Polyurethanes with pendant hydroxy groups: polycondensation of D-mannitol-1,2:5,6-dicarbonate with diamines

Abstract

The bis(ethylene carbonate) monomers 3,4-O-isopropylidene-D-mannitol-1,2:5,6-dicarbonate (2) and D-mannitol-1,2:5,6-dicarbonate (1) were prepared fromD-mannitol in yields of 81 and 74%, respectively. These AA-type monomers were reacted with α, ω-diamines (H2N—(CH2) x –NH2; x = 2–10 and 12) as BB-type monomers in the sense of a polycondensation reaction. The molecular weights of the polyurethanes with pendant hydroxy groups obtained were determined by means of gel permeation chromatography in dimethylacetamide/LiCl and are in the range of 20 × 103 to 87 × 103 with polydispersity indices of ca. 1.6. The polyurethanes show primary and secondary hydroxy groups with a ratio of ca. 15:85. This is a consequence of the different direction of opening of the substituted ethylene carbonate ring which results in structurally isomeric repeating units. The polyurethanes obtained from 2 and diamines with two free hydroxy groups and two protected hydroxy groups in the repeating unit are semicrystalline materials with melting points between 160 and 190°C and glass transition temperatures of 64 to 79°C. The polyurethanes derived from 1 and diamines with four free hydroxy groups in the repeating unit show glass transition temperatures of 50 to 70°C; no melting transition is observed before decomposition starts at ca. 200°C. Polymer analogous esterification reactions were successfully performed with acyl chlorides; the properties of the acylated polyurethanes differ from those of the starting polymers and depend on the acyl chloride used.