CN108641100B - Preparation method of high-ionic-conductivity nanocellulose/polyvinyl alcohol hydrogel film - Google Patents
Preparation method of high-ionic-conductivity nanocellulose/polyvinyl alcohol hydrogel film Download PDFInfo
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- C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2429/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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Abstract
A preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane comprises the following steps: (1) preparing nano-cellulose and dispersing the nano-cellulose in an aqueous solution to obtain a nano-cellulose solution; (2) adding polyvinyl alcohol into the nano-cellulose solution obtained in the step (1), and uniformly dispersing to obtain a nano-cellulose/polyvinyl alcohol mixed solution; (3) and (3) adding isopropanol into the nano-cellulose/polyvinyl alcohol mixed solution obtained in the step (2), uniformly stirring, pouring into a culture dish, and performing freezing-unfreezing cycle to obtain the nano-cellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity. The nanocellulose/polyvinyl alcohol hydrogel film gel has large free volume among molecular chains, more pore structures and very high ionic conductivity.
Description
Technical Field
The invention belongs to the field of polymer composite materials, and particularly relates to a preparation method of a hydrogel film.
Background
The hydrogel is a hydrophilic water-retaining material with a three-dimensional network structure. Polyvinyl alcohol (PVA) hydrogel is a nontoxic material with high mechanical strength and excellent biocompatibility, and is widely applied to the fields of biomedicine, food, agriculture and the like. In recent years, the application of PVA composite hydrogel as a solid electrolyte membrane in a super capacitor is a research hotspot.
Nanocelluloses (CNFs) are fibrils with diameters on the nanometer scale obtained by disassembling natural plant fibers by methods of strong acid, oxidation, mechanical shearing and the like. Due to the large length-diameter ratio and the large number of surface hydroxyl groups, the composite material is mutually entangled in a water system to form a three-dimensional network structure. The composite hydrogel prepared by adopting the CNFs and the PVA has a nanofiber/polymer double-network structure and physical or chemical cross-linking points formed by more active sites and hydroxyl groups on the surface of the CNFs, so that the mechanical strength and flexibility of the gel can be improved.
In the prior art, CN102786642A discloses a nano-cellulose/polyvinyl alcohol gel composite material, more chemical reagents such as a cross-linking agent and an initiator are used in the preparation process of the material, the preparation process is difficult to control and is not green enough, and the ionic conductivity of the finally prepared composite material is not mentioned.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background technology, and provide a preparation method of a nano-cellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity, no toxicity and environmental protection. In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane comprises the following steps:
(1) preparing nano-cellulose and dispersing the nano-cellulose in an aqueous solution to obtain a nano-cellulose solution;
(2) adding polyvinyl alcohol into the nano-cellulose solution obtained in the step (1), and uniformly dispersing to obtain a nano-cellulose/polyvinyl alcohol mixed solution;
(3) and (3) adding isopropanol into the nano-cellulose/polyvinyl alcohol mixed solution obtained in the step (2), uniformly stirring, pouring into a culture dish, and performing freezing-unfreezing cycle to obtain the nano-cellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity.
In the preparation method, preferably, the freezing-unfreezing cycle times are 4-6 times, the freezing temperature is-20 to-50 ℃, and the culture dish is always kept open in the freezing-unfreezing process. The isopropanol and the water can be volatilized in time by opening the opening. In the freezing process, the nanofiber and the polyvinyl alcohol macromolecular chain are frozen, the isopropanol melting point is-87.9 ℃, the nanofiber and the polyvinyl alcohol macromolecular chain can be quickly volatilized in the freezing process, and after water is frozen into ice, the water can be sublimated into water vapor to be volatilized under the driving of the volatilization of the isopropanol, so that a large number of pores are generated under the condition that the macromolecular skeleton structure is not collapsed, and ion transfer is facilitated.
In the above preparation method, preferably, in the step (1), the preparation method of the nanocellulose is as follows: adding the cellulose without the lignin into a sulfuric acid solution, stirring and hydrolyzing, adding ultrapure water after the hydrolysis is finished to stop the reaction, then carrying out centrifugal treatment, collecting a precipitation product, washing the precipitation product with the ultrapure water until the pH value of supernatant is 6-7 to obtain cellulose precipitate subjected to sulfuric acid hydrolysis treatment, and then carrying out high-pressure homogenizing and shearing on the cellulose precipitate to obtain the nano-cellulose. In the preparation method, the cellulose raw material without lignin and hemicellulose is treated by sulfuric acid to further break the non-crystallization area in the cellulose molecular chain, and then treated by a homogenizer to obtain the nano-cellulose with uniform size.
In the above preparation method, preferably, in the preparation method of the nanocellulose, the concentration of the sulfuric acid solution is 40wt% to 50 wt%; during hydrolysis, the stirring speed is kept between 200rpm and 300rpm, the hydrolysis time is between 1.5h and 2.5h, and the hydrolysis temperature is between 40 ℃ and 50 ℃; keeping the rotating speed of the centrifugal machine to be 8000 rpm-10000 rpm during centrifugal treatment, and keeping the centrifugal treatment time to be 5 min-10 min; and (3) keeping the pressure at 90-120 MPa during high-pressure homogeneous shearing, and circularly shearing for 8-20 times.
In the preparation method, preferably, in the preparation method of the nanocellulose, the cellulose is any one of wood cellulose, wheat straw cellulose, rice straw cellulose, cotton cellulose, bamboo cellulose and hemp cellulose.
In the above preparation method, the mass fraction of the nanocellulose in the nanocellulose solution is preferably 0.1% to 1%. The mass fraction of the nano-cellulose is too high, the viscosity of the nano-cellulose is too high, and the nano-cellulose is difficult to disperse in polyvinyl alcohol; the mass fraction is too low, the three-dimensional network structure of the nano-cellulose in water is not obvious, and the nano-cellulose is difficult to play a network skeleton supporting role in the gel film.
In the above preparation method, the mass fraction of the polyvinyl alcohol in the mixed solution of nanocellulose and polyvinyl alcohol is preferably 1% to 10%. Too high a mass fraction of polyvinyl alcohol exceeds its solubility in water, and too low a mass fraction makes it difficult to form a hydrogel film.
In the preparation method, preferably, the dispersion process in the step (2) is specifically ultrasonic treatment at an ultrasonic intensity of 500-800W for 10-20 min, then the ultrasonic solution is heated at 60-95 ℃ for 1-6 h, and then the temperature is reduced to 45-50 ℃.
In the above production method, the amount of the isopropyl alcohol is preferably 10% to 60% of the total mass of the nanocellulose/polyvinyl alcohol mixed solution. Experimental research shows that the effect is not obvious when the addition amount of the isopropanol is too low, and finally the prepared film is too thin and easy to break when the addition amount of the isopropanol is too high.
The nano-cellulose used in the invention has high specific surface area, the surface of the nano-cellulose contains a large amount of hydroxyl groups, so that the nano-cellulose has good compatibility with polyvinyl alcohol, the addition of the nano-cellulose with rigid molecular chains increases the free volume among gel molecular chains, and improves the ion conduction capability in a gel network. In addition, after the nanocellulose is treated by the acid, the surface of the nanocellulose is provided with a large number of charges, so that the ionic conductivity of the hydrogel membrane can be improved. In addition, isopropanol is added into the mixed solution of the nano-cellulose and the polyvinyl alcohol to be used as a defoaming agent, the low-toxicity isopropanol is used as the defoaming agent to eliminate a large amount of bubbles generated during compounding of the nano-cellulose and the polyvinyl alcohol, and the isopropanol is quickly volatilized during low-temperature freezing to ensure that a porous structure is obtained under the condition that a molecular structure of a hydrogel membrane is not collapsed, so that ion conduction is facilitated.
Compared with the prior art, the invention has the advantages that:
the nanocellulose/polyvinyl alcohol hydrogel film gel has large free volume among molecular chains, more pore structures and very high ionic conductivity. In addition, the nano-cellulose and the polyvinyl alcohol used in the invention are degradable materials, and the prepared composite hydrogel film is non-toxic and environment-friendly, and can be used as a solid electrolyte to be applied to the fields of wearable equipment, integrated super capacitors and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a graph showing AC impedance measured by a two-electrode method for hydrogel films prepared in example 1 of the present invention and comparative examples 1 and 2.
Detailed Description
In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Comparative example 1:
a preparation method of a polyvinyl alcohol hydrogel film comprises the following steps:
(1) weighing 5g of polyvinyl alcohol (PVA) solid powder, adding 95g of ultrapure water, heating at 80 ℃, and preparing into a PVA solution with the mass fraction of 5%;
(2) and (2) adding 10g of isopropanol into the PVA solution obtained in the step (1), uniformly stirring, pouring 10g of mixed solution into a culture dish with the phi of 6cm, keeping the culture dish in an open state all the time, freezing at the temperature of minus 40 ℃, then unfreezing at normal temperature, and circulating for 5 times to obtain the polyvinyl alcohol hydrogel membrane.
Example 1:
a preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane comprises the following steps:
(1) weighing 5g of lignocellulose subjected to lignin removal, adding 100g of concentrated sulfuric acid with the mass fraction of 48%, hydrolyzing for 2.5h under the condition of water bath at 45 ℃, simultaneously stirring by using a mechanical stirring paddle at 200rpm, and adding a large amount of ultrapure water after the hydrolysis is finished to stop the reaction, thereby obtaining a cellulose mixed solution subjected to sulfuric acid hydrolysis;
(2) placing the cellulose mixed solution subjected to sulfuric acid hydrolysis treatment obtained in the step (1) into a high-speed centrifuge for centrifugation for 10min, wherein the rotation speed of the centrifuge is 8000rpm, removing supernatant liquid after centrifugation, and repeatedly washing the precipitate after centrifugation with ultrapure water until the pH of the supernatant liquid is 6.5 to obtain a cellulose precipitate subjected to sulfuric acid modification treatment and washing;
(3) circularly shearing the washed cellulose precipitate obtained in the step (2) for 10 times in a high-pressure homogenizing cavity with the diameter of 200 microns and 87 microns and the pressure of 100MPa respectively to obtain a semitransparent cellulose nanofiber aqueous dispersion, and adjusting the solid content of the cellulose nanofiber aqueous dispersion to be 0.3%;
(4) weighing 5g of polyvinyl alcohol (PVA) solid powder, adding the PVA solid powder into 95g of the nano-Cellulose (CNFs) aqueous dispersion obtained in the step (3) to enable the mass fraction of the PVA to be 5%, and obtaining a PVA/CNFs mixed solution;
(5) heating the PVA/CNFs mixed solution obtained in the step (4) at 60 ℃ for 6 hours to completely dissolve PVA, then carrying out ultrasonic treatment for 20min at the ultrasonic intensity of 500W, uniformly mixing, and cooling to 40 ℃;
(6) and (3) weighing 10g of isopropanol, adding the isopropanol into the mixed solution obtained in the step (5), uniformly stirring, pouring 10g of mixed solution into a culture dish with the diameter of 6cm, keeping the culture dish in an open state all the time, freezing at the temperature of minus 40 ℃, then unfreezing at normal temperature, and circulating for 5 times to obtain the high-ionic-conductivity nano cellulose/polyvinyl alcohol hydrogel membrane.
In fig. 1, a and b are ac impedance diagrams measured by a two-electrode method for the polyvinyl alcohol hydrogel film prepared in comparative example 1 and the nanocellulose/polyvinyl alcohol hydrogel film prepared in example 1, respectively. Obtaining the nano-cellulose/polyvinyl alcohol hydrogel film and the polyvinyl alcohol hydrogel film with the thickness of 6 mol.L by the fitting of Zview software-1The bulk resistance in KOH solution was 5.084 Ω and 10.52 Ω, respectively. The ionic conductivity (δ) of the hydrogel membrane can be calculated according to the following formula:
δ＝l/(Rb·S)
wherein l is the wet thickness of the hydrogel film, RbThe bulk resistance is given and S is the area of the hydrogel membrane. The ion conductivity of the nano-cellulose/polyvinyl alcohol hydrogel film is calculated to be 3.65 multiplied by 10-2S/m, the ionic conductivity of the polyvinyl alcohol hydrogel film is 1.26 multiplied by 10-2And (5) S/m. From this, it is known that the nanocellulose/polyvinyl alcohol hydrogel film has one time higher ion conductivity than the polyvinyl alcohol hydrogel film, and exhibits excellent ion conductivity.
Comparative example 2:
this comparative example is different from example 1 in that isopropanol was not added in step (6).
The ionic conductivity of the nano-cellulose/polyvinyl alcohol hydrogel film prepared in the comparative example is 1.65 multiplied by 10-2S/m (as shown in FIG. 1 c).
Example 2:
a preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane comprises the following steps:
(1) weighing 5g of lignocellulose subjected to lignin removal, adding 100g of concentrated sulfuric acid with the mass fraction of 48%, hydrolyzing for 2.5h under the condition of water bath at 45 ℃, simultaneously stirring by using a mechanical stirring paddle at 250rpm, and adding a large amount of ultrapure water after the hydrolysis is finished to stop the reaction, thereby obtaining a cellulose mixed solution subjected to sulfuric acid hydrolysis;
(2) placing the cellulose mixed solution subjected to sulfuric acid hydrolysis treatment obtained in the step (1) into a high-speed centrifuge for centrifugation for 7min, wherein the rotation speed of the centrifuge is 9000rpm, removing supernatant liquid after centrifugation, and repeatedly washing the precipitate after centrifugation with ultrapure water until the pH of the supernatant liquid is 6.5 to obtain a cellulose precipitate subjected to sulfuric acid modification treatment and washing;
(3) circularly shearing the washed cellulose precipitate obtained in the step (2) for 15 times in a high-pressure homogenizing cavity with the diameter of 200 microns and 87 microns and the pressure of 100MPa respectively to obtain a semitransparent cellulose nanofiber aqueous dispersion, and adjusting the solid content of the cellulose nanofiber aqueous dispersion to be 0.4%;
(4) weighing 7g of PVA solid powder, adding the PVA solid powder into 63g of the CNFs aqueous dispersion obtained in the step (3) to ensure that the mass fraction of PVA is 10 percent, and obtaining PVA/CNFs mixed liquor;
(5) heating the PVA/CNFs mixed solution obtained in the step (4) at 80 ℃ for 4h to completely dissolve PVA, then carrying out ultrasonic treatment for 15min at the ultrasonic intensity of 700W, uniformly mixing, and cooling to 45 ℃;
(6) and (3) weighing 20g of isopropanol, adding the 20g of isopropanol into the mixed solution obtained in the step (5), uniformly stirring, pouring 15g of mixed solution into a culture dish with the diameter of 6cm, keeping the culture dish in an open state all the time, freezing at the temperature of minus 40 ℃, then unfreezing at normal temperature, and circulating for 6 times to obtain the nano-cellulose/polyvinyl alcohol hydrogel membrane.
The ionic conductivity of the nanocellulose/polyvinyl alcohol hydrogel membrane prepared in this example was determined to be 3.43 × 10-2S/m。
Example 3:
a preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane comprises the following steps:
(1) weighing 5g of lignocellulose subjected to lignin removal, adding 100g of concentrated sulfuric acid with the mass fraction of 48%, hydrolyzing for 1.5h under the condition of 50 ℃ water bath, simultaneously stirring by using a mechanical stirring paddle at 300rpm, and adding a large amount of ultrapure water after the hydrolysis is finished to stop the reaction, thereby obtaining a cellulose mixed solution subjected to sulfuric acid hydrolysis;
(2) placing the cellulose mixed solution subjected to sulfuric acid hydrolysis treatment obtained in the step (1) into a high-speed centrifuge for centrifugation for 5min, wherein the rotation speed of the centrifuge is 10000rpm, removing supernatant liquid after centrifugation, and repeatedly washing the precipitate after centrifugation with ultrapure water until the pH of the supernatant liquid is 6.5 to obtain a cellulose precipitate subjected to sulfuric acid modification treatment and washing;
(3) circularly shearing the washed cellulose precipitate obtained in the step (2) for 20 times in a high-pressure homogenizing cavity with the diameter of 200 microns and 87 microns and the pressure of 100MPa respectively to obtain a semitransparent cellulose nanofiber aqueous dispersion, and adjusting the solid content of the cellulose nanofiber aqueous dispersion to be 0.5%;
(4) weighing 3g of PVA solid powder, adding into 47g of the CNFs aqueous dispersion obtained in the step (3) to ensure that the mass fraction of PVA is 6 percent, and obtaining PVA/CNFs mixed liquor;
(5) heating the PVA/CNFs mixed solution obtained in the step (4) at 95 ℃ for 3h to completely dissolve PVA, then carrying out ultrasonic treatment for 10min at the ultrasonic intensity of 800W, uniformly mixing, and cooling to 45 ℃;
(6) and (3) weighing 25g of isopropanol, adding the isopropanol into the mixed solution obtained in the step (5), uniformly stirring, pouring 10g of mixed solution into a culture dish with the diameter of 6cm, keeping the culture dish in an open state all the time, freezing at the temperature of minus 40 ℃, then unfreezing at normal temperature, and circulating for 5 times to obtain the nano-cellulose/polyvinyl alcohol hydrogel membrane.
The ionic conductivity of the nanocellulose/polyvinyl alcohol hydrogel membrane prepared in this example was determined to be 3.52 × 10-2S/m。
Claims (8)
1. A preparation method of a high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane is characterized by comprising the following steps:
(1) preparing nano-cellulose and dispersing the nano-cellulose in an aqueous solution to obtain a nano-cellulose solution;
(2) adding polyvinyl alcohol into the nano-cellulose solution obtained in the step (1), and uniformly dispersing to obtain a nano-cellulose/polyvinyl alcohol mixed solution;
(3) adding isopropanol into the nano-cellulose/polyvinyl alcohol mixed solution obtained in the step (2), uniformly stirring, pouring into a culture dish, and performing freezing-thawing cycle to obtain a nano-cellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity;
the culture dish is always kept open in the freezing-unfreezing process;
the addition amount of the isopropanol is 10-60% of the total mass of the mixed solution of the nano-cellulose and the polyvinyl alcohol.
2. The preparation method of the nanocellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity as claimed in claim 1, wherein the number of freezing-unfreezing cycles is 4-6, and the freezing temperature is-20 to-50 ℃.
3. The method for preparing a nanocellulose/polyvinylalcohol hydrogel film with high ionic conductivity as described in claim 1 or 2, wherein in the step (1), the nanocellulose is prepared as follows: adding the cellulose without the lignin into a sulfuric acid solution, stirring and hydrolyzing, adding ultrapure water after the hydrolysis is finished to stop the reaction, then carrying out centrifugal treatment, collecting a precipitation product, washing the precipitation product with the ultrapure water until the pH value of supernatant is 6-7 to obtain cellulose precipitate subjected to sulfuric acid hydrolysis treatment, and then carrying out high-pressure homogenizing and shearing on the cellulose precipitate to obtain the nano-cellulose.
4. The method for preparing the nanocellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity as claimed in claim 3, wherein in the method for preparing nanocellulose, the concentration of the sulfuric acid solution is 40wt% -50 wt%; during hydrolysis, the stirring speed is kept between 200rpm and 300rpm, the hydrolysis time is 1.5h to 2.5h, and the hydrolysis temperature is 40 ℃ to 50 ℃; keeping the rotating speed of the centrifugal machine to be 8000 rpm-10000 rpm during centrifugal treatment, and keeping the centrifugal treatment time to be 5 min-10 min; and (3) keeping the pressure at 90-120 MPa during high-pressure homogeneous shearing, and circularly shearing for 8-20 times.
5. The method for preparing the high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane as claimed in claim 3, wherein in the method for preparing nanocellulose, the cellulose is any one of wood cellulose, wheat straw cellulose, straw stalk cellulose, cotton cellulose, bamboo cellulose or hemp cellulose.
6. The method for preparing the high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane as claimed in claim 1 or 2, wherein the mass fraction of nanocellulose in the nanocellulose solution is 0.1% -1%.
7. The method for preparing the nanocellulose/polyvinyl alcohol hydrogel membrane with high ionic conductivity according to claim 1 or 2, wherein the mass fraction of polyvinyl alcohol in the nanocellulose/polyvinyl alcohol mixed solution is 1% -10%.
8. The preparation method of the high ionic conductivity nanocellulose/polyvinyl alcohol hydrogel membrane as claimed in claim 1 or 2, wherein the dispersion process in the step (2) is specifically ultrasonic at an ultrasonic intensity of 500W-800W for 10 min-20 min, then the ultrasonic solution is heated at 60-95 ℃ for 1-6 h, and then the temperature is reduced to 45-50 ℃.
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| CN111499998B (en) * | 2020-04-27 | 2022-06-03 | 广西大学 | Preparation method of cellulose polyvinyl alcohol composite membrane and super capacitor based on phase inversion |
| CN111554444A (en) * | 2020-05-09 | 2020-08-18 | 陕西科技大学 | PVA/carbonized hollow wood fiber composite material and preparation method and application thereof |
| CN112259832B (en) * | 2020-09-24 | 2021-09-28 | 江苏理工学院 | Preparation method and application of graphene-modified all-solid-state electrolysis |
| CN113150314B (en) * | 2021-01-26 | 2023-08-11 | 上海工程技术大学 | Composite gel electrolyte material with interpenetrating network porous structure, preparation and application thereof |
| CN114015085A (en) * | 2021-11-26 | 2022-02-08 | 燕山大学 | Preparation method of ion-conductive bioelectrode |
| CN115260530A (en) * | 2022-08-03 | 2022-11-01 | 华东理工大学 | Polyvinyl alcohol/lignin hydrogel with adjustable mechanical property and preparation method thereof |
| CN115646210A (en) * | 2022-11-17 | 2023-01-31 | 北京慧荣和科技有限公司 | Preparation method of bioaerosol sampling membrane |
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