Synthesis of triamine-functionalized rigid crosslinkers for materials science†

In this study, a primary amine-terminated star-shaped polystyrene (PS) was synthesized using an Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) protocol, yielding products with low dispersity (<1.2) and molar masses in the range of 2 to 12 kDa. The influence of the trifunctional initiator's reactivity on the resulting polymer topology was investigated. The bromo-terminated PS was efficiently converted to its azide-terminated counterpart as confirmed by online ATR FT-IR and NMR spectroscopy. The targeted amine-terminated PS was then obtained by a Staudinger reduction of the azide groups using tributylphosphine. To assess the applicability of these novel amine-terminated PSs as well-defined trifunctional crosslinking agents, traditional epoxy thermoset networks and covalent adaptable networks (CANs) were synthesized using diepoxides or diacetoacetates, respectively. The resulting materials exhibited excellent thermal resistance, attributed to the high PS content. Moreover, by making use of the option of tuning the molar mass of such macromolecular crosslinkers, the network's crosslinking density could be tailored, enabling control over swelling degree, glass transition temperature, and, in the case of the obtained vinylogous urethane vitrimers, even reprocessability.