Tough while Recyclable Plastics Enabled by Monothiodilactone Monomers

Abstract

The current scale of plastics production and the attendant waste disposal issues represent an underexplored opportunity for chemically recyclable polymers. Typical recyclable polymers are subject to the trade-off between the monomer's polymerizability and the polymer's depolymerizability as well as insufficient performance for practical applications. Herein, we demonstrate that a single atom oxygen-by-sulfur substitution of relatively highly strained dilactone is an effective and robust strategy for converting the "non-recyclable" polyester into a chemically recyclable polymer by lowering the ring strain energy in the monomer (from 16.0 kcal mol −1 in dilactone to 9.1 kcal mol −1 in monothiodilactone). These monothio-modification monomers enable both high/selective polymerizability and recyclability, otherwise conflicting features in a typical monomer, as evidenced by regioselective ring-opening, minimal transthioesterifications, and quantitative recovery of the pristine monomer. Computational and experimental studies demonstrate that an n→π* interaction between the adjacent ester and thioester in the polymer backbone has been implicated in the high selectivity for propagation over transthioesterification. The resulting polymer demonstrates high performance with its mechanical properties being comparable to some commodity polyolefins. Thio-modification is a powerful strategy for enabling conversion of six-membered dilactones into chemically recyclable and tough thermoplastics that exhibit promise as next-generation sustainable polymers.

Lithium catalysed sequence selective ring opening terpolymerisation: a mechanistic study

“…26,27,[35][36][37] Moving down the periodic table, sulfur containing ROCOP monomer combinations likewise exist which mostly remain to be explored in terpolymerisation reactions. 33,[38][39][40][41][42][43][44][45] Phthalic thioanhydride (PTA)/epoxide ROCOP for example yields poly[ester-alt-thioesters] while CS 2 /epoxide ROCOP can yield poly(monothio-alttrithiocarbonate) as reported by Werner and coworkers although the formal product of alternating ROCOP would be a poly(dithiocarbonate). 41,[46][47][48] Combining these ROCOPs, we recently reported a lithium catalysed PTA/CS 2 /epoxide ring-opening terpolymerisation (ROTERP, with propylene oxide (PO) or butylene oxide (BO)) and observed the formation of poly(ester-alt-ester-alttrithiocarbonates) with a few erroneous thioester links (Figure 1).…”

Hybrid Monomer Design Synergizing Property Trade‐offs in Developing Polymers for Circularity and Performance

“…The hybrid lactone/thiolactone monomer can be recycled at 120 °C under vacuum with PhSNa as the catalyst, highlighting the dilactone/dithiolactone hybrid as an effective strategy for converting "non-recyclable" polyester into a chemically recyclable polymer. [121] Notably, in both hybrid lactone/lactam and lactone/thiolactone monomers, the contrast in bond stability (amide, ester, and thioester bonds) gives rise to perfect ROP regioselectivity.…”

Closed-loop recyclable and biodegradable thioester-based covalent adaptable networks

“…11 These polythioesters are readily depolymerizable in the presence of a thiol functionality and a base at 25 1C 11 or in the presence of sodium thiophenolate at 60 1C. 12 The simulated biodegradation studies of poly(b-thioesters) in phosphate buffer at 40 1C have revealed the onset of degradation after 14 days, supporting their swift degradability. 13 However, the number of examples in the literature is notably limited, and the reported systems have undergone stress relaxation under mild temperature conditions, resulting in a narrow service temperature.…”