Degradability, thermal stability, and high thermal properties in spiro polycycloacetals partially derived from lignin

A series of partially bio-based spiro polycycloacetals was synthesized using lignin-based feedstocks, vanillin and its derivative syringaldehyde, along with pentaerythritol and commercially available co-monomers including 4,4′-difluorobenzophenone (DFP) and bis(4-fluorophenyl) sulfone (DFS). These spiro polycycloacetals displayed high thermal stabilities (degradation temperatures in the range of 343-370 °C, as quantified by 5% mass loss) and high glass transition temperatures (in the range of 179-243 °C). While DFS-containing polymers were amorphous, DFP-containing polymers were semi-crystalline with high melting temperatures (in the range of 244-262 °C). The hydrolytic degradation behavior of one spiro polycycloacetal, derived from vanillin and DFP, was investigated. Importantly, the spiro polycycloacetal was rapidly degraded to small molecules and oligomeric byproducts under acid-catalyzed conditions. This class of spiro polycycloacetals is therefore an important contributor to the development of more easily degradable polymers which also retain sufficiently high thermal properties and thermal stability. Spiro polycycloacetals were synthesized from vanillin and syringaldehyde, along with high-performance co-monomers, exhibiting high glass transition temperatures and thermal stabilities, and rapid rates of hydrolysis in acidic solutions.