## 1 Introduction  
Among the rapid advancements in smart high polymer materials, the innovation of thermoplastic polyurethanes (TPUs) is a key area [1, 2, 3]. Compared with polyurethane (PU), TPU is a type of high polymer elastomer material. Specifically, it is a type of thermoplastic elastomer (TPE). In recent years, the amount of research related to TPUs has increased substantially. TPU is composed of hard to soft rubbery polymers; it has excellent abrasion resistance, is tough, and is oil and solvent resistant. Additionally, it possesses characteristics such as high elasticity, high tensile strength, and high ductility. Recent research directions in developing TPU are related to the polymer structure. The structure of TPU is a main block copolymer, which is made up of alternating soft and hard chain segments that endow the materials with softness and rigidity, respectively. The polymerization of TPU involves three constituents, namely isocyanate, polyol (i.e., macrodiol), and the diol that acts as the chain extender. The hard chain segment is composed of isocyanate and the chain extender, whereas polyalcohol is the main structure of the soft chain segment. Currently, the polyols commonly used in the TPU market are polyether and polyester, but both types of polyols have application limitations. Only recently did polycarbonate become the new generation of polyols. Because the polycarbonate functional group has a high level of polarity and a strong intermolecular force, strong and tough mechanical performance could be achieved with the use of polycarbonate [4]. It offers good resistance to hydrolytics and oxidation, so polycarbonate could also be an excellent candidate for the biostability polymer [5]. Hence, new discoveries were made from the transition of CO\({}_{2}\) into polycarbonate due to the awareness of greenhouse gas [6]. [PERSON] and co-workers showed that waterborne polyurethane from CO\({}_{2}\)-polyol may achieve better hydrolysis resistance than poly (butyl acrylate) (PBA) [7]. Although the cost associated with polycarbonate is relatively high [8; 9], the number of relevant studies has increased markedly in recent years. Application problems have been solved based on the constituents of the polymers, and this could be extended to the development of new types of high molecular polymers. TPU is a type of block copolymer. The thermal incompatibility between the chain segments is a crucial factor affecting the structure. The miscibility of TPU affects the microphase separation of the structure, including the transition temperature from a glassy state to a rubbery state and the formation of hard and soft zones through modification of soft and hard chain segments. Many researchers have investigated the influence of the constituents and the contents of the hard chain segments on TPU [10; 11; 12]; the constituent structure is also extensively used in material science applications. The rubber-like form of TPU can be used to achieve the shape memory effect. By manipulating the constituents of soft and hard chain segments, TPU with an amorphous reversible phase may cause shape memory [13; 14; 15; 16; 17]. In the past decades, considerable attention has been focused on smart high polymer materials on shape memory [14; 15], which is also applicable in smart textile products [18]. One point worth noting is that the recent research has focused on isocyanate; it is believed to be the main influence in the formation of hard zones [19], soft zones [20], and the soft/hard zone structure ratio [21]. Using a chain extender could enhance the glass-transition temperature (T\({}_{\mathrm{g}}\)) and elastic modulus by changing the hard/soft segment interrelation [22]. Without using a chain extender, polyurethanes reacted by isocyanates and macrodiols were lacking physical properties and microphase separation [23]. However, few studies have actually discussed the influence of the chain extender on the chain segment.