**1. Introduction**

Shape memory polymer (SMP) is a stimuli-responsive polymer which has an ability to fix a temporarily deformed shape and to return from the deformed shape to its original permanent shape while induced by an external stimulus such as thermal, humidity, pH, light, magnetic energy, electric field, and so on [1–5]. SMP possesses two phases viz. frozen phase or net hard phase and reversible or switching soft phase. In case of polyurethane (PU), they may have reversible amorphous or crystalline phase [6, 7]. PU has a unique structural characteristic because of the presence of inherent incompatibility due to microphase in-homogeneity in its chain molecules. It possesses a wide-ranging temperature for shape recovery, high recoverable strain (up to 400%), inherent soft-hard segments, high control on the softening and retraction temperatures with good biophysical properties [8–11]. Further, the properties including switching transition temperature like glass transition temperature (*T*<sup>g</sup> ) or melting temperature (*T*m) can be tuned much easily by proper choice and using suitable composition

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of the components during polymerization process. A large number of versatile components with different structures and properties are available for this polymerization [12]. Thus, PU is versatile with respect to its structure and properties. Further, it is available in various forms, thermoplastic, foam, elastomer, and fiber [13, 14]. Thus, among the different types of SMP, PU is a good candidate as SMP for various advanced applications. In this chapter, we focus on the raw materials required for the synthesis of shape memory polyurethane (SMPU), the principle of shape memory function, the design of protocol of SMPU, the recent research progress of SMPU, and their potential applications.
