Water as a monomer: synthesis of an aliphatic polyethersulfone from divinyl sulfone and water

A Greener and More Scalable Synthesis of Biogenic Polydisulfides from Lipoic Acid

Ring-opening polymerization (ROP) of 1,2-dithiolanes form polydisulfides, an emergent class of dynamic covalent polymers. However, both monomer and polymer syntheses typically require anaerobic and moisture-free conditions, often employing hazardous reagents and solvents that limit scalability. Herein, efficient, scalable syntheses for poly(ethyl lipoate) and ethyl lipoate that incorporate Green Chemistry principles are disclosed. The synthesis of ethyl lipoate from lipoic acid on a 100-gram scale (>80% yield) is optimized lowering the E-factor (2.27) by an order of magnitude compared to conventional methods. Diphenyl phosphate, a nonhazardous commercial organic acid, is used to synthesize ultra-high-molecular-weight poly(ethyl lipoate) on a 50-gram scale from cationic ROP (CROP). The polymerizations proceed under ambient atmosphere in low-hazard and renewable solvents, and a mild depolymerization strategy to regenerate the monomer is developed. Due to their extreme molar mass, the materials possess unique mechanical and physical properties. Life cycle assessment (LCA) conducted on synthetic and recycling processes shows that the polydisulfide has competitive environmental impacts comparable to several commodity polymers, despite the latter having an efficiency advantage due to economies of scale. These discoveries establish an economical and scalable closed-loop polymer platform that can be broadly applied to various polydisulfides sourced from 1,2-dithiolanes such as lipoic acid.

Thermally and Base-Triggered "Debond-on-Demand" Chain-Extended Polyurethane Adhesives

A series of novel chain-extended polyurethanes (CEPUs) featuring degradable sulfonyl ethyl urethane chain-extenders that permit degradation under base-triggered conditions to afford "debond-on-demand" elastomeric adhesives are reported. Exposure of the CEPUs to tetra-butylammonium fluoride (TBAF) triggered the degradation of the sulfonyl ethyl urethane chain-extenders. Lap shear adhesion tests of the CEPUs exposed to TBAF revealed reductions in shear strength of up to 65% for both aluminum and glass substrates, from 2.18 to 0.76 MPa and from 1.13 to 0.52 MPa, respectively. The selective depolymerization of these polymers makes them suitable candidates as debondable binders for inkjet inks and coatings, enabling removal of inks and adhesive residues from substrates before they enter the recycling process, to prevent surface contaminants decreasing the quality of the recycled material.

Water as a Reactant: DABCO-Catalyzed Hydration of Activated Alkynes for the Synthesis of Divinyl Ethers

A practical and efficient addition of water to readily available activated alkynes delivering divinyl ethers is reported. The reaction proceeds with full atom economy in a very straightforward experimental procedure. Additionally, of all the tertiary amines studied to catalyze the reaction, the best and most efficient is clearly DABCO (1,4-diazabicyclo[2.2.2]octane). Finally, the solvent choice is crucial for the efficiency of this process and we have found that the reaction is best performed in wet dichloromethane for propiolic esters and alkynones, and in wet acetonitrile for propiolamides.

Poly(ether)s derived from oxa-Michael polymerization: a comprehensive review

Poly(ether)s represent an important class of polymers and are typically formed by ring-opening polymerization, Williamson ether synthesis, or self-condensation of alcohols. The oxa-Michael reaction presents another method to form poly(ether)s with additional functional groups in the polymer backbone starting from di- or triols and electron deficient olefins such as acrylates, sulfones, or acrylamides. However, research on oxa-Michael polymerization is still limited. Herein, we outline the principles of the oxa-Michael polymerization and focus on the synthesis and preparation of poly(ether-sulfone)s, poly(ether-ester)s, poly(ether)s, and poly(ether-amide)s. Further, challenges as well as future perspectives of the oxa-Michael polymerization are discussed.

Graphical abstract

Tris(2,4,6-trimethoxyphenyl)phosphine – a Lewis base able to compete with phosphazene bases in catalysing oxa-Michael reactions

The performance of the fairly airstable and commercially available “Lewis base beast” TTMPP in catalysing oxa-Michael reactions and the control of its activity by dilution and solvent choice are disclosed.

Polymers from S-vinyl monomers: reactivities and properties

This review summarises the work of several decades on the polymerisation of S-vinyl monomers, ranging from the early reports of suitable polymerisation techniques for these monomers to their recent renaissance in various applications.