Monomers with Spirocyclic Acetal Units for Synthesis of Sustainable and Recyclable Polymers with Improved Properties

Multi‐functional molecules with spirocyclic acetal structures are emerging as attractive monomers to prepare high‐performance polymers designed to be depolymerized and recycled under specific physicochemical conditions. Spirocyclic acetal structures are formed by condensation of a suitable aldehyde or ketone with a polyol so that the functionalities necessary for the polymerization are retained. In general, rigid spirocyclic acetal units can efficiently enhance the glass transition temperature ( T g ) of the polymer. This typically increases, for example, the stiffness and use‐temperature of the materials. Furthermore, the inherent sensitivity of spirocyclic acetal units to acidic conditions may be utilized to develop polymers that may be conveniently and selectively cleaved into, for example, monomers or oligomers under controlled acidic conditions. This opens up opportunities for producing new chemically recyclable polymers and plastics. Herein, the recent progress in molecular design and synthesis of functional monomers with spirocyclic acetal structures and their use for the design and preparation of chemically recyclable high‐ T g polymers is highlighted. Monomers and polymers with the potential to be derived from sustainable bio‐based resources are given special attention.