Vinyl esters reactivity ratios

Tables 7 and 8 give properties of some diaHyl esters. DimethaHyl phthalate [5085-00-7] has been copolymerized with vinyl acetate and benzoyl peroxide, and reactivity ratios have been reported (75).

In studies of the polymerization kinetics of triaUyl citrate [6299-73-6] the cyclization constant was found to be intermediate between that of diaUyl succinate and DAP (86). Copolymerization reactivity ratios with vinyl monomers have been reported (87). At 60°C with benzoyl peroxide as initiator, triaUyl citrate retards polymerization of styrene, acrylonitrile, vinyl choloride, and vinyl acetate. Properties of polyfunctional aUyl esters are given in Table 7 some of these esters have sharp odors and cause skin irritation. 

The co-monomers such as vinyl acetate, acrylate esters, or carbon monoxide are fed together with ethylene, or introduced by liquid pumps, into the suction of the secondary compressor. The concentration in the feed of the co-monomer which is required to achieve a certain level of the co-monomer in the resulting polymer depends on the reactivity ratios, ri and r2, which are the ratios of rate constants of chain-propagation reactions [5]. The values for the co-monomers used in the high-pressure process are presented in Table 5.1-3. In the case of vinyl acetate, both reactivity ratios are identical and therefore the composition of the copolymer is the same as that of the feed. The concentration of vinyl acetate, for example, in... 

M 2. —, and W. G. de Pierri Reactivity ratios of vinyl esters of aliphatic acids and some common vinyl monomers. J. Polymer Sci. 27, 39 (1958). 

According to literature data vinyl esters of saturated aliphatic carboxylic acid copolymerize randomly with each other (I), the monomers being incorporated into the copolymer in about the same ratio at which they are present in the monomer mixture. This means that for practical purposes the relative reactivity ratios ri and r > can be taken to be equal and unity. 

If two of the three monomers belong to the group described above and one is weakly conjugated, i.e. of the group of vinyl chloride, vinyl esters, olefins and the like, the product probabilities are approximately 0.006. It is evident that knowledge of the product probabilities permits to predict relative reactivity ratios for a wide variety of monomers. 

Comparing the acetylene dicarboxylic ester with the fumaric ester, a slightly higher reactivity of the C=C over the C=C dienophile is noted. The efficiency of C=C and C=N bonds as dienophiles was compared by studying the reaction of butadiene with acrylonitrile mainly cyanocyclohexene and no vinyl-pyridine was found in the product, proving that the C=C bond is far more reactive than the C=N bond, at least in the homogeneous gas-phase reaction (heterogeneous catalysts lower the reactivity ratio to ca. 10) . 

The reactivities of various vinyl esters in copolymerizations are generally very similar. The sampling of reactivity ratios given in Table XII indicates this quite clearly. The somewhat unique behavior of vinyl benzoate is indicated in the Table XII. 

TABLE XII Reactivity Ratios of Selected Vinyl Esters... 

A variety of copolymers of vinyl esters have been prepared in solution. For example, vinyl 2-ethylhexanoate and 2-ethylhexyl acrylate have been copolymerized in feed ratios ranging from 1 to 1 to 1 to 3 (on a molar basis). The acrylic monomer was said to have a greater reactivity than the vinyl ester. The product was studied as a possible viscosity index improver [112]. 

TABLE IXa Reactivity Ratios and Q-e Parameters for Copolymerization of Allyl Esters (A/ ) with Vinyl Acetate (A/2) [64]... 

As discussed above, differences in reactivity ratios can lead to drift in the copolymer composition from that of the starting materials. Noel et al. [39] studied a unique set of monomers, namely VAc, vinyl 2,2-dimethylpropionate and vinyl 2-ethylhexanoate, and determined their reactivity ratios with methyl acrylate. Their work led to the conclusion that the three vinyl esters can be described with one set of reactivity data. This greatly simplifies any potential for compositional drift since only one variable must now be dealt with, namely interphase partitioning of the monomer. Copolymers or terpolymers produced with VAc and vinyl esters have the potential to outperform VAc/acrylic copolymers due to the mote random copolymerization of VAc with other vinyl ester monomers compared with acrylic monomers [40], as is discussed in Section 16.9. 

The chemical reactivities of the unsaturated groups at the ends of vinyl ester resin and vinyl urethane resin chains are different in several respects from those of the same groups when situated in mid-chain positions, as they are in polyester resins. As a consequence of the different reactivity ratios, the two kinds of cured resin behave differently from moisture and chemical resistance points of view. The structural differences are also reflected in the mechanical properties, such as fracture toughness. 

That water solubility of the comonomers plays a significant role is clearly shown in a different study by Noel et al. MA was copolymerized with vinyl esters of different hydro-phobicity. Vinyl acetate (VAc) has a fairly similar water solubility as MA. The result is that the apparent reactivity ratios are hardly influenced by the M/W ratio. Figure 11 shows the copolymerization of MA and VAc at two strongly different M/W ratios. Clearly, the results are virtually identical. On the other hand, MA was copolymerized with vinyl 2,2-dimethylpropanoate (VPV). VPV has a very similar reactivity compared to VAc due to their similar chemical stmctures. However, the water solubility of VPV is 2 orders of magnitude lower than that of VAc. The difference in water solubility has a clear influence on the apparent reactivity ratios as can be seen from Figure 12. 

Table 3.5 summarizes typical reactivity ratio values for binary systems including styrene, alkyl methacrylate, alkyl acrylate and vinyl acetate. Values for the (meth)acrylates have negligible differences within the series of alkyl esters (e.g., methyl, butyl, dodecyl) [27]. Figure 3.1... 

Acrylic ester monomers are, in general, readily copolymerized with other acrylic and vinylic monomers. Table 7 presents data for the free-radical copolymerization of a variety of monomers 1 1 with acrylic ester monomers. These numbers are calculated through the use of reactivity ratios ... 

Copolymerizations with less hindered monomers such as acrylates, NVF, or vinyl acetate were faster and went easily to high conversion. Copolymerizations in methanol to partial conversions indicate reactivity ratios similar to those of NVF, with slightly faster conversion of either acrylates or NVF and slightly slower conversions of vinyl esters than the Michael adduct comonomers (Figure 2). 

Methylenesulphones are more acidic than the simple esters, ketones and cyano compounds and are more reactive with haloalkanes [e.g. 48-57] to yield precursors for the synthesis of aldehydes [53], ketones [53], esters [54] and 1,4-diketones [55] (Scheme 6.4). The early extractive alkylation methods have been superseded by solidtliquid phase-transfer catalytic methods [e.g. 58] and, combined with microwave irradiation, the reaction times are reduced dramatically [59]. The reactions appear to be somewhat sensitive to steric hindrance, as the methylenesulphones tend to be unreactive towards secondary haloalkanes and it has been reported that iodomethylsulphones cannot be dialkylated [49], although mono- and di-chloromethylsulphones are alkylated with no difficulty [48, 60] and methylenesulphones react with dihaloalkanes to yield cycloalkyl sulphones (Table 6.5 and 6.6). When the ratio of dihaloalkane to methylene sulphone is greater than 0.5 1, open chain systems are produced [48, 49]. Vinyl sulphones are obtained from the base-catalysed elimination of the halogen acid from the products of the alkylation of halomethylenesulphones [48]. 

Most of the reported polyfvinyl ether) macromonomers have been prepared with a methacrylate end group which can be radically polymerized and which is non-reactive under cationic polymerization conditions [71-73]. Generally, the synthesis was based on the use of the functional initiator 30, which contains a methacrylate ester group and a function able to initiate the cationic polymerization of vinyl ethers. Such initiator can be obtained by the reaction of HI and the corresponding vinyl ether. With initiator 30 the polymerization of ethyl vinyl ether (EVE) was performed using I2 as an activator in toluene at -40 °C. The MW increased in direct proportion with conversion, and narrow MWD (Mw/Mn= 1.05-1.15) was obtained. The chain length could be controlled by the monomer to initiator feed ratio. Three poly(EVE) macromonomers of different length were prepared by this method Mn=1200,5400, and 9700 g mol-1. After complete... 

Typically, polymers of these acrylic and methacryUc esters are produced as copolymers with other acrylic and vinyl monomers. For example, acrylonitrile is often added to impart additional water and solvent resistance. Other features that can be improved include abrasion resistance, adhesion, elasticity, flexibility and film hardness. Enhanced durability to laundering can be achieved by incorporating reactive, especially crosslinking, monomers such as A -methylol acrylamide, hydroxyethyl acrylate, acrylamide, acrylic and methacrylic acid. Optimisation of polymer properties with the large variety of available monomers leads to near endless combinations of copolymers that are limited only by the imagination of the chemist and by the reality of the cost-efficiency ratio. 

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