Polysaccharides are also a major source of biobased polyols, especially for the synthesis of polyurethanes and polyesters .
Starch is a polysaccharide composed of the covalent sequence of D-glucose units which is found in many plant resources (wheat, potato, corn, cassava, etc.). It can undergo multiple chemical modifications at the level of the primary and secondary alcohol functions of the glycosyl units through reactions of oxidation, esterification, etherification, hydrogenation, etc. For example, its complete acid hydrolysis releases 98 to 99% of D-glucose in the form of two homopolymers, Amylose (linear) and Amylopectin (branched).
Maltitol (4-O-α-glucopyranosyl-D-sorbitol) is a disaccharide polyol which contains 9 hydroxyl -OH groups and which comes from the processing of maltose isolated by vegetable fermentation from starchy cereals, usually corn.
A number of commercial biosourced polyols derived from polysaccharides already exist: Cerenol™ (Dupont de Nemours) is a polyol derived from corn and is used for the synthesis of polyurethane fibres. Neosorb® (based on Sorbitol obtained by hydrogenation of Glucose) and Polysorb® (based on Isosorbide , obtained by dehydration of Sorbitol ) are two polyols marketed by Roquette.
Common sugars from fruits, plants and honey are used after chemical reaction in the polyurethane and epoxy industry. We are talking about Glucose, Fructose, Sucrose etc… which are generally alkoxylated: Glucose propoxylate [159170-54-4]; Sucrose Propoxylate [9049-71-2]
Lignin is a natural polymer , the most abundant on earth after cellulose and which contains a multitude of phenolic and aliphatic hydroxyl groups which can be isolated in the form of biobased polyols after various chemical depolymerization reactions. The three precursors are p-Coumaryl, Sinapyl , and Coniferyl alcohols .