Graft copolymerization details

The organization of the book follows a logical sequence After a thorough presentation of basic thermodynamic principles and the Jacobson-Stockmayer cycliza-tion theory, the authors discuss in depth all kinds of aspects of the various heterocyclic compound classes. In addition to detailed discussions of mechanisms, many other facets of heterocyclic polymerizations are treated, e.g., monomer synthesis, contemporary research trends, industrial significance. The treatise ends with an excellent up-to-date discussion of random, block and graft copolymerizations of heterocyclics. 

Poly(dextran-g-acrylamides) from ferrous ion—hydrogen peroxide initiation Graft copolymerization of acrylamide onto dextran with ferrous ion-hydrogen peroxide initiation is being studied in detail. The effect of variation of each reaction parameter on graft copolymerization behavior may be measured by direct gel permeation chromatographic analysis of the final product polymer solution. 

Oxazolines undergo polymerization upon exposure to a variety of cationic initiators such as strong Lewis acids or strong protic acids. Copolymerization between different oxazolines of defined composition can be carried out in a random manner or in a controlled fashion resulting in block polymers. Alternatively, oxazolines can also be grafted onto other types of polymers. It is beyond the scope of this chapter to review in detail this enormous and important subject. Instead, the... 

Waak14) successfully copolymerized co-allylpolystyrene macromonomers with acrylonitrile and several other monomers. Graft copolymers resulted in spite of the fact that allylic double bonds are not very suitable for free-radical copolymerization. However, a detailed characterization of these copolymers has not been given. 

For block and graft copolymers, to which the classical copolymerization equations cannot be applied, there is frequently no theoretical or experimental basis for a prediction of the detailed polymer structure. In such cases, new analytical methods are clearly needed. 

So far in our discussion of micros tincture, we have considered homopolymers. To some degree, however, there is an element of semantics involved in our definition. Is a branched polyethylene a true homopolymer or should it be considered a copolymer of ethylene and whatever units comprise the branches Here our concern is real copolymers, those synthesized from two (or more) distinct monomers. The simplest possible arrangements are shown in Figure 2-22 and are self-explanatory. But, as we will see, real life is more complex. True random copolymers are rare and in most cases there are tendencies to blockiness or alternating arrangements. There are also graft copolymers, but we will discuss all this in more detail when we consider copolymerization. 

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). 

Various graft copolymers were synthesized by metal-catalyzed radical polymerizations, as detailed in Figure 30. Most of them were from random copolymerization of a macromonomer with a low molecular weight comonomer. 

After synthesis, the methacryloxy-terminated PDMS macromonomers were purified, and the macromonomers were copolymerized with methyl methacrylate using free-radical, anionic, and group transfer polymerization. Detailed descriptions of the polymerization are provided by DeSimone (1990) and Hellstern (1989). In addition to well-defined graft copolymers, there is... 

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