P-Vinyl benzylates

By using the Milkovich method, Asami et al. [38] prepared (p-vinyl benzyl) polystyrene containing no... 

Functionalization of these reactive anionic chain ends can be achieved by a variety of methods all based on the general concepts of carbanion chemistry. For example, reaction with C02 or succinnic anhydride leads to the carboxy terminated derivatives [10], while hydroxy-terminated polymers can be easily obtained by reaction with ethylene oxide (Scheme 3) [11]. In select functionalization reactions, such as alkylation with p-vinyl benzyl chloride, the nucleophilicity of the carbanionic species may be necessary and this can be achieved by reaction of the chain end with 1,1-diphenylethene followed by functionalization [12,13]. 

The chloromethylated polystyrene is usually obtained by chloromethylation of polystyrene (Eq. 9-38), although polymerization of p-vinyl benzyl chloride has also been used [Arshady et al., 1976]. A less desirable variation of this approach is the physical entrapment of a catalyst, substrate, or reagent within a polymer. 

Whether all chains bear a terminal vinylic double bond has not been clearly established, and it would be somewhat astonishing if vinylic double bonds did not undergo side reactions since their reactivity in cationic polymerization is quite high. However, the occurrence of terminal p-vinyl benzyl groups is confirmed by the fact that the formed macromonomer readily copolymerizes with butyl acrylate. 

The most common example of macromonomers in this category are polyethylene oxide and propylene oxide. From their method of preparation they have one or two end -OH groups which can be used for post-polymerization reactions. Acryloylchloride, methacryloylchloride, p-vinyl benzyl chloride, and iso-cyanatomethylmethacrylate are some of the reagents reacted with PEO or poly(propylene oxide) (PPO) to prepare macromonomers. A few of these reactions [195,196] are presented in the following schemes (Scheme 61). 

In a study of the flame retardance of styrene-methyl methacrylate copolymer with covalently bound pyrocatechol-vinyl phosphate, diethyl p-vinyl benzyl phosphonate, or di(2-phenyl ethyl phosphonate) groups. Ebdon and co-workers [23] obtained data on their decomposition behaviour. This was achieved by reducing the rate of liberation of flammable methyl methacrylate monomer during combustion. Possible mechanisms for these processes are suggested. Other methacrylate copolymers which have been the subject of thermal degradation studies include PMMA-N-methylmaleimide-styrene [24] and PMMA-ethylene vinyl acetate [25-27]. 

Recently Asami et al. improved the method of preparing (p-vinylbenzyl) polystyrene macromer by direct reaction of living polystyrene with p-vinyl-benzyl chloride, in the presence of tetrahydrofuran without using a capping agent. 

Macromonomers have been also prepared by post-polymerization reactions. Poly(ethylene oxide) (PEO) or poly(propylene oxide) (PPO) has one or two —OH end groups depending on the method of their preparation. These —OH groups may react with (meth)acryloyl chloride, p-vinyl benzyl chloride, norbomenyl chloride, 4-vinyl benzoyl chloride, etc. for the synthesis of the corresponding macromonomers (109,110) (eq. 33). 

Fractional precipitation Poly(styrene-co-p-vinyl benzyl chloride) Toluene/methanol 2708... 

Indeed, cumyl carbocations are known to be effective initiators of IB polymerization, while the p-substituted benzyl cation is expected to react effectively with IB (p-methylstyrene and IB form a nearly ideal copolymerization system ). Severe disparity between the reactivities of the vinyl and cumyl ether groups of the inimer would result in either linear polymers or branched polymers with much lower MW than predicted for an in/mcr-mediated living polymerization. Styrene was subsequently blocked from the tert-chloride chain ends of high-MW DIB, activated by excess TiCU (Scheme 7.2). 

Organometallics are formed at the cathode if transient radicals produced in reductions react with the active electrode. This occurs as a side reaction in cathodic coupling (Sect. 12.2, Eq. (185)) of carbonyl compounds, e.g., of acetone 3 9 or of activated olefins, e.g., of methyl vinyl ketone 41or acrylonitrile. Furthermore, in cathodic cleavage (Sect. 13.2, Eq. (227) ) of alkyl bromides or iodides organometallics are formed, e.g., ME(CH2CH2CN)2(ME = Pb, Tl, Sn, Hg) 481 bis(p-substituted benzyl)mercury 485 or dicyclopropylmercury 489 ... 

Hyperbranched polymers may be prepared by the self-condensing vinyl polymerization (SCVP) [257] of AB star monomers by a controlled free radical process, such as ATRP [258]. The result, under certain conditions, is a highly branched, soluble polymer that contains one double bond and, in the absence of irreversible termination, a large quantity of halogen end groups equal to the degree of polymerization which can be further functionalized [87] (Fig.35). Two examples explored in detail by ATRP are vinyl benzyl chloride (VBC, p-chlo-romethylstyrene) [258] and 2-(2-bromopropionyloxy)ethyl acrylate (BPEA) [259-261] both depicted in Fig. 35. Several other (meth)acrylates with either 2-... 

You will have realised that the Suzuki coupling is the best of those we have mentioned. It is regiospecific as the positions for coupling are marked, one with a boronic acid and one with a halide. It does not use toxic tin. It can be used for all the aryl, heteroaryl, vinyl, benzyl and other groups that Heck and Stille use and in addition it can be used for saturated alkyl boronic acids with P-hydrogen atoms without P-elimination. It is not surprising that it is very widely used and we give a few representative examples. 

Fig. 6.28 Selectivity plot for PVA( ) [329] and PVA-based membranes SSA-GA ( ) [330] PSSA-MA (a) [331, 332], SSA/PSSA-MA (a) [333] sulfonated phenolic resin (sPh) (v) [334] PI/3,6-pyrenetrisulfonic acid (TSGEPS) ( ) [335] SSA/PVP (0) [336] bis (4-y-aminopropyldiethoxysilylphenyl)sulfone (APDSPS) ( ) [337] Organophosphorous acid/ chitosan (o) [329] aminopropyl triethoxysilane (APTES) (a) [338] sulfonated PVA (O) [339], methylpropane sulfonic acid (MPSA) ( ) [340, 341], sPOSS ( ) [342] DSDSBA (o) [343] SSA/Si02 (a) [344] PAA/Si02 (v) [345] N-p-carboxy benzyl chitosan (CBC)/Si02 ( ) [346] benzene-silica ( ) [347] Si-sPS/A)/PWA ( ) [348] sulphated p-CD (a) [349] Montmorillonite ( ) [350, 351] Organoclay ( ) [352] PVA-co-Poly(vinyl acetate-co-itaconic acid/PMA (T) [353] poly(ether sulfone/PWA (ffl) [354] Zirconium phosphate/Cs-salt SWA (X) [355]...

To understand the reasons for different predictions of different methods, Li et al. [83] measured the adhesion between a variety of polymers with well-controlled backbone chemistry These polymers include poly (4-methyl 1-pentene) [TPX], poly(vinyl cyclohexane) [PVCH], polystyrene [PS], poly(methyl methacrylate) [PMMA], and poly(2-vinyl pyridine) [PVP], poly(4-tert-butyl styrene) [PtBS], poly(acrylonitrile) [PAN], poly(p-phenyl styrene) [PPPS], poly(vinyl benzyl chloride) [PVCB]. It may be noted that, among the polymers listed above, TPX and PVCH are purely dispersive in nature. PS is predominantly dispersive with some dipole-induced dipole interactions. 

Preparation of hyperbranched polymers using ATRP involves self-condensing vinyl polymerization (SCVP) (Frechet et al., 1995) of AB monomers, which contain two active species, viz., the double bond A group (polymerizable) and the initiating site B. Two main examples explored in detail within the context of ATRP are p-chloromethyl styrene or vinyl benzyl chloride (VBC) and 2-(2-bromopro-pionyloxy) ethyl acrylate (BPEA) (Fig. 11.30). Several other (meth)acrylates with either 2-bromopropionate or 2-bromoisobntyrate gronps have also been used. 

Stability and performance of AEM prepared using poly(4-vinyl pyridine-costyrene), quaternized with 1-bromooctane, and deposited on fibrous woven paper was unsatisfactory [189]. Sanchez and coauthors [190] discussed problems related to the use of certain AEMs. They pointed out that the so-called Hoffman degradation that involves attack of a hydroxyl on a-hydrogen in p-position to a quaternary ammonium attached to an aliphatic chain may cause its removal, followed by release of a tertiary amine and formation of a double bond at the end of a broken chain. Attachment of DABCO on short leash prevented chain break due to Hoffman degradation, but release of DABCO and generation of a double bond attached to the chain could take place. Perhaps thermal cross-linking by DABCO of poly(vinyl benzyl chloride) may solve this problem. Sulfonated polymers prepared by polymerization or copolymerization of phosphazene, siloxans, styrene, vinylidene fluoride, and various monomers with aromatic backbones, and possibly with aliphatic spacers, have been used. Various imides as well as PPS, PEK, PEEK, PSU, PEEKK, and PPSU can also be used [190,191]. 

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