REDUCTION KIT, REDUCING COMPOSITION AND USE OF SAID KIT AND COMPOSITION

Abstract

Disclosed is a reduction kit including a reducing compound and an open-cell polymer foam, the surface of which includes a polymer having a catechol unit. Also disclosed is a reducing composition including an open-cell foam, the surface of which includes a polymer having a catechol unit, the foam being functionalized by a reducing compound. The use of the kit or composition as a reagent in reduction reactions is also disclosed.

Claims

1-11. (canceled)

12. A reduction kit comprising: a reducing compound, and an open cell polymer foam and comprising on the surface a catechol pattern polymer.

13. The reduction kit according to claim 12, wherein the reducing compound is selected from a non-metallic compound, hydrogen, a metal compound, a hydride, Na SO.sub.3, Na.sub.2S.sub.2O.sub.4, Na.sub.2S.sub.2O.sub.3 or N.sub.2H.sub.4, and their mixture.

14. The reduction kit according to claim 12, wherein the reducing compound is a hydride selected from LiBH.sub.4, NaBH.sub.4, KBH.sub.4, NaBH.sub.3CN, LiH, NaH, KH, CaH.sub.2, BH.sub.3, AlH.sub.3, GaH.sub.3, InH.sub.3, T1H.sub.3, a dialkylaluminum hydride, diisobutylaluminum hydride (DIBAL), their derivative and their mixture.

15. The reduction kit according to claim 12, wherein the reducing compound is solid, liquid or gaseous.

16. The reduction kit according to claim 12, wherein the reducing compound is included in a reducing solution, the concentration of reducing compound in the reducing solution being from 0.001 mol/l to 14.7 mol/l.

17. The reduction kit according to claim 12, wherein the open cell polymer foam comprising on the surface a catechol pattern polymer is selected from an expanded polypropylene foam comprising on the surface a catechol pattern polymer, a polystyrene foam comprising on the surface a catechol-patterned polymer, a polyurethane foam comprising on the surface a catechol-patterned polymer, a polydimethylsiloxane (PDMS) foam comprising on the surface a catechol-patterned polymer, a PVC (polyvinyl chloride) foam) comprising on the surface a catechol-patterned polymer and their mixture.

18. The reduction kit according to claim 12, wherein the catechol pattern polymer present on the surface of the open-cell polymer foam is obtained by polymerization of a compound comprising a catechol unit selected from catecholamines or polyphenols, caffeic acid, catechol, catechin and its stereoisomers, epigallocatechin, epigallocatechin gallate, hydroxyhydroquinone, morine (2,3,4,5,7-pentahydroxyflavone), pyrogallol, tannic acid, and their mixture.

19. The reduction kit according to claim 12, wherein the catechol-patterned polymer present on the surface of the open-cell polymer foam is polydopamine.

20. A reducing composition comprising: a reducing compound selected from a non-metallic compound, hydrogen, a metal compound, a hydride, Na SO.sub.3, Na.sub.2S.sub.2O.sub.4, Na.sub.2S.sub.2O.sub.3 or N.sub.2H.sub.4, and their mixture, an open-cell polymer foam comprising on the surface a catechol-patterned polymer selected from an expanded polypropylene foam comprising on the surface a catechol pattern polymer, a polystyrene foam comprising on the surface a catechol-patterned polymer, a polyurethane foam comprising on the surface a catechol-patterned polymer, a polydimethylsiloxane (PDMS) foam comprising on the surface a catechol-patterned polymer, a PVC (polyvinyl chloride) foam) comprising on the surface a catechol-patterned polymer and their mixture, wherein the open-cell polymer foam comprising at the surface a catechol-patterned polymer is partially or fully functionalized by the reducing compound.

21. The method for synthesizing a reducing composition as defined in claim 20 comprising a step of contacting the open-cell polymer foam comprising the catechol-patterned polymer on the surface, and an aqueous solution comprising the reducing compound, wherein the pH of the aqueous solution at the beginning of the contacting step is adjusted to at least 7.

22. A reagent of a reduction reaction comprising the reduction kit as defined in claim 12.

Description

DESCRIPTION OF THE FIGURES

[0105] FIG. 1 shows two images of Scanning Electron Microscopy (SEM). On the left, a polyurethane foam, on the right, a polyurethane foam comprising polydopamine on the surface (see Example 1).

[0106] FIG. 2 shows a graph illustrating the evolution of the reduction rate of methylene blue (MB) by six different samples (A-F, see Example 3) as a function of time.

[0107] FIG. 3 shows a graph illustrating the repeated use of the reduction kit according to the invention for the reduction of MB.

[0108] FIG. 4 shows a graph illustrating the repeated use of the reducing composition according to the invention for the reduction of MB.

[0109] FIG. 5 shows a graph illustrating the evolution of the reduction rate of MB by the reducing composition according to the invention (A) and two commercial products (G and H).

[0110] FIG. 6 shows an SEM of a reducing composition according to the invention comprising silver nanoparticles on the surface.

[0111] FIG. 7 shows a graph illustrating the total mass of reduced MB by reducing compositions according to the invention, which were synthesized with aqueous solutions of NaBH.sub.4 of different pH (5, 7, 10 and 12).

[0112] FIG. 8 shows the evolution over time of the ratio r=Area (benzyl alcohol)/[Area (benzyl alcohol)+Area (benzaldehyde)] measured by HPLC coupled to a UV-visible spectrophotometer.

EXAMPLES

Example 1: Synthesis of a Polyurethane Foam Comprising the Surface of Polydopamine

[0113] The polyurethane foam is a sample of Regicell 20 foam (Foampartner) of 8 cm.sup.3 and about 200 mg.

[0114] An aqueous solution of dopamine hydrochloride is prepared by dissolving dopamine hydrochloride (2 mg/ml) in an aqueous solution (60 ml) of tris (hydroxymethyl) aminomethane (TRIS) at a molar concentration of 10 mM, the pH of which is adjusted to 8.5 by dropwise addition of 1M of HCl aqueous solution.

[0115] The polyurethane foam is immersed at room temperature for 24 hours in the stirred aqueous solution of dopamine in an illuminated room. The dopamine polydopamine polymerization is characterized by a change in the color of the aqueous solution to dark brown. The polyurethane foam comprising polydopamine on the surface is then rinsed with ultrapure water (MiliQ).

[0116] Foam surface analysis obtained by X-ray photoelectron spectroscopy (XPS) and SEM images (see FIG. 1) confirm the presence of a uniform polydopamine coating on the surface of the polyurethane foam. The mass of polydopamine on the surface of the polyurethane foam is about 2 mg.

[0117] The foam obtained in this example is therefore a polyurethane foam comprising polydopamine on the surface.

Example 2: Synthesis of the Reducing Composition in Which the Reducing Compound is NaBH.SUB.4

[0118] The polyurethane foam comprising polydopamine on the surface of Example 1 is immersed, at room temperature and for 10 minutes, in a stirred aqueous solution of 150 ml comprising 0.1 mold of NaBH.sub.4 and whose pH is 10. The functionalization of the polyurethane foam comprising polydopamine on the surface is characterized by the appearance of a slight yellow coloration of the aqueous solution and a low production of H.sub.2(g).

[0119] The amount of boron from NaBH.sub.4 in the reducing composition is measured by ICP-AES. This amount is about 1600 mg/kg of reducing composition.

[0120] The reducing composition obtained in this example therefore comprises a polyurethane foam comprising polydopamine on the surface functionalized with NaBH.sub.4.

Example 3: Evaluation of the Reducing Properties of the Reduction Kit and the Reducing Composition According to the Invention During the Reduction of Methylene Blue (MB)

[0121] The reduction properties of six different but related mass samples (i.e. 20020 mg) were evaluated during BM reduction.

[0122] List of tested samples: [0123] A: reducing composition according to the invention of Example 2, [0124] B: reduction kit according to the invention comprising the foam of Example 1+aqueous solution of NaBH.sub.4 (15 ml, 0.1 mol/l of NaBH.sub.4) [0125] C: polyurethane foam with NaBH.sub.4 adsorbed on the surface [0126] D: polyurethane foam+aqueous solution of NaBH.sub.4 (15 ml, 0.1 mol/l of NaBH.sub.4) [0127] E: foam of Example 1 [0128] F: polyurethane foam

[0129] Six 50 ml MB solutions are prepared. The concentration of MB in these solutions is 2.10.sup.5 mol/l of MB.

[0130] One of the six samples is immersed in one of six stirred MB (with agi700 rpm) of MB (50ml) solutions at room temperature. For samples B and D, the aqueous solution of NaBH.sub.4 is added together with the foam of Example 1 or polyurethane. For samples A, C, E and F, no NaBH.sub.4 solution is added.

[0131] The variation of MB concentration in the MB solution is monitored for 25 minutes. Every 5 minutes a sample of MB solution is taken. The sample is then analyzed by spectrophotometry at the wavelength of 664 nm, which is the maximum absorption wavelength of the MB (UV-Vis Varian 50 Probe spectrophotometer).

[0132] The reduction rate (%) of MB is calculated according to the following formula:

R(%)=100*(1C.sub.MB(t)/C.sub.MB(0))

[0133] wherein R is the BM reduction rate, C.sub.MB(0) is the initial MB concentration in the MB solution, and C.sub.MB(t) is the MB concentration at the instant tin the MB solution.

[0134] The evolution over time of MB reduction is shown in FIG. 2.

[0135] As the graph in FIG. 2 shows, after 25 minutes: [0136] the sample A (reducing composition according to the invention) reduced 99% of MB, of which 80% after 5 min [0137] the sample B (reduction kit according to the invention) reduced 90% of MB, of which 50% after 5 min [0138] samples C and D reduced between 65% and 70% of MB, of which respectively 40% and 25% after 5 min [0139] samples E and F reduced less than 10% of MB, of which 2% after 5 min

[0140] In the case of sample A, more than 90% of MB is reduced after only 10 minutes.

[0141] The polyurethane foam and the foam of Example 1 degrade only very little MB. The reduction of MB by samples C and D therefore results from adsorbed NaBH.sub.4 and aqueous NaBH.sub.4 solution, respectively.

[0142] As illustrated by FIG. 2 and the evolutions of the MB reduction rates by the samples A and B, the combination of the polyurethane foam comprising on the surface of the polydopamine and the NaBH.sub.4 confers on the reducing composition of the invention (sample A) and the reduction kit of the invention (sample B) reducing properties that are superior to the reducing properties of the foam of Example 1 alone, of the polyurethane foam alone, or in combination with the aqueous solution of NaBH.sub.4 or the adsorbed NaBH.sub.4 surface.

Example 4: Evaluation of the Repeated Use of the Reduction Kit According to the Invention During the Reduction of Methylene Blue (MB)

[0143] The repeated use of the reduction kit according to the invention was evaluated. The reduction kit tested is sample B of Example 3.

[0144] The protocol followed is as follows: [0145] five MB solutions (50 ml and 2.10.sup.5 mold of MB), numbered from 1 to 5, are prepared, [0146] five aqueous solutions of NaBH.sub.4 (15 ml, 0.1 mold of NaBH.sub.4), numbered from 1 to 5, are freshly prepared before each use, the foam of Example 1 is immersed in the solution of MB_1 with stirring and the aqueous solution of NaBH.sub.4.sub._1 is added simultaneously, [0147] the rate of reduction of MB in the MB_1 solution is followed according to the protocol of Example 3 for 25 minutes, after 25 minutes, the foam of Example 1 is removed from the MB_1 solution and then immersed in the MB_2 solution and the aqueous solution of NaBH.sub.4.sub._2 is added simultaneously. The MB reduction rate in the MB_2 solution is followed according to the protocol of Example 3 for 25 minutes. [0148] etc . . . . until the MB_5 solution.

[0149] The time course of the MB reduction rate for the MB_1 to 5 solutions is shown in FIG. 3.

[0150] As shown in FIG. 3, the change over time in the MB reduction rate is similar for solutions from MB_1 to 5.

[0151] The morphology of the foam of Example 1 was not impaired by these repeated immersions. The reduction kit according to the invention may therefore be used repeatedly (at least 5 times).

[0152] With samples C and D of Example 3, a single immersion is effective in terms of reduction of methylene blue. Unlike the reduction kit according to the invention, samples C and D of Example 3 can not be used repeatedly.

Example 5: Evaluation of the Repeated Use of a Single Reducing Composition According to the Invention of Example 2 During the Reduction of Methylene Blue (MB)

[0153] The repeated use of the reducing composition according to the invention was evaluated. The reducing composition tested is that of Example 2.

[0154] The protocol followed is similar to Example 4. The differences are as follows: [0155] seven MB solutions (50 ml and 2.10.sup.5 mold of MB), numbered from 1 to 7, are prepared, and [0156] no aqueous solution of NaBH.sub.4 is prepared and added to the solutions of MB_1 to 7.

[0157] The time course of the MB reduction rate for the MB_1 to 7 solutions is shown in FIG. 4. The change over time in the reduction rate of the MB in the MB_1 solution by the reduction kit according to the invention (see Example 4) is also shown.

[0158] As illustrated in FIG. 4, the change over time in the MB reduction rate is similar in the MB_1 to 5 solutions and this MB reduction rate is higher than that obtained by the reduction kit according to the invention in the MB_1 solution.

[0159] In the MB_6 solution, the reduction kinetics of the MB is slowed down a little and the reduction rate is less important than that obtained by the reducing composition according to the invention in the solutions of MB_1 to 5. However during the first 15 minutes, this reduction rate is higher than that obtained by the reduction kit according to the invention in the MB_1 solution, and is of the same order of magnitude.

[0160] In the MB_7 solution, the kinetics of MB reduction is slowed down but, after 25 minutes, the reduction rate is about 80% without a plateau being reached, which suggests that over a longer period, a higher rate of reduction could be achieved.

[0161] In addition, the morphology of the reducing composition of Example 2 was not impaired by these repeated immersions.

[0162] This example demonstrates that the reducing composition according to the invention may be used repeatedly without adding NaBH.sub.4. With the samples C and D of Example 3, only one immersion allows the reduction of methylene blue. Unlike the reduction kit according to the invention, samples C and D of Example 3 can not be used repeatedly. Advantageously, this greatly reduces the amount of NaBH.sub.4 used to reduce methylene blue.

Example 6: Comparison of the Reducing Properties of the Reducing Composition According to the Invention of Example 2 with Commercial Products in the Reduction of Methylene Blue (MB)

[0163] The reduction properties of three different samples were evaluated according to the protocol described in Example 3.

[0164] List of tested samples: [0165] A: reducing composition according to the invention of Example 2, [0166] G: NaBH.sub.4 supported on alumina (Ref: 243620 ALDRICH) [0167] H: NaBH.sub.4 supported on balls of polymer material (Ref: 328642 ALDRICH)

[0168] The evolution over time of the MB reduction rate is shown in FIG. 5.

[0169] As the graph in FIG. 5 shows, after 25 minutes: [0170] the sample A (reducing composition according to the invention) reduced 99% of MB [0171] sample G was reduced less than 20% of MB, and [0172] sample H was reduced less than 10% of MB.

[0173] As illustrated by FIG. 5 and the evolutions of the MB reduction rates by the three samples, the combination of the polyurethane foam comprising, on the surface of the polydopamine functionalized with NaBH.sub.4, gives the reducing composition of the invention superior reducing properties compared with the two commercial products tested.

Example 7: Evaluation of the Reducing Properties of the Reducing Composition According to the Invention of Example 2 for the Synthesis of Silver Nanoparticles (NpAg)

[0174] The reducing properties of the reducing composition according to the invention were studied during the synthesis of silver nanoparticles.

[0175] The reducing composition of Example 2 was immersed, with stirring in an aqueous solution of AgNO.sub.3 at 50 mmol/l for 24 hours at room temperature. The reducing composition is then removed from the aqueous solution of AgNO.sub.3 and then rinsed with ultrapure water (MiliQ).

[0176] The SEM image of FIG. 7 confirms the presence of silver nanoparticles on the surface of the reducing composition. An EDX (Energy Dispersive X-ray) analysis of this SEM image as well as mass measurements make it possible to determine that the silver mass on the surface of the reducing composition is about 17.5 mg.

[0177] The reducing composition obtained in Example 7 thus comprises a polyurethane foam comprising polydopamine on the surface functionalized with NaBH.sub.4 and silver nanoparticles.

[0178] When the reducing composition of Example 2 according to the invention is used for the synthesis of silver nanoparticles, then, and without wishing to be bound by any theory, the inventors are of the opinion that when the reducing composition is used as the reducing agent, the reducing properties of polydopamine reduce Ag.sup.+ ions stabilize and protect from oxidation the silver particles (0) present on the surface of the reducing composition.

Example 8 Study of the Effect of the pH of the Aqueous Solution of NaBH.SUB.4 .on the Amount of NaBH.SUB.4 .in the Reducing Composition According to the Invention and the Reducing Properties of the Reducing Composition According to the Invention

[0179] a) Synthesis and Characterization of the Compositions

[0180] The synthesis protocol is similar to that of Example 2, the difference being that four solutions of NaBH.sub.4 were prepared by adjusting their pH to 5, 7 and 10.

[0181] After the synthesis of four reducing compositions according to the invention, their amount of boron from NaBH.sub.4 is determined by ICP-AES.

[0182] The results are shown in the following table.

TABLE-US-00001 Aqueous Aqueous Aqueous Solution solution pH 5 solution pH 7 solution pH 10 Amount of B in 1.6 2.1 1607 the composition (mg/kg)

[0183] b) Study of the Reducing Properties of the Compositions, Reduction of Methylene Blue

[0184] The reducing properties of these compositions are then evaluated during the reduction of methylene blue (MB). The protocol followed is that of Example 3.

[0185] The total mass of reduced MB is calculated from MB reduction rates, and is represented on the histogram of FIG. 7.

[0186] As shown in the histogram of FIG. 7, the total mass of reduced MB is limited when the pH of the aqueous solution is 5, wherein it increases when the pH of the aqueous solutions is 7 and 10, and it is maximum when the pH of the aqueous solution is equal to 10.

[0187] This example thus demonstrates that the reduction properties of the composition synthesized with the aqueous solution of pH=5 are not sufficient for industrial use, whereas the reducing properties of the reducing compositions according to the invention synthesized with the aqueous solutions pH=7 and 10 are sufficient for industrial use.

[0188] c) Studies of the Reducing Properties of the Reducing Compositions Synthesized with Aqueous Solutions of pH=10 and pH=5, Synthesis of Silver nanoparticles (NpAg)

[0189] The reducing properties of the reducing compositions according to the invention obtained with the aqueous solutions of pH=10 and pH=5 are then evaluated for the synthesis of silver nanoparticles (NpAg). The protocol followed is that of Example 7.

[0190] The silver mass on the surface of the reducing composition obtained from the solution of pH=10, measured as described in Example 7, is about 17.5 mg. The silver mass on the surface of the reducing composition obtained from the pH=5 solution is about 2.3 mg.

Example 9: Evaluation of the Reducing Properties of the Reduction Kit of the Invention During the Benzaldehyde Reduction Reaction to Benzyl Alcohol

[0191] The reduction of benzaldehyde by the reduction kit was evaluated as follows. The polyurethane foam coated with polydopamine used is that described in Example 1 (volume of the foam used: 30 cm.sup.3). The NaBH.sub.4 solution is freshly prepared before use. A quantity of 114 mg of NaBH.sub.4 is dissolved in ultrapure water (1.0 mL, without the use of sodium hydroxide) and then this reducing solution is immediately added to the foam of the reduction kit suspended in a 1000 mL of methanolic solution of benzaldehyde. The concentration of benzaldehyde is 9.44 mM. It should be noted that the amount of NaBH.sub.4 used represents 0.32 molar equivalents relative to the amount of benzaldehyde, i.e. 1.28 equivalents of hydrides. The conversion of benzaldehyde to benzyl alcohol takes place at room temperature and was followed by HPLC chromatography coupled with a UV-visible spectrophotometer (Column SUPELCOSIL ABZ+PLUS 3 M 15CM4.6MM HPLC (Sigma-Aldrich), isocratic eluent H.sub.2O+0.1% TFA 60/40 acetonitrile, 1 mL/min flow rate, 250 nm detection for benzaldehyde and benzyl alcohol). The reaction medium is removed and then analyzed by HPLC every 3 minutes: the evolution of the proportion of benzyl alcohol formed as well as the reduction of the proportion of starting benzaldehyde is monitored thanks to the retention times characteristic of benzaldehyde (t=4.4 min) and benzyl alcohol (t=3.1 min) under the analytical conditions used. No other peak is observed on the chromatogram. The evolution over time of the area ratio r represented in FIG. 8 is defined as follows:

r=Area (benzyl alcohol)/[Area (benzyl alcohol)+Area(benzaldehyde)]

[0192] Two curves are present in FIG. 8: one curve showing the evolution of r using the reduction kit and a curve without a reduction kit but with an equivalent quantity of NaBH.sub.4 in both cases. In the absence of the polyurethane foam coated with polydopamine, the reduction of benzaldehyde to benzyl alcohol by direct reaction of NaBH.sub.4 is linear and very slow: after 40 minutes, a 13% conversion to benzyl alcohol is measured. When the reduction kit is used, it leads to a rapid reduction reaction: after 40 minutes, a 93% conversion to benzyl alcohol is measured.

Example 10: Evaluation of the Reducing Properties of the Reductive Composition of the Invention of Example 2 in the Benzaldehyde Reduction Reaction

[0193] The reducing composition was prepared using a solution of 10 mL of 22% NaBH.sub.4, 22% NaOH and 56% pure water (weight ratio). The polyurethane foam was soaked in this solution for 1 minute with stirring and then dried with compressed air. This foam was immersed in a first methanolic solution of benzaldehyde at 9.8 M with stirring and at room temperature, and then identically in a second methanolic B solution of benzaldehyde at 9.8 M. The conversion to benzyl alcohol was determined by HPLC as described in Example 9. The ratio r is determined after 10 minutes of reaction in solution A and B because beyond this time, the conversion no longer evolves. It is 100% conversion to benzyl alcohol in solution A and 70% in solution B.