*3.5. X-Ray Diffractometry (XRD)*

In X-ray diffractometry, X-rays were used to irradiate XTPU polymers, and the scattering pattern was noted. Basically, the scattered radiations intensity noted as a function of the scattering angle θ. The X-rays scattering is due to electron density difference. A small angle scattering of X-Rays is used to investigate the microstructures in the range of tens to thousands angstrom ( ´ Å). It is basically a phase segregation in polymers. Meanwhile, X-ray scattering of a wide angle was also applied to calculate the crystallinity of the polymer samples at atomic level. The different reflections of XRD were the result of crystalline behavior of the polymer samples, which was calculated by using Bragg's law.

$$2d\sin\Theta = n\lambda\_\prime\tag{1}$$

where *d* is the basically distance between crystalline planes, θ is the angle of X-ray beam which it makes with the planes, *n* is an integer, and λ is the wavelength. The dispersion range (2θ) of 0–70◦ was used to record the relative intensity [32].

#### **4. Results and Discussion**

### *4.1. FT-IR Analysis*

Figure 2 represents the FT-IR spectra of 1,4-butanediol, Isophrone Diisocyanate, HTPB, Xanthan Gum, NCO-terminated Prepolymer, and XTPU final Polymer. Figure 2a shows the FT-IR spectrum of 1, 4-butanediol and indicated that, due to the OH group, a very strong peak appeared at 3400 cm−1. Due to the CH2 group the peak appeared at 2900 cm<sup>−</sup>1. In Figure 2b, the FT-IR spectrum of IPDI showed the anti-symmetric stretching peak of the CH2 group at 2939.52 cm−<sup>1</sup> and symmetric stretching peak of the CH2 group at 2862.0 cm−<sup>1</sup> was also observed. In the spectrum of IPDI, due to the NCO group, a sharp peak at

2250.71 cm−<sup>1</sup> was also observed. In Figure 2c, the FT-IR spectrum of HTPB where the peak of hydroxyl (OH) appeared at 3736.12 cm−<sup>1</sup> due to stretching vibration is shown. There appeared a peak due to anti-symmetric stretching vibration of the CH2 group, observed at 2945.30 cm−1. Figure 2d shows the most significant bands for the xanthan gum in the range of 4000–500 cm<sup>−</sup>1. It includes an axial deformation of OH at 3300–3450 cm−<sup>1</sup> and an axial deformation of C-H at 2855–2926 cm<sup>−</sup>1, which may due to absorption of symmetrical and asymmetrical stretching of -CH3 or may be due to -CH2-groups. There was also an aldehydic (-CHO) peak at 1710–1730 cm−1. An axial deformation of C-O of enols was observed at 1530–1650 cm−1. An axial deformation of C-O at 1045–1150 cm−<sup>1</sup> was also observed. In Figure 2e, the NCO-terminated prepolymer clearly showed that peaks due to the OH group diminished. The peak due to the NH group appeared at 3325 cm−1. The NCO group's intensity was lower to some extent, which means that isocyanate groups reacted completely. The formation of the prepolymer was confirmed by the appearance of peak of the NH group at 3325 cm−<sup>1</sup> and supported its proposed structure. The antisymmetric peak of the CH2 group was seen at 2945.30 cm<sup>−</sup>1. The stretching peak of –C=O was observed at 1724.36 cm−1. Figure 2f shows, by extending prepolymer with 1,4-BDO, that the FT-IR spectra showed a very strong peak at about 1707 cm<sup>−</sup>1, which was assigned to C=O stretching of urethane. Peaks corresponding to the absorption of NH, C=O, and C=O were observed at 3325 cm−1, 1707 cm−<sup>1</sup> (non-hydrogen bonded), 1643 cm−<sup>1</sup> (hydrogen bonded), and 1225 cm<sup>−</sup>1, respectively, which indicate the new synthesized product being in the urethane group. The observed N-H bending vibrations at 1598 cm<sup>−</sup>1, C-O-C stretching absorption band corresponding to linkage between OH and NCO groups to form urethane bond in the range 1057–1130 cm<sup>−</sup>1, also provide strong evidence for the formation of XTPU.

The FT-IR spectra of XTPU 1 to 6 with varying weight % age of TiO2 and constant weight % age, i.e., 1% xanthan gum, are shown in Figure 3. All the spectra confirm the formation of urethane linkage in the final XTPU polymer samples. In Figure 3, the XTPU-1 spectra showed the formation of urethane linkage NH at the peak 3750.17 cm−1, by the disappearing peak of NCO at 2156 cm−1. It showed the symmetric and asymmetric peak at 2840 cm−<sup>1</sup> of the –CH2 group and 2913.45 cm<sup>−</sup>1, respectively. The peak of –C=O group appeared at 1697.82 cm−1. FT-IR spectra of XTPU-2 is shown in Figure 3. This spectra showed the formation of urethane linkage NH at the peak 3750 cm<sup>−</sup>1. It also displayed the symmetric and a-symmetric peak of the –CH2 group at 2800 cm−<sup>1</sup> and 2912.59 cm<sup>−</sup>1. The –C=O group peak appeared at 1698.02 cm−1. The peak of NCO disappeared at 2160 cm<sup>−</sup>1. The FT-IR spectra of XTPU-3 is shown in Figure 3. This spectrum characterizes the peak of –C=O group at 1698.02 cm<sup>−</sup>1. The peak of N-H forms at 3750.13 cm−1. It also gives the symmetric and a-symmetric peak at 2850 cm−<sup>1</sup> and 2911.38 cm<sup>−</sup>1. Figure 3 shows the FT-IR spectra of XTPU-4. This spectrum characterizes the peak of –C=O group at 1698.02 cm−1. The peak of N-H forms at 3853.72 cm<sup>−</sup>1. It also gives the symmetric and a-symmetric peak at 2843.05 cm−<sup>1</sup> and 2913.05 cm−1. In Figure 3, the FT-IR spectra of XTPU-5 shows the formation of N-H at 3760 cm−1. It shows the formation of –C=O peak at 1698.05 cm−1. It also shows the a-symmetric and symmetric peaks of CH2 group at 2950 cm−<sup>1</sup> and 2840 cm−1. Furthermore, it gives information about the disappearing peak of the NCO group at 2300 cm−1. Figure 3 also shows FT-IR spectra of XTPU-6 and confirmed the formation of N-H at 3753 cm−1. Moreover, it illustrates the formation of –C=O peak at 1697.97 cm−1. It shows the a-symmetric and symmetric peaks of –CH2– group at 2912.56 cm−<sup>1</sup> and 2843 cm<sup>−</sup>1. It also gives information about the disappearing peak of the NCO group at 2300 cm<sup>−</sup>1.

#### *4.2. Evaluation of Antimicrobial Activity*

The gram positive, as well as gram negative, bacteria and fungi were used for antimicrobial activity, so they can be classified as evaluation of antibacterial activity and evaluation of antifungal activity.

**Figure 2.** FT-IR spectra of (**a**) 1,4-Butanediol (BDO), (**b**) Isophrone diisocyanate, (**c**) Hydroxyl Terminated Polybutadiene (HTPB), (**d**) Xanthan Gum (XG), (**e**) NCO-terminated Prepolymer, and (**f**) XTPU final Polymer.

#### 4.2.1. Evaluation of Antibacterial Activity

Biocompatibility is necessary for any material to be in contact with living tissues without resulting any harm to living body. Most polyurethane polymers are biocompatible, and their biocompatibility was evaluated by antibacterial activity. Antibacterial analysis was carried out through the disc diffusion technique, and *Escherichia coli* and *Macrococcus* (a gram negative and gram positive, respectively) strains of bacteria were used for this purpose. On agar plates, the bacterial cultures were spread, and punched samples of polyurethane polymer of 5 mm diameter samples were applied over the plates. This complete setup was carried out at 37 ◦C in an incubator overnight. The results for biocompatibility with *E. coli* and *Macrococcus* are presented in Figure 4. The resistance of polyurethane samples against *E. coli* the gram negative and *Macrococcus* the gram positive bacteria are shown in the inhibition zone. It was found that antibacterial ability or biodegradability of a polymer depends upon the concentration of TiO2, along with content of xanthan gum used. We may

increase the quality by changing the composition. It was observed that samples based on BDO show less antibacterial activity against *E. coli*. Antibacterial activity was influenced by bacterial strain used as given in results as reported in literature [30].

**Figure 3.** FT-IR spectrum of polyurethane samples XTPUs having 0–5% TiO2, respectively.
