News Coatings Technologies
In situ reductive polymerisation from bio-based α-lipoamides
A new in situ reductive polymerisation strategy converts bio-based cyclic disulfides derived from α-lipoic acid directly into functional poly(β-hydroxy thioether)s. The approach eliminates thiol oxidation, ensures equimolar stoichiometry and enables the introduction of diverse functional groups, opening up new routes to structurally tunable, sustainable polymers.
Thiol-based polymerisations enable the efficient construction of structurally diverse macromolecules thanks to the high reactivity of thiol groups. However, free thiols are prone to oxidation, which disrupts the equimolar stoichiometry required for step-growth polymerisation. Conventional disulfide monomers, in turn, offer only limited versatility for the installation of functional groups. To address these challenges, Zhang, Wang and Li developed an in situ reduction strategy that converts cyclic disulfides into dithiols directly during polymerisation.
In this approach, bio-sourced α-lipoic acid was derivatised into N-substituted α-lipoamides as cyclic disulfide-containing monomers. These were reduced in situ using sodium borohydride and subsequently polymerised with diepoxides to yield poly(β-hydroxy thioether)s. The strategy eliminates thiol oxidation, ensures equimolar stoichiometry and enables the introduction of various functional groups via the disulfide backbone.
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Structural diversity and post-polymerisation modification
After optimisation of the polymerisation conditions, a series of structurally diverse polymers was synthesised with a maximum weight-average molecular weight of 25.2 kDa. The structural variability allows for tunable glass transition temperatures and thermal stabilities, providing a versatile platform for material design.
Additional functionalisation was demonstrated through oxidation of the polymers to sulfone-containing analogues with enhanced intermolecular forces. Furthermore, post-polymerisation modification enabled the introduction of acetoacetate and β-enamino ester groups, further enriching the structural and functional diversity of the polymer family. The combination of a bio-based feedstock, mild polymerisation conditions and broad functional versatility highlights the potential of this route for the development of sustainable functional polymers relevant to coatings, adhesives and specialty materials.
Source: Zhang, Z., Wang, L. & Li, L., In situ reductive polymerization of bio-based α-lipoamides toward functional poly(β-hydroxy thioether)s. Polymer Chemistry 17 (27), 2958–2965 (2026).
