P-Divinylbenzene

FIGURE 27 14 A section of polystyrene showing one of the benzene rings modified by chloromethylation Indi vidual polystyrene chains in the resin used in solid phase peptide synthesis are con nected to one another at various points (cross linked) by adding a small amount of p divinylbenzene to the styrene monomer The chloromethylation step is carried out under conditions such that only about 10% of the benzene rings bear —CH2CI groups... 

A typical system is a chlorome thy late d polystyrene resin cross-linked with 2 or 4% p-divinylbenzene and different amounts of chloromethylated sites (0.7—3.7 mequiv. of Cl per g of polymer) . The reaction is shown schematically in Eq. (6.19) and additional information may be found in Sects. 8.3 and 8.8. 

When, styrene, C6HSCH = CH2 is copolymerized in the presence of a few percent p-divinylbenzene, a hard, insoluble, cross-linked polymer is obtained. Show how this cross-linking of polystyrene chains occurs. 

The 1 2 complex of Hg2+ with the tacn derivative mono-N-(4-vinylbenzyl)-l,4,7-triazacyclono-nane copolymerizes with p-divinylbenzene to give an Hg-templated polymer which, after deme-talation with 6N HC1, is a highly selective gathering material for Hg2+ in competition with other transition metals like Cd2+, Ag+, Pb2+, Cu, and Fe3+ at low pH values.211... 

Starting from the corresponding hydroxymethyl-benzocrown, it has been possible to generate the immobilized system (186) by reacting the above precursor with chloromethylated polystyrene (which is available commercially as Merrifield s resin). Typically, systems of this type contain a polystyrene matrix which has been cross-linked with approximately 1-4% p-divinylbenzene. In one study involving (186), a clean resolution of the alkali metal halides was achieved by HPLC using (186) as the solid phase and methanol as eluent (Blasius etal., 1980). In other studies, the divalent alkaline earths were also separated. 

It is interesting that statistical copolymers 343, containing m-phenylene linkages that are supposed to interrupt conjugation, showed a PL maximum of 475 nm, similar to 342. Due to efficient energy transfer from the meta- to the para-linked chromophores, the emission maxima did not depend on the ratio of m- and p-divinylbenzenes, unless 100% loading of the meta units was used [420] (Scheme 2.54). 

To increase heat and impact resistance without affecting other useful qualities, polystyrene is copolymerised with a small amount of P-divinylbenzene p-CH2 = CHCH6H4CH = CH2 when cross-... 

Note Normally inhibited with 8-12 ppm 4-7er7-butylcatechol to prevent polymerization. According to Chevron Phillips Company (March 2002), 99.93% styrene contains the following components (ppm) benzene (<1), toluene (<1), ethylbenzene (50), a-meth ylstyrene (175), m + p-xylene (120), o-xylene (125), isopropylbenzene (100), / -propylbenzene (60), m + p-ethyltoluene (20), vinyltoluene (10), phenylacetylene (50), m + p-divinylbenzene (<10), o-divinylbenzene (<5), aldehydes as benzaldehyde (15), and peroxides as benzoyl-peroxides (5). 

The stable anion-radical in Scheme 3.63 contains two perchlorotriphenylmethyl radical units linked by an all-trani-p-divinylbenzene bridge. At 200 K, the unpaired electron of the anion-radical is localized (within the ESR timescale) on one stilbenelike moiety only. At 300 K, thermal activation forces the nnpaired electron at one strong electrophilic center to move to another one. Such an electron transfer takes place between two eqnivalent redox sites (Bonvoisin et al. 1994). In contrast to this situation, no electron transfer was observed for the anion-radical that contains two perchlorotriphenylmethyl radical units linked by an all-trani -m-divinylbenzene bridge (Rovira et al. 2001). Such results can be ascribed to the localization of frontier orbitals in the meta-isomeric anion-radical because of the meta connectivity of this non-Kekule structure. 

Catalysts synthesized from crown ether monomers 61 and 62 by copolymerization with styrene and either p-divinylbenzene or p,p -divinylbiphenyl (63) are listed in Table 14 along with their relative activities for solid/solid/liquid reactions of potassium acetate with benzyl chloride (Eq. (13)) and potassium cyanide with 1,4-dichlorobutane (Eq. (14)) in acetonitrile 183). 

Styrene Acrylonitrile a-Methylstyrene p-Divinylbenzene Figure 10.1 Monomers used for SAN Copolymers... 

Popcorn polymer only forms in those polymerizing systems where a certain amount of crosslinking takes place. In all systems investigated, an optimum crosslinking range for popcorn polymer formation exists (11) In thermal polymerization of a styrene-p-divinylbenzene mixture... 

The presence of cross-associated species needs to be considered in the interpretation of copolymerization kinetics. It has been found 269) that the reaction of poly(butadie-nyl)lithium with p-divinylbenzene in benzene solution proceeds at a rate which increases markedly with time. Such a result implies that the poly(butadienyl)lithium aggregate is less reactive than the mixed aggregate formed between the butadienyl-and vinylbenzyllithium active centers. Interestingly, no accelerations with increasing reaction time were found with poly(butadienyl)lithium and m-divinylbenzene nor with poly(isoprenyl)lithium and either the m- or p-divinylbenzenes. This general behavior was subsequently verified 270) by a series of size exclusion chromatography measurements on polydiene stars (linked via divinylbenzene) as a function of conversion. 

The formation and reactivity of microgels of a dense structure has been investigated by Funke and Seitz (46-53). By use of pure p-divinylbenzene and techn. DVB (55%), respectively, the polymers have a vinyl content corresponding to a 40 to 90% consumption of the second vinyl group of DVB. Depending on the reactants and the reaction conditions subsequent reactions may be localized at the surface of the particle. 

When applied to p-divinylbenzene (DVB), this reaction exhibits an interesting feature 81) a monoadduct is easily obtained and isolated because of the rather large difference in the reactivity between the two double bonds of p-DVB. However, when the reaction time is increased, the second DVB double bond may also be involved in the addition. The rate of the first step is roughly 20 times faster than that of the second ... 

The method ofTsuruta was also extended to the synthesis of macromonomers containing piperazine cycles, and even diaza crown ethers81 84185). Here again the first step involves preparation of 1 1 adducts of p-divinylbenzene and the corresponding heterocyclic compound ... 

The same kind of addition reaction as described in Section IV 1) and 2) can be performed with substituted bisacryl amides such as bisacryloylpiperidide and N,N -dimethylethylenediamine. However, the difference in the reactivity between the two acrylic double bonds is much less pronounced than in the case of p-divinylbenzene, so that a mere polycondensation occurs. Upon using a calculated excess of 1,4-bis-acryloylpiperidine bifunctional macromonomers of a known average molecular weight have been obtained by Ferruti et al. 90) ... 

At this stage, the self-condensation of the p-divinylbenzene-N,N -ethylenediamine monoadduct 83-84) should be mentioned again as the only type of self-condensation leading directly to a macromonomer without any additional reaction the final species always carries an unsaturation at one chain end. 

It thus appears that most of the techniques developed for (or adapted to) the macromonomer synthesis were derived from methods or concepts that had been well known beforehand. There are only few exceptions the most striking of which is the self-condensation of the monoadduct between p-divinylbenzene and a diamine developed by Tsuruta and his coworkers. 

The catalysts used industrially in the MTBE process are sulphonated polystyrene resins of the macroreticular type. These strongly acidic materials are prepared by copolymerizing styrene and p-divinylbenzene in the presence of an organic compound that is a good solvent for the monomers but a poor swelling... 

The final product contains polystyrene chains cross-linked by p-divinylbenzene units. 

In agreement with these findings, Worsfold [136] has shown that the reaction of the first double bond of p-divinylbenzene with styryllithium is about ten times more rapid than that of styrene. 

These Pd complexes are unique in several respects. No cross-linked polymer was detected in the reaction with p-divinylbenzene. A completely soluble linear polymer was obtained. No indane units were formed from the reaction of styrene with Pd(PPh3)2(BF4)2. a-Methylstyrene is usually much more reactive than styrene in reactions involving carbenium ion intermediates. However, the treatment of a mixture of styrene and a-methylstyrene with Pd(PPh3)2(BF4)2 resulted in the selective dimerization of styrene. 

On this basis the first stationary phase using LEC consisted of a polymeric stationary phase obtained by copolymerizaiton between styrene-p-divinylbenzene and L-profine. The stationary phase was loaded with an aqueous solution of CUSO4 dissolved in ammonium hydroxide. Using water as mobile phase, the chiral phase afforded the enantiomeric separation of d,l-... 

In this investigation EDMA appears to be a superior cross-linker compared to p-divinylbenzene (p-DVB) or butylene dimethacrylate (BDMA). To evaluate other possible cross-linkers, we tested pure o-, p- and m-DVB and a number of dimetha-... 

The most important types of ion-exchange materials are the synthetic resins, which are composed of networks of relatively loosely cross-linked polymers with attached cationic or anionic groups. For example, a copolymer of styrene and p-divinylbenzene may be cross-linked to the desired extent by choosing the fraction... 

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