CN114197088B

CN114197088B - Method for preparing nanofiber or nanoparticle by ultrasonic induction and film formed by nanomaterial

Info

Publication number: CN114197088B
Application number: CN202111319255.0A
Authority: CN
Inventors: 钟林新; 彭新文; 卓浩
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2021-11-09
Filing date: 2021-11-09
Publication date: 2023-04-21
Anticipated expiration: 2041-11-09
Also published as: CN114197088A

Abstract

The invention belongs to the technical field of self-assembled nano materials, and discloses a method for preparing nanofibers or nanospheres by ultrasonic induction and a film formed by the nano materials. The method comprises the following steps: and mixing sodium alginate and chitosan in a solvent, and performing ultrasonic treatment to obtain a nano material, wherein the nano material is nanofiber or nanoparticle. The invention drives self-assembly through the interaction between raw materials and prepares the supermolecule nanofiber or nanoparticle through an ultrasonic flow field. The nano material has stable structure. The method of the invention is simple. The nano material forms a film with high mechanical strength, good water resistance and humidity stimulus response through film formation. The film of the invention is used in the field of humidity response, in particular in the field of intelligent sensing and actuation. The film may also be used as a flexible substrate or as a plastic substitute.

Description

Method for preparing nanofiber or nanoparticle by ultrasonic induction and film formed by nanomaterial

Technical Field

The invention belongs to the technical field of self-assembled nano materials, and particularly relates to a preparation method of ultrasonic-induced nanofiber or nanoparticle and a film formed by the nanofiber or nanoparticle.

Background

Supermolecules in biological systems are of great interest due to their unique structure and function. Natural supermolecules always work in non-equilibrium states. Researchers have struggled to find kinetically controlled self-assembly that is not achieved through spontaneous thermodynamic processes. Despite some progress in recent years, the synthesis of kinetically controlled supramolecular nanofibers from biomacromolecules remains a great challenge due to the complexity of natural macromolecules. The prior natural polymer nanofiber is mostly prepared by adopting a top-down and electrostatic spinning method for the natural polymer, the preparation process is complex and greatly influenced by raw materials, and the structure of the material is difficult to regulate and control.

The invention patent CN201610856609.8 prepares the nano-fiber of chitosan and sodium alginate by a standing method, but the standing method has long time (6-120 hours) for forming the nano-fiber, and the morphology is difficult to regulate and control. Because a random three-dimensional network structure is easy to form under the condition of strong electrostatic acting force, the chitosan and the sodium alginate are taken as raw materials, and the nano-fiber and the nano-microsphere are difficult to prepare efficiently by a standing method.

Disclosure of Invention

In view of the above drawbacks and shortcomings of the prior art, a primary object of the present invention is to provide a method for preparing nanofibers or nanospheres by ultrasonic induction. The invention prepares the nanometer material with controllable morphology and stable dynamics through ultrasonic induction. The method is simple and efficient.

It is another object of the present invention to provide a thin film formed of the nanomaterial prepared by the above method. The film of the invention is a biodegradable film material. The invention utilizes the nanometer material (nanometer fiber or nanometer microsphere) prepared by the ultrasonic induced sodium alginate and the chitosan to form the film with high mechanical strength, good water resistance and humidity stimulation response.

The film of the invention is used in the field of humidity response, in particular in the field of intelligent sensing and actuation. The film may also be used as a flexible substrate.

The invention aims at realizing the following technical scheme:

a method for preparing nanofibers or nanospheres by ultrasonic induction, comprising the following steps:

1) Mixing sodium alginate and chitosan in a solvent, and performing ultrasonic treatment to obtain a nano material, wherein the nano material is nanofiber or nanoparticle;

when the mass ratio of the sodium alginate to the chitosan is 1:1, the ultrasonic treatment time is 1-8 hours, and the nano material is nano fiber;

when the mass ratio of the sodium alginate to the chitosan is 1:1, the ultrasonic treatment time is 10 seconds to 15 minutes, and the nano material is nano microsphere;

when the mass ratio of the sodium alginate to the chitosan is not 1:1, the nano material is nano microsphere (ellipsoidal at this time).

The mass ratio of the chitosan to the sodium alginate is 1:10-10:1.

The solvent is a solution formed by acid and water, and the acid is hydrochloric acid, acetic acid, oxalic acid, citric acid, dilute hydrochloric acid/sulfuric acid and the like.

The mass concentration of the acid solution is 0.02-15%.

The molecular weight of the chitosan is 5 kDa-500 kDa, and the deacetylation degree is 30% -99%; the molecular weight of the sodium alginate is 5kDa to 100kDa.

The ultrasonic frequency of the ultrasonic treatment is 20 kHz-50 kHz, and the power is 10-750W.

The specific steps of the step 1) are that sodium alginate and chitosan are respectively prepared into solutions to obtain sodium alginate solution and chitosan solution; mixing the sodium alginate solution with the chitosan solution, and performing ultrasonic treatment to obtain the nano material.

The sodium alginate solution refers to an aqueous solution of sodium alginate; the mass concentration of the sodium alginate solution is 0.01-10%;

the chitosan solution is an acid solution of chitosan, and is obtained by dissolving chitosan in the acid solution; the mass concentration of chitosan in the chitosan solution is 0.01-10%; the concentration of the acid solution is 0.1% -20%.

The mass ratio of the chitosan solution to the sodium alginate solution is 1:10-10:1.

The chitosan can be replaced by other polycations (polyallylamine hydrochloride, cationic starch and the like), and the sodium alginate can be replaced by other polyanions (sodium carboxymethyl cellulose, polyacrylic acid and the like).

At this time, the method for preparing nanofibers or nanospheres by ultrasonic induction comprises the following steps: mixing a cationic polymer and an anionic polymer compound in a solvent, and performing ultrasonic treatment to obtain a nano material, wherein the nano material is nanofiber or nanoparticle;

when the cationic polymer is a cationic polymer other than chitosan; the polycation polymer is more than one of polyallylamine hydrochloride and cationic starch;

when the anionic polymer is an anionic polymer other than sodium alginate; the anionic polymer is more than one of sodium carboxymethyl cellulose and polyacrylic acid.

The nanofiber or the nanoparticle is used for preparing a film.

A film is prepared from the nanofiber or the nanoparticle;

the preparation method of the film comprises the following steps: and (3) forming a film from the dispersion liquid of the nano fibers or the nano microspheres to obtain a film of the nano material.

The specific preparation method of the film comprises the following steps: mixing a cationic polymer and an anionic polymer in a solvent, and performing ultrasonic treatment to obtain a nanomaterial dispersion, wherein the nanomaterial is nanofiber or nanoparticle; then forming a film from the nano material dispersion liquid to obtain a film;

when the mass ratio of the cationic polymer to the anionic polymer is 1:1, the ultrasonic treatment time is 1-8 hours, and the nano material is nano fiber;

when the mass ratio of the cationic polymer to the anionic polymer is 1:1, the ultrasonic treatment time is 10 seconds to 15 minutes, and the nano material is nano microsphere;

when the mass ratio of the cationic polymer to the anionic polymer is not 1:1, the nano material is nano microsphere.

The cationic polymer is more than one of chitosan, polyallylamine hydrochloride and cationic starch;

the anionic polymer is one or more of sodium alginate, sodium carboxymethylcellulose and polyacrylic acid.

The film can be formed by suction filtration or air drying, or by coating or spin coating, and drying.

The concentration of the dispersion liquid is 0.01-10wt%.

When the cationic polymer is chitosan and the anionic polymer is sodium alginate, the specific preparation method of the nano material dispersion liquid comprises the following steps: preparing sodium alginate and chitosan into solutions respectively to obtain sodium alginate solution and chitosan solution; mixing the sodium alginate solution with the chitosan solution, and performing ultrasonic treatment to obtain the nano material.

The film of the invention has high mechanical strength, good water resistance and humidity stimulus response.

The films are useful in the field of humidity response, particularly in the field of smart sensing and actuation. The film may also be used as a flexible substrate.

The principle of the invention is as follows: the natural polysaccharide is used as a raw material, and the supermolecule nano-fiber and supermolecule microsphere are prepared by a dynamic control way of an ultrasonic flow field. Electrostatic interactions between natural polysaccharides (sodium alginate and chitosan) drive self-assembly. The ultrasonic energy promotes intermolecular aggregation, and the ultrasonic flow field overcomes unordered arrangement of molecules, so that parallel orientation of polysaccharide chains is induced, and formation of nano fibers and nano microspheres with stable dynamics is accelerated. Initially, irregular clusters are formed due to electrostatic interactions between the interwoven molecules. Electrostatic interactions drive microphase separation and then mass aggregation occurs immediately after mixing and complexation. In general, large scale aggregation will convert to spherical micelles after thermodynamic equilibrium. Such spherical micelles may minimize the gibbs free energy of the overall system, stabilizing the system. In sharp contrast to the thermodynamically controlled pathway, parallel oriented molecules can form metastable structures after sonication, with energy in the minimum of a local energy landscape. Thus, the assembled supramolecules can remain stable for a longer period of time. Finally, after reestablishing electrostatic interactions (fission/fusion processes), chain rearrangement and chain exchange processes, the transition from nanofibers to spherical micelles can be achieved over time. Therefore, we achieved kinetic controlled self-assembly of polysaccharide supramolecules by overcoming the disordered aggregation of the molecules. The supermolecular structure can be accurately regulated and controlled through experimental conditions, and the invention realizes the self-assembly of the supermolecular fiber and the supermolecular microsphere. And through simple filtration, the supermolecule nano fiber and the supermolecule microsphere can form a film with high mechanical strength and water resistance, and can replace a plastic film. In addition, the supramolecular films exhibit a humidity stimulus response.

The preparation method of the invention and the obtained nano-fiber and nano-microsphere have the following advantages and beneficial effects:

(1) The prepared raw materials are derived from natural polysaccharide, so that the cost is low, and the raw materials are green and renewable;

(2) The preparation method is simple and has short time consumption;

(3) The nanofiber prepared by the invention has stable structure and can be stably stored for 1-3 months;

(4) The nano-morphology prepared by the method is controllable, can realize controllable preparation of fibers and microspheres, and is beneficial to application in various fields;

(5) The chitosan/sodium alginate film prepared by the invention has excellent mechanical property and water resistance, and can be used for plastic substitution;

(6) The chitosan/sodium alginate film prepared by the invention has humidity response behavior and quick response, and can be applied to the braking field.

Drawings

FIG. 1 is an aqueous solution of sodium alginate (left), acetic acid solution of chitosan (middle) and dispersion of sodium alginate/chitosan nanofibers (right) prepared in example 1;

FIG. 2 is an AFM plot of the sample prepared in example 1 at various ultrasonic times (10 seconds, 0.5 hours, 1 hour, and 2 hours); a, b, c, d correspond to figures of 10 seconds, 0.5 hours, 1 hour, 2 hours of ultrasound, respectively;

FIG. 3 is an electron microscope (a) and atomic force microscope (b) of the sodium alginate/chitosan nanoparticle prepared in example 2;

FIG. 4 is an atomic force micrograph of sodium alginate/chitosan nanoparticle prepared in example 3; a is mixed with the chitosan solution and the sodium alginate solution according to the ratio of 2:1, and b is mixed with the chitosan solution and the sodium alginate solution according to the ratio of 1:2;

FIG. 5 is a graph showing the effect of water resistance of the sodium alginate/chitosan nanofiber composite membrane prepared in example 4; a corresponds to the sodium alginate/chitosan nanofiber composite membrane prepared in the embodiment 4, and b corresponds to a film formed by chitosan;

FIG. 6 is a graph showing the humidity response of the sodium alginate/chitosan nanofiber composite membrane prepared in example 4 and the effect of the composite membrane in brake application;

FIG. 7 is a graph showing the mechanical properties of the sodium alginate/chitosan film prepared in example 4; 1-1 corresponds to the film prepared in example 4, and 1-2 and 2-1 correspond to the films prepared by mixing the chitosan solution and the sodium alginate solution in example 3 according to the mass ratio of 1:2 and 2:1, respectively.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.

Example 1

(1) Sodium alginate (50 kDa) is dissolved in water to obtain sodium alginate solution with the mass fraction of 5%; chitosan (50 kDa, degree of deacetylation 90%) was dissolved in acetic acid solution with a mass fraction of 1wt% to obtain chitosan solution with a mass fraction of 5%;

(2) Mixing the sodium alginate solution and the chitosan solution in the step (1) according to the mass ratio of 1:1, and carrying out ultrasonic treatment for 2 hours (500W, 20 kHz) to obtain a dispersion liquid of chitosan/sodium alginate nanofibers;

(3) And (3) performing film forming (suction filtration or air drying treatment) on the dispersion liquid of the chitosan/sodium alginate nanofiber obtained in the step (2) to obtain the chitosan/sodium alginate film.

Fig. 1 shows an aqueous solution of sodium alginate (left), an acetic acid solution of chitosan (middle) and a dispersion of sodium alginate/chitosan nanofibers (right) prepared in example 1. FIG. 2 is an AFM plot of the sample prepared in example 1 at various ultrasonic times (10 seconds, 0.5 hours, 1 hour, and 2 hours); a, b, c, d correspond to figures of 10 seconds, 0.5 hours, 1 hour, 2 hours of ultrasound, respectively. FIG. 2 is a process of forming the supramolecular fiber of example 1. The ultrasonic action is an important factor for promoting molecular movement and reconstructing a gel network, and a sound field and a flow field can orient chitosan and sodium alginate molecules. The ultrasonic flow field and sound field are beneficial to the formation of nanofibers. After 0.5 hours of sonication, the randomly formed gel network (10 seconds of sonication, a in fig. 2) was stretched by the flow field into a prolate structure (b in fig. 2) with some nanofibers present. The formation of nanofibers can be attributed to the orientation and attachment of chitosan and sodium alginate molecules. The formation of elongated clusters is related to the charge balancing process and shearing action of the flow field. The reorganization and orientation of the random gel network is energy-demanding and requires a period of time under ultrasound to form nanofibers. After 1h of sonication (c in fig. 2), more of the gel network was converted into supramolecular nanofibers. After 2h of sonication, separated nanofibers can be formed (d in fig. 2).

Example 2

(1) Sodium alginate (50 kDa) is dissolved in water to obtain sodium alginate solution with the mass fraction of 2%; chitosan (50 kDa, degree of deacetylation 95%) was dissolved in 1wt% acetic acid to obtain a 2% mass fraction chitosan solution;

(2) Mixing the sodium alginate and chitosan solution in the step (1) according to the mass ratio of 1:1, and carrying out ultrasonic treatment for 10 minutes (500W, 20 kHz) to obtain a dispersion liquid of dispersed spherical microgel;

(3) And (3) carrying out suction filtration or air drying treatment on the dispersion liquid of the chitosan/sodium alginate spherical microgel obtained in the step (2) to obtain the chitosan/sodium alginate film.

FIG. 3 is an electron micrograph (a) and an atomic force micrograph (b) of the spherical microgel obtained in example 2, which is different from the supramolecular fiber in example 1, the formation of spherical micelles is a thermodynamically controlled spontaneous process, and the ultrasonic treatment accelerates this process.

In this example, spherical micelles were formed, and the time for the ultrasonic treatment was 1 hour, 2 hours, and 8 hours, and the fibers were changed to fiber state with the increase in time.

Example 3

(1) Sodium alginate (75 kDa) is dissolved in water to obtain sodium alginate aqueous solution with mass fraction of 2%; chitosan (100 kDa, degree of deacetylation 85%) was dissolved in 1wt% acetic acid to obtain chitosan solution;

(2) Mixing the chitosan solution and the sodium alginate solution in the step (1) according to the mass ratio of 2:1 and 1:2 respectively, and carrying out ultrasonic field orientation treatment (750W, 20 kHz) for 1 hour to obtain a dispersion liquid with the mass fraction of chitosan/sodium alginate nano microspheres;

(3) And (3) placing the dispersion liquid of the chitosan/sodium alginate nanoparticle obtained in the step (2) into a plastic box (45 mm multiplied by 60mm multiplied by 18 mm) for airing to obtain the chitosan/sodium alginate film.

FIG. 4 is an atomic force micrograph of the supramolecular spheroids obtained in example 3 (the microspheres in step (2)) and the resulting ellipsoidal microgel differs from the microgel in example 3 in that the molecules are stretched by a flow field to exhibit a prolate structure, wherein the excess chitosan makes the surface of the 2-1 sample (corresponding to the mixing of the chitosan solution and sodium alginate solution in a mass ratio of 2:1) positively charged (FIG. 4 a) and the excess sodium alginate makes the surface of the 1-2 sample (chitosan solution and sodium alginate solution respectively mixed in a mass ratio of 1:2) (FIG. 4 b) negatively charged, and the strong charge repulsion prevents the growth of the two samples in the axial direction, so that the final structure of the two samples is ellipsoidal.

Example 4

(1) Sodium alginate (100 kDa) is dissolved in water to obtain sodium alginate aqueous solution with the mass fraction of 1%; chitosan (200 kDa, degree of deacetylation greater than 70%) was dissolved in 1wt% hydrochloric acid to obtain chitosan solution;

(2) Mixing the sodium alginate aqueous solution and the chitosan solution in the step (1) according to the mass ratio of 1:1, and carrying out ultrasonic field orientation treatment for 1 hour (500W, 20 kHz) to obtain a dispersion liquid with the mass fraction of chitosan/sodium alginate nanofibers;

(3) And (3) carrying out suction filtration or air drying treatment on the dispersion liquid of the chitosan/sodium alginate nanofiber obtained in the step (2) to obtain the chitosan/sodium alginate film.

The water resistance test effect diagram of the chitosan/sodium alginate film obtained in the embodiment is shown in fig. 5; a corresponds to the sodium alginate/chitosan nanofiber composite membrane prepared in example 4, and b corresponds to the film formed by chitosan. The chitosan/sodium alginate film has excellent water resistance. The traditional biomass-based film has the disadvantages that the biomass molecules have a large number of oxygen-containing functional groups, and hydrogen bonds are easy to form among the molecules in the aqueous solution to permeate and swell, so that the performance of the material is greatly reduced. Unlike conventional biomass-based films, electrostatic interactions result in greater intermolecular binding forces, water molecules are less prone to break electrostatic interactions, and it takes a significant amount of time to reestablish strong electrostatic interactions between carboxylic acids and amino groups. Water molecules hardly penetrate into the inside of the fiber. Only the inter-fibers are permeable to water molecules. The strong electrostatic interaction makes the chitosan/sodium alginate film relatively stable in water. The material also shows humidity response behavior, when the chitosan/sodium alginate film is placed under infrared radiation, the upper surface is contracted due to the escape of water molecules among fibers on the upper surface, so that the film is bent upwards, and after the infrared lamp is removed, the film can absorb water vapor in the air to restore to the original state (figure 6), so that the chitosan/sodium alginate film can be applied to the fields of intelligent sensing and actuation. Meanwhile, the chitosan/sodium alginate film has higher strength. The tensile strength of the film can reach 85MPa (strength per unit area) (figure 7), and the film has excellent ductility (tensile strain can reach 27.2%), and the performance of the film can be comparable with other high-performance biomass-based films such as nanocellulose and the like. The high strength and excellent water resistance enable the chitosan/sodium alginate film to be used as a plastic substitute, a flexible substrate, a multifunctional actuator and the like.

Fig. 6 is a graph showing the humidity response of the sodium alginate/chitosan nanofiber composite membrane prepared in example 4 and the effect of the composite membrane in brake application.

In the method of the invention, the chitosan can be replaced by other polycations (polyallylamine hydrochloride, cationic starch and the like), and the sodium alginate can be replaced by other polyanions (sodium carboxymethyl cellulose, polyacrylic acid and the like).

when the anionic polymer is an anionic polymer other than sodium alginate; the anionic polymer is more than one of sodium carboxymethyl cellulose and polyacrylic acid;

when the mole ratio of the cations in the cationic polymer to the anions in the anionic polymer is 1:1, the ultrasonic treatment time is 1-8 hours, and the nano material is nano fiber;

when the mole ratio of cations in the cationic polymer to anions in the anionic polymer is 1:1, the ultrasonic treatment time is 10 seconds to 15 minutes, and the nano material is nano microsphere;

when the molar ratio of the cations in the cationic polymer to the anions in the anionic polymer is not 1:1, the nano material is nano microsphere.

The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the scope of the present invention.

Claims

1. A method for preparing nanofibers or nanospheres or ellipsoids by ultrasonic induction is characterized in that: the method comprises the following steps:

mixing sodium alginate and chitosan in a solvent, and performing ultrasonic treatment to obtain a nano material, wherein the nano material is nanofiber or nanoparticle or ellipsoid;

when the mass ratio of the sodium alginate to the chitosan is 1:1, the ultrasonic treatment time is 1-8 hours, the ultrasonic frequency is 20 kHz-50 kHz, the power is 10-750W, and the nano material is nano fiber;

when the mass ratio of the sodium alginate to the chitosan is 1:1, the ultrasonic treatment time is 10 seconds to 15 minutes, the ultrasonic frequency is 20kHz to 50kHz, the power is 10 to 750W, and the nano material is nano microsphere;

when the mass ratio of the sodium alginate to the chitosan is 2:1 or 1:2, the ultrasonic treatment time is 1 hour, the ultrasonic frequency is 20kHz, the power is 750W, and the nano material is ellipsoid;

the solvent is a solution formed by acid and water, and the acid is acetic acid, oxalic acid, citric acid, dilute hydrochloric acid or sulfuric acid;

the mass concentration of the acid solution is 0.02-15%;

the molecular weight of the chitosan is 5 kDa-500 kDa; the molecular weight of the sodium alginate is 5 kDa-100 kDa.

2. The method for preparing nanofibers or nanospheres or ellipsoids by ultrasonic induction according to claim 1, wherein:

the mixing specifically refers to dissolving sodium alginate in water to obtain sodium alginate solution; dissolving chitosan in an acid solution to obtain a chitosan solution; the sodium alginate solution was then mixed with the chitosan solution.

3. The method for preparing nanofibers or nanospheres or ellipsoids by ultrasonic induction according to claim 2, wherein: the concentration of the acid solution in the chitosan solution is 0.1% -20%.

4. A method for preparing nanofibers or nanospheres by ultrasonic induction is characterized in that:

a mixture of polyallylamine hydrochloride and cationic starch is used as a cationic polymer;

a mixture of sodium carboxymethyl cellulose and polyacrylic acid is used as an anionic polymer;

mixing the cationic polymer and the anionic polymer in a solvent, and performing ultrasonic treatment to obtain a nano material, wherein the nano material is nanofiber or nanoparticle;

when the mass ratio of the cationic polymer to the anionic polymer is 1:1, the ultrasonic treatment time is 10 seconds to 15 minutes, and the nano material is nano microsphere.

5. A nanomaterial obtained by the method of any of claims 1-4, characterized in that: the nanometer material is nanometer fiber or nanometer microsphere.

6. A film, characterized in that: is prepared by film forming of nano materials; the nanomaterial is as defined in claim 5.

7. The film according to claim 6, wherein: the preparation method comprises the following steps: and in a solvent, carrying out film forming treatment on the nano material dispersion liquid obtained through ultrasonic treatment to obtain a film.

8. The use of a film according to any one of claims 6 to 7, characterized in that: the films are useful in the fields of plastic substitutes, flexible substrates, and humidity response.

9. The use according to claim 8, characterized in that: the film is used in the field of intelligent humidity response sensing and/or braking.