“Sugar Diols” as Building Blocks of Polycondensates

Abstract

The term sugar diols is used throughout this review as a nickname for diols that are usually derived from saccharides. Typical examples of such “sugar diols” are the bicyclic ethers L-sorbitol (A), L-iditol (z), and L-mannitol (3),—where 1 and 1 are commercial monomers. Furthermore, the acetals 4, 5, 6, and 7 should be mentioned, which are all commercial. These sugar diols have recently attracted increasing interest as monomers for the synthesis of various polycondensates. Several reasons are responsible for this tendency.

1. All sugar diols can be prepared from saccharides (although other synthetic routes may also be available) and thus are monomers based on renewable resources.

2. Most sugar diols (e.g., 1–4 and 7) are nontoxic and their polyesters derived from aliphatic dicarboxylic acids are sensitive to hydrolysis. Such aliphatic polyesters will degrade in the course of several months in contact with warm neutral water and thus are considered to be useful biodegradable materials.

3. All sugar diols are chiral and belong to the least expensive chiral monomers (particularly 1). Potential applications of chiral polymers concern membranes, stationary phases for chromatography, and, above all, cholesteric oligomers and polymers.

4. Isosorbide (L-sorbitol) is a chemically and thermally unusually stable aliphatic diol. As discussed below, polyesters derived from 1 do not racemize or decompose when heated for a few minutes to temperatures up to 350°C.