Monitoring the Degree of Carbonyl-Based Open Structure in a Furanic Macromolecular System

Hydrolytic furan ring opening is exploited to open biobased furanic molecules into levulinic-like platform molecules. However, the occurrence of ring opening in furanic macromolecules-considered so far as a side reaction-has never been quantitatively assessed. Poly(furfuryl alcohol) (PFA) was chosen to highlight the concept that furan ring opening can be monitored during polymerization. Both oximation and F-19 NMR quantification methods were employed to address this issue. This investigation shows that a substantial quantity of carbonyl species is formed during the polymerization, thus introducing the concept of degree of open structure (DOS). Polymerization of furfuryl alcohol (FA) in a 50 wt % aqueous solution approximately doubles the fraction of structures that are opened-leading up to 15% of opened furanic entities (i.e., similar to 3.5 mmol of carbonyl per gram of PFA)-compared to FA polymerization conducted without additional water. The DOS was observed to increase continuously throughout the polymerization. Finally, steric hindrance has a role in the accessibility of carbonyls in PFA.

Automated summary

Hydrolytic furan ring opening is utilized to open biobased furanic molecules into levulinic-like platform molecules. The quantitative assessment of ring opening in furanic macromolecules, which has been considered as a side reaction, has not been conducted. This study highlights the concept of monitoring furan ring opening during polymerization using poly(furfuryl alcohol) (PFA). The investigation reveals that a significant amount of carbonyl species is formed during the polymerization process, introducing the concept of degree of open structure (DOS). Polymerizing furfuryl alcohol (FA) in a 50% aqueous solution doubles the fraction of opened structures, reaching up to 15% of opened furanic entities. The accessibility of carbonyls in PFA is influenced by steric hindrance.