Ferulic Acid as Building Block for the Lipase-Catalyzed Synthesis of Biobased Aromatic Polyesters

Abstract

Enzymatic synthesis of aromatic biobased polyesters is a recent and rapidly expanding research field. However, the direct lipase-catalyzed synthesis of polyesters from ferulic acid has not yet been reported. In this work, various ferulic-based monomers were considered for their capability to undergo CALB-catalyzed polymerization. After conversion into diesters of different lengths, the CALB-catalyzed polymerization of these monomers with 1,4-butanediol resulted in short oligomers with a DPn up to 5. Hydrogenation of the double bond resulted in monomers allowing obtaining polyesters of higher molar masses with DPn up to 58 and Mw up to 33,100 g·mol−1. These polyesters presented good thermal resistance up to 350 °C and Tg up to 7 °C. Reduction of the ferulic-based diesters into diols allowed preserving the double bond and synthesizing polyesters with a DPn up to 19 and Mw up to 15,500 g·mol−1 and higher Tg (up to 21 °C). Thus, this study has shown that the monomer hydrogenation strategy proved to be the most promising route to achieve ferulic-based polyester chains of high DPn. This study also demonstrates for the first time that ferulic-based diols allow the synthesis of high Tg polyesters. Therefore, this is an important first step toward the synthesis of competitive biobased aromatic polyesters by enzymatic catalysis.

Synthesis of Bio-Based Photo-Cross-Linkable Polyesters Based on Caffeic Acid through Selective Lipase-Catalyzed Polymerization

“…Indeed, aromatic compounds produce more notably carbonaceous char which induces a more important second degradation step. This phenomenon has already been observed for common polyesters such as PET as well as in polyesters based on natural cinnamic derivatives . The onset of the degradation (measured as T d5% ) increased with the content in CD for ratios between 0 and 20%.…”

“…CA by itself can be considered as a monofunctional monomer in enzymatic esterification, as phenols present a quasi-null reactivity toward CALB, and the only reactive function is the carboxylic acid. However, as depicted in the introduction and observed in our recent study on the CALB-catalyzed polymerization of ferulic acid, the carbonyl vicinal to the double bond of CA shows a limited reactivity toward CALB because of steric and most probably electronic effects. − Moreover, it has been proven that hydrogenation of the double bond of CA unlocks its reactivity toward CALB, allowing the synthesis of various esters …”

“…As mentioned earlier, the low activity of CALB toward the ethyl ester of the CD can be attributed to the electronic delocalization along the double bond and the aromatic ring, which is deleterious to the reactivity of this ester group. [47][48][49]62,63 For a ratio of CD of 10% and below, the peaks are difficult to discern for multiple reasons. First, the ratio of CD in these compounds is particularly low, diminishing the intensity of all peaks attributed to the CD.…”

“…The lipase B from Candida antarctica (CALB) is an enzyme commonly used to catalyze transesterification reactions . CALB has also been employed for the synthesis of various bio-based polyesters, replacing the potentially toxic and pollutant metal-based catalysts. − Recently, CALB was employed by our team for the synthesis of semi-aromatic polyesters based on 2,5-furandicarboxylic acid and polyesters based on ferulic acid, another cinnamic derivative . It was observed that the carbonyl of ferulic acid presented poor reactivity toward CALB.…”

“…42−45 Recently, CALB was employed by our team for the synthesis of semi-aromatic polyesters based on 2,5-furandicarboxylic acid 46 and polyesters based on ferulic acid, another cinnamic derivative. 47 It was observed that the carbonyl of ferulic acid presented poor reactivity toward CALB. Similarly, it has been shown that the carbonyl of CA also presented a poor to null reactivity toward CALB in esterification or transesterification.…”