High-performance special polyether material with directionally modified terminal group and preparation method thereof

Abstract

The invention belongs to the technical field of high-molecular polymer synthesis, and particularly relates to a high-performance special polyether material with a directionally-modified terminal group and a preparation method of the high-performance special polyether material. The preparation method comprises the following steps: sequentially grafting 4-bromobenzoate to methylene of crown ether and aminating bromine atoms to prepare an intermediate, and reacting amino of the intermediate with isocyanate-terminated polyether to form a urea bond, so that a terminal group of a polyether structure is chemically modified, and a special polyether material is endowed with separation performance; when the composite membrane is applied to a nanofiltration separation membrane, the water permeability can be remarkably improved, and magnesium ions and lithium ions can be efficiently and selectively separated. According to the invention, a terminal group of a polyether structure is chemically modified through a specific reaction, and the application potential of a special polyether material in emerging fields such as high-performance separation membranes is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of high molecular polymer synthesis, and particularly relates to a high-performance special polyether material with end group directionally modified and a preparation method thereof. Background Art

[0002] Polyether materials are linear polymers produced through the polyaddition reaction of initiators with ethylene oxide (EO), propylene oxide (PO), butylene oxide (BO), and other catalytic agents. These materials, either alone or in the form of modified compounds, are widely used in industries such as petrochemicals, mining, daily chemicals, agrochemicals, industrial cleaning, and lubricants. These materials hold a significant position in the industrial sector due to their highly designable molecular structures and wide range of performance adjustments.

[0003] As the application areas of polyether material products continue to expand and market demand continues to grow, the production requirements of the polyether industry are increasing. In particular, in high-end application areas such as high-performance separation membranes and new energy materials, traditional polyether materials have been unable to meet the growing technical demands. This is mainly manifested in the following aspects: First, the terminal groups of conventional polyether materials are mostly hydroxyl groups or simple end-capping groups, lacking functional modification, which limits their application in fields such as selective separation; second, existing polyether modification technologies are mostly focused on adjusting the main chain structure, and there is little research on the precise control of the terminal groups; third, in membrane separation applications, traditional polyether materials often find it difficult to meet the dual requirements of high permeability and high selectivity.

[0004] Therefore, there is an urgent need to develop efficient, environmentally friendly, domestically produced high-end specialty polyether preparation technologies, and to continuously promote the specialized, diversified, and personalized applications of specialty polyether materials, thereby promoting the polyether industry's development towards environmentally friendly, low-carbon, and high-value-added development. In particular, there is a need to develop novel modification methods that can precisely modify polyether end groups and introduce specific functional groups. Such methods should maintain the inherent excellent processing properties of polyether materials while imparting new functional properties to meet the needs of complex separation systems. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the primary purpose of the present invention is to provide a high-performance special polyether material with directed modification of terminal groups, which can be applied to nanofiltration separation membranes to significantly improve water permeability and have excellent magnesium-lithium selective separation performance.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned high-performance special polyether material with directed modification of the terminal groups, by chemically modifying the terminal groups of the polyether structure through specific reactions, thereby expanding the application potential of special polyether materials in emerging fields such as high-performance separation membranes.

[0007] The purpose of the present invention is achieved through the following technical solutions: A high-performance specialty polyether material with end group-directed modification, the structural formula of the high-performance specialty polyether material with end group-directed modification is: .

[0008] Further, the following steps are included: (1) Under an inert gas atmosphere, a dichloromethane solution of polyethylene glycol is added to a dichloromethane solution of hexamethylene diisocyanate, and then dibutyltin dilaurate is added, and the mixture is reacted under stirring. After the reaction is completed, the mixture is purified to obtain intermediate 1; The structural formula of the intermediate 1 is: ; (2) Under an inert gas atmosphere, a decane solution of tert-butyl hydroperoxide, tetrabutylammonium iodide, 4-bromobenzaldehyde and 12-crown ether-4 are mixed and reacted under heating conditions; after the reaction is completed, intermediate 2 is obtained through post-treatment; The structural formula of the intermediate 2 is: ; (3) Mix cuprous iodide, intermediate 2, sodium phosphate, ammonia water and PEG400 and react under heating conditions; after the reaction is completed, post-process to obtain intermediate 3; The structure of the intermediate 3 is: ; (4) adding the intermediate 1 and the intermediate 3 into dichloromethane and stirring the mixture under an inert gas atmosphere; after the reaction is completed, removing the solvent to obtain the high-performance special polyether material with the terminal group directionally modified.

[0009] Furthermore, in step (1), the mass ratio of polyethylene glycol, hexamethylene diisocyanate, and dibutyltin dilaurate is (1-2): (1.68-2.52): (0.02-0.04); and the reaction time is 12-15 h.

[0010] Furthermore, the usage ratio of tert-butyl hydroperoxide, tetrabutylammonium iodide, 4-bromobenzaldehyde, and 12-crown ether-4 in step (2) is (4.02-4.10) mmol: (0.1-0.15) mmol: (0.5-0.6) mmol: 2 mL.

[0011] Furthermore, the heating temperature in step (2) is 100-120° C., and the reaction time is 16-20 h.

[0012] Furthermore, in step (3), the usage ratio of cuprous iodide, intermediate 2, sodium phosphate, ammonia water and PEG400 is (0.05-0.06) mmol: 0.5 mmol: (0.5-0.6) mmol: 1 mL: (2-3) mL; and the concentration of ammonia water is 25-28 wt%.

[0013] Furthermore, the heating temperature in step (3) is 100-120° C., and the reaction time is 20-24 h.

[0014] Furthermore, in step (4), the mass ratio of intermediate 1 to intermediate 3 is 1:(3.11-6.22); and the stirring reaction time is 12-15 h.

[0015] Furthermore, the molecular weight of the polyethylene glycol in step (1) is 1000-2000 g / mol.

[0016] The present invention has the following effects compared to the prior art: 1. The present invention obtains an intermediate by sequentially grafting 4-bromobenzoate onto the crown ether methylene group and then aminating the bromine atom. The amino group of the intermediate is then reacted with an isocyanate-terminated polyether to form a urea bond, thereby chemically modifying the terminal groups of the polyether structure and imparting special polyether material separation properties. Application of the polyether material to nanofiltration separation membranes can significantly improve water permeability and exhibit excellent magnesium-lithium selective separation performance. The crown ether ring in the structure can selectively recognize Li + , giving the special polyether material excellent magnesium-lithium separation effect, and the ether bond (-O-) in the polyether chain can form a hydrogen bond network with water molecules, giving the membrane surface super hydrophilicity, reducing the interfacial energy barrier of water transmission, and significantly improving the water permeability; moreover, the formed urea bond cross-linking network can not only enhance the structural stability of the membrane, but also 2+ Produce electrostatic repulsion, further strengthening the Mg 2+ The retention rate.

[0017] 2. The present invention chemically modifies the terminal groups of the polyether structure through a specific reaction, expanding the application potential of special polyether materials in emerging fields such as high-performance separation membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The invention relates to a preparation process of a high-performance special polyether material with end group directionally modified; Figure 2 FT-IR images of the intermediate 1 and the high-performance specialty polyether material with directed modification of the terminal groups of the present invention; Figure 3 This is the result of the magnesium-lithium separation factor in the test example of the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only intended to illustrate the present invention and should not be construed as limiting the present invention. Specific conditions not specified in the examples are to be followed according to conventional conditions or the conditions recommended by the manufacturer. All reagents or instruments used, unless otherwise specified, are conventional products obtained from commercial channels.

[0020] Example 1 Example 1 provides a high-performance specialty polyether material with end group-directed modification, the structural formula of which is as follows: .

[0021] Example 1 also provides a method for preparing the high-performance special polyether material with the above-mentioned terminal group-directed modification. The reaction process is as follows: Figure 1 The specific steps are as follows: (1) Polyethylene glycol (Mw = 1000 g / mol, 1.0 g) was placed in a 50 mL round-bottom flask, connected to a vacuum pump, and evacuated at 40 ° C (≤ 0.1 mmHg) for 6 h; after turning off the vacuum, nitrogen protection was applied and the mixture was quickly dissolved in 15 mL of dichloromethane (previously ultra-dried with molecular sieves, water ≤ 30 ppm) to obtain a polyethylene glycol solution; then, under nitrogen protection and stirring, the above polyethylene glycol solution was slowly added dropwise to 50 mL of anhydrous DCM solution of hexamethylene diisocyanate (HDI, 1.68 g), and after the addition was completed, 1 drop of dibutyltin dilaurate (DBTDL, 20 mg) was added and stirred at room temperature for 14 h; after the reaction was completed, the solvent was concentrated by rotary evaporation, and then 300 mL of hexane was added to precipitate the product, the upper solution was separated, and the remaining viscous liquid was vacuum dried to obtain intermediate 1; the FT-IR spectrum of intermediate 1 is shown in Figure 2. Figure 2 As shown in curve a, at 2255 cm -1 The characteristic peak of isocyanate group appears at 3340 cm -1 The NH stretching vibration peak of the amide group appeared at , indicating the successful preparation of intermediate 1.

[0022] (2) Under nitrogen, tetrabutylammonium iodide (Bu4NI) (0.12 mmol), 4-bromobenzaldehyde (0.55 mmol), tert-butyl hydroperoxide (TBHP) in decane (0.74 mL, 5.5 M, 4.07 mmol), and 12-crown ether (2 mL) were added to a Schlenk tube and stirred at 110°C for 18 h. The volatiles were removed by rotary evaporation, and the residue was purified by silica gel column chromatography (petroleum ether / EtOAc = 20:1, v / v) to obtain intermediate 2. 1 H NMR (C15 H 19 BrO6, 400 MHz, d6-DMSO) δ 7.74-7.70(m, 4H, Ar-H), 6.67(t, 1H, CH), 4.10-4.07 (m, 1H, CH2), 3.85-3.82 (m, 1H,CH2), 3.60-3.40(m, 12H, CH2), ; HRMS (ESI + ): [M+H] + Calculated to be 375.04, found to be 375.04.

[0023] (3) Cuprous iodide (CuI) (0.055 mmol), intermediate 2 (0.5 mmol), sodium phosphate Na3PO4 (0.55 mmol), 26% ammonia water (1 mL) and PEG-400 (2 mL) were added to a sealed tube and stirred at 110°C for 22 h. The reaction solution was cooled to room temperature and extracted with ether three times. The combined organic phases were dried over anhydrous Na2SO4 and the solvent was removed under reduced pressure. The remaining residue was purified by silica gel column chromatography to obtain the desired intermediate 3. 1 H NMR (C 15 H 21 NO6, 400 MHz, d6-DMSO) δ 7.65(d, 2H, Ar-H), 6.67(t, 1H, CH), 6.47(d, 2H, Ar-H), 5.54(s, 2H, NH2), 4.10-4.07 (m, 1H, CH2), 3.85-3.82 (m, 1H, CH2), 3.60-3.40(m, 12H, CH2); HRMS (ESI + ): [M+H] + The calculation is 312.14, and the result is 312.14.

[0024] (4) Intermediate 1 (1 g) and intermediate 3 (4.66 g) were added to anhydrous DCM (90 mL) and stirred at room temperature for 13 h under a nitrogen atmosphere. The solvent was removed by a rotary evaporator to obtain a high-performance specialty polyether material with end group-directed modification. The FT-IR spectrum of the high-performance specialty polyether material with end group-directed modification is shown in FIG. Figure 2 As shown in curve b, compared with curve a, the 2255 cm -1 The characteristic peak of the isocyanate group disappears, indicating the successful preparation of high-performance special polyether materials with directional modification of the terminal groups.

[0025] Example 2 Example 2 provides a high-performance special polyether material with end group directionally modified, and its structural formula is the same as that of Example 1.

[0026] Example 2 also provides a method for preparing the high-performance special polyether material with the above-mentioned terminal group-directed modification. The reaction process is as follows: Figure 1 The specific steps are as follows: (1) Polyethylene glycol (Mw = 1500 g / mol, 1.5 g) was placed in a 50 mL round-bottom flask, connected to a vacuum pump, and evacuated at 40 ° C (≤ 0.1 mmHg) for 6 h; after turning off the vacuum, nitrogen protection was applied and the mixture was quickly dissolved in 15 mL of dichloromethane (previously ultra-dried with molecular sieves, water ≤ 30 ppm) to obtain a polyethylene glycol solution; then, under nitrogen protection and stirring, the above polyethylene glycol solution was slowly added dropwise to 50 mL of HDI (2.52 g) in anhydrous DCM solution. After the addition was complete, 1-2 drops of DBTDL (40 mg) were added and stirred at room temperature for 15 h; after the reaction was completed, the solvent was concentrated by rotary evaporation, and then 300 mL of hexane was added to precipitate the product. The upper solution was separated and the remaining viscous liquid was vacuum dried to obtain intermediate 1; the FT-IR of intermediate 1 was consistent with that of Example 1.

[0027] (2) Under nitrogen protection, Bu4NI (0.1 mmol), 4-bromobenzaldehyde (0.5 mmol), TBHP in decane (0.73 mL, 5.5 M, 4.02 mmol) and 12-crown-4-ol (2 mL) were added to a Schlenk tube and stirred at 100°C for 20 h. The volatiles were removed by rotary evaporation, and the residue was purified by silica gel column chromatography (petroleum ether / EtOAc = 20:1, v / v) to obtain intermediate 2; intermediate 2 1 H NMR and HRMS were consistent with Example 1.

[0028] (3) CuI (0.05 mmol), intermediate 2 (0.5 mmol), Na3PO4 (0.5 mmol), 25% ammonia water (1 mL) and PEG-400 (2 mL) were added to a sealed tube and stirred at 100°C for 24 h; the reaction solution was cooled to room temperature and extracted with ether three times, and the combined organic phase was dried over anhydrous Na2SO4 and the solvent was removed under reduced pressure. The remaining residue was purified by silica gel column chromatography to obtain the desired intermediate 3; intermediate 3 1 H NMR and HRMS were consistent with Example 1.

[0029] (4) Intermediate 1 (1 g) and intermediate 3 (3.11 g) were added to anhydrous DCM (80 mL) and stirred at room temperature under a nitrogen atmosphere for 12 h. The solvent was removed using a rotary evaporator to obtain a high-performance specialty polyether material with end group-directed modification. The FT-IR of the high-performance specialty polyether material with end group-directed modification was consistent with that in Example 1.

[0030] Example 3 Example 3 provides a high-performance special polyether material with end group directionally modified, and its structural formula is the same as that of Example 1.

[0031] Example 3 also provides a method for preparing the high-performance special polyether material with the above-mentioned terminal group-directed modification. The reaction process is as follows: Figure 1 The specific steps are as follows: (1) Polyethylene glycol (Mw = 2000 g / mol, 2.0 g) was placed in a 50 mL round-bottom flask, connected to a vacuum pump, and evacuated at 40 ° C (≤ 0.1 mmHg) for 6 h; after turning off the vacuum, nitrogen protection was applied and the mixture was quickly dissolved in 15 mL of dichloromethane (previously ultra-dried with molecular sieves, water ≤ 30 ppm) to obtain a polyethylene glycol solution; then, under nitrogen protection and stirring, the above polyethylene glycol solution was slowly added dropwise to 50 mL of HDI (2.52 g) in anhydrous DCM solution. After the addition was completed, 1-2 drops of DBTDL (30 mg) were added and stirred at room temperature for 15 h; after the reaction was completed, the solvent was concentrated by rotary evaporation, and then 300 mL of hexane was added to precipitate the product. The upper solution was separated and the remaining viscous liquid was vacuum dried to obtain intermediate 1; the FT-IR of intermediate 1 was consistent with that of Example 1.

[0032] (2) Under nitrogen protection, Bu4NI (0.1 mmol), 4-bromobenzaldehyde (0.6 mmol), TBHP in decane (0.75 mL, 5.5 M, 4.10 mmol) and 12-crown ether (2 mL) were added to a Schlenk tube and stirred at 120°C for 16 h. The volatiles were removed by rotary evaporation, and the residue was purified by silica gel column chromatography (petroleum ether / EtOAc = 20:1, v / v) to obtain intermediate 2; intermediate 2 1 H NMR and HRMS were consistent with Example 1.

[0033] (3) CuI (0.06 mmol), intermediate 2 (0.5 mmol), Na3PO4 (0.6 mmol), 28% ammonia water (1 mL) and PEG-400 (3 mL) were added to a sealed tube and stirred at 120 °C for 20 h; the reaction solution was cooled to room temperature and extracted with ether three times, and the combined organic phase was dried over anhydrous Na2SO4 and the solvent was removed under reduced pressure. The remaining residue was purified by silica gel column chromatography to obtain the desired intermediate 3; intermediate 3 1 H NMR and HRMS were consistent with Example 1.

[0034] (4) Intermediate 1 (1 g) and intermediate 3 (6.22 g) were added to anhydrous DCM (100 mL) and stirred at room temperature under a nitrogen atmosphere for 15 h. The solvent was removed using a rotary evaporator to obtain a high-performance specialty polyether material with end group-directed modification. The FT-IR of the high-performance specialty polyether material with end group-directed modification was consistent with that in Example 1.

[0035] Test example In order to verify the application of the high-performance specialty polyether materials with end group directionally modified prepared in Examples 1-3 in separation membranes, the high-performance specialty polyether materials with end group directionally modified prepared in Examples 1-3 were made into separation membranes, and the specific steps were as follows: Polyethyleneimine (PEI, molecular weight 70 kDa), a polyether material prepared in any of Examples 1-3, and Na2CO3 were added to water to form an aqueous phase. The concentrations of PEI, the polyether material prepared in Examples 1-3, and Na2CO3 in the aqueous phase were 0.75wt%, 0.075wt%, and 0.1wt%, respectively. Trimesoyl chloride (TMC) was dissolved in n-hexane to a TMC concentration of 0.1wt% to form an oil phase. The aqueous phase was slowly dripped onto the surface of a polysulfone (PSF) substrate. After 6 minutes, the oil phase was dripped onto the membrane. The membrane was reacted for 5 minutes, and then unreacted monomers were rinsed with hexane. The membrane was then heat-treated at 75°C to obtain a separation membrane. Simultaneously, a separation membrane prepared without the polyether material prepared in Examples 1-3 was used as a control.

[0036] The membrane permeation selectivity test system was used to test the water permeation flux and salt retention rate of each separation membrane. The test system includes a pump, membrane tank, pipeline, regulating valve, pressure and flow detectors. The effective membrane area tested is 12.56 cm 2The permeation time was 5 min and the test pressure was 5 bar. Before the test, the solution was pre-pressed at room temperature and 6 bar for 30 min to achieve a stable flux. When testing the retention rate of single salt magnesium chloride or lithium chloride, the concentration of magnesium chloride and lithium chloride solution was 1.0 g / L. When testing the magnesium-lithium separation performance, the total concentration of MgCl2 and LiCl was 2.0 g / L, of which Mg 2+ / Li + =5:1, 10:1, 20:1, 50:1, 80:1, 100:1, Mg 2+ He Li + The concentration was determined using inductively coupled plasma optical emission spectroscopy.

[0037] The calculation formula of membrane permeability J is as follows: J=V / (A×Δt×Δp), where V represents the permeate volume in L; A represents the effective membrane area in m 2 ; Δt represents the permeation time, unit is h; Δp represents the transmembrane pressure, unit is bar; The calculation formula of the membrane retention rate R is as follows: R=[1-(C p / C f )]×100%, where C p 、C f Represent the concentration of solute in the permeate and feed solution, respectively, in g / L; Magnesium-lithium separation factor S Li, Mg The calculation formula is as follows: , where C f, Mg and C f, Li are the concentrations of magnesium ions and lithium ions in the feed solution, C p, Mg and C p, Li are the concentrations of magnesium ions and lithium ions in the permeate, respectively, both in g / L; The test results of the above permeability and retention rate are shown in Table 1, and the test results of the magnesium-lithium separation factor are shown in Figure 3 shown.

[0038] Table 1 As shown in Table 1, the pure water permeability of the separation membranes prepared from Examples 1-3 of the present invention increased by 107.7%-121.2% compared to a control group without the high-performance specialty polyether material with end group-directed modification of the present invention, demonstrating that the specialty polyether material with end group-directed modification provided by the present invention effectively improved the mass transfer performance of the membranes. Furthermore, the MgCl2 retention rates of Examples 1-3 remained above 98%, comparable to those of the control group; while the LiCl retention rate was significantly lower than that of the control group. This selectivity difference provides favorable conditions for magnesium-lithium separation.

[0039] Depend on Figure 3 It can be seen that as the Mg content in the feed solution increases 2+ / Li + The ratio increased from 5:1 to 100:1, and the S Li, Mg It gradually increases, while the control group gradually decreases, which shows that the high-performance special polyether material with terminal group directionally modified in the present invention has excellent magnesium-lithium separation performance for high magnesium-lithium ratio solution, and as the magnesium-lithium ratio continues to increase, the prepared separation membrane has better magnesium-lithium separation performance.

[0040] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. The basic principles and main features of the present invention have been described above using specific implementation schemes. Modifications or substitutions may be made based on the present invention, but such modifications or substitutions do not detract from the essence of the corresponding technical solutions from the scope of protection claimed by the present invention.

Claims

1. A high-performance specialty polyether material with end group-directed modification, characterized in that: The structural formula of the high-performance special polyether material with end group direction modification is: 。 2. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 1, characterized in that: The following steps are involved: (1) Under an inert gas atmosphere, a dichloromethane solution of polyethylene glycol is added to a dichloromethane solution of hexamethylene diisocyanate, and then dibutyltin dilaurate is added, and the mixture is reacted under stirring. After the reaction is completed, the mixture is purified to obtain intermediate 1; The structural formula of the intermediate 1 is: ； (2) Under an inert gas atmosphere, a decane solution of tert-butyl hydroperoxide, tetrabutylammonium iodide, 4-bromobenzaldehyde and 12-crown ether-4 are mixed and reacted under heating conditions; after the reaction is completed, intermediate 2 is obtained through post-treatment; The structural formula of the intermediate 2 is: ； (3) Mix cuprous iodide, intermediate 2, sodium phosphate, ammonia water and PEG400 and react under heating conditions; after the reaction is completed, post-process to obtain intermediate 3; The structure of the intermediate 3 is: ； (4) adding the intermediate 1 and the intermediate 3 into dichloromethane and stirring the mixture under an inert gas atmosphere; after the reaction is completed, removing the solvent to obtain the high-performance special polyether material with the terminal group directionally modified.

3. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The mass ratio of polyethylene glycol, hexamethylene diisocyanate, and dibutyltin dilaurate in step (1) is (1-2): (1.68-2.52): (0.02-0.04); and the reaction time is 12-15 h.

4. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The usage ratio of tert-butyl hydroperoxide, tetrabutylammonium iodide, 4-bromobenzaldehyde, and 12-crown ether-4 in step (2) is (4.02-4.10) mmol: (0.1-0.15) mmol: (0.5-0.6) mmol: 2 mL.

5. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The heating temperature in step (2) is 100-120°C, and the reaction time is 16-20 h.

6. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The amount ratio of cuprous iodide, intermediate 2, sodium phosphate, ammonia water and PEG400 in step (3) is (0.05-0.06) mmol: 0.5 mmol: (0.5-0.6) mmol: 1 mL: (2-3) mL; the concentration of the ammonia water is 25-28 wt%.

7. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The heating temperature in step (3) is 100-120°C, and the reaction time is 20-24 h.

8. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The mass ratio of intermediate 1 to intermediate 3 in step (4) is 1:(3.11-6.22); the stirring reaction time is 12-15 h.

9. The method for preparing the high-performance specialty polyether material with end group-directed modification according to claim 2, characterized in that: The molecular weight of the polyethylene glycol in step (1) is 1000-2000 g / mol.

Images