Hydrosilylation polymerization scheme

Scheme 14.4 Synthesis of poly(phenylene-silylene-ethylene)s via hydrosilylation polymerization process.

As been shown by Weber, simultaneous hydrosilylation-polymerization can be accomplished with a Pt-catalyst <1995BSF551>, as shown in Scheme 20. 

Finally, the platinum-catalyzed hydrosilylation polymerization was also used very recently by Cassidy et al. [82,83] to prepare fluorine containing silicon-organic hybrid polymers in supercritical carbon dioxide (SCCO2) (cf. Scheme 32). 

Many other difiinctional organosilicon monomers containing both alkenyl groups and Si—H bonds in the molecule have also been successfully used in the platinum-catalyzed hydrosilylation polymerization (353-355) (Scheme 35). 

Scheme 12. Schematic structure of vinyl-eb-PDMS chains (dashed line) crosslinked with polymeric TMS-eb-PHMS through the hydrosilylation cure reaction. For illustration purpose the PDMS chains in this scheme are shorter and less abundant relative to PHMS than in real system.

For the hydrosilylation reaction various rhodium, platinum, and cobalt catalysts were employed. For the further chain extension the OH-functionalities were deprotected by KCN in methanol. The final step involved the enzymatic polymerization from the maltoheptaose-modified polystyrene using a-D-glucose-l-phosphalc dipotassium salt dihydrate in a citrate buffer (pH = 6.2) and potato phosphorylase (Scheme 59). The characterization of the block copolymers was problematic in the case of high amylose contents, due to the insolubility of the copolymers in THF. 

Scheme 6.79 Hydrosilylation of ketones [164], Dotz benzannulation chemistry [165], cobalt-mediated synthesis of angular [4]phenylenes [166], and nickel-mediated coupling polymerizations [167],...

Tho main routes for the insertion of fluorinated alkyl groups in the silicones are suggested either by organometallic or by hydrosilylation methods as shown in Scheme 2. Consequently, research can be pursued in two directions (a) synthesis of fluorohalides and alkenes, and (b) introduction in siliconated groups and polymerization. 

The synthesis and characterization of a series of dendrigraft polymers based on polybutadiene segments was reported by Hempenius et al. [15], The synthesis begins with a linear-poly(butadiene) (PB) core obtained by the sec-butyllithium-initiated anionic polymerization of 1,3-butadiene in n-hexane, to give a microstructure containing approximately 6% 1,2-units (Scheme 3). The pendant vinyl moities are converted into electrophilic grafting sites by hydrosilylation with... 

PMHS corresponding polymeric reagent (PMHS, polymethylhydrosiloxane), a substantial rate increase was observed over the monomeric model (complete reduction of acetophenone in less than 1 min with PMHS vs. only 60% conversion in 1 h with (EtO)2SiHMe) [55]. The related hydrosilylation of 86 by chiral PTC uses an interesting ep/iedra-derivedhalometallated catalyst 25 (Scheme 10.12) [56],... 

Percec and co-workers not only developed monomers suitable for radical polymerization but also presented systems suitable for the introduction into poly (methylsiloxane)s [34] via hydrosilylation (Scheme 12). Monomer 23 with a terminal double bond was added to the poly(methylsiloxane) using Cp2PtCl2 as a catalyst to give poly (23). The trends observed for poly (23) were also found for poly(17) as polymerization improves the mesophase stability significantly. 

As Weber has shown, polymers bearing reactive Si-H bonds can be formed by ring-opening polymerization of 1-silacyclobutane <1992PB281>. These polymers can be further converted into Si-functionally-substituted polycarbo-silanes by Pt-catalyzed hydrosilylation reaction of Si-H functionality with alkenes (Scheme 18) <1993MM563>. 

As exemplified by the reactions of Schemes 1 and 4, fluorotitanium compounds could open new possibilities for metal-catalyzed processes. Their fascinating structural diversity [7] as well as further catalytic possibilities in the field of olefin polymerizations [7i, 16] have been put forward by the pioneering work of Roesky, Noltemeyer and co-workers. Similar properties were also exhibited by the analogous zirconium and hafnium compounds [7b,i]. A Zr binaphtholate has already been successfully applied for the enantioselective allylstannylation of aldehydes [2f], Buch-wald and co-workers successfully used a chiral titanocene difluoride as precursor for the corresponding Ti(lII) hydride, a very efficient catalyst for the enantioselective hydrosilylation of imines [17]. 

Fig. 9.11. Reaciion scheme for the synthesis of network-polymeric CSPs and representative chromatograms, (a) Derivatization of A, A -diallyl-(R.R)-tartaric acid diamide (DATD) to give the bifunctional monomers used as chiral SO units, (b) Cross-linking and immobilization by hydrosilylation with multifunctional hydrosilane (alternatively, cross-linking and immobilization can be performed first with DATD followed by O-derivatization). (c) Enantioseparation of 2-(octylsulphinyl)benzoic acid. The chromatograms illustrate the column performance under non-overloadcd (left) and overloaded conditions (right). CSP network polymer from /V. -diallyl-i/il.Rl-tartaric acid diamide fc/.s-. i.S-dimethylbenzoatc bound to. ) pm 1.50 A Kromasil. Mobile phase hexane-THF (80 20 v/v) with 0.0.55 - of TFA (reprinted with permission from Ref. [194]).

Two AIBN-type radical polymerization initiators have been synthesized starting from commercial 4,4 -azo-bis(4-cyano)valeric acid (1) (Scheme 1) ACTP 3 -trichlorosilylpropyl-4,4 -azo-bis(4-cyano)valerate (4a) and ACTU 11 "-trichlorosilylundecyl-4,4 -azo-bis(4-cyano) valerate (4b). After thorough drying of the wet diacid 1, it was transformed into its chloride (2) using an excess of phosphorus pentachloride in dichloromethane. Reaction of 2 with the unsaturated alcohols allyl alcohol and 10-undecen-l-ol respectively gave the esters 3 in high yields which in turn led to ACTP (4a) and ACTU (4b) on Pt-catalyzed hydrosilylation. 

Polylithiated carbosilane dendrimers were also employed as multifunctional initiators for the polymerization of styrene, ethylene oxide, and hexa-methylcyclotrisiloxane (D3),27 according to Scheme 6. The dendrimers had 16 or 32 allyl groups at their periphery. A hydrosilylation route was performed to... 

A new type of resin for the attachment of alcohols and phenols, dubbed as Rasta silanes 60, has been prepared from TEMPO-mefhyl resin 58 with diaUcylsilane styrenes 59 by radical polymerization [63] (Scheme 27). The process of its preparation allowed for the adjustment of loading capacity, silane spacing, and the relative distance of the silane entities from resin cores. Hydrosilylation or transformation to silyl chlorides was applied to the couphng of alcohols and phenols. 

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