Graft copolymer, manufacturing method thereof, and film

Abstract

This disclosure provides a graft copolymer formed by reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane), wherein the polyimide has a structure as shown in Formula (1), where n is 100 to 200. This disclosure also provides a film comprising the aforementioned graft copolymer.

Description

Technical Field

[0001] This disclosure relates to a graft copolymer, its preparation method, and a thin film. Prior Technology

[0002] In recent years, global warming has become an increasingly serious problem. The continuous increase in emissions of greenhouse gases such as carbon dioxide has led to a year-on-year rise in global temperatures. In light of this, a method to reduce carbon dioxide emissions is needed. Summary of the Invention

[0003] This disclosure provides a graft copolymer formed by reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane), wherein the polyimide has the structure shown in formula (1). Equation (1), n ​​is 100~200.

[0004] In some embodiments, the weight ratio of polyimide to bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 1:9 to 9:1.

[0005] This disclosure provides a thin film comprising the aforementioned graft copolymer.

[0006] In some embodiments, the lattice spacing of the thin film is 6.5 Å to 9 Å.

[0007] In some embodiments, the free volume fraction of the film is 1.5% to 4.5%.

[0008] In some embodiments, the carbon dioxide permeability of the membrane is 30 to 300 bar at 35°C and 4.5 atmospheres.

[0009] In some embodiments, the carbon dioxide / nitrogen selectivity of the membrane is 25 to 37, which is the carbon dioxide permeability divided by the nitrogen permeability, and the carbon dioxide permeability and nitrogen permeability are measured independently at 35°C and 4.5 atm.

[0010] This disclosure provides a method for preparing a graft copolymer, comprising reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to form a graft copolymer, wherein the polyimide has a structure as shown in formula (1). Equation (1), n ​​is 100~200.

[0011] In some embodiments, the weight ratio of polyimide to bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 1:9 to 9:1.

[0012] In some embodiments, the reaction temperature for reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 25°C to 50°C.

[0013] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are intended to provide further explanation of the claimed content of this disclosure. Simple Explanation of the Diagram

[0014] This disclosure can be more fully understood by reading the following detailed description of the embodiments and referring to the accompanying drawings. Figure 1 is a schematic diagram of the structure of the graft copolymer according to various embodiments of the present disclosure. Figure 2 shows films according to various embodiments of the present disclosure. Figure 3 is a flowchart of a method for preparing graft copolymers according to various embodiments of the present disclosure. Figure 4 shows the Fourier transform infrared spectra of the thin films according to various embodiments of this disclosure. Figure 5 shows the X-ray diffraction spectra of the thin films according to various embodiments of this disclosure. Figure 6 is a thermogravimetric analysis (TGA) spectrum of the thin film according to various embodiments of this disclosure. Figure 7 is a differential scanning calorimeter of the thin film according to various embodiments of the present disclosure. Figure 8 is a graph showing the carbon dioxide permeability versus pressure of the membrane according to various embodiments of this disclosure. Figure 9 shows the adsorption isotherms of carbon dioxide and nitrogen in thin films according to various embodiments of this disclosure. Figure 10 is a stability test diagram of the thin film according to the present disclosure, showing its carbon dioxide permeability, nitrogen permeability, and carbon dioxide / nitrogen selectivity. Implementation

[0015] To make the description of this disclosure more detailed and complete, the following provides an illustrative description of the implementation methods and specific embodiments of this disclosure; however, this is not the only form of implementing or using the specific embodiments of this disclosure. The embodiments disclosed below can be combined or substituted with each other where advantageous, and other embodiments can be added to some embodiments without further description or explanation.

[0016] In this document, the range expressed as "from one value to another" is a concise way of representing a range to avoid listing all the values ​​in that range in the specification. Therefore, the description of a specific range of values ​​covers any value within that range as well as the smaller range of values ​​defined by that value, just as if the arbitrary value and the smaller range of values ​​were explicitly stated in the specification.

[0017] Although the methods disclosed herein are illustrated using a series of operations or steps, the order in which these operations or steps are shown should not be construed as a limitation of this disclosure. For example, some operations or steps may be performed in a different order and / or simultaneously with other steps. Furthermore, it is not necessary to perform all illustrated operations, steps, and / or features to achieve the implementation of this disclosure. In addition, each operation or step described herein may comprise several sub-steps or actions.

[0018] This disclosure provides a thin film exhibiting excellent carbon dioxide permeability and carbon dioxide / light gas selectivity. Therefore, it can effectively separate carbon dioxide from other gases (such as nitrogen and oxygen) or effectively capture carbon dioxide to reduce the carbon dioxide content in the atmosphere. This thin film comprises or is made from the graft copolymers described below.

[0019] This disclosure provides a graft copolymer formed by reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) (PDMS). The polyimide has a structure as shown in formula (1). Formula (1), where n is 100 to 200, for example 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, or 200. In some embodiments, the weight ratio of polyimide to bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 1:9 to 9:1 (e.g., 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1), preferably 1:1 to 9:1. Figure 1 is a schematic diagram of the structure of graft copolymer 100 according to various embodiments of the present disclosure. In some embodiments, the structure shown in Formula (1) and the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are bonded by amide bond A and hydrogen bond H, as shown in Figure 1. In some embodiments, the structure shown in Formula (1) and the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are copolymerized by amide bond A to form a graft copolymer, as shown in Figure 1. Specifically, the bond between the carbonyl group and -NC- in the structure shown in Formula (1) is broken to form a carbonyl group and an amide group, wherein the aforementioned carbonyl group is bonded to the terminal amino group of the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to form an amide bond (such as amide bond A). Furthermore, the aforementioned terminal amino group forms a hydrogen bond (such as hydrogen bond H) with the carbonyl group adjacent to the aforementioned terminal amino group in the structure shown in Formula (1), wherein the carbonyl group adjacent to the aforementioned terminal amino group is, for example, a carbonyl group between two benzene rings. The graft copolymers disclosed herein are not limited to the structure shown in Figure 1. Structures having the structure shown in Formula (1) can also be bonded to bis(3-aminopropyl)-terminated poly(dimethylsiloxane) via amide bonds A and hydrogen bonds H, with the bonding method / mechanism described above. Films made from the graft copolymers disclosed herein exhibit a higher free volume fraction and larger lattice spacing compared to polyimide films having the structure shown in Formula (1), thus enhancing carbon dioxide permeability while maintaining good carbon dioxide / nitrogen selectivity.

[0020] Figure 2 shows a thin film 200 according to various embodiments of the present disclosure. As shown in Figure 2, a thin film 200 includes the aforementioned graft copolymer. The lattice spacing (d-spacing) of the thin film 200 is 6.5 Å to 9 Å, for example 6.5, 6.8, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.2, 8.4, 8.6, 8.8, or 9 Å. The bis(3-aminopropyl)-terminated poly(dimethylsiloxane) added during the preparation of the thin film 200 of the present disclosure is bulky, causing the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to affect the packing of the molecular chains of polyimide having the structure shown in Formula (1), thus resulting in a large lattice spacing of the thin film 200. In some embodiments, the free volume fraction (FFV) of the thin film 200 is from 1.5% to 4.5%, for example, 1.5, 1.7, 1.9, 2, 2.1, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, or 4.5%. The thin film 200 of this disclosure has a lattice spacing and FFV within the above range, thus improving the carbon dioxide permeability of the thin film 200.

[0021] As shown in Figure 2, in some embodiments, the density of film 200 is 1.1 g / cm³ to 1.3 g / cm³, for example, 1.1, 1.12, 1.16, 1.20, 1.24, 1.25, 1.26, or 1.3 g / cm³. The film 200 of this disclosure is prepared by incorporating a bulky bis(3-aminopropyl)-terminated poly(dimethylsiloxane), thus resulting in a low density of film 200. In some embodiments, the tensile stress of film 200 is 10 MPa to 30 MPa, for example, 10, 14, 18, 22, 26, 28, or 30 MPa. In some embodiments, the elongation at break of film 200 is 10% to 15%, for example, 10, 11, 12, 13, 14, or 15%. In some embodiments, the Young's modulus of the film 200 is 400 MPa to 1100 MPa, for example, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, or 1100 MPa. The film 200 of this disclosure incorporates a rubbery bis(3-aminopropyl)-terminated poly(dimethylsiloxane) during its preparation, resulting in a high elongation at break and Young's modulus of the film 200.

[0022] As shown in Figure 2, in some embodiments, at 35°C and 4.5 atm, the carbon dioxide permeability of the membrane 200 is 30 barrer to 300 barrer, for example, 30, 35, 40, 45, 50, 55, 58, 60, 64, 68, 72, 76, 80, 82, 86, 92, 96, 100, 112, 124, 136, 148, 160, 172, 184, 196, 208, 220, 232, 244, 256, 260, 261, 265, 270, 275, 280, 285, 290, 295, or 300 barrer. In some embodiments, the nitrogen permeability of the membrane 200 at 35°C and 4.5 atm is 1 Barrer to 10 Barrer, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 Barrer. In some embodiments, the oxygen permeability of the membrane 200 at 35°C and 4.5 atm is 9 Barrer to 41 Barrer, for example, 9, 10, 15, 20, 25, 30, 35, 40, or 41 Barrer. In some embodiments, the carbon dioxide / nitrogen selectivity of the membrane 200 is 25 to 37, for example, 25, 27, 28, 29, 30, 31, 32, 33, 35, or 37, wherein the carbon dioxide / nitrogen selectivity is calculated by dividing the carbon dioxide permeability by the nitrogen permeability. The carbon dioxide and nitrogen permeability are measured independently at 35°C and 4.5 atm, and the measurement results for carbon dioxide and nitrogen permeability are described above. In some embodiments, the oxygen / nitrogen selectivity of the membrane 200 is 4 to 6, for example 4, 4.5, 5, 5.5, or 6, wherein the oxygen / nitrogen selectivity is calculated by dividing the oxygen permeability by the nitrogen permeability. The oxygen and nitrogen permeability are measured independently at 35°C and 4.5 atm. The measurement results of oxygen and nitrogen permeability are described above. The selectivity referred to herein is ideal selectivity.

[0023] As shown in Figure 2, in some embodiments, at 35°C and 4.5 atm, the carbon dioxide adsorption capacity per cubic centimeter of film 200 is 10 to 25 cubic centimeters* (STP) (standard temperature and pressure), for example, 10, 15, 20, or 25 cubic centimeters* (STP). In some embodiments, at 35°C and 4.5 atm, the solubility selectivity of carbon dioxide relative to nitrogen for film 200 is 9 to 12, for example, 9, 10, 11, or 12, wherein the solubility selectivity of carbon dioxide relative to nitrogen is calculated by dividing the solubility coefficient of carbon dioxide by the solubility coefficient of nitrogen. In some embodiments, at 35°C and 4.5 atm, the diffusion selectivity of carbon dioxide relative to nitrogen for the thin film 200 is 2 to 4, for example 2, 2.5, 3, 3.5 or 4, wherein the diffusion selectivity of carbon dioxide relative to nitrogen is the carbon dioxide diffusion coefficient divided by the nitrogen solubility coefficient.

[0024] Figure 3 is a flowchart of a method 300 for preparing a graft copolymer according to various embodiments of the present disclosure. Method 300 includes step 310. As shown in Figure 3, in step 310, polyimide is reacted with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to form a graft copolymer. The polyimide has a structure as shown in Formula (1) (see above). In some embodiments, the weight ratio of polyimide to bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is from 1:9 to 9:1 (e.g., 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1), preferably 1:1 to 9:1. Using the weight ratios within the aforementioned range, films exhibiting excellent carbon dioxide permeability and carbon dioxide / nitrogen selectivity can be prepared. In some embodiments, the reaction temperature for reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 25°C to 50°C, for example, 25, 30, 35, 40, 45, or 50°C. In some embodiments, the reaction time for reacting polyimide with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 1 hour to 12 hours, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hours. The mechanism by which polyimide reacts with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to form a graft copolymer can be referred to the description / implementation of graft copolymer 100 described above.

[0025] Prior to step 310, the polyimide and the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are dissolved separately in an organic solvent. In some embodiments, the organic solvent includes dichloromethane (DCM), N-methyl pyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), or combinations thereof. After forming the graft copolymer, the graft copolymer (in solution) is dried to form a film (film 200 as shown in Figure 2), wherein the drying temperature is from 50°C to 150°C, for example 50, 75, 100, 125, or 150°C.

[0026] The features of this disclosure will be described in more detail below with reference to Examples 1 to 6. Although the following embodiments are described, the materials used, their quantities and ratios, processing details, and processing procedures may be appropriately changed without departing from the scope of this disclosure. Therefore, this disclosure should not be interpreted restrictively from the embodiments described below.

[0027] Experimental Example 1: Preparation of Thin Films

[0028] In Examples A1-A3, poly(dimethylsiloxane) (hereinafter referred to as PDMS-NH2, weight average molecular weight 27000) having the structure shown in Formula (1) (n is 151) and bis(3-aminopropyl)-terminated was dissolved in 90 mL of DCM. The starting materials were then reacted at 25°C for 6 hours to form a graft copolymer (solution state). The graft copolymer was cast onto a glass plate, covered with aluminum foil, and the solvent was removed in a vacuum oven at 60°C to form films B1-B3. The weight ratio of the structure shown in Formula (1) to PDMS-NH2 can be found in Table 1. Examples A1, A2, and A3 correspond to films B1, B2, and B3, respectively.

[0029] Table 1 Example weight ratio A1 A2 A3 The structure shown in equation (1): PDMS-NH2 90:10 75:25 50:50

[0030] In Comparative Example A4, 10 grams of a compound having the structure shown in Formula (1) (n = 151) was dissolved in 90 ml of DCM at 25°C to form a solution. The solution was degassed and cast onto a glass plate. Subsequently, aluminum foil was placed over the solution and the solvent was removed in a vacuum oven at 60°C to form a thin film B4.

[0031] Experimental Example 2: Structural Identification Analysis

[0032] Figure 4 shows the Fourier transform infrared (FTIR) spectra of films B1 to B4 according to various embodiments of this disclosure. FTIR measurement conditions / parameters: 40 scans.

[0033] As shown in Figure 4, curves 410, 420, 430, and 440 are the FTIR spectra of films B4, B1, B2, and B3, respectively. As shown in Figure 4, compared to curve 410, the transmittance of curves 420-440 decreases at wavenumbers of 795 cm⁻¹, 1015 cm⁻¹, and 1259 cm⁻¹. This indicates that films B1-B3 have Si-C (795 cm⁻¹), Si-O-Si (1015 cm⁻¹), and Si-CH₃ (1259 cm⁻¹) bonds, while film B4 does not. This proves that PDMS-NH₂ was added during the preparation of films B1-B3. Furthermore, the transmittance of curves 420-440 also decreases at wavenumbers of 1566 cm⁻¹ and 1682 cm⁻¹. Therefore, it can be seen that the structures of films B1~B3 have CN (1566 cm⁻¹) and C=O (1682 cm⁻¹) bonds. This proves that amide groups are present in films B1~B3.

[0034] Table 2 shows the energy-dispersive X-ray spectroscopy (EDS spectroscopy) data of thin films B1 to B4 according to various embodiments of this disclosure.

[0035] Table 2 film element weight percentage (%) weight percentage σ Atomic percentage (%) B1 C 65.82 0.44 76.09 N 3.06 0.51 3.04 O 14.69 0.27 12.75 Si 16.43 0.16 8.12 B2 C 68.47 0.63 77.68 N 3.56 0.73 3.46 O 14.41 0.36 12.27 Si 13.57 0.19 6.58 B3 C 58.13 0.44 70.65 N 2.50 0.48 2.61 O 15.97 0.28 14.57 Si 23.40 0.23 12.17 B4 C 74.20 0.62 78.79 N 5.69 0.70 5.18 O 20.11 0.34 16.03

[0036] As shown in Table 2, films B1 to B3 all exhibit signals of C, N, O, and Si, while film B4 exhibits signals of C, N, and O. This indicates that film B4 contains C, N, and O elements, and the addition of PDMS-NH2 (as with films B1 to B3) introduces Si elements. Furthermore, the Si content increases with increasing PDMS-NH2 content.

[0037] Experimental Example 3: Physical Property Analysis

[0038] Figure 5 shows the X-ray diffraction (XRD) spectra of thin films B1 to B4 according to various embodiments of this disclosure. XRD measurement conditions / parameters: measurement range from 5° to 80°.

[0039] As shown in Figure 5, curves 510, 520, 530, and 540 are the XRD spectra of thin films B4, B1, B2, and B3, respectively. Using Bragg's law and the results (θ) in Figure 5, the lattice spacing (d-spacing) is obtained as shown in Table 3. Table 3 shows that the addition of PDMS-NH2 contributes to the increase of the lattice spacing.

[0040] Table 3 film B1 B2 B3 B4 d-spacing (Å) 7.43 7.46 7.49 6.11

[0041] Figure 6 shows the thermogravimetric analysis (TGA) spectra of thin films B1 to B4 according to various embodiments of this disclosure. Figure 7 shows the differential scanning calorimetry (DSC) spectra of thin films B1 to B4 according to various embodiments of this disclosure. The TGA measurement conditions / parameters were: heating rate of 10°C / min; the DSC measurement conditions / parameters were: heating rate of 10°C / min.

[0042] As shown in Figure 6, curves 610, 620, 630, and 640 are the TGA spectra of films B4, B1, B2, and B3, respectively (corresponding to the vertical axis TG, indicating the weight loss of the film as the temperature increases). After differentiating curves 610, 620, 630, and 640 once, curves 650, 660, 670, and 680 are obtained, respectively (corresponding to the vertical axis DTG). As shown in Figure 7, curves 710, 720, 730, and 740 are the DSC spectra of films B4, B1, B2, and B3, respectively. Figures 6 and 7 show that the addition / increase of PDMS-NH2 does not affect the glass transition temperature (Tg) of the structure shown in equation (1). Therefore, despite the increase in the PDMS-NH2 content, the thermal stability of film B4 can still be maintained.

[0043] Table 4 presents the results of the free volume fraction (FFV), density, and mechanical properties (tensile stress, elongation at break, and Young's modulus) of films B1 to B4 according to various embodiments of this disclosure. FFV was measured using positron annihilation lifetime spectroscopy (PALS). PALS measurement conditions / parameters: counting rate of 200 counts / second to 500 counts / second.

[0044] Table 4 film B1 B2 B3 B4 FFV (%) 2.122 2.174 3.729 0.520 Density (g / cm3) 1.25± 0.009 1.20± 0.029 1.16± 0.003 1.43± 0.011 Tensile stress (MPa) 27.36± 0.03 26.27± 1.51 14.32± 3.15 50.01± 2.14 Elongation at break (%) 10.34± 0.13 11.95± 1.10 12.53± 0.76 8.52± 1.16 Young's modulus (MPa) 1082.07 ±2.05 1012.46 ±1.07 457.69 ± 4.63 1490.06 ±2.24

[0045] The FFV results show that the FFV increases with increasing PDMS-NH2 content. This is because the bulky PDMS-NH2 disrupts the stacking of molecular chains, leading to an increase in FFV. Density decreases with increasing PDMS-NH2 content. This is because the lattice spacing increases with increasing PDMS-NH2 content (see Table 3). Furthermore, since PDMS-NH2 is rubbery, the elongation at break of the film increases and the Young's modulus decreases with increasing PDMS-NH2 content.

[0046] Experimental Example 4: Analysis of Gas Permeability and Gas Selectivity

[0047] Table 5 shows the results of gas (N2, O2, CO2) permeability and ideal selectivity (CO2 / N2, O2 / N2) of films B1 to B4 according to various embodiments of this disclosure. The gas permeability experiments were conducted at 35°C and 4.5 atm. The results of the ideal selectivity can be obtained by dividing the results of different gas permeability values.

[0048] Table 5 film B1 B2 B3 B4 Barrer (permeability) N2 1.77 ± 0.03 2.64 ± 0.11 9.58 ± 0.08 0.36 ± 0.01 O2 9.70 ± 0.15 14.72 ± 0.92 40.09 ± 0.36 2.43 ± 0.02 CO2 58.22 ± 2.49 82.60 ± 1.58 260.51 ± 1.26 12.01 ± 0.21 Ideal selectivity CO2 / N2 32.88 ± 0.85 31.32 ± 0.71 27.18 ±0.11 33.37 ± 0.48 O2 / N2 6.75 ± 0.14 5.48 ± 0.01 5.57 ± 0.12 4.18 ± 0.01

[0049] As shown in Table 5, the permeability of the film to N2, O2, and CO2 increases with the increase of PDMS-NH2 content, with the increase to CO2 permeability being particularly significant. The increase in N2, O2, and CO2 permeability is due to the increase in FFV and the increase in lattice spacing. Furthermore, despite the addition of PDMS-NH2, the stiffness of the chains with the structure shown in Equation (1) is still maintained. Therefore, the increase in PDMS-NH2 content does not significantly affect the ideal selectivity of CO2 / N2 and O2 / N2 of the film.

[0050] Figure 8 is a pressure graph showing the carbon dioxide permeability of films B1 to B4 according to various embodiments of this disclosure. The carbon dioxide permeability was measured at 35°C. As shown in Figure 8, data lines 810, 820, 830, and 840 sequentially represent the carbon dioxide permeability results of films B4, B1, B2, and B3 at different pressures. Figure 8 shows that the addition of PDMS-NH2 shifts the plasticization pressure to a higher pressure. This is attributed to the reduction in carbon dioxide adsorption (data results can be found in Figure 9) and the formation of hydrogen bonds in the film structure.

[0051] Experimental Example 5: Analysis of Adsorption Isotherms

[0052] Figure 9 shows the adsorption isotherms of carbon dioxide and nitrogen for films B1 to B4 according to various embodiments of this disclosure. The carbon dioxide and nitrogen adsorption isotherm experiments were conducted at 35°C. As shown in Figure 9, data lines 910, 920, 930, and 940 sequentially represent the carbon dioxide adsorption results of films B4, B1, B2, and B3 under different pressures. Data lines 950, 960, 970, and 980 sequentially represent the nitrogen adsorption results of films B4, B1, B2, and B3 under different pressures. As shown in Figure 9, the amount of carbon dioxide adsorbed decreases with increasing PDMS-NH2 content. The lower carbon dioxide adsorption explains why the plasticization onset pressure shifts to a higher value. Furthermore, the modified films (films B1 to B3) exhibit reduced carbon dioxide adsorption, thus making it difficult to exert a plasticizing effect at low pressures.

[0053] Table 6 shows the dual sorption parameters of films B1 to B4 according to various embodiments of this disclosure. Table 6 records the Henry's law constant, Langmuir saturation constant, and Langmuir affinity constant. Referring to Table 6, since the added PDMS-NH2 does not possess Langmuir sites, CH' decreases with increasing PDMS-NH2 content.

[0054] Table 6 film B1 B2 B3 B4 Henry's Law constant KD (cm3*(STP)*cm-3) 3.86 3.01 2.73 5.24 Langmuir saturation constant CH' (cm3*(STP)*cm-3) 7.78 4.91 3.39 13.45 Langmuir affinity constant b (atm-1) 3.33 2.71 4.29 2.93

[0055] Tables 7 and 8 show the gas (CO2, N2) solubility coefficients and gas (CO2, N2) diffusion coefficients of films B1 to B4 according to various embodiments of this disclosure. Table 9 shows the ideal selectivity of gas solubility and the ideal selectivity of gas diffusion for films B1 to B4 according to various embodiments of this disclosure. Both solubility and diffusion coefficients are results obtained at 35°C and 4.5 atm. The ideal selectivity of gas solubility and the ideal selectivity of gas diffusion were calculated using the solubility coefficients and diffusion coefficients of different gases, respectively. Referring to Tables 7 and 8, as the content of PDMS-NH2 increases, the solubility coefficient decreases and the diffusion coefficient increases. Furthermore, due to the differences in kinetic diameter, condensability, and affinity of CO2 and N2 with the film, at the same supply pressure, the solubility coefficient and diffusion coefficient of CO2 are higher than those of N2. Furthermore, the gas separation performance of membrane B4 is dominated by diffusion selectivity, but the addition of PDMS-NH2 changes the mechanism to be dominated by solubility selectivity (membranes B1 to B3).

[0056] Table 7 film Solubility coefficient S (cm3*(STP)*cm-3*atm-1) solubility Selective N2 CO2 CO2 / N2() B1 0.56 5.24 9.36 B2 0.32 3.84 12.00 B3 0.31 3.33 10.74 B4 1.62 7.57 4.67

[0057] Table 8 film Diffusion coefficient D (10⁻⁸ cm² s⁻¹) diffusion Selective N2 CO2 CO2 / N2() B1 2.39 8.42 3.52 B2 6.25 16.30 2.61 B3 23.41 59.27 2.53 B4 0.17 1.20 7.09

[0058] Table 9 film Ideal selectivity B1 9.36 3.52 32.95 B2 12.00 2.61 31.32 B3 10.74 2.53 27.17 B4 4.67 7.09 33.11

[0059] Experiment Example 6: Stability Test

[0060] Figure 10 shows the stability test results of the carbon dioxide permeability, nitrogen permeability, and carbon dioxide / nitrogen selectivity of the membrane B2 according to this disclosure. All stability tests were conducted at 35°C and 6 atm, using a 50 / 50 mole (mol.)% carbon dioxide / nitrogen mixture. Referring to Figure 10, data point 1010 (indicated by ■, corresponding to permeability on the vertical axis), data point 1020 (indicated by ▲, corresponding to CO2 / N2 selectivity on the vertical axis), and data point 1030 (indicated by □, corresponding to permeability on the vertical axis) represent the carbon dioxide permeability, carbon dioxide / nitrogen selectivity, and nitrogen permeability results of membrane B2, respectively. As shown in Figure 10, membrane B2 maintains excellent carbon dioxide permeability and carbon dioxide / nitrogen selectivity even under long-term testing, and also exhibits stable nitrogen permeability test results.

[0061] The thin film disclosed herein is prepared using a simple, low-cost, and easy-to-operate method, comprising the reaction of polyimide having the structure shown in Formula (1) with bis(3-aminopropyl)-terminated poly(dimethylsiloxane), wherein the polyimide having the structure shown in Formula (1) and the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are bonded by amide bonds and hydrogen bonds. Compared to polyimide thin films having the structure shown in Formula (1), the thin film disclosed herein has a higher free volume fraction and a larger lattice spacing, thereby improving the carbon dioxide permeability of the thin film while maintaining the excellent carbon dioxide / nitrogen selectivity of polyimide thin films having the structure shown in Formula (1).

[0062] Although this disclosure has been described in considerable detail with reference to certain embodiments, other embodiments may also be possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments included herein.

[0063] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of this disclosure without departing from its scope or spirit. In view of the foregoing, this disclosure is intended to cover modifications and variations of this disclosure that fall within the scope of the appended patent applications.

[0064] 100: Graft copolymer 200: Film 300: Method 310: Steps 410, 420, 430, 440, 510, 520, 530, 540, 610, 620, 630, 640, 650, 660, 670, 680, 710, 720, 730, 740: Curve 810, 820, 830, 840, 910, 920, 930, 940, 950, 960, 970, 980: Data cable 1010, 1020, 1030: Data points A: Acetamide bond H: Hydrogen bonding force

[0065] Domestic storage information (please note in order of storage institution, date, and number) none Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A graft copolymer formed by reacting a polyimide with a bis(3-aminopropyl)-terminated poly(dimethylsiloxane), wherein the polyimide has a structure as shown in Formula (1), where n is 100 to 200.

2. The graft copolymer as claimed in claim 1, wherein the polyimide and the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) are in a weight ratio of 1:9 to 9:

1.

3. A thin film, comprising: The graft copolymer as described in claim 1 or 2.

4. The thin film as claimed in claim 3, wherein a lattice spacing of the thin film is 6.5 Å to 9 Å.

5. The thin film as claimed in claim 3, wherein a free volume fraction of the thin film is 1.5% to 4.5%.

6. The membrane as claimed in claim 3, wherein the carbon dioxide permeability of the membrane is 30 to 300 bar at 35°C and 4.5 atm.

7. The film as claimed in claim 3, wherein the film has a carbon dioxide / nitrogen selectivity of 25 to 37, the carbon dioxide / nitrogen selectivity being the ratio of a carbon dioxide permeability to a nitrogen permeability, the carbon dioxide permeability and the nitrogen permeability being measured independently at 35°C and 4.5 atm.

8. A method for preparing graft copolymers, comprising: Polyimide is reacted with bis(3-aminopropyl)-terminated poly(dimethylsiloxane) to form a graft copolymer, wherein the polyimide has a structure as shown in Formula (1), where n is 100 to 200.

9. The method as described in claim 8, wherein the weight ratio of the polyimide to the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 1:9 to 9:

1.

10. The method as claimed in claim 8 or 9, wherein a reaction temperature for reacting the polyimide with the bis(3-aminopropyl)-terminated poly(dimethylsiloxane) is 25°C to 50°C.

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