Precise Synthesis of Poly(thioester)s with Diverse Structures by Copolymerization of Cyclic Thioanhydrides and Episulfides Mediated by Organic Ammonium Salts

Abstract

The precise synthesis of poly(thioester)s with diverse structures is still a significant challenge in the polymeric materials field. Herein, we report a novel approach to the synthesis of well‐defined poly(thioester)s by the controlled alternating copolymerization of cyclic thioanhydrides and episulfides induced by simple organic ammonium salts. Both the cation and anion have strong effects on the copolymerization. [PPN]OAc ([PPN]=bis(triphenylphosphine)iminium) with a bulky cation was proven to be efficient in initiating this polymerization, yielding poly(thioester)s with a completely alternating structure, controlled molecular weight, and narrow polydispersity. The poly(thioester) obtained from succinic thioanhydride and propylene sulfide is a typical semicrystalline material, possessing a high refractive index of up to 1.78. Because it uses readily available monomers, this method is expected to open up a new route to poly(thioester)s with diverse structures and properties.

Heterocycle/Heteroallene Ring‐Opening Copolymerization: Selective Catalysis Delivering Alternating Copolymers

“…Lu and co‐workers reported ROCOP of thiiranes with stearic (STA) or glutaric thioanhydride (GTA) using Lewis base/PPNX catalysts (Figure 29). [191] The most effective was PPNOAc, which delivered polymers quickly with molar masses close to theoretical expectations (TOF 787 h −1 , 25 °C, 0.4 mol %, M n =53.6 kg mol −1 , for STA/PS; Figure 30).…”

“…Very recently the sulphur analogues of anhydride/epoxide ROCOP were reported to deliver poly(thioester) structures inaccessible by conventional routes. [191][192][193] Figure 29: ROCOP of thioanhydride with epoxides or thiiranes.…”

“…Angewandte Chemie International Edition increase against conversion. [191] (Right) GPC traces before and after second monomer addition. Copyright © 2020 Wiley.…”

“… PPNOAc‐catalysed STA/PS ROCOP. Left: Controlled molecular weight increase versus conversion [191] . Right: GPC traces before and after second monomer addition.…”

S‐Carboxyanhydrides: Ultrafast and Selective Ring‐Opening Polymerizations Towards Well‐defined Functionalized Polythioesters

“…Lu very recently implemented transthioesterification‐free ROP of geminal‐dimethyl‐substituted thiolactones in the preparation of precision polythioesters, [6] but the the highest monomer conversion observed was 70 %. Another example of polythioester was produced through alternating copolymerization of cyclic thioanhydride and episulfide, [16] which addresses the increasing need for structurally diverse polythioesters. However, this approach faces similar compromise between selectivity and efficient chain propagation, and side reactions cannot be eliminated when running polymerizations to full conversion.…”