# Shape-Memory Property Acting as a Switch to Change the Surface Property of the Film
## 3 Results
### Surface Analysis of PNIPAAm-Grafted Polyester Composite  
The 3b-PCL-Cl film was grafted with PNIPAAm via surface-initiated ATRP, using CuCl as the catalyst, Me\({}_{6}\)TREN as the ligand, and ascorbic acid as the reducing agent [30; 31]. When the 3b-PCL-Cl film swelled, the NIPAAm monomer penetrated the film, and the graft polymerized inside the chloro groups of the films. When the ATRP of PNIPAAm was performed using a poor solvent for 3b-PCL-Cl, the NIPAAm monomer did not penetrate the interior of the film, leading to graft polymerization occurring exclusively on the surface. In this study, DMF was employed as a good solvent (G), whereas a mixture of DMF and water served as a poor solvent (DMF:H\({}_{2}\)O = 3:2 \(v/v\)) (P); DMF dissolved free 3b-PCL-Cl and PNIPAAm effectively. Polymerization with water as a poor solvent was also attempted; however, graft polymerization did not proceed. Thus, graft polymerization proceeded efficiently when the substrate was partially dissolved by added DMF. This result is consistent with the findings of [PERSON] et al. in their study of photoinitiated graft polymerization on urethane polymer films [32]. In graft polymerization that is allowed to proceed for 3 h using a good solvent, the film (as represented in \"G3\") exhibited a weight  
Figure 1: 1H-NMR spectra of the synthesized polyester. The spectra were recorded with TMS as standard in CDCl\({}_{3}\): **(a)** acryloyl group added reaction after 3b-PCL-Cl; **(b)** 3b-PCL-Cl.  
Figure 2: SEM-EDS images of polyester film surfaces with EDS peak detection and elemental mapping.  
gain of 129.2% after polymerization (see Figure 3). In contrast, when using a poor solvent, no significant weight gain was observed after polymerization. This negligible weight gain is consistent with the results of previous studies [6], indicating that graft polymerization by ATRP occurs primarily on the surface. The surface analysis of the synthesized PNIPAAm-grafted film was conducted via FTIR, with the results obtained by the ATR method shown in Figure 3. Sample G3 showed, in addition to the carbonyl bond (C=O: 1721 cm\({}^{-1}\)) derived from the 3b-PCL-Cl film, an amide bond (O=C-N: 1535 and 1635 cm\({}^{-1}\)) and the isopropyl group (-CH-(CH\({}_{3}\))\({}_{2}\): 2970 cm\({}^{-1}\)), as part of the primary structure of PNIPAAm, appeared newly compared to the sample before reaction (Figure 3) [33]. The sample grafted with the poor solvent DMF/H\({}_{2}\)O (P) showed only minimal PNIPAAm-derived absorption after 24 h of reaction (as represented in \"P24\" in Figure 3). Therefore, the reaction time was increased to 48 h (P48). For sample P48, the absorption attributed to PNIPAAm appeared more clearly. In the poor-solvent sample, the absorption intensity of the carbonyl bond derived from the 3b-PCL-Cl film, which is the substrate for graft polymerization, was compared with the intensity of each absorption derived from PNIPAAm, revealing a stronger carbonyl bond absorption from the 3b-PCL-Cl film. The stronger absorption intensity of the carbonyl bond suggests that the ratio of PNIPAAm in the sample with a poor solvent was relatively low. The infrared light used in the FTIR measurements slightly penetrates the sample surface [34], indicating that the PNIPAAm-derived absorption is strong in samples where PNIPAAm polymerizes internally, as it does in good solvents, whereas the absorption is weak in samples processed in poor solvents, where graft polymerization occurs only on the surface.