Photochromic polysaccharide and preparation method thereof

Abstract

The invention discloses a photochromic polysaccharide. A bipyridinium salt is grafted on a polysaccharide; the preparation method comprises the following steps: S1, dissolving polysaccharide in a first solvent, adding halogenated isocyanate, heating, adding a precipitating agent after the reaction is finished, and then centrifugally drying to obtain halogenated isocyanate polysaccharide; s2, dipyridine and the halogenated isocyanate polysaccharide obtained in the step S1 are dissolved in a second solvent, heating reflux is conducted, dialysis is conducted through a dialysis bag, and the photochromic polysaccharide is obtained. The prepared polysaccharide derivative becomes blue under ultraviolet irradiation, the blue color fades and recovers to the original color after ultraviolet light is removed, and the polysaccharide derivative has good photochromic reversibility, is applied to the fields of sensors, display materials and the like, further has the advantages of being simple in synthesis method and low in cost and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of color-changing materials technology, specifically to a photochromic polysaccharide and its preparation method. Background Technology

[0002] Color-changing materials are a class of functional materials that can change color in response to external stimuli. Depending on the stimulus, they can be classified into electrochromic materials, photochromic materials, thermochromic materials, mechanochromic materials, and solvent-chromic materials. Among these, photochromic materials, due to their reversible color change under light irradiation, have broad application prospects in display manufacturing, sensor design, and data storage.

[0003] Chinese patent CN104628928A discloses a photochromic fluorocarbon resin, which is prepared by grafting a diarylethylene-based photochromic material onto a fluorocarbon resin; wherein, by weight, the fluorocarbon resin is 10-20 parts by weight, and the diarylethylene-based photochromic material is 0.001-0.01 parts by weight. A method for preparing a photochromic fluorocarbon resin includes the following steps: (1) adding a dichloromethane solution of the diarylethylene-based photochromic material dropwise to a toluene solution of the fluorocarbon resin and stirring the reaction at room temperature; (2) pressing the material obtained in step (1) to distill off the solvent and hydrogen chloride produced in the reaction, then repeatedly adding dichloromethane to distill off the solvent and hydrogen chloride, and then adding toluene solvent to adjust the solid content to obtain the photochromic fluorocarbon resin.

[0004] Currently, existing photochromic materials have some shortcomings. Some materials have complicated synthesis steps and high costs, and the reversibility and stability of color change need to be improved, which limits their practical application. Summary of the Invention

[0005] The purpose of this invention is to provide a bipyridine ammonium salt-linked photochromic polysaccharide and its preparation method using polysaccharide raw materials. The synthesis steps are simple and the cost is low.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A photochromic polysaccharide, onto which a bipyridinium salt is grafted.

[0008] A method for preparing a photochromic polysaccharide includes the following steps:

[0009] S1. Dissolve the polysaccharide in the first solvent, add the haloisocyanate, heat, and after the reaction is complete, add the precipitating agent, then centrifuge and freeze dry to obtain the haloisocyanate polysaccharide.

[0010] S2. Dissolve bipyridine and the haloisocyanate polysaccharide obtained in step S1 in a second solvent, heat under reflux, and dialyze through a dialysis bag to obtain photochromic polysaccharide.

[0011] Preferably, the polysaccharide in step S1 is cellulose, agarose, dextran, or chitosan.

[0012] Preferably, the general molecular formula of the haloisocyanate in step S1 is C1 x H 2x N 1-2 C 1-2 O 1-2 X 1-2 X is F, Cl, Br or I; the amino group replaces the hydrogen on the hydroxyl group of the sugar ring in the polysaccharide molecule.

[0013] The structural formula of the haloisocyanate polysaccharide is as shown in formula (1):

[0014]

[0015] Preferably, the first solvent in step S1 is water, DMF, or DMSO;

[0016] In step S1, the heating time is 2 to 12 hours, and the heating temperature is 120 to 180°C.

[0017] The precipitant mentioned in step S1 is n-hexane, diethyl ether, benzene, toluene, or ethyl acetate.

[0018] Preferably, in step S1, the volume ratio of the first solvent to the precipitant is 1:1 to 10;

[0019] The ratio of polysaccharide to the first solvent is 1:25-50 g / mL;

[0020] The mass ratio of polysaccharide to haloisocyanate is 1:1 to 1.45.

[0021] Preferably, the temperature for centrifugal freeze drying in step S1 is -80℃ to -50℃, and the time is 5 to 20 hours.

[0022] Preferably, the bipyridine in step S2 is 4,4'-bipyridine or 2,2'-bipyridine;

[0023] In step S2, the second solvent is acetonitrile, DMF, DMSO, or water;

[0024] In step S2, the mass ratio of bipyridine to haloisocyanate polysaccharide is 0.1–10:1;

[0025] The ratio of haloisocyanate polysaccharide to the second solvent is 1:20-50 g / mL.

[0026] Preferably, the temperature of the heating and reflux in step S2 is 120-180°C, and the heating and reflux time is 2-20 hours;

[0027] In step S2, the molecular weight cutoff of the dialysis bag is one of 500, 1000, 2000, 3500, 8000, 10000, and 15000.

[0028] Preferably, the general molecular formula of the photochromic polysaccharide obtained in step S2 is [(C 12 H 20 O 11 N 1-2 C 1-2 O 1-2 C 20 H 16 N4)]n.

[0029] The color-changing principle of this invention:

[0030] A photochromic bipyridine ammonium salt is attached to the hydroxyl groups of a polysaccharide, which changes color from white to blue under ultraviolet light. The structure of the photochromic cellulose fiber is as follows:

[0031]

[0032] The beneficial effects of this invention are:

[0033] This invention first synthesizes haloisocyanate polysaccharides, then reacts them with bipyridine compounds to obtain photochromic polysaccharides. The synthesis method of this invention is simple, the raw materials are readily available, and the cost is low. The compound turns blue under ultraviolet light irradiation, and the blue color fades after the ultraviolet light is removed, exhibiting good reversible photochromic properties and a rapid response, thus showing broad application prospects in sensors, smart displays, and other fields. Attached Figure Description

[0034] Figure 1 This is the FTIR spectrum of the photochromic cellulose obtained in Example 1.

[0035] Figure 2 This is the FTIR spectrum of the photochromic agarose obtained in Example 1.

[0036] Figure 3-1 The color of the photochromic cellulose obtained in Example 1 before irradiation with 365nm light is shown.

[0037] Figure 3-2 The color of the photochromic cellulose obtained in Example 1 after irradiation with 365nm light is shown.

[0038] Figure 3-3 The color of the photochromic cellulose obtained in Example 1 is restored after irradiation with 365nm light. Detailed Implementation

[0039] The technical solution of the present invention will be further described and illustrated below with reference to specific embodiments and accompanying drawings.

[0040] Example 1

[0041] The preparation method of the photochromic polysaccharide described in this invention comprises the following steps:

[0042] 1. Synthesis of chloropropyl isocyanate cellulose: 0.4 g of cellulose and 15 mL of DMF were added to a single-necked flask and stirred until homogeneous. Then, 0.5 mL of 3-chloropropyl isocyanate was added to the suspension, and the mixture was heated in an oil bath at 120 °C for 6 hours. After the reaction was complete, the mixture was washed with 150 mL of n-hexane, filtered, and freeze-dried at -58 °C for 16 hours to obtain 0.49 g of chloropropyl isocyanate cellulose.

[0043] 2. Synthesis of color-changing polysaccharide: Weigh 0.5g of bipyridine and 0.49g of chloropropyl isocyanate cellulose, add 20ml of LDM, heat in an oil bath at 120℃ under reflux for 2 hours, cool to room temperature, put the mixture into a dialysis bag with a molecular weight cutoff of 8000, soak the dialysis bag in water for 2-3 days, after dialysis is completed, freeze dry at -58℃ for 16 hours to obtain 0.5g of color-changing cellulose.

[0044] like Figure 1 , 2 As shown in Figures 3-1 to 3-3, this compound turns blue under ultraviolet light irradiation, and the blue color fades after the ultraviolet light is removed, demonstrating good reversible photochromism.

[0045] Example 2

[0046] The preparation method of the photochromic polysaccharide described in this invention comprises the following steps:

[0047] 1. Synthesis of chloropropyl isocyanate cellulose: 2 g of cellulose and 100 mL of DMF were added to a single-necked flask and stirred until homogeneous. Then, 2 mL of 3-chloropropyl isocyanate was added to the suspension, and the mixture was heated in an oil bath at 150 °C for 2 hours. After the reaction was complete, the mixture was washed with 100 mL of benzene, filtered, and freeze-dried at -50 °C for 20 hours to obtain 1.8 g of chloropropyl isocyanate cellulose.

[0048] 2. Synthesis of color-changing cellulose: Weigh 2.5g of bipyridine and 1.8g of chloropropyl isocyanate cellulose, add 90mL of LDM, heat in an oil bath at 150℃ under reflux for 4 hours, cool, add 500mL of ethyl acetate to wash, filter, put the crude product into a dialysis bag with a molecular weight cutoff of 8000, soak the dialysis bag in water for 2-3 days, freeze dry at -50℃ for 20h to obtain 2.0g of color-changing cellulose.

[0049] The color-changing cellulose turns blue under ultraviolet light and fades when the ultraviolet light is removed, demonstrating good reversibility of photochromism.

[0050] Example 3

[0051] The preparation method of the photochromic polysaccharide described in this invention comprises the following steps:

[0052] 1. Synthesis of chloropropyl isocyanate agarose: 0.4 g agarose and 15 mL DMF were added to a single-necked flask and stirred until homogeneous. Then, 0.5 mL of 3-chloropropyl isocyanate was added, and the mixture was heated in an oil bath at 180 °C for 2 hours. After the reaction was complete, the mixture was washed with 100 mL ethyl acetate, filtered, and freeze-dried at -80 °C for 5 hours to obtain 0.50 g of chloropropyl isocyanate agarose.

[0053] 2. Synthesis of color-changing agarose: Weigh 0.5 g of bipyridine and 0.5 g of chloropropyl isocyanate agarose, add 15 mL of acetonitrile, heat in an oil bath at 180 °C under reflux for 12 hours, place the mixture into a dialysis bag with a molecular weight cutoff of 2000, immerse the dialysis bag in water for 2–3 days, and dialyze completely. Freeze-dry at -80 °C for 6 hours to obtain 0.58 g of color-changing agarose.

[0054] The color-changing agarose turns blue under ultraviolet light, and the blue color fades after the ultraviolet light is removed, demonstrating good reversibility of photochromism.

[0055] Example 4

[0056] The preparation method of photochromic agarose according to the present invention comprises the following steps:

[0057] 1. Synthesis of chloropropyl isocyanate agarose: 2 g of agarose and 50 mL of DMF were added to a single-necked flask and stirred until homogeneous. Then, 2 mL of 3-chloropropyl isocyanate was added to the suspension, and the mixture was heated in an oil bath at 150 °C for 12 hours. After the reaction was complete, the mixture was washed with 100 mL of toluene, filtered, and dried at -70 °C for 6 hours to obtain 2.2 g of chloropropyl isocyanate agarose.

[0058] 2. Synthesis of color-changing agarose: Weigh 2.5 g of bipyridine and 2.2 g of chloropropyl isocyanate agarose, add 50 mL of LDM, and heat under reflux in an oil bath at 150 °C for 20 hours. After cooling, wash with 100 mL of ethyl acetate, filter, and place the crude product into a dialysis bag with a molecular weight cutoff of 10,000. Immerse the dialysis bag in water for 2–3 days until dialysis is complete. Freeze-dry at -70 °C for 6 hours to obtain 2.55 g of color-changing agarose.

[0059] The color-changing agarose turns blue under ultraviolet light, and the blue color fades after the ultraviolet light is removed, demonstrating good reversibility of photochromism.

[0060] The above description is only a preferred embodiment of the present invention; however, the scope of protection of the present invention is not limited thereto; any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and improved concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A photochromic polysaccharide, characterized in that, Bipyridinium salts were grafted onto polysaccharides.

2. The method for preparing a photochromic polysaccharide according to claim 1, characterized in that, Includes the following steps: S1. Dissolve the polysaccharide in the first solvent, add the haloisocyanate, heat, and after the reaction is complete, add the precipitating agent, then centrifuge and freeze dry to obtain the haloisocyanate polysaccharide. S2. Dissolve bipyridine and the haloisocyanate polysaccharide obtained in step S1 in a second solvent, heat under reflux, and dialyze through a dialysis bag to obtain photochromic polysaccharide.

3. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, The polysaccharide mentioned in step S1 is cellulose, agarose, dextran, or chitosan.

4. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, In step S1, the general molecular formula of the haloisocyanate is C x H 2x N 1-2 C 1-2 O 1-2 X 1-2 X is F, Cl, Br or I; The structural formula of the haloisocyanate polysaccharide is as shown in formula (1):

5. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, In step S1, the first solvent is water, DMF, or DMSO; In step S1, the heating time is 2 to 12 hours, and the heating temperature is 120 to 180°C. The precipitant mentioned in step S1 is n-hexane, diethyl ether, benzene, toluene, or ethyl acetate.

6. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, In step S1, the volume ratio of the first solvent to the precipitant is 1:1 to 10; The ratio of polysaccharide to the first solvent is 1:25-50 g / mL; The mass ratio of polysaccharide to haloisocyanate is 1:1 to 1.

45.

7. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, In step S1, the temperature for centrifugal freeze drying is -80℃ to -50℃, and the time is 5 to 20 hours.

8. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, The bipyridine mentioned in step S2 is 4,4'-bipyridine or 2,2'-bipyridine; In step S2, the second solvent is acetonitrile, DMF, DMSO, or water; In step S2, the mass ratio of bipyridine to haloisocyanate polysaccharide is 0.1–10:1; The ratio of haloisocyanate polysaccharide to the second solvent is 1:20-50 g / mL.

9. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, In step S2, the reflux temperature is 120–180°C, and the reflux time is 2–20 hours. In step S2, the molecular weight cutoff of the dialysis bag is one of 500, 1000, 2000, 3500, 8000, 10000, and 15000.

10. The method for preparing a photochromic polysaccharide according to claim 2, characterized in that, The general molecular formula of the photochromic polysaccharide obtained in step S2 is [(C 12 H 20 O 11 N 1-2 C 1-2 O 1-2 C 20 H 16 N4)]n.

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