Vinylic surfmer

The maleic Surfmers were tested in core-shell emulsion polymerization of styrene/butyl acrylate in comparison with a standard nonreactive surfactant (nonyl phenol reacted with 30 mol of EO - NP30). While the methacrylic-derived Surfmer was completely incorporated during the polymerization (although about one-third of it was buried inside the particles) the NP30, the maleic Surfmer and the allylic and vinyl Surfmers were not incorporated and could be extracted with acetone (for the last two probably because of the formation of acetone-extractable oligomers due to a chain transfer behavior) [31]. 

Maleate Surfmers. Surfmers with allylic, acrylic and vinylic moieties tend to homopoly-merize and produce water-soluble polyelectrolytes if used above their CMC. This has shifted researchers attention to maleic derivatives that do not homopolymerize at normal temperatures because their ceiling temperature is too low. Tauer and co-workers have pioneered the synthetic work [4,15] which led originally to compounds like those given in Figure 6.49. An example of maleic-derived Surfmer used in emulsion polymerization lattices is reported in [16] and the advantages provided in commercial paint formulations are discussed later. 

One way to achieve this result relies on the change in the relative monomer reactivity following composition drifts. Thus, in a combination ofhigh and low reactivity monomers, the former will preferentially react first, leaving a considerable proportion of the latter for copolymerization when the supply of the high reactive monomer is depleted. This has been confirmed in the terpolymerization of methyl methacrylate/butyl acrylate/vinyl acetate in the presence of the maleate Surfmer reported in Figure 6.49. 

The acylation of alcohol-containing monomers, e.g. hydroxyethyl acrylates or vinyl benzyl alcohol with maleic, succinic or sulfosuccinic anhydride leads to bifunctional polymerizable surfactants. A range of such products has been synthesized and tested in batch polymerization and core-shell polymerization of styrene and butyl acrylate [26]. In both cases good stability, high conversion and little burying of the Surfmers were observed. Water rebound was also limited. These advantageous features were however offset by an unacceptable resistance to electrolytes and to freeze-thaw. 

In one example, a mixture of vinyl esters was added during the final discontinuous stage of an S-BA emulsion copolymerization carried out in a semibatch reactor using a maleate surfmer. In the absence of vinyl esters, the final conversion of the surfmer was 52%, whereas with vinyl esters the surfmer conversion increased from 52% to 80% in the last batch stage [44]. 

An example of this behavior is the emulsion terpolymerization of MMA/ BA/VA vinyl acetate (50 35 15 wt/wt/wt) using a maleate surfmer [VIII in Table 3]. VA vinyl acetate is by far the least reactive monomer and accumulates in some extent in the reactor during the semicontinuous operation. At the end of the addition period, the surfmer conversion was about 60%, and during the final discontinuous stage complete conversion of the surfmer was achieved. 

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