Synthesis of Vanillin-Based Polymers
Current interest in the development of renewable resources-based polymeric materials [99] has opened a new area of research into
abundant natural products that can be utilized as monomers or monomer precursors for the polymer industry. Several researchers have studied the possibility of using vanillin as one of these renewable resources-based building blocks for the polymer industry in addition to its present applications in food and pharmaceutical industries [100-102].
In one recent example of preparation of renewable resources — based polymers from vanillin, Mialon and coworkers first converted the vanillin to acetyldihydroferulic acid using the Perkin reaction as shown in Figure 10.3. Polymerization of this monomer yielded poly(dihydroferulic acid), which exhibits thermal properties functionally similar to those of polyethylene terephthalate (PET) plastics [100].
In a recent example of vanillin-based polymer synthesis, vanillin was first converted to divanillin by enzymatic oxidative coupling of vanillin. Next, electrochemical reductive polymerization of divanillin in aqueous sodium hydroxide using a lead cathode gave polyvanillin in 91% yield as shown in Figure 10.4 [101].
The same research group who prepared polyvanillin used divanillin for the synthesis of divanillin-Schiff base polymers by condensation of divanillin with different aliphatic diamines as shown in Figure 10.5. In addition, these polymers were shown to chelate with divalent metal ions forming organometallic polymers [102].
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