Addition polymerization of unsaturated monomers

Organoaluminum porphyrins with axial alkyl groups (la, lb) are effective for the living polymerization of unsaturated monomers such as acrylates (20)- and methacrylates (21),-2 whereas chloride, alcoholate, phenolate and carbox-ylate complexes (Ic-f) are totally inert for the polymerization of these monomers. In contrast to the polymerization of polar vinyl monomers, controlled polymerization of nonpolar vinyl monomers such as styrene with aluminum porphyrins has been unsuccessful. 

The wide applicability of aluminum porphyrin initiators (1) leads to a variety of tailored block copolymers such as polymethacrylate-polyether and polymethacrylate-polye-ster, as well as polymethacrylate-polymethacrylate and polymethacrylate-polyacrylate, that can be synthesized by sequential living polymerization of the corresponding monomers.- For example, when 1,2-epoxypropane (11, R = Me) is added to a polymerization mixture of methyl methacrylate (21, R = Me) with la at 100% conversion of 21, the polymerization of 11 takes place from the enolate growing end (32 ) to give a narrow MWD polymethacrylate-polyether block copolymer having an alcoholate growing terminal (Table 4). Likewise, the aluminum enolate species (32 ) can also react with lactones (14,15), thereby allowing the formation of a poly(methyl methacrylate)-polyester block copolymer with narrow MWD. 

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Addition polymerizations of unsaturated monomers leading to the formation of products of high molecular weight invariable proceed by chain reaction mechanisms. Primary activation of a monomer M (or a pair of monomers) is followed by the addition of other monomers in rapid succession... 

There are two general routes to the synthesis of conjugated polymers addition polymerization of unsaturated monomers and condensation polymerization or stepwise coupling of monomers with difunctional groups. 

Figure I shows a schematic representation for addition polymerization of unsaturated monomer (M) with initiator (1- ), where the chain growth of a polymer molecule starts by the reaction of I- with M to generate an active species (1-M- ) (initiation step), followed by repeated additions of...

Aluminum porphyrins are versatile initiators which are applicable to controlled ring-opening polymerization of various heterocyclic monomers (Table 1) such as epoxides (11)," oxetanes (12) lactones with four-, six-, and seven-membered rings (13-15), lactide (16), six-membered cyclic carbonates (17) and cyclic siloxanes (19).-" They are also excellent initiators for the controlled addition polymerization of unsaturated monomers such as acrylates (20), methacrylates (21)-- and methacrylonitrile (22).- - ... 

We have considered a variety of precedents for radical/ionic addition polymerization of unsaturated monomers to yield polymeric materials. However, ntme of the aforementioned techniques offer stereoselective control over the growing polymer chain, resulting in purely atactic polymers. In order to introduce such control, it is necessary to spatially confine the reactive site to control the direction of incoming monomer/growing polymer. The most common method used to control the tacticity of the resulting polymer is Ziegler-Natta polymerization. 

Addition polymerization of unsaturated phosphate monomers has been extensively investigated, but to date only a few industrial applications have been found. Dental anticaries applications of phosphoenol pyruvate polymers and copolymers with acrylic acid have been demonstrated in vitro (123). 

In the second chapter (Preparation of polymer-based nanomaterials), we summarize and discuss the literature data concerning of polymer and polymer particle preparations. This includes the description of mechanism of the radical polymerization of unsaturated monomers by which polymer (latexes) dispersions are generated. The mechanism of polymer particles (latexes) formation is both a science and an art. A science is expressed by the kinetic processes of the free radical-initiated polymerization of unsaturated monomers in the multiphase systems. It is an art in that way that the recipes containing monomer, water, emulsifier, initiator and additives give rise to the polymer particles with the different shapes, sizes and composition. The spherical shape of polymer particles and the uniformity of their size distribution are reviewed. The reaction mechanisms of polymer particle preparation in the micellar systems such as emulsion, miniemulsion and microemulsion polymerizations are described. The short section on radical polymerization mechanism is included. Furthermore, the formation of larger sized monodisperse polymer particles by the dispersion polymerization is reviewed as well as the assembling phenomena of polymer nanoparticles. 

The first stereochemical analysis of the polymerization mechanism of unsaturated monomers was proposed by Arcus 30 years ago (58, 269). The diaste-reomeric relationships within a single chain may be connected to monomer configuration by two factors the type of addition to the double bond (cis or trans) and the way in which successive monomer molecules approach the growing chain. For a CHA=CHB olefin the relationship between the stmcture of the monomer and that of the adding monomeric unit is illustrated in Scheme 22 (31), where cis or trans addition indicates that the new bonds are formed in the same half-space or in the two opposite half-spaces, provided there is no rotation aroimd the central C—C single bond. 

Acyclic an open-chained compound Addition Polymerization bonding of monomers without the elimination of atoms, formation of polymer by the bonding of unsaturated monomers Adhesion attraction between the surface of two different bodies... 

WeVe seen only a few examples of radical reactions because they re 1< common than polar reactions. Those we have studied can be dassified as eith radical addition reactions or radical substitution reactions. Radical additio-such as the benzoyl peroxide-catalyzed polymerization of alkene monome (Review Table 1, reaction Ij), involve the addition of a radical to an unsaturated substrate. The reaction occurs through three kinds of steps, all of whicli involve odd-electron species (1) initiation, (2) propagation, and (3) termination. 

There are two fundamental polymerization mechanisms. Classically, they have been differentiated as addition polymerization and condensation polymerization. In the addition process, no by-product is evolved, as in the polymerization of vinyl chloride (see below) whereas in the condensation process, just as in various condensation reactions (e.g., esterification, etherification, amidation, etc.) of organic chemistry, a low-molecular-weight by-product (e.g., H2O, HCl, etc.) is evolved. Polymers formed by addition polymerization do so by the successive addition of unsaturated monomer units in a chain reaction promoted by the active center. Therefore, addition polymerization is called chain polymerization. Similarly, condensation polymerization is referred to as step polymerization since the polymers in this case are formed by stepwise, intermolecular condensation of reactive groups. (The terms condensation and step are commonly used synonymously, as we shall do in this book, and so are the terms addition and chain. However, as it will be shown later in this section, these terms cannot always be used synonymously. In fact, the condensation-addition classification is primarily applicable to the composition or structure of polymers, whereas the step-chain classification applies to the mechanism of polymerization reactions.)... 

You will recall that the propagation step in the polymerization of diene monomers (monomers with two double bonds) can proceed by either of two mechanisms 1,2, and 1,4 additions. In 1,2 addition the resulting polymer imsaturation is part of the pendant group, while in 1,4 addition the unsaturation is part of the backbone. In the latter case, the backbone has a rigid stracture and rotation is not free around it. Therefore, two different configurations, known as cis and trans, are possible. For example, 1,4-poly isoprene ... 

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