Syringaresinol, a triple A bisphenol

A natural molecule arising from lignin, syringaresinol is an interesting alternative to the bisphenols synthesized by the petrochemicals industry: it is not toxic, it can be synthesised at a large scale in the laboratory and materials that contain it display good thermal and mechanical properties.

 

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PLASTIC PACKAGING. © INRA, C. Aouf
Updated on 07/13/2017
Published on 05/30/2017

The polymers industry uses bisphenols such as bisphenol A (BPA) to manufacture numerous plastic materials, as a plasticizer and/or as antioxidant additives. Although inexpensive and efficient in this type of application, these compounds display proven toxicity and will gradually be banned from use in packaging materials used by the agri-food industry. It has therefore become necessary to find compounds that can replace those of a petrochemical origin.

An interesting alternative to fossil energies, plant biomass can be used to obtain valuable biosourced products which are currently the subject of major challenges.

Syringaresinol

Research scientists from INRA and AgroParisTech focused their work on syringaresinol, a natural dimer of sinapyl alcohol which is present in the secondary cell walls of plants.

It displays strong structural similarities with BPA: in other words, two phenolic functions which mean it can be included in polymer chains around a rigid core, endowing the polymers with their plastic qualities.

Syringaresinol does not have the toxicity attached to BPA. It does not exert any oestrogenic activity and it does not suffer from any problems of potential release from the materials in which it is present.

Optimising its synthesis

Although it offers a promising alternative to petrochemical bisphenols, its synthesis nevertheless represents an important challenge.

In the context of studies based on mechanistic considerations resulting from the chemical study of lignin biosynthesis, its optimization has been made possible by the biocatalytic dimerization of biosourced sinapylic alcohol.  

Syringaresinol is now accessible at a laboratory level in batches of more than 15 g, which augurs well for its industrial potential.  

It has been used to synthesise polyolefin polymers through derivatisation and polymerisation using ADMET-type processes (polymerisation by diene metathesis) and also to formulate epoxy resins by using different diamines as hardeners. In all cases, the materials obtained displayed good thermal and mechanical properties.

 

In light of all these results, syringaresinol is clearly a bisphenol of choice to replace BPA in most of its applications.

Find out more

Optimization of the Laccase-Catalyzed Synthesis of (±)-Syringaresinol and Study of its Thermal and Antiradical Activities. Samad A . et al. Chemistry Select, 2016, 1, 5165.

ADMET polymerization of biobased monomers deriving from syringaresinol. Hollande L. et al. RSC Advances 2016, 6, 44297.

Syringaresinol: a renewable and safer alternative to bisphenol-A for epoxy-amine resins. Janvier M. et al. Chem Sus Chem, 2017, 10, 738.