Vinyl functions

Table 11. Maleic Anhydride Copolymers with Vinyl Functionality...

Newer silicone adhesives having solids levels up to 97% are also commercially available [109]. Instead of using silanol condensation reactions, they rely on addition chemistry between vinyl functional silicone oligomers and silicon hydride terminated silicones. This addition reaction is typically facilitated with platinum derived catalysts. This hydrosilation process can be run at reduced oven temperatures, but the finished products typically do not yield the same balance of properties as seen for condensation cure materials. 

Hydrosilation silicones or addition cure systems utilize a hydride functional crosslinker with a vinyl functional base polymer and a noble metal catalyst. While the cure can be initiated with UV [48,49], thermal cure versions dominate the commercial market [23,50]. In thermal cure systems, inhibitors are necessary for processing and anchorage additives are common. 

Thermal cure system. The thermal cure system is based on a hydrosilylation addition reaction between vinyl-functionalized and silicon-hydrido functionalized polysiloxanes [32,33,35], Unsaturated organic groups react with a Si-H functionality in the presence of a platinum-based catalyst (Scheme 10). 

The composition of the products derived from hydrogenation of vinyl functions is determined by the relative rates of two competing reactions. 

Extensive hydrogenolysis of vinyl ethers does not occur always over platinum. Reduction of 28 proceeded smoothly to 29 (/09). It is likely that the high pressure and low temperature used in this experiment helped to minimize hydrogenolysis. For effective use of subambient ( —30°C) temperatures in stopping hydrogenolysis of vinyl functions, see (/Oa). 

Nitriles [153, 211] are tolerated by an equivalent of reagent in the presence of a particularly reactive site of unsaturation, such as a terminal alkyne or vinyl function, whereas methacrylonitrile gives only C N hydrozirconation (Scheme 8-26) [215]. 

We can create crosslinks during chain growth polymerization by copolymerizing dienes with vinyl monomers. When the two vinyl functions of the diene are incorporated into separate chains, a crosslink is formed. This process is shown in Fig. 2.18. When we use a low concentration of dienes, we produce a long chain branched polymer, while high concentrations of dienes create a highly crosslinked polymer network... 

Hyperbranched polymers can be synthesized in several different ways, the most commonly used being classical condensation reactions. These reactions are made either in bulk or in solution where the A,jB monomers are condensed by themselves or in combination with a By core monomer. The use of a By core monomer improves the control over the molecular weight and dispersity of the hyperbranched polymer. Hyperbranched polymers can also be synthesized by self-condensing vinyl polymerization using vinyl-functional monomers. The introduction of this approach has greatly increased the number of possible monomers that can be used for this type of polymer. 

Other recent reports of interesting terpolymerization processes involving cyclohexene oxide and diglycolic anhydride or vinylcyclohexene oxide have appeared in the literature [66-68]. These processes are indicated in (7) and (8), and were carried out in the presence of p-diiminate zinc catalysts. The vinyl functionalized polymer was intramolecularly crosslinked by a metathesis reaction to afford nanoparticles. 

Ni phosphorus-ylide complexes were reported by Ittel and co-workers to be active for the co-polymerization of ethylene and non-vinyl-functionalized monomers, yielding functionalized polyethylenes (PEs). These results demonstrate the high potential of late transition metal complexes for the production of co-polymers from hydrocarbon and polar monomers. 

Figure 1. Two commercially available difunctional compounds featuring isocyanate and acrylate (vinyl) functionality.

Side chain furan functionalization has been accomplished by acetalization (Section 1.11.4.4.3) of poly(vinyl alcohol) (180) with furan-3-carbaldehyde (181 Scheme 87) (72MI11106). The adduct (182) was utilized as the diene reactant in a Diels-Alder reaction to bind vinyl-functional siloxane oligomers to the polymer. 

Lubrication oil additives represent another important market segment for maleic anhydride derivatives Maleic anhydride is used in a multitude of applications in which a vinyl copolymer is produced hy the copolymerization of maleic anhydride with other molecules having a vinyl functionality. The use of maleic anhydride in llie manufacture of agricultural chemicals has declined ill the L ,S. since the early 1980s. 

SCHEME 6. Mechanism of radical addition of EMA to vinyl functional PDMS... 

The reaction of vinylindoles containing the vinyl function incorporated in a carbocyclic ring provide access to novel polycyclic indole derivatives. The reaction of 46 with DMAD under forced conditions gave a mixture of Diels-Alder (47), Michael (48), and ene (49) adducts (91LA357). 

The vinyl function can be incorporated into a carbocyclic ring. In this context the reactivity of the readily available 3-(l-cyclohexenyl)indole 46 toward different dienophiles was studied (91LA357). In some cases (DMAD, NPMI) the Diels-Alder cycloadducts were obtained (Sections II,A,4 and II,C,4) however, reaction with DEAZD and PTAD afforded the ene adducts 254 and 255. 

The vinyl functionality attached to the 3-position of the thienyl ring should be an excellent candidate for radical-induced cross-linking of these systems since poly thiophenes are relatively inert to free radicals (95MM4608). Two different synthetic routes were used to achieve the target polymers. One of the routes leads to polymers which adhere very strongly to polar substrates. The photoluminescence properties of some of these compounds have been studied (95SM(69)377). 

A catalytic enantio- and diastereo-selective aldol reaction of ketones with ketene (g) silyl acetals, H2C=C(OTMS)-OMe, gives fair to good yields and ee.129 With further substitution of the vinyl function, the reaction is diastereoselective, up to 97%. A highly developed catalyst/promoter protocol is employed a copper fluoride complex is combined with a Taniaphos auxiliary (a chiral ferrocenyldiphosphine), plus (EtO)3SiF. Evidence for the formation of species (EtO)4 SiF (n > 2) as active... 

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