China 
Africa 
Explore chapters and articles related to this topic
Poly(siloxane)s, Poly(silazane)s and Poly(carbosiloxane)s
Published in Narendra Pal Singh Chauhan, Functionalized Polymers, 2021
Claire E. Martin, Giovanni Fardella, Ricardo Perez, Joseph W. Krumpfer
The final two polymerization techniques require a transition metal catalyst. Figure 8C shows the polymerization of 1,1,3,3-tetramethyldisiloxane and 1,1,3,3-dimethyl-1,3-divinyldisiloxane catalyzed by a platinum catalyst. Given the high efficiency and exothermic nature of hydrosilylation reactions, such preparations must have very careful temperature control in order to prevent explosions. Acyclic diene metathesis (ADMET) is another route towards creating polycarbosiloxanes, especially those containing unsaturated bonds in the backbone. ADMET requires the use of common ruthenium catalysts, such as Grubb’s II, to prepare polymer (Smith and Wagener 1993). Both hydrosilylation and ADMET can also be used in the preparation of polycarbosilanes through the use of difunctional silanes or monomers that do not contain siloxane bonds. Furthermore, the number of different addition techniques shown here opens up many avenues to orthogonal syntheses, particularly for dendrimer preparations, which are briefly discussed later in this chapter.
Silicon-based core–shell nanostructures
Published in Klaus D. Sattler, Silicon Nanomaterials Sourcebook, 2017
Mallar Ray, Sayak Dutta Gupta, Atrayee Hazra
Surface termination methodologies of Si NCs with organics are very different from that of other semiconductor NCs. In contrast to ligand exchange, which is by far the most common technique used for surface modification of other semiconductor NCs, hydrosilylation is the most important method for Si NCs. Hydrosilylation is a process by which unsaturated surface bonds across a Si NC are passivated by H, that is, Si–H bonds are formed. The Si–H bonds on NC surfaces can subsequently be replaced with suitable groups to prepare alkyl-terminated, amine-terminated, and carboxyl-terminated Si NCs. All that needs to be done to replace the Si–H bonds with a suitable organic ligand is to supply appropriate thermal or mechanical or photochemical energy in the presence of the organic moiety. Si–H bonds are then replaced with stable Si–C bonds on Si NC surface. Table 9.1 summarizes the different methods used for the preparation of H-terminated Si NCs, followed by the functionalization techniques. In all the cases listed in Table 9.1, the initial core that is developed consists of H-terminated Si NCs.
Foaming Chemistry and Physics
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Kalman Koczo, Mark D. Leatherman, Kevin Hughes, Don Knobloch
The SiH fluid can be made by various processes, for example, by modifying the Direct Process (see Equation 19.5) and then re-equilibrating with cyclics (similarly to Equation 19.8) to obtain the required number of repeat units in the polymer backbone (x and y). Many types of catalysts can be used for hydrosilylation, but Pt-based ones are most typical, such as chloroplatinic acid (H2PtCl6) and Karstedt’s catalyst (Pt((CH2═CH)(CH3)2SiOSi(CH3)2(CH═CH2))3). The reaction is exothermic and temperature control is important to minimize side reactions. A significant side reaction in the hydrosilylation of allyl-functional species is the isomerization of the allyl group to propenyl: H2C=CH-CH2-R′→H3C-HC=CH-R′ The propenyl group typically does not react with SiH, and therefore, a molar excess of allyl reagent (10%–40% with polyethers) may be used to completely consume all of the SiH groups. The hydride fluids react not only with allyl groups, but with active hydrogens as well (such as those in water or alcohols), forming hydrogen gas via dehydrocondensation. This is not only a side reaction, but may also lead to increased flammability and pressure in closed systems, and therefore the purity of the starting reaction mixture is critical, as is complete reaction of the SiH groups. Additionally, if the allyl species being hydrosilylated contains reactive hydrogen groups, cross-linking and gelation may occur due to dehydrocondensation. This can be minimized with careful temperature and pH control during the hydrosilylation reaction or can be avoided by protecting the reactive end groups (e.g., by converting a C─OH end group into a nonreactive group, such as C─OMe).
Rhodium(I) complexes with N-heterocyclic carbene ligands: synthesis, biological properties and catalytic activity in the hydrosilylation of aromatic ketones
Published in Journal of Coordination Chemistry, 2021
Naceur Hamdi, Ichraf Slimani, Lamjed Mansour, Faisal Alresheedi, Ismail Özdemir, Nevin Gürbüz
Hydrosilylation is a vital industrial process which is employed to synthesize polysiloxanes and polysilanes, inter alia [31]. Moreover, it is employed in the conversion of ketones to secondary alcohols [32]. Generally, the term hydrosilylation refers to the addition of hydrosilanes to double and triple bonds within the laboratory. Hydrosilylation could be convenient to make a range of organosilicon compounds. The evolution of various hydrosilylation catalysts has already been summarized [33].
Applications of atomic force microscopy-based imaging and force spectroscopy in assessing environmental interfacial processes
Published in Critical Reviews in Environmental Science and Technology, 2022
Yuyao Zhang, Xiaoying Zhu, Chiheng Chu, Xin Xiao, Baoliang Chen
Hydrosilylation, in comparison, makes full use of the reaction of 1-alkenes with Si-H-terminated silicon to form covalent Si-C bonds (Figure S2c, Supplementary material) (Buriak, 2002). Prior to hydrosilylation, the tip is cleaned and activated, followed by immersed in 5% HF solution to get a Si-H-terminated surface. Finally, C = C bonds of 1-alkenes is broken and inserted onto Si-H groups by a thermally-induced method or a chemical-induced method (Buriak, 2002; Sieval et al., 1999).
Chemical modification of group IV graphene analogs
Published in Science and Technology of Advanced Materials, 2018
Hideyuki Nakano, Hiroyuki Tetsuka, Michelle J. S. Spencer, Tetsuya Morishita
(SiH)n can be also be functionalized with a variety of unsaturated functional groups using a hydrosilylation reaction. In these reactions, Lewis acids or Pt are found to efficiently catalyze the hydrosilylation reaction. Rieger’s group reported the surface modification of silicanes with a variety of unsaturated substrates, and they demonstrated the synthesis of new silicon/semiconducting polymer-based field-effect transistors [87].