Bio-based non-isocyanate poly(hydroxy urethane)s (PHU) derived from vanillin and CO2

Abstract

As an alternative to the use of hazardous phosgene-based isocyanates for polyurethane preparation, non-isocyanate poly(hydroxy urethanes) (PHU) based on 5-membered cyclic carbonates have been developed. However, to date, most aromatic PHUs are oil-based or based on toxic precursors such as bisphenol-A. In this work, bio-based non-isocyanate poly(hydroxy urethanes) (PHUs) prepared from vanillin are reported for the first time. First, three different vanillin-derived bis-cyclic carbonates were synthesized. Subsequently, each monomer was reacted with two different bis-amines to yield six different PHUs, which were characterized in depth by ¹H and ¹³C NMR spectroscopy, FTIR, SEC and DSC. PHUs based on vanillic acid were found to exhibit thermal properties superior to bisphenol A-based PHUs, with a T_g of around 66 °C. It is envisioned that vanillin-based PHUs could potentially be a safer alternative to harmful bisphenol A-based PHUs and provide a useful strategy for CO₂ revalorization, especially considering that vanillin is an abundant byproduct of Kraft lignin production.