Macromonomers styrene-functionalized

These rod-like PAMAM dendrimers [83] are formally derived from the core functionalized aziridinyl macromonomer (dendron) A, just as Frechet et al. [104] have produced similar rod-like dendrimers by polymerization of the styrene functionalized monodendron (B) which was prepared via the convergent approach (see Fig. 21). 

Hawker and Frechet [50] prepared a dendritic macromonomer using the convergent-growth route to prepare a polyether dendron. The dendron core functional group (R in Scheme 9) was a hydroxymethyl group that was reacted with chloromethylstyrene to form the styrene-functionalized dendritic macromonomer. This macromonomer was copolymerized with slyrene monomer using standard free-radical polymerization conditions. 

Surprisingly, after this very first example, there was a 20 year delay in the literature in the appearance of the second report on siloxane macromonomers. However, during this period there have been numerous studies and developments in the vinyl and diene based macromonomers91 -94). The recent approach to the synthesis of siloxane macromonomers involves the lithiumtrimethylsilanolate initiated anionic polymerization of hexamethyltrisiloxane in THF 95,123). The living chain ends were then terminated by using styrene or methacrylate functional chlorosilanes as shown in Reaction Scheme X. 

Recently it has been shown that anionic functionalization techniques can be applied to the synthesis of macromonomers — macromolecular monomers — i.e. linear polymers fitted at chain end with a polymerizable unsaturation, most commonly styrene or methacrylic ester 69 71). These species in turn provide easy access to graft copolymers upon radical copolymerization with vinylic or acrylic monomers. 

In our own research, the functional termination of the living siloxanolate with a chlorosilane functional methacrylate leading to siloxane macromonomers with number average molecular weights from 1000 to 20,000 g/mole has been emphasized. Methacrylic and styrenic monomers were then copolymerized with these macromonomers to produce graft copolymers where the styrenic or acrylic monomers comprise the backbone, and the siloxane chains are pendant as grafts as depicted in Scheme 1. Copolymers were prepared with siloxane contents from 5 to 50 weight percent. 

The stable polymer dispersions with small-sized polymer particles of diameter >60 nm were prepared by dispersion copolymerization of PEO-MA macromonomer with styrene, 2-ethylhexyl acrylate, acrylic and methacrylic acids, and butadiene at 60 °C [79]. The particle size was reported to decrease with increasing macromonomer fraction in the comonomer feed. Besides, it varied with the type of the classical monomer as a comonomer. Tg of polymer product was found to be a function of the copolymer composition, the weight ratio macromonomer/monomer, and monomer type and varied from 50.6 to 220.4 °C. 

Larpent and Tandros [102] prepared microlatex particles by polymerization of PEO-MA macromonomer with MMA, styrene, and vinyl acetate. The nonionic latexes are very stable, giving no flocculation up to 6 mol dm 3 NaCl or CaCl2 and a critical flocculation concentration (CFC) of 0.6 mol dm 3 for Na2S04 or MgS04 was estimated. Charged latexes are less stable than the nonionic ones. The CFC of all latexes are determined as a function of electrolyte concentration. With the nonionic latexes, however, the critical flocculation temperature (CFT)... 

The latex particle diameter produced in the emulsion copolymerization of styrene with partially neutralized poly(methacrylic acid) macromonomers, 48, was studied as a function of degree of neutralization [127]. The latex particle... 

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. 

For example, the vinyl group on styrene monomers is activating and ortho-para-directing. This leads to macromonomers of polystyrene with styrene end groups functionalized at the p-position [Eq. (92)]. 

A class of end-functionalized polymers with polymerizable terminal groups are generally called macromonomers. By both functional initiator and terminator methods, a variety of macromonomers have been synthesized in living cationic polymerization of vinyl ethers, styrenes, and isobutene, as summarized in Table 3 [16,31,147,149-151,155,158-171]. Some of these macromonomers are used in the synthesis of graft polymers (Section VI.C). 

The polymerizable groups include methacryloyl, styrenic, epoxide, vinyl ether, and others, among which the methacryloyl-capped macromonomers are most widely available from vinyl ethers, styrene, and its derivatives. For example, the a-end methacryloyl group can be introduced by the functional initiator method, with the hydrogen halide-adduct of 2-... 

The synthesis and purification of polystyrene methacryloyl macromonomers (PS-MA) in the molecular weight range Mn= 1000-2000 g mol 1 by living anionic polymerization of styrene (S), termination with ethylene oxide (EO), and subsequent reaction with methacrylic chloride has already been described in detail elsewhere [180] (see also Scheme 16). In this context it has to be emphasized that the hydroxyethyl-terminated PS-MA macromonomer precursor (PS-OH) as obtained after purification of the crude PS-OH by silica column chromatography (cyclohexane/dichloromethane 1/1 v/v) and as charged in the PS-MA synthesis still contains up to about 15 wt-% of non-functionalized polystyrene (PS-H). This PS-H impurity of the PS-MA macromonomer does not interfere with the PS-MA synthesis and the subsequent TBA/PS-MA copolymerization and is easily and conveniently removed from the resulting PTBA-g-PS graft copolymer (see below). 

If such EO oligomerization occurs, an amphipolar poly(styrene-block-ethylene oxide) methacryloyl macromonomer (PS-fo-PEO-MA) is obtained after further end group functionalization with methacryloyl chloride. As it is evident from the molecular structure (see Scheme 16) of the possible amphipolar PS-fr-PEO-MA macromonomer, such hydrophilically modified macromonomers offer the opportunity to further tune the amphipo-larity of the graft copolyelectrolytes this will be investigated in further studies. 

End-functionalized polymers with polymerizable groups such as double bonds and heterocycles of course provide macromonomers allyl, vinyl ester, vinyl ether, lactone, and epoxy are examples of such a category whose a-ends are not susceptible or have little susceptibility to metal-catalyzed radical polymerization. As discussed above, for example, allyl chloride and bromide (FI-33 and FI-34) are effective initiators to be used for styrene with CuCl and CuBr catalysts,161 while allyl compounds with remote halogens such as FI-35 and FI-36 allow the polymerization of methacrylates with high initiation effi-... 

The self-condensing copper-catalyzed polymerization of macromonomer of poly(tBA) with a reactive C—Br bond (H-6) affords hyperbranched or highly branched poly(tBA).447 Copolymerization of H-1 and TV-cyclohexylmaleimide induced alternating and self-condensing vinyl polymerization.448 The residual C—Cl bond was further employed for the copper-catalyzed radical homopolymerization of styrene to give star polymers with hyperbranched structures. Hyperbranched polymers of H-1 further serve as a complex multifunctionalized macroinitiator for the copper-catalyzed polymerization of a functional monomer with polar chromophores to yield possible second-order nonlinear optical materials.325... 

The deuterium-labelled initiator method was also applied to the polymerization of macromonomer to determine the number of initiator fragments in a polymacromonomer chain (N) and initiator efficiency (/)-77 Isotactic and syndiotactic PMMA macromonomers having a styrene group as polymerizable function were polymerized with AIBN-<7 2 in toluene at 60°C and the resultant polymacromonomers were analysed by 2H NMR spectroscopy (Table 8). The N values were less than unity (0.50 0.72), indicating some kind of chain transfer reaction in the radical polymerization of macromonomer. The / values were 0.18 0.28 and much smaller than those for styrene polymerization (0.5 0.7). The isotactic macromonomer gave larger N and / values than the syndiotactic... 

In a similar way, Wood and Cooper [268] used isopropoxyethanol as a transfer agent and the telomers were then functionalized with methacry-loyl chloride however, only 28% of the telomers were functionalized with methacryloyl chloride. Macromonomers were then copolymerized with styrene in dispersion copolymerization, in the presence of 1,1,2,2-tetrafluoroethylene. Such copolymers have been used as dispersing agents for the styrene polymerization in supercritical CO2. 

The functional initiator 4-pentenylithium was used to initiate the polymerization of styrene resulting in low polydispersity, vinyl terminated macromonomers [91]. 

Although styrene is the most common monomer used for the preparation of macromonomers anionically, other monomers capable of anionic polymerization have been used. Several papers have appeared in the literature concerning the anionic ring opening polymerization of hexamethyl cyclotrisiloxane (D3) followed by suitable termination for the preparation of macromonomers. One of the methods that widely used functionalization reactions, capable of producing monodisperse macromonomers with controlled functionality, is illustrated in the following Scheme 36. 

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