P-Vinylbenzyl group

It is well known that primary amines are efficient initiators for the polymerization of Leuch s anhydrides (oxazolidinediones) and that initiation proceeds by the addition of the amine to the monomer. This pathway has been utilized recently to synthesize polypeptide macromonomers bearing a terminal p-vinylbenzyl group 88). Copolymerization of these macromonomers with a vinylic or acrylic comonomer yields graft copolymers with polypeptide grafts. Alternately, the monomer adduct (IV) was copolymerized with styrene, and the primary amine functions of this polymer were used to initiate the polymerization of an oxazolidinedione whereby polypeptide grafts are formed 89). Such graft copolymers may be of interest for biomedical applications. 

In some but not so rare cases, however, reactivity of macromonomers was found to be apparently reduced by the nature of their polymer chains. For example, p-vinylbenzyl- or methacrylate-ended PEO macromonomers, 26 (m=l) or 27b, were found to copolymerize with styrene (as A) in tetrahydrofuran with increasing difficulty (l/rA is reduced to one half) with increasing chain length of the PEO [41]. Since we are concerned with polymer-polymer reactions, as shown in Fig. 3, the results suggest that any thermodynamically repulsive interaction, which is usually observed between different, incompatible polymer chains, in this case PEO and PSt chains, may retard their approach and hence the reaction between their end groups, polystyryl radical and p-vinylbenzyl or methacrylate group. Such an incompatibility effect was discussed in terms of the degree of interpenetration and the interaction parameters between unlike polymers to support the observed reduction in the macromonomers copolymerization reactivity [31,40]. Similar observations of reduction of the copolymerization reactivity of macromonomers have recently been reported for the PEO macromonomers, 27a (m=ll) with styrene in benzene [42], 27b with acrylamide in water [43], and for poly(L-lactide), 28, with dimethyl acrylamide or N-vinylpyr-rolidone in dioxane [44]. 

Sharkey20 found that living poly(methyl methacrylate) reacts efficiently and without side reaction with p-vinylbenzyl iodide (or bromide) at low temperature yielding poly(methyl methacrylate) macromonomers bearing at the chain end a styryl group (poly(methyl methacrylate)macromonomer). 

It has been detected that each molecule contains a terminal p-vinylbenzyl or p-iso-propenylbenzyl group. 

An elegant alternative to living polymerization for the preparation of block polymers is to use functionalized Grignard initiators. The polymerization of methyl methacrylate to isotactic (in toluene at — 78"C) or syndiotactic polymers (in THF at — llO C) can be initiated by o-, m-, and p-vinylbenzylmagnesium chloride. The polymers had a low polydispersity and contained one vinylbenzyl group at the chain end, by H-NMR. The poly(methylmethacrylate) macromers thus obtained were polymerized or copolymerized with styrene to give graft and block polymers of controlled architecture [50,51]. 

A number of polymers containing a heterocyclic group have been prepared using the Reissert alkylation sequence.92 94 Thus, for example, the reaction of the isoquinoline Reissert anion (26) with polyfvinylbenzyl chloride) and sodium hydride gave 36, which on hydrolysis with base gave 37.92,93 A similar condensation takes place with quinoline, phenanthridine, and benzo-[/Jquinoline Reissert compounds.94 The Reissert anion 26 has also been alkylated with a mixture of m- and p-vinylbenzyl chloride and the product polymerized to a polymer of type 37.93 Copolymerization has also been studied.93... 

Group-transfer polymerizations yield very narrow molecular weight distribution polymers. When mixtures of monomers are used, random copolymers form. The polymerization reaction is very tolerant of other functional groups in the monomer. Thus, for instance, p-vinylbenzyl methacrylate is converted to poly(p-vinylbenzyl methacrylate) without the polymerization of the vinyl... 

Two new synthetic methods for the preparation of functional polymers containing 2-oxazoline pendant groups were developed. The first concerns the synthesis of m- and p-vinylbenzyl ethers of 2-(p-hydroxyphenyl)-2-oxazoline, followed by their radical poljnnerization. 2-(p-Hydroxyphenyl)-2-oxazo-line was reacted with a mixture of m- and p-chloromethylstyrene (60% m and 40% p) under phase transfer catalysis conditions at room temperature. The m-and p-vinylbenzyl ethers of 2-(p-hydroxyphenyl)-2-oxazoline obtained were separated by selective crystallization from methanol. Radical polymerization of these ethers was carried out in dioxane at 60 C, giving polymers with pendant 2-oxazoline groups. 

Bria et al. synthesized a tetracationic cyclophane-aromatic crown ether-type side-chain poly[2]catenane 59 by employing click chemistry, via route iii (Scheme 17.18) [111]. First, the template-directed coupling reaction between bis(bipyridinium) salt 28 and the alkyne-substituted p-xylylene dibromide 55, in the presence of dinaphtho crown ether 54, afforded an alkyne-functionalized [2]catenane 56 [112], Substitution of the chloro group on styrene-vinylbenzyl chloride copolymer 57 (M = 3.7 kDa, M , = 6.3 kDa) with sodium azide gave the azide-functionalized polymer 58 [83,113-115]. By employing CuS04/ascorbic acid as catalyst [116-120], click chemistry between azide-functionaUzed polymer 58 and alkyne-functionalized [2]catenane 56 afforded the side-chain poly[2]catenane 59, the successful formation of which was confirmed with Fourier transform infrared (FTIR) and NMR analyses. Unfortunately, both of these techniques revealed that the reaction of the azide groups was incomplete, and the observation was ascribed to a Coulombic repulsion of the cyclophane units and steric hindrance caused by the bulky catenane units[121]. 

An interesting approach to polymercaptans utilizes the mercaptide ion as a blocking group. Vinylbenzyl thioacetate (26) (IX) was prepared in 68.5% yield by treating vinylbenzyl chloride (Villa) (70 30 p to o-isomer) with potassium thioacetate. Basic hydrolysis of DC yielded... 

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