Thiol-dibromomaleimide polymerization: A simple strategy for easily degradable and modifiable polythioether synthesis

Abstract

In this work, 2,3-dibromomaleimide (DBM) and multiple dithiol monomers were polymerized into linear poly(maleimide thioether)s through the thiol-dibromomaleimide (thiol-DBM) reaction. Numerous dithiols with varying structural characteristics reacted with DBM to produce a range of polymer structures under optimized conditions. These polymerizations proceeded via a substitution mechanism, allowing the formation of new polymer backbones carrying unsaturated maleimide units along the main chain and free imide N−H functional groups in the side chains. The produced polymers were isolated in high yields, and their molecular weights ranged from 7.3 to 68.2 kDa, thereby opening up a wide range of applications. Following polymerization, an imide-yne click reaction using different propiolates was employed to modify the free N-H groups in the polymers' side chains. The 1,4-diazabicyclo[2.2.2]octane (DABCO) organocatalyst was effectively utilized to carry out this modification process, resulting in notable changes in the structural characteristics of the polymers. All synthesized poly(maleimide thioether)s exhibited a wide range of glass transition temperatures (Tg) depending on the structure of the dithiol used, indicating that the thermal properties of the material can be adjusted according to the desired applications. In addition, it was experimentally demonstrated that the obtained poly(maleimide thioether)s could be easily degraded in the presence of a monothiol. For this purpose, detailed degradation studies were carried out on a model polymer and a cross-linked network using an excess amount of 1-propanethiol in the presence of triethylamine (TEA). Degradation experiments revealed that the formation of chemically inducible degradable structures, enabling the design of recyclable or biodegradable materials. As a result, the method developed in this study draws attention in terms of its practical applicability, time and energy savings, and high structural flexibility. The findings are expected to make significant contributions to future studies on polymer synthesis, functionalization strategies, and controlled degradability.