Functionalised PEGs with photo-dimerisable, anthracenyl end-groups: new UV-curable materials for use in inkjet formulations

The synthesis and characterisation of two novel poly(ethylene glycol)-based materials featuring UV-dimerisable anthracenyl end-groups are described. These low molecular weight polymers exhibited good solubility (ca. 100 g/L) in common organic solvents and were deposited successfully using a drop-on-demand (DOD) inkjet printhead to produce clear prints. UV-vis irradiation of a linear bis-anthracene terminated PEG material resulted in polymerisation via photodimerisation of the anthracenyl end-groups, maintaining polymer solubility in common organic solvents and enabling solution state analysis of the polymerisation process using UV-vis and 1H NMR spectroscopies. In contrast, UV irradiation of a three-armed, tris-anthracenyl-terminated PEG resulted in the formation of an insoluble cross-linked network, which was characterised using rheometry, differential scanning calorimetry and lap shear tensiometry. It was found that the incorporation of solvent-soluble dyes into formulations of the tris-anthracenyl PEG resulted in an increase in UV-cure time when compared to the polymer alone, but did not prevent curing. The results highlight the suitability of this latter material as a UV-curable system for inclusion in inkjet formulations