Vinyl-substituted monomers

For example, a proline-based chiral ligand was attached to a vinyl-substituted monomer (Fig. 42.15) by reacting vinylbenzoyl chloride with the amine functionality of the ligand [106]. As mentioned previously, the apolar Merrifield resin as a support is not swollen in polar solvents. Hence, in order to match the polarity of the resin with that of the typically used substrates in enantioselective hydrogenation, the functionalized monomer was copolymerized with polar units of methacrylic acid 2-hydroxyethyl ester. 

BH3 Copolymerisation of the vinyl-substituted monomer with styrene and Promotor in Mukaiyama aldol reactions Scheme 1.6 JO). Yields are comparable but enantiomeric excesses are lower than those obtained with the soluble Ts-Val-OH.257 Catalyst for Diels-Alder reaction of cyclopentadiene and methacrolein (Scheme 1.6.30) P ... 

The reactivities of substituted monomers are different from those of the unsubstituted ones. For example, in crosspropagation an electron donating methyl group introduced to the C = C bond of a vinyl monomer makes it less reactive in anionic copolymerization, while it increases its reactivity in a cationic process. Thus, in THF at 25 °C the reactivity of isoprene towards polystyrene anion is lower by about a factor of 2 than that of butadiene (only one end of this bivalent monomer is affected),... 

Figure 4 Sketch of two possible stereochemical arrangements for a chiral monomer. P represents the polymer chain, R represents a vinyl substitutent on a carbon, H represents hydrogen, (a) Linear sketch showing one conformation and two configurations (bracketed and unbracketed). The apex of bonds is a tetrahedrally bonded carbon atom (solid and dashed circles), (b) Newman projection of the same monomer showing the free rotation about the C-C bond.

Vinyl substituted cyclic hemlamidals 2 and their Interconvertible acetal precursors (eg. acrylamldo-butyraldehyde dimethyl acetal 1) were Incorporated as latent crosslinkers and substrate reactive functional comonomers In solution and emulsion copolymers. Some use and applications data for copolymers prepared with these new monomers are presented. They show low energy cure potential, long shelf life and high catalyzed pot stability In solvent and aqueous media, good substrate reactivity and adhesion, and good product water and solvent resistance. They lack volatile or extractable aldehyde (eg. formaldehyde) components and show enhanced reactivity and hydrolytic stability with amines and diol functional substrates. 

Three types of stationary phases based on the free-radical reaction of monocationic and dicationic vinyl-substituted imidazolium cations were studied [42]. Two examples of such monomers are given by ILs 9 and 10 in Table 4.1. The formation of a linear IL polymer stationary phase was performed by the free radical polymerizafion of monocationic monomers. 

Figure 4.3 Scheme illustrating the development of immobilized ionic liquids by thermally induced free radical polymerization of vinyl-substituted imidazolium-based monocationic and dicationic monomers. 

When the Heck vinylic arylation reaction is carried out with an olefin which is either a gas or a low boiling liquid, it must be run in a pressure vessel. Depending upon the product desired, the olefin is usually present in an excess concentration in order to insure formation of vinyl substituted products. In the case of the reaction of ethylene with 2 the stoichiometry of the reactants is critical (Fig. 5). If 4-bromobenzocyclobutene 2 is present in higher concentrations than ethylene, a different monomer, l,2-di(4-benzocyclobutenyl)-ethylene 11 is obtained. 

A fluorescent MIP chemosensor for determination of 9-ethyladenine was fabricated [56]. It contained porphyrin as a luminescent functional monomer. The interaction of 9-ethyladenine with the porphyrin quenched the MIP luminescence at 605 nm when excited at 423 nm. The polymer was sensitive to 9-ethyladenine in the range of 0.01-0.1 mM however, it was already saturated at 0.15 mM. The same researchers used vinyl-substituted zinc(II) porphyrin and methacrylic acid as functional monomers for imprinting of (-)-cinchonidine [57]. The MIP luminescence, when excited at 404 nm, was significantly quenched at 604 nm upon binding of (-)-cinchonidine, even in the low concentration range of 0.01-2 mM. 

Danusso extended the above work with various substituted vinyl aromatic monomers (304) and discussed the reaction mechanisms based on these results (277). Some of the conclusions which are pertinent to this discussion are summarized below. 

Let us consider a vinyl polymer from an unsymmetrically substituted monomer in the planar conformation. The neighbouring C—C bonds can form one of the two possible diads, meso (m) and racemic (r),... 

Acetic acid is used in the manufacture of a wide variety of products including adhesives, polyester fibres, plastics, paints, resins and solvents. About 40% of the acetic acid made industrially is used in the manufacture of vinyl acetate monomer for the plastics industry other large uses are to make cellulose acetate, a variety of acetate esters that are used as solvents, as well as monochloracetic acid, a pesticide. Acetic acid is also used as a solvent for the oxidation of p-xylene to terephthalic acid, a precursor to the important polyester, polyethylene terephthalate (PET). A minor, but important use is as non-brewed condiment, a vinegar substitute widely used in British fish and chip shops this is made using food-grade industrial acetic acid and is less expensive than fermentation vinegar. 

Finally, the polymerization of vinyl monomers usually proceeds as a practically irreversible reaction. Exceptions are heavily substituted monomers like a-methylstyrene for which propagation is clearly reversible. In the ring-opening polymerization, the driving force for polymerization comes from ring strain, thus it varies greatly for different monomers. 

If one wishes to prepare a positive photoresist it is important to obtain polymers vdiich undergo efficient chain scission in the solid phase. Recently we reported studies on a series of copolymers of styrene with a variety of ketone functional groups which were introduced by copolymerization with substituted vinyl ketone monomers. The copolymer structures are shown schematically in Table V. Two processes are responsible for the reduction in molecular weight in these polymers when irradiated with either UV light or electron beams. These are shown schematically below. 

SCHEME 18.28 Synthesis of boron-modified polysilazanes by ammonolysis of tris(chlorosilylethylene)boranes (M, monomer route) and by hydroboration of vinyl-substituted polysilazanes (P, polymer route). 

The bulk of the isopropoxy groups on the vinyl and methacryl silanes is unique among silane monomers in that, through their enhanced stability, levels of incorporation of silane an order of magnitude greater than standard methoxy-substituted monomers is possible. Thus, much higher performance can be achieved using these silane monomers. 

Polymerization of vinyl monomers proceeds much slower than the natural polymerization of for example, phenolic compounds. This can be exploited for the chemoselective polymerization of vinyl-substituted phenols and aminophe-nols (see Chapter 7) [41, 43]. Kobayashi and coworkers reported the selective polymerization of methacrylate-esters [41]. Thus, phenol-esters were selectively polymerized via the phenolic moieties leaving the methacrylate functionality unmodified (Figure 6.9). The latter was only attacked in the absence of polymerizable phenols. 

More recently, a diastereoselective molecularly imprinted fluorescent polymer for (-)-cinchonidine was prepared by the combined use of methacrylic acid and vinyl-substituted zinc(II) porphyrin monomer as functional monomers [24], Compared to the reference imprinted polymers using either MAA or zinc(II) porphyrin as a functional monomer, the imprinted polymer prepared with both MAA and the porphyrin... 

In the oxidation of anionic 1,3-dicarbonyl compounds (Table 8, entries 1-8) at potentials between 0.6 and 1.4 V (see) and in the presence of butadiene, only the additive dimer 87 is obtained in the presence of ethyl vinyl ether only the di-substituted monomers 91 or 92 arise, but with styrene both types of products 87 and 91 are formed. This result indicates that the primary adduct 88 is oxidized fast between 0.6 to 1.4 V to the carbenium ion in the case of an ethoxymethyl radical (Y = OEt) and slowly in the case of an allyl radical (Y = vinyl). 

Figure 3. Typical patterns of radical ring-opening polymerization of exomethylene-sub stttuted and vinyl-substituted cyclic monomers.

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