Formation of pigmented polymers

Hayasaka, Y., Kennedy, J.A. (2003). Mass spectrometric evidence for the formation of pigmented polymers in red wine. Am. J. Grape Wine Res. 9, 210-220. 

Formation of Pigmented Polymers during Commercial Scale Winemaking Trials... 

Precursors involved in Formation of Pigmented Polymers. The concentration of pigmented polymers in the four treatments at pressing is shown in Figure 2. It was closely correlated to the concentrations of M3G. This observation served as indirect evidence that anthocyanins, not unsurprisingly, were required as chromophores for the formation of pigmented polymers (77). 

Formation of Pigmented Polymers in Model Fermentation Experiments... 

Figure 3. Formation of pigmented polymers in chemically-defined ff ape juice medium. Average concentration by HPLC, values are the mean of triplicate fermentations, A anthocyanins, T tannins, s sugar (200 g/L glucose), y standard inoculation with yeast (0.4 ODad),...

While the identity of the relevant yeast metabolites in the fermented medium sampled at day 2 needs to be clarified, previously published data have provided some evidence about the role of acetaldehyde-mediated condensation of catechin with MSG (13-20). We therefore aimed to extend these model studies and to confirm chemical formation of pigmented polymers from condensed tannins, which are commercially used in red winemaking, and anthocyanins. The model reactions were conducted with vatying concentrations of acetaldehyde and SO2 as shown in Table 2 and analysed by HPLC after 2, 4 and 7 days. After 7 days visible precipitation of unidentified material started to occur in presence of acetaldehyde and the reactions were discontinued. 

In step 4, p-phenylenediamine adds to the indophenol in a 1,4 manner [25, 33], producing the trinuclear species (XXVIII), which is then oxidized to the trinuclear green pigment (XXI). Several routes exist for formation of polymeric indophenols, and all are analogous to steps 4 and 5. Repetition of these steps will result in the formation of higher polymers. Because most oxidation dyes contain both p-phenylenediamine and resorcinol, the formation of these tri- and polynuclear pigments is important in the oxidative dyeing of human hair. 

With the objective of promoting polymer formation at the surface of Ti02 pigments and prevent secondary nucleation, Haga et al. used a diazoic amidinium initiator previously anchored on the mineral surface [213], whereas Janssen used redox initiators [208]. Although real benefit was taken from the nature of the initiator, in particular in the case of hydrophilic monomers like MMA, there was still a competition between the formation of surface polymer and free latex particles in these systems. In both cases, better results were obtained when the monomer was introduced under starved-feed conditions, which enabled a significant decrease in the extent of secondary nucleation. 

Various finishes can be achieved — gloss, satin (or egg-shell) or matt. This is accomplished by the addition of particles of size 1-5 pm of, for example, silica, china clay or the white pigment, TiCK The degree of mattness depends on various factors, such as particle size, surface treatment of the particles, rate of film formation, and the polymer composition, e.g., urethane/acrylate compared with epoxy/acrylate. The former requires smaller particles larger particles cannot be used as they create a rough surface. 

These thermoplastic resoles and novolacs are mixed with lubricants, pigments and additives, such as wood flour. The molding compound is converted to an infusible resin by heating it under pressure in a mold. A typical sequence of chemical reactions associated with the formation of this complex, three-dimensional polymer is shown in Figure 15.4. Typical properties of phenolic plastics are shown in Table 15.4. 

---