Polymerization of different monomers

Recently, Smigol et al. [75] extensively studied emulsifier-free emulsion polymerization of different monomers including styrene, methyl methacrylate, and glycidyl methacrylate in an aqueous medium by using potassium peroxydisulfate as the initiator. In this study. 

The two monomers enter into the copolymer in overall amounts determined by their relative concentrations and reactivities. The simultaneous chain polymerization of different monomers can also be carried out with mixtures of three or more monomers. Such polymerizations are generally referred to as multicomponent copolymerizations the term terpolymerization is specifically used for systems of three monomers. 

Table 2. Rate Parameters for Plasma Polymerization of Different Monomers...

The possible application of these materials to form surface barrier solar cells, and to make conductor/insulator/conductor sandwiches by sequential polymerization of different monomers has been explored376,379,381. 

Retarders and inhibitors differ only in the frequency with which propagating radicals react with them rather than with monomer and possibly also in the ability of the radicals resulting from such reactions to reinitiate. It is lo be expected, then, that a compound may not exert the same elTect in the polymerization of different monomers. For example, aromatic nitro compounds that are inhibitors in vinyl acetate polymerizations are classified as retarders in polystyrene syntheses. 

A wide variety of photoinitiators have been investigated for polymerization of different monomers, such as acrylates, epoxides, vinyl ethers, and thiol-ene monomers. From this point of view, the D-rc-D or A-rc-A chromophores are favored sensitizers if they are combined with a coinitiator [269, 563], The sensitizer excited by TPA can be either oxidized (route A) or reduced (route B) by the coinitiator, depending on the chemical structure of the coinitiator (Fig. 3.64). 

To enable a comparison of polymerization of different monomers and of catalysts based on different metals, activities are usually given as turnovers per hour, TO h (TO = mol substrate converted per mol of metal). When comparing activities determined by different authors under strongly varying conditions the values should be taken as an indication of the order of magrtitude. The same holds true for polymer molecular weights. 

In the 1960s a number of publications on aqueous polymerizations of different monomers appeared. Rinehart et al. and Canale and co-workers independently reported aqueous polymerization of butadiene catalyzed by rhodium salts. Utilizing Rh "Cl3 3H2O as a catalyst precursor, semicryslallirie trans-l,4-polybutadiene was obtained stereoselectively [Eq. (4) >99% trans] [20, 21]. 

But studies of the kinetics of polymerization of different monomers, under different conditions and chemical environments, indicate that ideal behavior is probably more an exception than the rule. Most practical free-radical polymerizations will deviate to a greater or lesser extent from the standard conditions outlined in the reaction scheme (6.3) to (6.10) either because the actual reaction conditions are not entirely as postulated in the ideal kinetic scheme or because some of the assumptions that underlie the ideal scheme are not valid. 

There are many reports on polymerization of different monomers showing different degrees of kinetic complexity where the observed effects are well explained and understood on the basis of equilibrium complex formation between the initiator used and the monomer [45-47]. 

The orders of magnitude of the values of Gp (molecules/lOOeV) for real processes of radiation-induced polymerization of different monomers are very different, e.g. diene hydrocarbons 10-102, whereas tetrafluoroethylene 105-106. 

The discovery of Ziegler-Natta catalysts led to many industrial and academic investigations on other kinds of metallic complexes for polymerization of different monomers. Several organometallic and coordination compounds have been synthesized and probed as catalytic systems. They have been classified based on generations or groups, transition-metal type, the chemical structure, the type of activator, and their applications in polymerization processes [2]. Currently, there are different groups of initiator systems based on early and late transition metals or lanthanide complexes, which have been studied in polymerization catalysis [3]. 

Table 15 Polymerization of different monomers leading to substituted polybutadienes. 

UV irradiation of polymers has been observed to be an effective technique to modify polymers for biomolecule immobilization. The polymer surface is modified by photo-induced graft polymerization of different monomers, such as acrylic acid,. -acrylamidomethylpropane sulfonic acid, and styrene sulfonic acid. All these monomers have ionic functionality and lead to high graft densities for the immobilization of collagen and other proteins. The surface density of polyacrylic acid grafts reaches up to lOOpg/cm under appropriate reaction conditions and Is enough for protein immobilization [36]. 

Figure 3.8. Number of particle nuclei per unit volume of water versus time profiles for surfactant-free emulsion polymerization of different monomers obtained from the model developed by Song and Poehlein [47, 48], The symbols St, BA, MMA, VCI, and VA denote styrene, n-butyl acrylate, methyl methacrylate, vinyl chloride, and vinyl acetate, respectively.

Representative computer simulation results for surfactant-free emulsion polymerizations of different monomers obtained from the model of Song and Poehlein [47, 48] are illustrated in Figure 3.8. The rate of particle nucleation during the early stage of polymerization in increasing order is styrene < n-butyl acrylate < methyl methacrylate < vinyl chloride < vinyl acetate. This trend... 

Figure 3.9. Rayleigh light scattering intensity versus time data obtained from the surfactant-free emulsion polymerizations of different monomers. The symbols MA, EA, and BA denote methyl acrylate, ethyl acrylate, and />butyl acrylate, respectively.

The possibility of preparing wdl-defined polymers from these monomers depends on the operating polymerization mechanism, more particularly on control of the initiation reaction and the occurrence or absence of transfer and/or termination reactions. In this chapter, the mechanism of polymerization of different monomer types will be described, with emphasis on control of the polymer stmctures formed. This control applies not only to molecular wdght and molecular wdght distribution (MWD) but also to the stereochemistry and the nature of the polymer end groups. 

Polymerization in clathrates was revived by Di Silvestro and Sozani. " More than 50 examples of polymerization of different monomers in clathrates were described. 

Thermal analysis showed that initial degradation steps occurred between 200 and 300°C. At higher temperatures, Pb02 was determined to be the residue formed. Table 2 shows the percent yields and percent lead measured for the polymerization of different monomers. ... 

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