Università degli studi di Modena e Reggio Emilia

Atom Transfer Radical Polymerization (ATRP) allows for the production of polymers with precise control over molecular weight, dispersity, topology, composition, and functionality. Functional groups can be introduced into the polymer through post-functionalization of chain ends, or on the alkyl residue of the initiator, or by introducing functionalized (co)monomers, greatly greatly enhancing the targetable applications. In addition, the desired functional group can also be carried by the ATRP initiator. Some researchers have explored initiators with hydrolysis- or heat-sensitive functionalities to impart self-healing properties to the final polymer. However, the commonly used aliphatic halide ester initiators have shown poor thermal stability. To address this issue, we recently developed a novel bifunctional benzamide-containing initiator employed in ARGET ATRP of styrene, demonstrating enhanced thermal stability. Covalent Adaptable Networks (CANs) have emerged as a solution for improving the recyclability of thermoset materials. CANs can reorganize connectivity between chains upon thermal treatment, enabling reprocessing. Our goal is to modify the structure of the benzamide-containing initiator to develop a trifunctional initiator bearing adaptable bonds.

Atom transfer radical polymerization (ATRP) is one of the most powerful techniques to synthesize precisely tailored polymers and macrostructures. Activators regenerated by electron transfer (ARGET) ATRP was developed as a “green” strategy to decrease the load of the metal catalyst. However, ARGET ATRP usually uses not-so-green reducing agents (e.g. Sn2+) or expensive and industrially impractical procedures. For these reasons, we report an ARGET ATRP of styrene with various carbonates as reducing agents, both alone and paired with ascorbic acid (AA), using monofunctional initiators and Cl or Br as exchanging atoms. The solvent mixture is composed of the green combination of EtOAc and EtOH, even in the presence of modest amounts of H2O. Cyclic voltammetry was used to evaluate the effect of H2O on the catalyst, as well as the absence of AA. The system returned high yields and low dispersities with low amounts of catalyst (~60 ppm) and moderate reaction times. Excellent results were obtained only with the Cl-ATRP system. NMR spectroscopy and kinetic analyses proved the livingness of the final polymer chains.