Furan-functionalised melamine-formaldehyde particles performing Diels-Alder reactions

Functionalised particles are highly requested in materials research, as they can be used as vital components in many advanced applications such as smart materials, functional coatings, drug carrier systems or adsorption materials. In this study, furan-functionalised melamine-formaldehyde (MF) particles were successfully prepared for the first time using an organic sol-gel process. Commercially available 2-Aminomethylfuran (AMF) and 2-Aminomethyl-5-methylfuran (AMMF) were used as modifying agents. In the isolated polymer particles, a melamine (M) to modifying agent ratio of M:AMF mol/mol 2.04:1 and M:AMMF ratio of mol/mol 1.25:1 was used. The obtained particles were isolated in various centrifugation and re-dispersion cycles and analysed using ATR-FT-IR, Raman and solid state C-13 NMR spectroscopy, TGA, SEM and DSC measurements. Upon functionalisation the size of the MF particles increased (MF 1.59 mu m, 27% CV (coefficient of variation); MF-AMF 2.56 mu m, 25% CV; MF-AMMF 2.20 mu m, 35% CV). DSC measurements showed that another type of exothermic residual reactivity besides condensation-based curing takes place with the furan-modified particles that is not related to the liberation of volatile compounds. The newly obtained particles are able to undergo Diels-Alder reactions with maleimide groups. The characteristic IR and Raman absorbance bands of the reaction products after the particles were reacted with 4,4'-Diphenylmethanebismaleimide reagent confirm the formation of a Diels-Alder adduct.