Main macromonomers

Watanabe et al,25-5 52s applied AMS dimer (116) as a radical trap to examine the reactions of oxygen-centered radicals (e.g. r-butoxy, cumyloxy, benzoyloxy). AMS dimer (116) is an addition fragmentation chain transfer agent (see 6.2.3.4) and reacts as shown in Scheme 3,96. The reaction products are macromonomers and may potentially react further. The reactivity of oxygen centered radicals towards 116 appears to be similar to that of S.2 1 Cumyl radicals are formed as a byproduct of trapping and are said to decay mainly by combination and disproportionation. 

Brushes with long side chains can be synthesized by polymerization of macromonomers [117-119] or by grafting of the side chains to [16-20] or from [21] a main chain. In contrast to globular dendrimers, these molecules have an anisotropic primary structure and experience bending or coiling of the molecular contour. Depending on the relative stiffness of the main and side chains, one may distinguish four types of molecular cylinders (Fig. 20). 

Compomers contain no water, but rather are mainly formulated from the same components as conventional composite resins. Typically this means macromonomers, such as bis-glycidyl ether dimethacrylate (bisGMA) or its derivatives and/or urethane dimethacrylate, blended with viscosity-reducing diluents, such as triethylene glycol dimethacrylate (TEGDMA). These polymer systems are filled with non-reactive inorganic powders, for example, quartz or a silicate glass [271]. 

The dispersion copolymerization of PEO-MA macromonomer and styrene is presented in Figs. 1 and 2 [70]. The rate-conversion plot is curved with a maximum at very low conversion. In all runs, neither the gel effect nor the stationary interval were observed. The strong decrease of the rate of polymerization with increasing conversion results from a decrease in the monomer concentration at the reaction loci (mainly in the polymer particles). The low monomer concentration in particles is a reason why the gel effect may be operative only at very low conversion. 

This model is based on the particle formation during polymerization where the polymer particles are sterically stabilized by graft-copolymerized PEO chains on the particle surface. In the later stage the polymer particles were supposed to grow in size mainly by copolymerization of monomers occluded in the particles which may favor the substrate monomer (styrene) over the macromonomer as compared to the composition in the continuous phase. 

Figure 4.6 IR spectra of macromonomers A-I. (Left) Macromonomers A-E exhibit only one band for the amide A absorptions between 3283 and 3290cm-1, a very sharp and greatly predominating main amide I absorption at 1630-1632cm-1 with a halfheight width of about 11 cm-1, and an amide II absorption at 1538-1543cm-1, attributed to...

P-Pinene which is a main component of natural turpentine can be polymerized by living cationic isomerization polymerization [82] (Scheme 10) using TiCl3(OfPr) as a Lewis acid in conjunction with rc-Bu4NCl in CH2C12 at -40 °C. When initiator 31 was used, polymerization led to a poly(P-pinene) macromonomer with a methacrylate function at the a end and a chlorine atom at the co chain end [83]. Three macromonomers were prepared with DPn=8,15, and 25 respectively they had narrow MWD (Mw/Mn= 1.13-1.22) and the reported functionality was close to 1 (Fn=0.90-0.96). 

The variety of branched architectures that can be constructed by the macromonomer technique is even larger. Copolymerization involving different kinds of macromonomers may afford a branched copolymer with multiple kinds of branches. Macromonomer main chain itself can be a block or a random copolymer. Furthermore, a macromonomer with an already branched or dendritic structure may polymerize or copolymerize to a hyper-branched structure. A block copolymer with a polymerizable function just on the block junction may homopolymerize to a double comb or double-haired star polymer. 

Kennedy 67,77 118) studied the ability of w-styryl-polyisobutene macromonomers to undergo free-radical copolymerization with either styrene or butyl or methyl methacrylate. Here, the macromonomers exhibited a relatively high molecular weight of 9000, and the reaction was stopped after roughly 20% of the comonomer had been converted. The radical reactivity ratios of styrene and methyl methacrylate with respect to macromonomer were found to be equal to 2 and to 0.5, respectively. From these results, Kennedy concluded that in the ra-styrylpolyisobutene/styrene system the reactivity of the macromonomer double bond is reduced whereas with methacrylate as the comonomer the polar effect is the main driving force, yielding reactivities similar to those observed in the classical system styrene/MMA. 

The chief objective of all research in the field of macromonomers is to get an easy access to a wide choice of graft copolymers. The main limitation of the earlier procedures to synthesize graft copolymers is the small number of systems to which grafting onto or grafting from techniques could be efficiently applied. The random copolymerization of a macromonomer with another monomer offers a much broader choice, and it is also much easier to carry out, in most cases by means of free-radical initiators. 

Macromonomers are polymers or oligomers with polymerizable end groups, widely investigated for the preparation of functional polymers and polymer microspheres by dispersion polymerization. For microspheres, the macromonomers should be designed to copolymerize with the main monomers in such a way as to produce graft chains that serve as efficient stabilizers in other words, their main chain should be firmly bound to the particle surface and the graft chains should extend into the polymerization medium. 

A wide variety of polymer microspheres can be made by dispersion polymerization. A key component in all of these systems is the stabilizer (dispersant) both during particle formation and for the stability of the resulting colloidal particles. Functionality can be introduced into colloidal particles in various ways by copolymerization of functional monomers (like HEMA), or incorporation of functional dispersants, initiators, chain transfer agents, or macromonomers. Many different types of macromonomer are prepared and used to prepare functional microspheres. Amphiphilic macromonomers provide a particularly versatile component in these systems, being the source of both stabilizer and functional residue. They act as stabilizer because they are covalently grafted onto the particles surface by copolymerization with main monomers, and form tightly bound hairy shells on the particles surface. 

In the following text we focus on cylindrical brushes prepared by polymerization of macromonomers, in particular on two systems. First, cylindrical brushes consisting of poly-2-vinylpyridine side chains and a poly-methacrylic main chain are discussed these were converted into cationic polyelectrolyte brushes by quaternization of the pyridine units by alkyl halides. The second system comprises sulfonated anionic cylindrical brushes, i.e. polymacromonomers with polystyrene side and main chains and polymacromonomers with polymethacrylic main and polymethacrylic acid side chains. 

Combination of a living ionic polymerization and a metal-catalyzed radical polymerization also leads to comb polymers, where both the molecular weights of the arm and main-chain polymers are well controlled. PMMA with poly(vinyl ether) arm polymers of controlled molecular weights (C-l) were prepared by the copper-catalyzed radical polymerization of methacrylate-capped macromonomers carrying a poly-(isobutyl vinyl ether), which were obtained by living cationic polymerization with a methacryloxy-capped end-functionalized initiator.428 Comb polymers with... 

Such a macromonomer was utilized in the synthesis of polyurethanes as adhesives, with very low surface tension (9-12 dynes crrr1), mainly for PVC by using very low rates (1% w/w) [290]. 

The recent investigations concerning CCT were mainly focused on improving the catalytic system by using new cobalt complexes [302-307]. But CCT reactions usually lead to the synthesis of a large variety of structured monofunctional macromonomers terminated by a vinylic functionality [308,309]. It is important to note that CCT can be conducted with rate constants Ctr hundreds or thousands of times faster than the best mercaptans [69], which... 

Some Japanese teams developed a novel technique, based on unimolecular termination, which allows separating both initiation and termination (or transfer) processes. After growing chains are obtained, the macroradical formed is able to react with another molecule (mainly unsaturated) to lead to a stable radical. This one may transfer to give another radical able to reinitiate a polymerization. This process was developed, aiming at synthesizing either telechelic oligomers [85] (Scheme 78) or macromonomers [86] (Scheme 79). 

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