Thermal and X-ray powder diffraction studies of aliphatic polyester dendrimers

The syntheses and thermal and X-ray powder diffraction analyses of three sets of aliphatic polyester dendrimers based on 2,2-bis(hydroxymethyl)propionic acid as a repeating unit and 2,2-dimethyl-1,3-propanediol, 1,5-pentanediol, and 1,1,1-tris(hydroxymethyl)ethane as core molecules are reported. These dendritic polyesters were prepared in high yields with the divergent method. The thermal properties of these biodendrimers were evaluated with thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the compounds occurred around 250°C for the hydroxyl-ended dendrimers and around 150°C for the acetonide-protected dendrimers. In addition, the crystallinity of the lower generation dendrimers was evaluated with X-ray powder diffraction. The highest crystallinity and the highest melting points were observed for the first-generation dendritic compounds. The higher generation dendrimers showed weaker melting transitions during the first heating scan. Only the glass-transition temperatures were observed in subsequent heating scans.