Hydrolytic degradation of ROMP thermosetting materials catalysed by bio-derived acids and enzyme: from network to linear materials

TL;DR

This study demonstrates the first successful enzymatic and acid-catalyzed hydrolysis of ROMP thermosetting materials, converting them into soluble linear polymers while maintaining their thermal properties.

Contribution

It introduces a novel method for degrading ROMP thermosetting networks using bio-derived acids and enzymes, enabling recyclability of these materials.

Findings

Complete solubilization of cross-linked materials after hydrolysis.

Retention of thermal properties in degraded linear polymers.

Effective enzymatic degradation using Thc_Cut1.

Abstract

This paper reports the first example of the degradable ROMP thermosetting materials catalysed by bio-derived acids and cutinase from Thermobifida cellulosilytica (Thc_Cut1). The ROMP thermosetting materials are based on norbornene dicarboximides containing acetal ester groups only in the crosslink moiety. The insoluble cross-linked materials were subjected to acid-catalysed hydrolysis using bio-derived acetic and citric acids as well as enzymatic degradation using Thc_Cut1, resulting in the materials becoming completely soluble in dichloromethane. 1H NMR and rheological analysis performed on materials after acid-catalysed hydrolysis showed characteristics indistinguishable to that of the linear polymer analogues. These analyses confirmed the cleavage of the crosslink moiety upon degradation with the main backbone chains remaining intact. The glass transition temperatures of the polymer materials after acid-catalysed hydrolysis were the same of those observed for the linear polymer analogue. TGA showed that the cross-linked polymers thermally stable to 150 {\deg}C, beyond which showed weight losses due to the thermal cleavage of the acetal ester linkages.