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AbstractHydrosilylation reactions, also known as the catalytic hydrosilylation, the reaction usually produces anti-Markovnikov additions alkane 1 (i.e., silicon on the terminal carbon) by the addition of Si-H bonds to unsaturated bonds. It also present in compounds in the form of alkenes and alkynes, offering numerous unique and advantageous properties for the preparation of polymeric materials, such as high yields and stereoselectivity. Hydrosilylation reactions requires to be catalyzed, and for which the most used catalyst are platinum compounds. Popular industrial catalysts are “Speier’s catalyst,” H2PtCl6, and Karstedt’s catalyst, an alkene-stabilized platinum(0) catalyst 2. Hydrosilylation has been called the “most important application of platinum in homogeneous catalysis”3. This review will discuss about the non-thermal stimulated hydrosilylation reactions and potential industrial applications.IntroductionHydrosilylation reactions has a wide range of applications, especially in the production of functional silanes and siloxanes. First report of hydrosilylation in history was from 1947 (70 years ago) 4 and the first report of Speier’s platinum catalyst was in 1957 (60 years ago) 5, the time of first application of a hydrosilylation reaction in polymer science can be dated back to 1967 6. The current trend along with the academia and industry are searching for both price-efficient and durable catalysts that meets the increasing demand of silicon-based polymers. The properties are targeted at catalysts selectivity, activity (TOF) and stability (TON). The Speier’s catalyst (H2PtCl6) and Karstedt’s catalysts (fig.1) are most used in industrial hydrosilylation reactions, due to their high performance in activity and selectivity.fig.1 Karstedt’s catalyst.Non-Thermal Stimulated Hydrosilylation ReactionConventional hydrosilylation reaction are spontaneous with the presence of catalysts, for the purpose of some industrial applications, it is required to have it reacted by external triggering. A formulation consist of catalyst and crosslinking components is the ideal setup and aimed to be stable for storage for months. With such specific demands, which were the main driving force for the development of externally triggered hydrosilylation reactions. Heat triggering has been most commonly used in industry. In this section, non-thermally triggered hydrosilylation reactions will be described.Microwave-Initiated Hydrosilylation ReactionsMicrowave irradiation works in a way that the radiation transfers heat to materials with the characteristic of separated or partial separated charges such as metals, ions and dipoles, it is challenging to differentiate between visible thermal initiation and the non-thermal microwave effects. Wei Sun and the group has been researching and proven that microwave-assisted heating had no visible or distinct acceleration effect on the reaction rate of hydrosilylation compared correspondingly to the conventional thermal heating 7.Rabah Boukherroub and the group reported that the functionalization of hydrogen-terminated porous silicon surfaces with functional alk-1-enes under microwave irradiation 8. Organic monolayers that are covalently attached to the surface by Si–C bonds were assumed that was originate from microwaves as energy source and it accelerated the reaction and it gives a higher yield on the surface coverage compared to conventional method. The reaction was performed at 180?C in an oil bath and it hardly yielded any chemical grafting on the particles’ surfaces, but with the method of microwave irradiation for 30 min at 170?C, the efficiency was reported to be 38%, at the end, no further improvement was done upon the variant of increasing temperature. Electrochemically-Initiated Hydrosilylation ReactionsEdward G. Robins and the group has reported in ‘Anodic and cathodic electrografting of alkynes on porous silicon’ that the terminal alkynes can be electrochemically grafted to porous silicon surfaces with either positive or negative bias 9. Through the process of cathodic electrografting (CEG), alkynes were directly attached to the surface, but with anodic electrografting (AEG), alkyl surface was generated. In the article it is suggested that the CEG method is continued by a silyl anion intermediate generated by the reduction of surficial Si–H bonds, followed with an in-situ generation of carbanion and the carbanion is from the deprotonation of acidic alkyne which leads to a nucleophilic Si–Si bond attack.Industrial ApplicationsThe catalysts used in industrial hydrosilylation processes has to show high selectivity, efficiency and stability. Few points need to be address here, increasing demand, existence of high efficient and low-cost catalysts, functional products that’s produced by hydrosilylation reaction in industrial applications will be described.CoatingsHu Liu and the group prepared an anti-graffiti film by combining PMHS polymer grafted with hexafluoro butyl acrylate into polyurethane 10. The free surface energy was reduced from 30.7 to 21.4 mN·m?1, values are polyurethane and anti-graffiti-polyurethane respectively. By lowering the free surface energy, the wetting capabilities were also correspondingly degraded. Cleaning tests shown that anti-graffiti-coated areas could be easily cleaned completely with just using water and isopropanol.Printing TechnologyMicro-contact printing is a method to transfer a master mold pattern onto a substrate. The master mold is usually created by 2.5-dimensional photolithography. The transfer mold is made by applying a layer of PDMS followed by a treatment through hydrosilylation reactions at an increasing temperature to yield an PDMS mold with elasticity 11. One disadvantage of PDMS is that it swells in common organic solvents, this shows the process of heat treatment.ConclusionsBy choosing carefully the catalyst, products can be synthesized with high purity and high yields. Platinum-based catalysts are commonly used, external stimulation other than heat can be applied to start the hydrosilylation reaction. Despite the achievements in the research of recent years, various challenges has been solved for many industrial applications. In my opinion, approaches related to triggered hydrosilylation, solvent-free processes and selectivity has tremendous potential for improving hydrosilylation suitabilities in industry.References1 “Hydrosilylation A Comprehensive Review on Recent Advances” B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009. doi:10.1007/978-1-4020-8172-92 C. Elschenbroich, Organometallics (2006) Wiley and Sons-VCH: Weinheim. ISBN 978-3-527-29390-23 Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; Lang, J.; Kreuzer, T.; Knödler, A.; Starz, K. A.; Dermann, K.; Rothaut, J.; Drieselman, R. (2002). “Platinum group metals and compounds”. Ullmann’s Encyclopedia of Industrial Chemistry. Wiley. doi:10.1002/14356007.a21_0754 Sommer, L.H.; Pietrusza, E.W.; Whitmore, F.C. Peroxide-catalyzed addition of trichlorosilane to 1-octene. J. Am. Chem. Soc. 1947, 69, 188. 5 Speier, J.L.; Webster, J.A.; Barnes, G.H. The addition of silicon hydrides to olefinic double bonds. Part II. The use of group VIII metal catalysts. J. Am. Chem. Soc. 1957, 79, 974–979.6 Marciniec, B. Hydrosilylation: A Comprehensive Review on Recent Advances; Springer Science & Business Media: Berlin, Germany, 2008; ISBN 978-1-4020-8172-9.7 Sun, W.; Qian, C.; Mastronardi, M.L.; Wei, M.; Ozin, G.A. Hydrosilylation kinetics of silicon nanocrystals. Chem. Commun. 2013, 49, 11361–11363.8 Boukherroub, R.; Petit, A.; Loupy, A.; Chazalviel, J.-N.; Ozanam, F. Microwave-Assisted Chemical Functionalization of Hydrogen-Terminated Porous Silicon Surfaces. J. Phys. Chem. B 2003, 107, 13459–13462.9 Robins, E.G.; Stewart, M.P.; Buriak, J.M. Anodic and cathodic electrografting of alkynes on porous silicon. Chem. Commun. 1999, 2479–2480.10 Liu, H.; Fu, B.; Li, Y.; Shang, Q.; Xiao, G. Antigraffiti polyurethane coating containing fluorocarbon side chains grafted polymethylsiloxane. J. Coat. Technol. Res. 2013, 10, 361–369.11 Perl, A.; Reinhoudt, D.N.; Huskens, J. Microcontact Printing: Limitations and Achievements. Adv. Mater. 2009, 21, 2257–2268.

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