Polymerization and Copolymerization of Macromonomers

To the first category belong the homo- and copolymerization of macromonomers. For this purpose, macromolecules with only one polymerizable end group are needed. Such macromonomers are made, for example, by anionic polymerization where the reactive chain end is modified with a reactive vinyl monomer. Also methacrylic acid esters of long-chain aliphatic alcohols or monofunctional polyethylene oxides or polytetrahydrofurane belong to the class of macromonomers. 

In this review we summarize and discuss the amphiphilic properties of polyoxyethylene (PEO) macromonomers and PEO graft copolymer molecules, the aggregation of amphiphilic PEO macromonomers into micelles, the effect of organized aggregation of macromonomers on the polymerization process, and the kinetics of radical polymerization and copolymerization of PEO macromonomer in disperse (dispersion, emulsion, miniemulsion, microemulsion, etc.) systems [1-5]. 

Thus in the emulsifier-free emulsion copolymerization the emulsifier (graft copolymer, etc.) is formed by copolymerization of hydrophobic with hydrophilic monomers in the aqueous phase. The ffee-emulsifier emulsion polymerization and copolymerization of hydrophilic (amphiphilic) macromonomer and hydro-phobic comonomer (such as styrene) proceeds by the homogeneous nucleation mechanism (see Scheme 1). Here the primary particles are formed by precipitation of oligomer radicals above a certain critical chain length. Such primary particles are colloidally unstable, undergoing coagulation with other primary polymer particles or, later, with premature polymer particles and polymerize very slowly. 

So far, a great number of well-defined macromonomers as branch candidates have been prepared as will be described in Sect. 3. Then a problem is how to control their polymerization and copolymerization, that is how to design the backbone length, the backbone/branch composition, and their distribution. This will be discussed in Sect. 4. In brief, radical homopolymerization and copolymerization of macromonomers to poly(macromonomers) and statistical graft copolymers, respectively, have been fairly well understood in comparison with those of conventional monomers. However, a more precise control over the backbone length and distribution by, e.g., a living (co)polymerization is still an unsolved challenge. 

Radical homopolymerization and copolymerization of macromonomers are fairly well understood and reveal their characteristic behaviors that have to be compared with those of conventional monomers. A detailed mechanism of the polymer-polymer reactions involved, however, appears still to be an issue. Ionic or, desirably, living polymerization and copolymerization are still an important... 

Yoshida T, Xia Z, Takeda K et al (2005) Peroxidase-catalyzed polymerization and copolymerization of lignin-based macromonomer (lignocresol) having high content of p-cresol and thermal properties of the resulting polymers. Polym Adv Technol 16 783-788... 

The basic principle behind the preparation of a stable mini-emulsion lies in the decrease of solubility of monomer in the aqueous phase. This approach was applied to the fine emulsion polymerization and copolymerization of MMA, EA, nonyl methacrylate (NMA) and methacryloyl-terminated polyoxyethylene macromonomer (PEO-MA) initiated by UV light at room temperature by Capek [121,122]. At low temperature, the monomer droplet degradation is suppressed due to the lower water-solubility of monomer. Under these circumstances, the dependence of the rate of polymerization of MMA, EA or NMA is described by a curve with two maximal rates or four distinct non-stationary rate intervals, typical for the mini-emulsion polymerization. The effect of the restricted monomer droplets degradation is also considered as the result of accumulation of hy-... 

The microemulsion polymerization and copolymerization of amphiphilic monomers and macromonomers can produce the fine polymer latex in the absence of emulsifier [98-100], The surface active block or graft copolymer stabilizes the latex particles. The chemically bound emulsifier (surface active copolymer) onto the particles surface is known to be much more efficient emulsifier than the emulsifier physically adsorbed onto the particle surface and, therefore, very stable and fine polymer latexes are formed. The similar behavior is expected with the transferred emulsifier radicals. For example, the surface-functionalized nanoparticles in the 12 - 20 nm diameter range can be prepared by a one-step or two-step microemulsion copolymerisation process of styrene (and/or divinylbenzene (DVB)) with the polymerisable macromonomer (Fig. 7) [93, 101]. 

Copolymerization of macromonomers formed by backbiting and fragmentation is a second mechanism for long chain branch formation during acrylate polymerization (Section 4.4.3.3). The extents of long and short chain branching in acrylate polymers in emulsion polymerization as a function of conditions have been quantified.20 ... 

One of the major advantages of radical polymerization over most other forms of polymerization, (anionic, cationic, coordination) is that statistical copolymers can be prepared from a very wide range of monomer types that can contain various unprotected functionalities. Radical copolymerization and the factors that influence copolymer structure have been discussed in Chapter 7. Copolymerization of macromonomers by NMP, ATRP and RAFT is discussed in Section 9.10.1. 

The grafting through approach involves copolymerization of macromonomers. NMP, ATRP and RAFT have each been used in this context. The polymerizations are subject to the same constraints as conventional radical polymerizations that involve macromonomers (Section 7.6.5). However, living radical copolymerization offers greater product uniformity and the possibility of blocks, gradients and other architectures. 

Since macromonomers are already polymers with MW between 103 and 104, their polymerization and copolymerization involves polymer-polymer reactions. Thus a question of continuing concern has been how and why a macromonomer is different in its reactivity from a corresponding conventional monomer of low MW. 

To summarize, macromonomers in polymerization and copolymerization are only fairly well understood compared to the conventional monomers. Effects, such as conformational, morphological, or due to incompatibility caused by the macromonomer chains, remain to be further investigated. As a result, the macromonomer technique is expected to lead to other unique applications including construction of novel branched architectures. 

A number of well-defined macromonomers differing in the types of the monomer and the end functionality have been made available in these two decades. Their polymerization and copolymerization have provided a relatively easy access to a variety of branched polymers and copolymers, including comb-, star-, brush-, and graft-structures. Progress will no doubt continue to disclose further different types of macromonomers and branched polymers. 

This contribution discusses the molecular characteristics of a series of original nonlinear and yet well-defined architectures based on PS, PB and PEO that were obtained by ROM polymerization or copolymerization of the corresponding macromonomers. Unlike other "living" chain addition polymerization, ROMP is robust and versatile and could successfully be applied to shape very common polymers into particular forms. 

Graft copolymers containing styrene in the main chain and other monomers in their side chains are available by numerous methods, including conventional radical [171], controlled radical, anionic [174], and cationic [175] polymerization and by copolymerization of macromonomers [80,174], Grafting methods via conventional radical polymerization are reviewed by Nuyken and Weidner [171], The following reaction scheme demonstrates the principles and universality of the methods applying polymeric initiators ... 

Another example of the flexibility of ADMET is the demonstration of successful polymerization of o /v-telechelic diene carbosilane macromonomers.45 The synthesis of macromonomer 30 is achieved using catalyst 23 and copolymerized with a rigid small-molecule diene, 4,4/-di-trans-l-propenylbiphenyl (Fig. 8.17). 

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