Diphenylethylenes DPE

This strategy, based on 1,1-diphenylethylenes, which are non-homopolymeri-zable monomers, has been developed mainly by the Quirk [174] and Hi-rao [178] groups. DPEs continue to find applications for the synthesis of the /z-stars. A few recent examples are given below. 

In an extension of the methodology involving DPEs, the preparation of chain-end and in-chain functionalized polymers with a definite number of chloromethylphenyl or bromomethylphenyl groups and their utilization in 

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Diphenylethylene (DPE) was obtained from Eastman Kodak Co. and was purified by vacuum distillation from -butyllithium. 

Table 22 Substituent and solvent effects in the bromination of 1,1-diphenylethylenes, DPE, and a-methylstyrenes, a-MS. 1...

In the case of LASIP with clay nanoparticles, polystyrene was grafted using a DPE coinitiator. The montmorillonite clay surface and intergallery interfaces were intercalated with 1,1-diphenylethylene (DPE) modified to be an organic cation as shown in Fig. 4. Its intercalation was confirmed by a series of characterization methods including X-ray diffraction (XRD), FT-IR spectroscopy, TGA, and XPS. The results showed a complete replacement of... 

To overcome the difficulty in the crossover step a general methodology has been developed in our laboratory for the synthesis of block copolymers when the second monomer is more reactive than the first one. It involves the intermediate capping reaction with non-(homo)polymerizable monomers such as i) 1,1-diphenylethylene (DPE) and its derivatives and ii) 2-substitut-ed furans. 

An early report of the beneficial influence of 1,1-diphenylethylene (DPE) on the yields of alkylaryl ether obtained in the reaction of diaryliodonium salts with sodium alkoxides showed that radical chain reactions compete efficiently with the 0-arylation reaction. By contrast, addition of diphenylpicrylhydrazyl, a stable free radical species, had no significant influence on the yields of products obtained in e absence of additives. In this case, the 0-arylation reaction was considered to be a direct nucleophilic aromatic substitution reaction, without the involvement of any transient covalent intermediate. (Table 2.11)... 

Similarly, a number of other arylation reaction systems were tested for the presence and study of the influence of free radicals. Addition of 1,1-diphenylethylene (DPE) in reactions of organobismuth, organolead and organosulfiu reactions failed to affect the outcome of these reactions, which therefore were considered as occurring without the intervention of free radical species. 

A structure resembling that of the dumbbell polymers was made by Frechet et al. In this case the connector is linked with polyether dendritic groups [272, 273]. The synthetic approach involved the preparation of a difunctional polystyrene chain in THF using potassium naphthalenide as initiator. The living polymer was end-capped with 1,1-diphenylethylene (DPE) to reduce its nucle-ophilicity and avoid side reactions with benzylic halomethyl groups. Addition of the fourth generation dendrimer [G-4] -Br led to the final product (Scheme 100). 

A new synthetic route for the preparation of polyisobutylene (PIB) based block copolymers was developed by combining living carbocationic and anionic polymerizations. Living PIB chains were quantitatively end-capped with 1,1-diphenylethylene (DPE) leading to 1,1-diphenyl-l-methoxy (DPOMe) and/or 2,2-diphenyl vinyl (DPV) termini. This end-capping process is very sensitive to temperature, and retroaddition of DPE occurs in an equilibrium reaction above about -70 °C. Both the DPOMe and DPV terminated PIBs, and the mixtures of the two endgroups were quantitatively metalated with K/Na alloy, Cs metal and Li dispersion in THF at room temperature. 

In another approachlithiation of tolyl-telechelic PIB obtained by Friedel-Crafts alkylation of r rr-chlorine-ended PIB and subsequent addition of 1,1-diphenylethylene (DPE) to the metalated chain ends were applied to initiate the polymerization of MMA. Living PMMA chains were also attached to PIB containing short endblocks of poly(p-vinylbenzylbromide). Although detailed characterization of the products is not available, this method is expected to yield PMMA branches at the PIB termini. 

In a series of recent publications, we also demonstrated synthetic applications of non-(homo)polymerizable monomers such as 1,1-diphenylethylene (DPE) and 1,1-ditolylethylene (DTE) in carbocationic macromolecular engineering [8-17]. These... 

Anionic initiator, ec-Butyllithium 1.3 M solution in cyclohexane (Aldrich) was used as obtained. Free-radical initiator, 1,1 -Azobiso(cyclohexane carbonitrile)(ACHN, Aldrich) was purified by recrystallization in methanol. l,r-Diphenylethylene (DPE, Aldrich) was purified by two consecutive distillations over CaH2 and n-butyl-lithium. The solvent, tetrahydrofuran (THF, Aldrich) used in anionic polymerization was dried by distillation over sodium wire in the presence of benzoquinone until a blue color developed and remained, and by consecutive vacuum distillations over LiAlH4 and n-butyllithium. Toluene used for fi e-radical polymerization was purified by distillation over CaH2 in a vacuum apparatus. All other chemicals used in monomer synthesis were used as purchased. 

Organoalkaline-Earth Initiators Both styrene and 1,3-dienes can be polymerized by organoalkaline-earth metal compounds, specifically those of magnesium, calcium, barium, and strontium. In general, hydrocarbon-soluble benzyl, 1,1-diphenylalkyl and triphenylmethyl derivatives have been investigated. For example, the adduct of 1,1-diphenylethylene (DPE) with dibenzylbarium, that is, bis(l,l,3-triphenylpropyl)barium, is hexane-soluble and polymerizes styrene with controlled molecular... 

Living polymerization of azo monomers is one of the most effective ways to prepare well-defined azo BCs. Generally, a monodispersed macroinitiator should be prepared first. It is then used as an initiator for the subsequent polymerization of azo monomers. Finkelmann and Bohnert (1994) first reported the synthesis of LC-side chain AB azo BCs by direct anionic polymerization of an azo monomer. As shown in Scheme 12.1, the polymerization of polystyrene (PS)-based diblock copolymers was carried out from a PS-lithium capped with 1,1-diphenylethylene (DPE), whereas the poly(methyl methacrylate) (PMMA)-based diblock copolymers were prepared by addition of methyl methacrylate (MMA) monomers to the living azo polyanion, obtained by reaction of l,l-diphenyl-3-methylpentylithium (DPPL) with the azo monomer in tetrahydrofuran (THF) at lower temperature. By this method, a series of well-defined azo BCs were obtained with controlled molecular weights and narrow polydispersities (Lehmann et al., 2000). 

In this case, chlorosilane reagents (XVIII, XIX), halomethyl benzene reagents (XX), and 1,1-diphenylethylene (DPE) derivatives (XXI) carrying aUsyUialide functions are typical coupling agents used to deactivate anionically derived polymers, mostly PS, PB, and PI. A variety of star-like polymers of precise functionality, including multiarm stars, star-block copolymers, asymmetric and miktoarm stars, and other branched architectures, are accessible in this way [1, 12-14, 35]. This... 

The OH group was protected by reaction with tert-butyldimethylsilyl chloride (TBDMS) in order to obtain the living anionic polymerisation. Diphenylethylene (DPE) was used to lower the living chain reactivity. The monomers were added in order styrene, styrene-o-TBDMS, DPE, MMA to the solvent tetrahydrofuran (THF) at 78°C in nitrogen with stirring. The reaction was terminated with methanol and precipitated by hexane to give the product PS-b-poly(styrene-o-TBDMS)-b-PMMA which was dried in vacuum at 130°C then... 

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