or six-carbon polypropionate stereosequences (Scheme 13.15) [28],... 

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