1. Introduction

The exhaustible nature of the oil reserves and the pollution that oil-based technological polymers cause on the environment because of their low degradability have intensified the interest in natural renewing resources for the chemical synthesis of polymers. Thus, sustained efforts have been extensively devoted to render new polymers based on natural renewing resources with higher degradability [1, 2].

Among the diverse natural sources, carbohydrates constitute highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. They are produced in large amounts by plants and microorganisms every year, and in some cases they even come from agricultural wastes. So, in the last few decades many research groups have been investigating on the preparation of new polymers, analogous to the more significant technical polymers, but based on monomers synthesized from natural and available sugars [3]. However, although several polymers have been synthesized using sugar-derived

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monomers with free hydroxyl groups [4–6], most syntheses of high-molecular-weight linear polymers involve derivatives having the hydroxyl groups appropriately blocked [3, 7].

Synthetic polymers obtained from sugar-based monomers are innocuous for human health. Their hydrophilic nature ensures a greater hydrolytic degradability [3], and reduces their environmental impact compared to classic polymers. Thus, the incorporation of sugar-derived units into traditional step-growth polymers constitutes an excellent approach to prepare novel biodegradable and biocompatible materials for application in the biomedical field and other sectors such as foodstuff packaging.

This chapter describes polyurethanes (PU) having the sugar units incorporated into themain chain. This topic has been partially reviewed before, but during the recent years numerous papers on the subject have been published. Thus, the following sections report on the syntheses, main properties, and applications of this type of sugar-based polymers that have been published mainly during the past decade. Patents have not been included so as to make the reference list more concise.
