Polycycloacetals via polytransacetalization of diglycerol bisacetonide†
Diglycerol bisacetonide was synthesized and isolated from acetone and diglycerol, which is renewable and available in large scale. DGA was directly used in polytransacetalization with 1,4-cyclohexanedione or 4,4′-bicyclohexanone as diketone monomers. Polycycloacetals were obtained with molecular weights (Mn) of up to 28 kg mol−1, broad dispersities (Đ = 1.5–4.0) and as semi-crystalline polymers with high melting points (Tm = 210–241 °C) and glass transition temperatures (Tg) of 48 °C or 65 °C. Introducing di(trimethylolpropane) (di-TMP) in the polymerization of DGA and 1,4-cyclohexanedione resulted in copolymers as confirmed by 1H-NMR and 13C-NMR spectroscopy. Increasing the di-TMP content from 10 to 50 mol% reduces the crystallinity of the polycycloacetals and increases the Tg, eventually yielding amorphous polymers (Tg = 60–71 °C). For the amorphous polycycloacetals, Young's moduli could be determined by tensile strength testing (E = 1.1–1.4 GPa). The polycycloacetals with renewable carbon contents in the range of 33–100% cover a wide range in material properties and are stable against hydrolysis at pH > 1–3, depending on the polycycloacetal composition.