Lauric Diacid-Derived Sulfur-Decorated Functional Polymers Displaying Programmable Thermal and Unconventional Luminescence Properties by Simple Thionation

Abstract

Aliphatic polythioesters (featuring the (C═O)─S linkage) are recognized as useful complements to polyesters that possess intriguing properties, such as high optical features, metal coordination ability and affinity for metal surfaces, self-healing capability, and improved crystallinity amongst others. Still, conventional synthetic approaches often require the use of toxic acyl chlorides. Thus, in this study, two semi-crystalline polythioesters, P1 and P2, were synthesized via a step-growth polycondensation between a long-chain bioderived diacid (1,12-dodecanedioic acid, aka lauric diacid) and two commercially available dithiols, namely, 1,6-hexanedithiol or 2,2'-(ethylenedioxy)diethanethiol). The activation was achieved using 1,1'-carbonyldiimidazole, which eliminates the need for acyl chlorides and leads to the formation of a useful by-product, 1,8-diazabicycloundec-7-ene imidazolium salt. An exemplary polythioester (i.e., P2) underwent a previously less-reported post-polymerization modification (hereafter referred to as modification, for clarity) with Lawesson's reagent to yield polydithioester PP2. This transformation induced a distinct change in material behavior, converting a semi-crystalline structure (melting temperature: 67.7°C) into an amorphous one characterized by a glass transition temperature of -40°C, and significantly reducing its luminescent response. Thus, this study provides a more sustainable synthetic platform for the development of functional polythioesters with tunable thermal and optical properties.

Keywords: aliphatic polythioesters; bio‐based; cluster‐triggered emission; polycondensation; post‐polymerization modification.