Poly methacrylate esters

As mentioned above, the new method Lewis acid promoted living polymerization of methacrylic esters, by using enolatealuminum porphyrin (2) as nucleophilic initiator in conjunction with organoaluminum compounds, such as methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate) (3e), as Lewis acids has enabled us to synthesize poly(methacrylic ester) of narrow molecular-weight distribution [51]. On the other hand, some reactions of aluminum por-... 

A comparison between the optical activity of some poly-acrylic or poly-methacrylic esters and of some model compounds, having approximately the same optical purity, shows that in general the optical activity is in both cases of the same order of magnitude (Table 19). 

However, as the optical rotation dispersion curves between 250 and 589 m/t of some poly-acrylic and poly-methacrylic esters seem to be anomalous1 relationship between optical activity and conformation in... 

The polymer studied in the series of poly(methacrylic ester)s with a mesogenic side group was polymer labeled la shown in Scheme 1.1... 

As our first case study, dealing with pol)miers, we consider Langmuir mono-layers of poly(methacrylic ester), PMA, at the water-air interface. Data for these layers can be used to illustrate some trends and principles, laid down in sec. 3.41. In that section we discussed how the surface pressure of physisorbed polymers depends on surface concentration. In a dilute monolayer of pancakes, the surface pressure was found to be given by the ideal term plus an excluded-area contribution. We rewrite [3.4.56] in terms of the adsorbed amount r = n°/A = N°/ N A) in moles of chains per unit area... 

Pyrolysis of poly(methyl methacrylate) occurs with a significant proportion of monomer formation. Table 2.1.1. indicates 95% monomer yield, while the results from Table 6.7.20 show only about 59%. The disparity is caused by the differences in the pyrolysis conditions. As shown in Section 2.1, the thermal decomposition of poly(methacrylate esters) is dominated by unzipping, which is a radical propagation reaction with the cleavage of the bond in p-position to the atom bearing the unpaired electron and also p to the double carbonyl bond. This reaction leads to the formation of monomer as shown below (R = CHs for the methyl ester) ... 

Sterically Restricted Poly (methacrylate ester)s. It was recognized by Okamoto and coworkers150 that the anionic polymerization of tri-phenylmethyl methacrylate (TrMA, 41) (Chart 8) at low temperature in the presence of an optically active initiator results in the formation of an isotactic, optically active polymer. The helical conformation of the backbone in these macromolecules is the result of steric interactions between the bulky trityl groups, as was shown by the loss of optical activity upon their conversion to methyl ester groups. This class of bulky... 

Screening of an impressive series of polymers derived from different bulky methacrylate esters, e.g., 42 (Chart 8), and using a variety of chiral ligands has revealed the scope of the process of forming helical poly(methacrylate ester)s and their applicability in, for example, the separation of chiral compounds.151 These polymers were prepared not only by anionic polymerization, but also by cationic, free-radical, and Ziegler—Natta techniques. Recently, Nakano and Okamoto reported the use of a co-balt(II)—salophen complex (43) in the polymerization of methacrylate ester 41.155 The free-radical polymerization in the presence of this optically active metal complex resulted in the formation of an almost completely isotactic polymer with an excess of one helical sense. 

Lewis acid-assisted high-speed living anionic polymerization can be applied not only to the accelerated synthesis of naiTOw MWD poly(methacrylic esters) but also to the synthesis of polyethers from epoxides (11) and polyesters from lactones (14 and 15) with aluminum porphyrins as initiators. Furthermore, ring-opening polymerization of episulfides (18) with zinc AT-substituted porphyrins (5) can also be accelerated by Lewis acids. 

The thermal degradation of polymers of acrylic and methacrylic alkyl esters is a process of depolymerization to monomers at temperatures up to 250°C, provided that the alkyl group is small, less than butyl [468]. Poly(f-butyl methacrylate) yields quantitatively isobutene instead. It was shown that thermal depolymerization to monomers is probably common to all poly(methacrylate ester)s. As the size of the alkyl group increases, however, particularly within secondary or tertiary structures, there is increased tendency for the alkyl group to also decompose. This decomposition interferes with the depolymerization process... 

Figure 4-13. Dependence of the hindrance parameter a on the formula molecular weight for a series of poly(methacrylic esters) -fCH2—CCH3(COOR) (O), and poly(itaconic esters) -FCH2—C(C00R)(CH2C00R) ( ) in toluene solution at 25 C (after J. Velickovic and S. Vasovi ).

Figure 10-19. Brittleness temperature of poly(acrylic esters) (PAES) and poly(methacrylic esters) (PMES) as a function of the number N of carbon atoms in the aliphatic side chains.

Emulsion polymerization is similar to suspension polymerization in the sense that the reaction also takes place in the presence of a water phase and the applied monomer forms a second liquid phase. However, in this case the added radical initiator is not soluble in the monomer droplets but in the water phase. To allow the monomer to come into contact with the initiator an emulsifier is added to the reaction mixture that creates micelles in the systems. By diffusion processes both monomer molecules and initiator molecules reach the micelle. Polymerization takes places and a polymer particle suspended in the water phase forms that is much smaller than the original monomer droplet (see Figure 5.3.12 for a graphical illustration of these steps). At the end of the overall emulsion polymerization process, all monomer droplets have been consumed by the polymerization reaction in the micelles. Typical emulsifiers for emulsion polymerization are natural or synthetic detergents, such as, for example, sodium palmitate or sodium alkyl sulfonates. Emulsion polymerization is very versatile and is applied for many polymers [e.g., PVC, styrene copolymers, poly(methacryl esters)] in batch, semi-continuous, and continuous processes. In some cases, the obtained polymer particles in water are directly applied as technical products for coatings, lacquer applications, or as adhesives. In other cases the formed product is further treated to obtain the dry polymer. Note that the aqueous phase in emulsion polymerization always contains some isolated emulsifier and also some monomer. Moreover, the formed polymer contains the emulsifier as impurity. 

Photodegradation of poly(methacrylic esters of p-acetylated-2-phenoxy-ethanols has also been reported [1014]. 

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