Synthesis and Characterisation of Degradable Thermosetting Materials

Abstract

Abstract
Traditional thermosetting materials generally display good durability, yet poor tractability, reworkability, and degradability. This project, however, provides a class of thermoset ring-opening metathesis polymerization (ROMP) materials based on norbornene dicarboximide moieties containing acetal ester group linkage which is degradable when subjected to heat or acidic-catalysis.
In this study, acetal ester linkages were introduced into di-functional monomer by a one-step neat reaction between a functionalised imidonorbornene containing a terminal carboxylic acid group and a 1,4-butanediol divinyl ether. Each monomer and product was characterised by 1H and 13C NMR analysis, while the obtained polymers were analysised by thermogravimetric analysis (TGA), FTIR, dynamic mechanical analysis (DMA) and oven. The results of TGA indicated that the cross-linked materials started losing weight at 150℃ and the extent of the weight loss at 300℃. The IR spectra as it showed the reduction in the intensity of acetal ester band not the complete disappearance. The samples were heated in the oven at 300℃ and 250℃. The results showed the higher the DFM content of the cross-linked materials and the heating temperature and the duration of the heating. 1H NMR analysis of cross-linked sample C11, after the heating treatment in the oven at 300℃ for 2hr, indicates the partial formation of linear polymer upon heating. The cross-linked materials were also subjected to acid-catalysed hydrolysis. The samples after hydrolysis in dilute acid were completely soluble in DCM and were therefore characterised by NMR, which shows all the acetal ester linkages were broken down during hydrolysis and that cross-linked polymers changed into linear polymers. Dynamic mechanical analysis was carried out on the cross-linked polymer, linear polymer, polymer after heating, and polymer after hydrolysis, which support that the crosslinking in the polymer were breakdown during heating, but a new kind of network was formed, and the complete breakdown of actela ester linkages after hydrolysis.