In 2013, an entirely novel lignin was reported to occur in the seed coat of vanilla orchid (Vanilla planifolia) and Melocactus cacti. This lignin is a homopolymer of caffeyl alcohol; it is commonly referred to as catechyl lignin, and it has since been discovered to occur also in the nutshell of Aleurites moluccanus (candlenut). In this presentation, we describe our efforts to measure the in situ glass transition in candlenut shells and vanilla bean seed coats. Neither of these sample types provides typical bar-shaped specimens that are amenable to simple bending or tensile analysis. Consequently, we employed compressive-torsion where particulate and/or misshaped specimens may be compressed between parallel-plates while subjected to torsional oscillation. Furthermore, we conducted these analyses with specimens immersed in plasticizers like ethylene glycol and N-methyl-2-pyrrolidone. Measurements using ground or solid candlenut shell are relatively easy- as expected they revealed glass transitions about 30°C higher than for in situ guaiacyl lignins. Measurements of vanilla bean seed coats are much more difficult because of the need to isolate the seed coat from the seed endosperm and embryo. We describe the isolation process and the progression of glass transition measurement as a function of seed coat purity.

Measuring the in situ glass transition of catechyl lignin

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.