Preparation method of camphor complexes for regulating chirality of nanocellulose

Abstract

The invention discloses a preparation method of nanocellulose chirality regulated by a camphor complex, and the specific process is as follows: camphor rare earth complex is used to modify nanocellulose to prepare chiral composite nanocellulose. The nanocellulose used in the invention has the advantages of being natural, renewable, green and sustainable, and the chirality of the nanocellulose is transferred by regulating the nanocellulose with a camphor rare earth complex, thereby breaking the inherent chiral structure of the nanocellulose and preparing nanocellulose with special chirality. The invention has good application prospects in 3D screen display, optoelectronic devices and biomedical applications.

Description

Technical Field

[0001] The invention belongs to the technical field of nano polymer materials and relates to a preparation method for controlling the chirality of nano cellulose by using a camphor complex. Background Art

[0002] As the most abundant and widely distributed natural polymer material in nature, cellulose has become a hot topic in the study of nanofunctional materials. Cellulose is a macromolecular polysaccharide composed of glucose units connected by 1,4-β-glycosidic bonds, which is endowed with a unique chiral structure. On the other hand, chiral substances can rotate the polarization plane of light and produce special optical properties, which makes it also play an important role in the field of optoelectronic devices. However, due to the inherent chiral structure of cellulose, its application in the field of circularly polarized materials is limited. Therefore, it is still a challenge to generate multipolarized circularly polarized light only from nanocellulose materials with inherent chiral structures. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation method for regulating the chirality of nanocellulose by using a camphor complex, wherein the method modifies the nanocellulose by introducing a camphor complex, thereby changing the inherent chiral structure of cellulose.

[0004] The technical solution adopted by the present invention is a preparation method for regulating the chirality of nanocellulose by a camphor complex, which specifically comprises the following steps:

[0005] Step 1, dissolving D / L-3-trifluoroacetyl camphor and EuCl3·6H2O in a DMF aqueous solution and stirring to dissolve, and then pouring into a polytetrafluoroethylene-lined reactor for reaction;

[0006] Step 2, dissolving the nanocellulose in a DMF aqueous solution, and then pouring it into the reactor in step 1, cooling to room temperature after the reaction is completed, filtering the precipitate, washing with anhydrous ethanol, and then vacuum drying the product.

[0007] The present invention is also characterized in that:

[0008] In step 1, the amount of D / L-3-trifluoroacetylcamphor used is 30 μl to 50 μl, and the amount of EuCl3·6H2O used is 15 mg to 25 mg.

[0009] In step 1 and step 2, in the DMF aqueous solution, the volume ratio of DMF to H2O is 1:1-2.

[0010] In step 1 and step 2, the reaction temperature of the reactor is 75° C. to 75° C., and the reaction time is 4 h to 6 h.

[0011] In step 2, the vacuum drying time is 20 h to 30 h, and the vacuum drying temperature is 100° C. to 110° C.

[0012] The invention has the beneficial effects that the invention prepares chiral composite nanocellulose by modifying nanocellulose with camphor rare earth complex. Nanocellulose is regulated by camphor rare earth complex to transfer its chirality, thereby breaking the inherent chiral structure of nanocellulose and preparing nanocellulose with special chirality. The method of the invention adopting camphor to regulate the chirality of nanocellulose is natural, renewable, green and sustainable, and has good application prospects in 3D screen display, optoelectronic devices and biomedical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the CD spectrum of nanocellulose MCF in Example 1 of the preparation method of camphor complex for regulating chirality of nanocellulose of the present invention;

[0014] Figure 2 It is the CD spectrum of the chiral small molecule D / L-TFC (D / L-3-trifluoroacetyl camphor) in Example 1 of the preparation method of the camphor complex for regulating the chirality of nanocellulose of the present invention;

[0015] Figure 3 This is a CD spectrum of the composite chiral cellulose (MCF-Eu-TFC) prepared in Example 1 of the preparation method of the camphor complex for regulating the chirality of nanocellulose of the present invention. DETAILED DESCRIPTION

[0016] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] The preparation method of the camphor complex for regulating the chirality of nanocellulose comprises the following steps:

[0018] Take 30-50 μl D / L-TFC (D / L-3-trifluoroacetyl camphor) and 15-25 mg EuCl3·6H2O and dissolve them in a solution of DMF (N,N-dimethylformamide):H2O=1:1-2 by volume, stir and dissolve, pour into a polytetrafluoroethylene liner, and react in a high-pressure reactor at 75-75°C for 4-6 hours; then dissolve 50 mg nanocellulose (MCF) in a DMF aqueous solution with a volume ratio of 1:1-2, and then pour into a polytetrafluoroethylene liner, and react in a high-pressure reactor at 75-75°C for 4-6 hours. After the reaction is completed, cool to room temperature, filter the precipitate, wash with anhydrous ethanol, and then vacuum dry the product. The vacuum drying time is 20h-30h, and the vacuum drying temperature is 100°C-110°C.

[0019] The preparation process of D / L-3-trifluoroacetyl camphor is as follows: 1.2g D / L-camphor and 8ml tetrahydrofuran are added to a 50ml double-necked flask under N2 environment, ice bath is stirred for 45min, 1.2ml ethyl trifluoroacetate is slowly added dropwise during stirring, and stirred and refluxed for 4h, and the stirring reaction is continued at room temperature overnight to obtain a crude product 3-trifluoroacetyl camphor. The crude product is poured into a beaker filled with 20mL ice water, and a mass fraction of 10% hydrochloric acid is added dropwise to adjust the Ph value to 2, the sample color slowly fades to yellow, is poured into a separating funnel, ether is extracted (3×20ml), and the ether layer is combined. Subsequently, the ether layer is successively washed once in a mass fraction of 5% sodium bicarbonate solution, saturated salt water, and deionized water, and finally anhydrous magnesium sulfate is added for drying. The solvent was evaporated off at 32°C, and further separated and purified by silica gel column chromatography to obtain an orange-red liquid, namely D / L-3-trifluoroacetylcamphor (D / L-TFC).

[0020] Example 1

[0021] Take 30 μl D / L-TFC (D / L-3-trifluoroacetyl camphor) and 15 mg EuCl3 . 6H2O was dissolved in a solution of DMF:H2O=1:1 by volume, stirred and dissolved, poured into a polytetrafluoroethylene liner, and reacted at 75°C in a high-pressure reactor for 6 hours; then 50 mg of nanocellulose was dissolved in a DMF aqueous solution of 1:1 by volume, poured into a polytetrafluoroethylene liner, and reacted at 75°C in a high-pressure reactor for 6 hours. After the reaction was completed, it was cooled to room temperature, the precipitate was filtered, washed with anhydrous ethanol, and then the product was vacuum dried for 24 hours at a drying temperature of 105°C.

[0022] Figure 1 This is the circular dichroism (CD) spectrum of nanocellulose MCF. The ellipticity of MCF in the range of 200nm-800nm ​​is positive, which proves the left-handed chiral structure of nanocellulose. Figure 2 This is the CD spectrum of the chiral small molecule D / L-TFC (D / L-3-trifluoroacetylcamphor). The two enantiomers show almost the same absorption spectrum and a pair of perfect mirror-symmetric CD signals, and there is a pair of sharp absorption peaks at 333nm. Figure 3 The CD spectrum of the composite chiral cellulose (MCF-Eu-TFC) prepared by introducing a chiral small molecule camphor rare earth complex in the present invention shows a mirror-symmetric Cotton effect in the range of 250-450nm. It shows that the supramolecular self-assembly of MCF and TFC leads to chirality transfer, thereby changing the asymmetric environment of MCF-Eu-TFC. The purpose of regulating the chirality of nanocellulose is achieved, thereby preparing nanocellulose with special chirality.

[0023] Example 2

[0024] Take 40 μl D / L-TFC (D / L-3-trifluoroacetyl camphor) and 20 mg EuCl3 . 6H2O was dissolved in a solution of DMF:H2O=1:1.5 by volume, stirred and dissolved, poured into a polytetrafluoroethylene liner, and reacted at 80°C in a high-pressure reactor for 5 hours; then 50 mg of nanocellulose was dissolved in a DMF aqueous solution of 1:1.5 by volume, poured into a polytetrafluoroethylene liner, and reacted at 80°C in a high-pressure reactor for 5 hours. After the reaction was completed, it was cooled to room temperature, the precipitate was filtered, washed with anhydrous ethanol, and then the product was vacuum dried. The drying time was 20 hours and the drying temperature was 110°C.

[0025] Example 3

[0026] Take 50 μl D / L-TFC (D / L-3-trifluoroacetyl camphor) and 25 mg EuCl3 . 6H2O was dissolved in a solution of DMF:H2O=1:2 by volume, stirred and dissolved, poured into a polytetrafluoroethylene liner, and reacted at 75°C in a high-pressure reactor for 4 hours; then 50 mg of nanocellulose was dissolved in a DMF aqueous solution of 1:2 by volume, poured into a polytetrafluoroethylene liner, and reacted at 75°C in a high-pressure reactor for 4 hours. After the reaction was completed, it was cooled to room temperature, the precipitate was filtered, washed with anhydrous ethanol, and then the product was vacuum dried. The drying time was 30 hours and the drying temperature was 110°C.

[0027] The present invention takes nanocellulose as a research object, and introduces camphor complexes to modify nanocellulose, thereby changing the inherent chiral structure of cellulose. Since camphor has two bridgehead carbon atoms that contain four different groups, they are two chiral carbon atoms, and the carbon atom on the carbonyl group is a potential chiral carbon atom, which makes it optically active. Under the action of a catalyst, it reacts with an ester through a Claisen condensation reaction to generate a β-diketone with a chiral structure. At the same time, the β-diketone ligand has a strong coordination ability for rare earth ions, and the formed β-diketone rare earth complex can effectively transmit the interaction of the central rare earth ion. When the chiral structure of the β-diketone rare earth complex is introduced, the linear chain of nanocellulose is not only retained but also has a unique circular dihedral property. Therefore, the present invention utilizes camphor rare earth complexes to regulate the chirality of nanocellulose, uses natural polymers as raw materials, not only follows the sustainable development of materials and reduces the harm to the environment, but also prepares nanocellulose with special chirality from nanocellulose materials with inherent chiral structures.

Claims

1. A method for preparing a camphor complex to regulate the chirality of nanocellulose, characterized in that: The specific steps include: Step 1, dissolving D / L-3-trifluoroacetyl camphor and EuCl3·6H2O in a DMF aqueous solution and stirring to dissolve, and then pouring into a polytetrafluoroethylene-lined reactor for reaction; The preparation process of D / L-3-trifluoroacetyl camphor is as follows: 1.2 g D / L-camphor and 8 ml tetrahydrofuran are added to a 50 ml double-necked flask under N2 environment, stirred in an ice bath for 45 min, 1.2 ml ethyl trifluoroacetate is added dropwise during stirring, and then stirred and refluxed for 4 h, and the reaction is continued to be stirred at room temperature overnight to obtain a crude product 3-trifluoroacetyl camphor; the crude product 3-trifluoroacetyl camphor is poured into a beaker containing 20 mL ice water, 10% hydrochloric acid is added dropwise to adjust the Ph value to 2, the color of the sample gradually fades to yellow, and the sample is poured into a separatory funnel, extracted with ether, and the ether layers are combined; subsequently, the ether layers are washed in a 5% sodium bicarbonate solution, a saturated salt solution once, and a deionized water wash twice, and finally anhydrous magnesium sulfate is added to dry; the solvent is evaporated off at 32°C, and separated and purified by a silica gel column to obtain an orange-red liquid, namely D / L-3-trifluoroacetyl camphor; Step 2, dissolving the nanocellulose in a DMF aqueous solution, and then pouring it into the reactor in step 1, cooling to room temperature after the reaction is completed, filtering the precipitate, washing with anhydrous ethanol, and then vacuum drying the product.

2. The method for preparing a camphor complex for regulating the chirality of nanocellulose according to claim 1, characterized in that: In the step 1, the amount of D / L-3-trifluoroacetyl camphor is 30 μl to 50 μl, and the amount of EuCl3·6H2O is 15 mg to 25 mg.

3. The method for preparing a camphor complex for regulating the chirality of nanocellulose according to claim 1, characterized in that: In the steps 1 and 2, in the DMF aqueous solution, the volume ratio of DMF to H2O is 1:1-2.

4. The method for preparing a camphor complex for regulating the chirality of nanocellulose according to claim 1, characterized in that: In step 1 and step 2, the reaction temperature of the reactor is 75° C. to 95° C., and the reaction time is 4 h to 6 h.

5. The method for preparing a camphor complex for regulating the chirality of nanocellulose according to claim 1, characterized in that: In the step 2, the vacuum drying time is 20 h to 30 h, and the vacuum drying temperature is 100° C. to 110° C.

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