CN109337130B - Preparation of polysaccharide polyelectrolyte self-supporting film and self-supporting film obtained by preparation - Google Patents

Preparation of polysaccharide polyelectrolyte self-supporting film and self-supporting film obtained by preparation Download PDF

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CN109337130B
CN109337130B CN201811143793.7A CN201811143793A CN109337130B CN 109337130 B CN109337130 B CN 109337130B CN 201811143793 A CN201811143793 A CN 201811143793A CN 109337130 B CN109337130 B CN 109337130B
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film
molecular weight
polysaccharide polyelectrolyte
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polyelectrolyte
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CN109337130A (en
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隋坤艳
崔慧琳
范汶鑫
潘娜
谭业强
张文强
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Qingdao University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/246—Intercrosslinking of at least two polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
    • C08J2305/04—Alginic acid; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
    • C08J2305/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C08J2405/04—Alginic acid; Derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C08J2405/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof

Abstract

The invention discloses preparation of a polysaccharide polyelectrolyte self-supporting film and the obtained self-supporting film, wherein a low molecular weight polysaccharide polyelectrolyte spread film with a certain concentration is used as a template to be immersed into a high molecular weight polysaccharide polyelectrolyte with a certain concentration, and the polysaccharide polyelectrolyte self-supporting film can be formed through spontaneous interfacial diffusion reaction; meanwhile, the obtained film has a gradient porous structure, and by combining the properties of two polyelectrolytes, different parts of the film are subjected to complexation and conformational change at high temperature, acid and salt to cause the film to generate complex deformation, so that the disadvantages of toxicity and incompatibility of the traditional stimulus response material synthetic polymer are solved, and meanwhile, the strong electrostatic interaction between the materials endows the film with extremely high mechanical performance. The preparation method is simple, low in cost, time-saving and suitable for large-scale production.

Description

Preparation of polysaccharide polyelectrolyte self-supporting film and self-supporting film obtained by preparation
Technical Field
The present invention relates to membranes, particularly to polysaccharide polyelectrolyte membranes, and in particular to the preparation of polysaccharide polyelectrolyte self-supporting membranes and the resulting self-supporting membranes.
Background
The natural polysaccharide polyelectrolyte is obtained from nature, has the characteristics of biocompatibility, degradability, environmental friendliness and the like, and can be used for preparing films.
However, in the prior art, a common method for preparing a film material by using polyelectrolyte is a layer-by-layer self-assembly method (LBL), which is a process of treating a template to make the template have positive (negative) charges, then immersing the template into a solution with negative (positive) charges, washing and alternately performing the steps, and removing the template to obtain a film with controllable structure and performance, easy endowment of various unique functions and accordance with the use requirements of end products.
However, this method is time-consuming, complicated in steps, high in cost, and the formed film is poor in self-supporting property, and thus mass production is impossible.
Disclosure of Invention
In order to overcome the problems, the inventor of the invention makes a keen study to provide a preparation method of a polysaccharide polyelectrolyte self-supporting film, which has simple process and low preparation cost and is suitable for large-scale production; meanwhile, the prepared self-supporting film has excellent mechanical property, can be quickly deformed under the regulation and control of temperature, ionic strength and pH value, and lays a foundation for the environment-friendly property and biocompatibility of the polysaccharide polyelectrolyte in the fields of biological medicine, tissue engineering and the like.
One of the purposes of the invention is to provide a preparation method of a polysaccharide polyelectrolyte self-supporting film, which is embodied in the following aspects:
(1) a method for preparing a polysaccharide polyelectrolyte self-supporting film, wherein the method comprises the following steps:
step 1, adding low molecular weight polysaccharide polyelectrolyte into water to obtain a solution A;
step 2, adding high molecular weight polysaccharide polyelectrolyte into water to obtain solution B;
step 3, placing the solution A obtained in the step 1 into a container (such as a culture dish), and then immersing the container into the solution B for reaction to form the self-supporting film; wherein the content of the first and second substances,
in step 1, the low molecular weight polysaccharide polyelectrolyte is selected from chitosan oligosaccharide, sodium alginate oligosaccharide or carrageenan oligosaccharide;
in step 2, the high molecular weight polysaccharide polyelectrolyte is selected from chitosan, sodium alginate or carrageenan.
(2) The production method according to the above (1), wherein the low-molecular-weight polysaccharide polyelectrolyte and the high-molecular-weight polysaccharide polyelectrolyte have opposite charges.
(3) The production method according to the above (1) or (2), wherein, in the step 1,
the molecular weight of the low molecular weight polysaccharide polyelectrolyte is 2000-10000 Da, preferably 2000-6000 Da; and/or
In the step 2, the molecular weight of the high molecular weight polysaccharide polyelectrolyte is 100000-800000 Da, preferably 300000-700000 Da, and more preferably 400000-600000 Da.
(4) The production method according to one of the above (1) to (3), wherein,
in the step 1, in the solution A, the mass percentage concentration of the low molecular weight polysaccharide polyelectrolyte is 30-60%, preferably 40-50%; and/or
In the step 2, the mass percentage concentration of the high molecular weight polysaccharide polyelectrolyte in the solution B is 0.5-5%, preferably 0.5-3%.
(5) The production method according to one of the above (1) to (4), wherein in the step 3, the reaction is performed for 1 to 20min, preferably for 5 to 10 min.
(6) The production method according to one of the above (1) to (5), wherein, in the step 2, NaCl is optionally added, preferably, 0.1 to 1M NaCl is optionally added, and more preferably, 0.2 to 0.5M NaCl is optionally added.
(7) The production process according to one of the above (1) to (6), wherein, in the step 1, the pH of the solution A is optionally adjusted to 2 to 6, preferably, the pH of the solution A is optionally adjusted to 3.5 to 5.
(8) A polysaccharide polyelectrolyte self-supporting film, preferably obtained by the production method as described in one of the above (1) to (7), more preferably the film has a thickness of 0.2mm to 2 mm.
(9) The polysaccharide polyelectrolyte self-supporting film according to the above (8), wherein the film has a gradient structure, one side of the film has a loose structure, and the other side of the film has a dense structure.
(10) The polysaccharide polyelectrolyte self-supporting film according to the above (8) or (9), wherein the film has an external stimulus responsiveness, and preferably, the external stimulus includes temperature, ionic strength and pH.
Drawings
FIG. 1 shows an electron micrograph of a sodium alginate/chitosan oligosaccharide thin film obtained in example 1 (mainly showing the entire cross section of the thin film, magnification: 400 times);
FIG. 2 is an electron micrograph of a sodium alginate/chitosan oligosaccharide capsule prepared in example 1 (mainly showing a cross section of the membrane on the side close to the contact, magnification: 10000 times);
FIG. 3 is a second electron micrograph of the sodium alginate/chitosan oligosaccharide capsule prepared in example 1 (mainly showing a cross section of the side of the film away from the contact, magnification: 10000 times);
FIG. 4 is a schematic view of the gradient pores of the sodium alginate/chitosan oligosaccharide thin film prepared in example 1;
FIG. 5 is an IR spectrum of chitosan oligosaccharide, sodium alginate and the sodium alginate/chitosan oligosaccharide film prepared in example 1;
FIG. 6 shows the tensile properties of the sodium alginate/chitosan oligosaccharide film prepared in example 1;
FIG. 7 is the X-ray photoelectron spectroscopy detection of the sodium alginate/chitosan oligosaccharide film prepared in example 1;
FIG. 8 is a diagram showing the deformation process of the sodium alginate/chitosan oligosaccharide film prepared in example 1 at different temperatures;
FIG. 9 shows the deformation process of the sodium alginate/chitosan oligosaccharide film prepared in example 1 in NaCl;
FIG. 9-1 is a partial enlarged view showing FIG. 9;
FIG. 10 shows the deformation process of the sodium alginate/chitosan oligosaccharide film prepared in example 1 in HCl;
FIG. 11 shows the results of the deformation recovery test of the sodium alginate/chitosan oligosaccharide film obtained in example 1;
FIGS. 12a to 12h show the 2D and 3D shapes of the sodium alginate/chitosan oligosaccharide film prepared in example 1.
Detailed Description
The present invention will be described in further detail below with reference to examples and experimental examples. The features and advantages of the present invention will become more apparent from the description.
The invention provides a preparation method of a polysaccharide polyelectrolyte self-supporting film, which comprises the following steps:
step 1, adding low molecular weight polysaccharide polyelectrolyte into water to obtain a solution A;
step 2, adding high molecular weight polysaccharide polyelectrolyte into water to obtain solution B;
and 3, placing the solution A obtained in the step 1 into a container (such as a culture dish), and then immersing the container into the solution B for reaction to form the self-supporting film.
According to a preferred embodiment of the invention, in step 1 and step 2, the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte are oppositely charged.
In a further preferred embodiment, in step 1, the low molecular weight polysaccharide polyelectrolyte is selected from chitosan oligosaccharide, sodium alginate oligosaccharide or carrageenan oligosaccharide;
in a still further preferred embodiment, in step 2, the high molecular weight polysaccharide polyelectrolyte is selected from chitosan, sodium alginate or carrageenan.
Wherein, the electrostatic interaction between low molecular weight polysaccharide polyelectrolyte and high molecular weight polysaccharide polyelectrolyte (with opposite positive and negative charges) is utilized to complex the two to form a polyelectrolyte complex membrane; then, under the driving action of osmotic pressure, the low molecular weight polysaccharide polyelectrolyte (namely the lower side of the film) can spontaneously penetrate through the complexing film to continuously diffuse towards the high molecular weight polysaccharide polyelectrolyte (namely the upper side of the film) and then is complexed with the high molecular weight polysaccharide polyelectrolyte again to form a new complexing film. The solution is spontaneously and continuously repeated with the complexing-diffusing-re-complexing process, so that films with different thicknesses can be obtained, and the thickness of the film can be controlled by controlling the reaction time. According to a preferred embodiment of the present invention, in step 1, the low molecular weight polysaccharide polyelectrolyte has a molecular weight of 2000 to 10000 Da.
In a further preferred embodiment, in step 1, the low molecular weight polysaccharide polyelectrolyte has a molecular weight of 2000 to 6000 Da.
When the number average molecular weight of the low molecular weight polysaccharide polyelectrolyte is less than 2000Da, the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte have complexation reaction, and the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte have few binding sites and are not entangled enough to support a film, and finally, compound precipitate particles are formed. Meanwhile, if the number average molecular weight of the low molecular weight polysaccharide polyelectrolyte is more than 10000Da, a complexing layer structure formed by electrostatic complexing reaction of the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte is compact, the low molecular weight polysaccharide cannot pass through, the diffusion process is prevented, and finally a self-supporting film cannot be formed.
According to a preferred embodiment of the present invention, in step 2, the molecular weight of the high molecular weight polysaccharide polyelectrolyte is 100000-800000 Da.
In a further preferred embodiment, in step 2, the high molecular weight polysaccharide polyelectrolyte has a molecular weight of 300000 to 700000 Da.
In a further preferred embodiment, in step 2, the high molecular weight polysaccharide polyelectrolyte has a molecular weight of 400000 to 600000 Da.
If the molecular weight of the high molecular weight polysaccharide polyelectrolyte exceeds the range, the polyelectrolyte film formed by the complexation reaction of the high molecular weight polysaccharide polyelectrolyte and the low molecular weight polysaccharide polyelectrolyte is too compact, which may cause that the low molecular weight polysaccharide polyelectrolyte molecules cannot penetrate through the polyelectrolyte film, thereby hindering the further diffusion of the low molecular weight polysaccharide polyelectrolyte, and the complexation-diffusion-re-complexation process cannot be carried out, and finally, only one layer of film with a compact structure can be obtained, and the film with insufficient thickness can not be supported.
According to a preferred embodiment of the present invention, in the solution a in step 1, the concentration of the low-molecular weight polysaccharide polyelectrolyte is 30 to 60% by mass.
In a further preferred embodiment, in the solution a in step 1, the concentration of the low-molecular-weight polysaccharide polyelectrolyte is 40 to 50% by mass.
According to a preferred embodiment of the present invention, in the solution B in step 2, the concentration of the high molecular weight polysaccharide polyelectrolyte is 0.5 to 5% by mass.
In a further preferred embodiment, in the solution B in the step 2, the concentration of the high molecular weight polysaccharide polyelectrolyte is 0.5 to 3% by mass.
Wherein the low molecular weight polysaccharide polyelectrolyte is controlled at a higher concentration, and the high molecular weight polysaccharide polyelectrolyte is controlled at a relatively low concentration, so that the low molecular weight polysaccharide polyelectrolyte diffuses into the high molecular weight polysaccharide polyelectrolyte under osmotic pressure due to the difference in ion concentration, and then the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte are combined by electrostatic action to form a membrane.
According to a preferred embodiment of the present invention, in step 3, the reaction is performed for 1 to 20 min.
In a further preferred embodiment, in step 3, the reaction is carried out for 5 to 10 min.
Wherein the reaction time is controlled to control the thickness of the film, so that the film with controllable thickness can be obtained. Meanwhile, when the reaction time is too short, a self-supporting structure is not easily formed, and when the reaction time is too long, the film is too thick and the response to the outside is not obvious.
According to a preferred embodiment of the invention, in step 2, NaCl is optionally added.
In a further preferred embodiment, in step 2, optionally 0.1 to 1M NaCl is added.
In a further preferred embodiment, in step 2, optionally 0.2 to 0.5M NaCl is added.
The sodium chloride is used as a micromolecular electrolyte, can shield the charges of the low-molecular-weight polysaccharide polyelectrolyte and the high-molecular-weight polysaccharide polyelectrolyte, and weakens the electrostatic effect between the low-molecular-weight polysaccharide polyelectrolyte and the high-molecular-weight polysaccharide polyelectrolyte, so that the film structure is looser, a structure with larger pore diameter is obtained, and the film with looser structure is beneficial to the application of oil absorption. In addition, after the sodium chloride is added, part of polysaccharide polyelectrolyte is temporarily shielded from charges, and some binding sites capable of reacting with organic dyes are stored/reserved, so that the obtained film has excellent adsorption performance on the organic dyes.
According to a preferred embodiment of the present invention, in step 1, the pH of solution A is optionally adjusted to 2-6.
Wherein, because low molecular weight polysaccharide polyelectrolyte and high molecular weight polysaccharide polyelectrolyte all have certain acidity coefficient pKa, through the pH of adjusting reaction system, can change charge density, and then influence the static complexation degree between low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte. Specifically, the farther from the acidity coefficient pKa, the greater the charge density, the stronger the binding force between the low-molecular-weight polysaccharide polyelectrolyte and the high-molecular-weight polysaccharide polyelectrolyte, and the tighter the structure of the resulting complex film; conversely, the closer to the acidity coefficient pKa, the smaller the charge density, the weaker the binding force between the low-molecular-weight polysaccharide polyelectrolyte and the high-molecular-weight polysaccharide polyelectrolyte, and the looser the structure of the resulting complex film.
In a further preferred embodiment, in step 1, the pH of solution A is optionally adjusted to 3.5 to 5.
Therefore, under the acidic pH environment, a film with a loose structure can be obtained, and the film is endowed with more excellent adsorption performance.
In another aspect, the invention provides a polysaccharide polyelectrolyte self-supporting film obtained by the preparation method of the first aspect of the invention.
According to a preferred embodiment of the present invention, the film has a thickness of 0.2mm to 2 mm.
According to a preferred embodiment of the invention, the film exhibits a gradient structure.
In a further preferred embodiment, the membrane is loose on one side and dense on the other side.
Wherein, the structure of one side close to the solution A is compact, and the structure of one side close to the solution B is loose. Since the diffusion direction is the diffusion of the low molecular weight polysaccharide polyelectrolyte in the solution a to the high molecular weight polysaccharide polyelectrolyte in the solution B (i.e., from bottom to top), the film becomes loose from dense and the pore size gradually increases along the diffusion direction.
According to a preferred embodiment of the invention, the membrane is responsive to an external stimulus.
In a further preferred embodiment, the external stimulus comprises temperature, ionic strength and pH.
The obtained self-supporting film can respond to the change of the external environment and generate deformation. The reason is that: (1) the self-supporting film prepared has an obvious gradient structure, one side of the self-supporting film has a loose structure, and the other side of the self-supporting film has a compact structure, when the two sides respond to external stimuli differently, the two sides can generate differential swelling or contraction, and the self-supporting film can become a potential deformation material; (2) the prepared film is polysaccharide polyelectrolyte which has positive charges and negative charges, and the positive charges and the negative charges have electrostatic interaction or generate electrostatic interaction, even if the positive charges and the negative charges are subjected to complexation reaction, a molecular chain still has a chain segment which does not participate in the reaction, and the complexation part and the uncomplexed part can generate different conformational changes under external stimulation, which is a potential reason for the film as a deformation material; (3) the temperature has certain influence on the complex structure of the polysaccharide polyelectrolyte film, when the temperature rises, the complex structure of the film can be increased, the increase of the complex can inevitably lead to dehydration shrinkage, and the difference of the shrinkage degree of the two sides leads to the deformation of the film; (4) the film can be changed in conformation in salt, NaCl can affect the complex part and the uncomplexed part of the film, and on one hand, NaCl can shield the molecular chain of the uncomplexed part to change the chain from straightening to curling, the film shrinks and drains water, and the difference of the two-side shrinkage causes the deformation; on the other hand, NaCl can cause the complex part to be subjected to crosslinking at a higher temperature, and the difference of the swelling properties of the films on the two sides causes the second heavy deformation; (5) likewise, the change in film conformation in acid and the difference in the rate and extent of change of the two layers constitute the nature of the deformation.
The invention has the advantages that:
(1) the preparation method is simple, the preparation of the self-supporting film can be completed at normal temperature and normal pressure, the preparation process is carried out at normal temperature and normal pressure, the process parameters are easy to control, and the production efficiency is high;
(2) the preparation time of the invention is extremely short, the film can be formed only a few minutes, even only 1min, and the thickness of the film is gradually increased along with the increase of time, so that the thickness of the visible film can be arbitrarily adjusted and controlled as required;
(3) the raw materials adopted by the invention are pure natural and degradable polysaccharide polyelectrolytes which are all nontoxic and harmless, so that the polysaccharide polyelectrolytes can be applied to the aspects of biological medicines, tissue engineering and the like;
(4) the film obtained by the preparation method has high mechanical strength, and can prevent the material from being damaged in the deformation field;
(5) the film obtained by the preparation method provided by the invention deforms under external conditions such as high temperature, ionic strength and pH, the deformation time is extremely short, and the film can realize 2D and 3D complex shapes by designing the film.
Detailed Description
The present invention will be described in further detail below with reference to examples and experimental examples. The features and advantages of the present invention will become more apparent from the description.
Examples
The invention is further described below by means of specific examples. However, these examples are only illustrative and do not limit the scope of the present invention.
Example 1
According to the mass ratio of 20:1, respectively weighing chitosan oligosaccharide with molecular weight of 2000Da and sodium alginate with molecular weight of 30 ten thousand Da for later use;
dissolving the chitosan oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 40%;
dissolving the sodium alginate in deionized water to obtain a solution B with the mass fraction ratio concentration of 1%;
placing the solution A into a culture dish, then immersing the culture dish into the solution B, and reacting for 6min to form a self-supporting film.
The thickness measurement of the obtained film was carried out, and the thickness was found to be about 0.5 mm.
The obtained thin film was examined by an electron microscope, and the results are shown in FIGS. 1 to 3, which show that:
(1) in fig. 1, the whole cross section of the film is shown, the magnification is 10 times, and specifically, it can be seen that the prepared chitosan oligosaccharide/sodium alginate capsule has a gradient structure with gradually reduced pore size along the diffusion direction, and the lower side is compact and the upper side is loose. The upper side hole is about 80 μm and the lower side hole is about 50nm according to statistics;
(2) FIG. 2 primarily shows the underlying structure of the gradient film, i.e., near the contact side;
(3) FIG. 3 shows mainly the superstructure of the gradient film, i.e. away from the contact side;
the contact side is the interface of the solution A and the solution B immediately after the solution A enters the solution B;
(4) FIG. 4 shows mainly the schematic distribution of the holes forming the gradient, i.e. the side just in contact is structurally dense, the holes are small, along the diffusion direction, the structure gradually becomes loose, the holes are enlarged;
therefore, it was found that the pore diameter of the obtained chitosan oligosaccharide/sodium alginate thin film gradually increased along the diffusion direction, and gradient pores were formed. The pore diameter is observed to gradually increase from the lower side (. apprxeq.50 nm) to the upper side (. apprxeq.80 μm), which indicates that the pore diameter of the obtained chitosan oligosaccharide/sodium alginate film sequentially increases from bottom to top, and a gradient porous structure is formed. The analysis reason is that the sodium alginate and the chitosan interact with each other when in contact, the structure formed by electrostatic complexation is compact, and the chitosan diffuses under the action of osmotic pressure, so that sufficient complexation cannot be formed with the sodium alginate, and the complexing effect is strong, the structure is compact, the pore diameter is small, and the amino content is high when in contact; along with the diffusion, the structure is loose, the pore diameter is increased, the content of amino is reduced, and the final gradient porous film is formed.
(5) The obtained film was subjected to X-ray photoelectron spectroscopy, and as shown in fig. 7, it was found that the N content of the upper side of the prepared chitosan oligosaccharide/sodium alginate self-supporting film was 3.89%, and the N content of the lower side was 4.52%;
example 2
Respectively weighing chitosan oligosaccharide with the molecular weight of 2000Da and sodium alginate with the molecular weight of 30 ten thousand Da for later use according to the mass ratio of 20: 1;
dissolving the chitosan oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 40%;
dissolving the sodium alginate in deionized water to obtain a solution B with the mass fraction ratio concentration of 0.5%;
placing the solution A in a culture dish, immersing the solution A in the solution B, and reacting for 4min to form a self-supporting film.
The thickness measurement of the obtained gradient film was carried out, and the thickness was found to be about 0.5 mm.
The obtained film was examined by an electron microscope, and it was found that the structure was similar to that obtained in example 1, that the film had a gradient structure, and the film was dense on the lower side and loose on the upper side.
And (3) carrying out X-ray photoelectron spectroscopy detection on the obtained gradient film, wherein the N content of the upper side of the prepared chitosan oligosaccharide/sodium alginate self-supporting film is 4.52%, and the N content of the lower side of the prepared chitosan oligosaccharide/sodium alginate self-supporting film is 4.97%.
Example 3
Respectively weighing chitosan oligosaccharide with the molecular weight of 2000Da and sodium alginate with the molecular weight of 30 ten thousand Da for later use according to the mass ratio of 20: 1;
dissolving the chitosan oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 40%;
dissolving the sodium alginate in deionized water to obtain a solution B with the mass fraction ratio concentration of 2%;
the solution A was placed in a petri dish, immersed in the solution B, and reacted for 8min for a self-supporting membrane.
The thickness measurement of the obtained gradient film was carried out, and the thickness was found to be about 0.5 mm.
The obtained gradient film was subjected to X-ray photoelectron spectroscopy, and it was found that the content of N on the upper side of the prepared chitosan oligosaccharide/sodium alginate self-supporting film was 4.37% and the content of N on the lower side was 4.78%.
Comparative examples 1 to 3 show that the time required for forming a film of the same thickness is different when the sodium alginate concentration is varied, and the higher the sodium alginate concentration is, the longer the time required for forming a film of a certain thickness is.
The main reason is that when the concentration of sodium alginate is increased, the complexation between the two is obviously increased, and the formed holes are more compact, so that the chitosan is difficult to diffuse upwards through the compact holes.
Example 4
According to the mass ratio of 20:1, respectively weighing chitosan oligosaccharide with molecular weight of 2000Da and sodium alginate with molecular weight of 30 ten thousand Da for later use;
dissolving the chitosan oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 40%;
dissolving sodium alginate in 1.17% sodium chloride (0.2M NaCl) solution to obtain solution B with mass percent concentration of 1%;
placing the solution A in a culture dish, immersing the solution A in the solution B, and reacting for 6min to form a self-supporting film.
The obtained film was examined by electron microscopy and found to have a structure similar to that obtained in example 1, a gradient structure, and a lower dense side and an upper loose side
Example 5
Respectively weighing sodium alginate oligosaccharide with the molecular weight of 2000Da and chitosan with the molecular weight of 75 ten thousand Da for later use according to the mass ratio of 20: 1;
dissolving the sodium alginate oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 30%;
adding deionized water and acetic acid (50:1) into the chitosan to prepare a solution B with the mass percentage concentration of 2%, wherein the purpose of adding the acetic acid is to better dissolve the high molecular weight chitosan;
placing the solution A in a culture dish, immersing the solution A in the solution B, and reacting for 6min to form a self-supporting film.
The obtained film was examined by electron microscopy and found to have a structure similar to that obtained in example 1, a gradient structure, and a lower dense side and an upper loose side
Example 6
Respectively weighing chitosan oligosaccharide with the molecular weight of 3000Da and carrageenan with the molecular weight of 20 ten thousand Da for later use according to the mass ratio of 40: 1;
dissolving the chitosan oligosaccharide in deionized water to obtain a solution A with the mass percentage concentration of 40%;
dissolving the carragheenan in water to prepare a solution B with the mass percentage concentration of 1%;
placing the solution A in a culture dish, immersing the solution A in the solution B, and reacting for 6min to form a self-supporting film.
The obtained film was examined by electron microscopy and found to have a structure similar to that obtained in example 1, a gradient structure, and a lower dense side and an upper loose side
Example 7
The procedure of example 2 was repeated except that: (1) adopting chitosan oligosaccharide with molecular weight of 6000 Da; (2) adopting sodium alginate with molecular weight of 70 ten thousand Da; (3) the mass percentage concentration of the obtained solution A is 50 percent; (4) the mass percentage concentration of the obtained solution B is 3 percent; (5) the reaction time was increased to 10 min.
The obtained film was examined by an electron microscope, and it was found that the structure was similar to that obtained in example 2, that the film had a gradient structure, and the film was dense on the lower side and loose on the upper side.
Example 8
The procedure of example 2 was repeated except that: (1) adopting chitosan oligosaccharide with the molecular weight of 10000 Da; (2) adopting sodium alginate with molecular weight of 60 ten thousand Da; (3) the mass percentage concentration of the obtained solution A is 60 percent; (4) the mass percentage concentration of the obtained solution B is 5 percent; (5) the reaction time was increased to 15 min.
The obtained film was examined by an electron microscope, and it was found that the structure was similar to that obtained in example 2, that the film had a gradient structure, and the film was dense on the lower side and loose on the upper side.
In the embodiment of the present invention, when the low molecular weight polyelectrolyte is chitosan oligosaccharide, since the purchased chitosan oligosaccharide itself is acidic (pH is about 3 to 5), no pH control is required.
Comparative example
Comparative example 1
The procedure of example 2 was repeated except that: the concentration of sodium alginate in solution B was very low, only 0.1% by mass.
As a result, it was found that when the concentration of sodium alginate (high molecular weight polyelectrolyte) is very low, a support film cannot be formed. Due to insufficient entanglement between sodium alginate chains and insufficient entanglement between sodium alginate and chitosan oligosaccharide, insufficient binding sites of sodium alginate and chitosan oligosaccharide are available to support the membrane.
Comparative example 2
The procedure of example 2 was repeated except that: the concentration of sodium alginate in solution B was very high, reaching 5% by mass.
As a result, it was found that when the concentration of sodium alginate (high molecular weight polyelectrolyte) is very high, a thin film having a non-uniform thickness is produced. When the concentration of the sodium alginate is increased, the viscosity of the solution is greatly increased, so that the solution A cannot be uniformly covered by the solution B in the process of immersing the solution A into the solution B, the formed film is not uniform, in addition, when the concentration of the sodium alginate is very high, the complexation of the solution A and the solution B is very strong, the diffusion of low-molecular-weight natural polyelectrolyte polysaccharides is more difficult, and the film with the thickness of less than 0.2mm can be formed even if the reaction is carried out for a long time.
Examples of the experiments
Experimental example 1 Infrared detection
The infrared detection of the gradient porous film obtained in example 1 showed that chitosan oligosaccharide, sodium alginate and the film were sequentially present from bottom to top in fig. 5, as shown in fig. 5.
As can be seen in the figure, the hollow capsules are 1531cm in the amide II band compared with pure chitosan oligosaccharide and sodium alginate-1A new peak is shown, and this result indicates that the electrostatic complexation reaction between the amine group of the chitosan oligosaccharide and the carboxyl group of the alginate was successful.
Experimental example 2 mechanical Property test
The mechanical property test of the self-supporting film obtained in example 1 showed that the breaking strength of the film was 1.83MPa and the elongation at break was 58%, as shown in FIG. 6.
Experimental example 3 high temperature deformation measurement
The film obtained in example 1 was subjected to a deformation test by measuring the bending angle in water at different temperatures, as can be seen from FIG. 8.
(1) When the polysaccharide film is placed in water at a temperature higher than the preparation temperature (T < 70 ℃ C. < 25 ℃), the film bends to the loose side
(2) The bending angle gradually increases with the temperature, and the time for reaching the maximum bending degree is shortened with the temperature
(3) The bending angle of 360 degrees can be achieved only by 2s at 40 ℃.
The reason for the analysis is: (A) the loose side has weak complexation and large pores, and the dense side has strong complexation and small pores. (B) An increase in temperature will increase the degree of complexation of the SA/CS membrane. (C) The relative complexing degree of the loose side is increased more, and the drainage shrinkage causes the deformation to bend to the loose side.
Wherein SA represents sodium alginate, and CS represents chitosan oligosaccharide.
Experimental example 4 detection of ion intensity deformation
The film obtained in example 1 was placed in 1M NaCl at different temperatures and subjected to deformation measurement by measuring the bending angle, as shown in FIG. 9 and FIG. 9-1 (which is a partial enlarged view of FIG. 9, and is 25 ℃, 37 ℃ and 60 ℃ from the top), in which:
(1) the bending phenomenon to the loose side occurs in the saline solution at 25 ℃, and the bending angle can reach 360 degrees.
(2) The saline solution at 37 ℃ undergoes deformation and recovery, and the deformation only needs 2 s.
(3) The saline solution at 60 ℃ undergoes a smaller deformation angle but an increased recovery rate.
The reason for the analysis is: (A) NaCl has influence on both the complex part and the uncomplexed part of the film, can shield molecular chains of the uncomplexed part, enables the chains to be changed from straightening to curling, and enables the complex part to be subjected to crosslinking release at a higher temperature; (B) NaCl electrostatic screening molecular chains, wherein the chains are changed from straightening to curling, and the network collapses to drain water; (C) when the temperature rises, the movement speed of NaCl molecules is increased, the decomplexation of NaCl on the molecular chains is dominant gradually, so that the deformation is recovered, and the inversion phenomenon can be caused by continuously increasing the temperature. In conclusion, the nature of the deformation in salt is constituted by the competition between the draining action of the NaCl electrostatic screen, which makes the molecular chains coil, and the action of NaCl on the complexing moieties, which makes it decrosslinked.
Experimental example 5 detection of pH deformation
The film obtained in example 1 was subjected to deformation measurement by measuring the bending angle by placing it in 1MHCl at different temperatures, as can be seen from FIG. 10
(1) The process of firstly deforming and then recovering inversion can occur at 25 ℃;
(2) the deformation time is shortened at 37 ℃, the bending angle is increased, the recovery time is shortened, and the process of inversion is accompanied;
(3) when the temperature reached 60 ℃, the deformation was fast but the bending angle was small, and recovery and inversion were immediate.
The reason for the analysis is: (A) h+May cause uncomplexed partial NH3 +Increased, protonated NH3 +One part of the water-soluble organic acid complex can form complexation with sodium alginate, and the other part of the water-soluble organic acid complex can continuously enable molecular chains to repel, swell and absorb water. (B) The dense side has a higher amino content than the loose side and a greater degree of swelling so that the dense side first bends to the loose side and then immediately becomes protonated NH3 +The resulting increased degree of complexation, and thus drainage, results in greater strengthening of the complexation on the dense side, and therefore, in deformation recovery and inversion. (C) In addition, the temperature increases by H+The free speed of (2) leads to the shortening of the whole deformation time, and simultaneously, the competitive relationship of the two effects is also influenced, thus leading to the difference of the deformation degree.
Experimental example 6 detection of recovery from deformation
The film obtained in example 1 was immersed in water at 37 ℃ and then in NaCl at 37 ℃ and subjected to deformation measurement by measuring the bending angle, and the results are shown in FIG. 11.
As can be seen from FIG. 11, the film is firstly deformed in water at 37 ℃ until the deformation angle reaches 360 degrees, and then is placed in NaCl at 37 ℃ for deformation recovery, and the above process is repeated, so that the material can be circulated for about 10 times without obvious damage to the film, and the film is proved to have good cyclicity.
Experimental examples 72D and 3D Pattern design
The film obtained in example 1 was crosslinked at different sites with metal ions and placed in water at 50 ℃, as shown in fig. 12a to h, various complicated shapes such as 2D and 3D can be prepared by local crosslinking of the film.
The main reason is that the prepared film can generate crosslinking elimination gradient under the action of metal ions, and after the gradient is eliminated, the material cannot generate different swelling or shrinkage on the upper side and the lower side, so that deformation only occurs on the non-crosslinked part, and complex shapes such as 2D, 3D and the like can be realized through ingenious design.
The invention has been described in detail with reference to the preferred embodiments and illustrative examples. It should be noted, however, that these specific embodiments are only illustrative of the present invention and do not limit the scope of the present invention in any way. Various modifications, equivalent substitutions and alterations can be made to the technical content and embodiments of the present invention without departing from the spirit and scope of the present invention, and these are within the scope of the present invention. The scope of the invention is defined by the appended claims.

Claims (10)

1. A method for preparing a polysaccharide polyelectrolyte self-supporting film, which is characterized by comprising the following steps:
step 1, adding low molecular weight polysaccharide polyelectrolyte into water to obtain a solution A;
step 2, adding high molecular weight polysaccharide polyelectrolyte into water to obtain solution B;
step 3, placing the solution A obtained in the step 1 into a container, then immersing the container into the solution B, and reacting for 1-20 min to form the self-supporting film;
wherein the content of the first and second substances,
in step 1, the low molecular weight polysaccharide polyelectrolyte is selected from chitosan oligosaccharide, sodium alginate oligosaccharide or carrageenan oligosaccharide; the high molecular weight polysaccharide polyelectrolyte is selected from chitosan, sodium alginate or carrageenan;
the low molecular weight polysaccharide polyelectrolyte and the high molecular weight polysaccharide polyelectrolyte have opposite charges;
the molecular weight of the low molecular weight polysaccharide polyelectrolyte is 2000-10000 Da, and the molecular weight of the high molecular weight polysaccharide polyelectrolyte is 100000-800000 Da; in the solution A in the step 1, the mass percentage concentration of the low molecular weight polysaccharide polyelectrolyte is 30-60%, and in the solution B in the step 2, the mass percentage concentration of the high molecular weight polysaccharide polyelectrolyte is 0.5-5%.
2. The production method according to claim 1, wherein in step 1, the low-molecular-weight polysaccharide polyelectrolyte has a molecular weight of 2000 to 6000 Da; and/or
In the step 2, the molecular weight of the high molecular weight polysaccharide polyelectrolyte is 300000-700000 Da.
3. The production method according to claim 1,
in the solution A in the step 1, the mass percentage concentration of the low molecular weight polysaccharide polyelectrolyte is 40-50%; and/or
In the solution B in the step 2, the mass percentage concentration of the high molecular weight polysaccharide polyelectrolyte is 0.5-3%.
4. The method according to claim 1, wherein the reaction is carried out for 5 to 10min in step 3.
5. The method of claim 1, wherein in step 2, NaC1 is added.
6. The method according to claim 5, wherein 0.1 to 1M NaC1 is added in step 2.
7. The method according to any one of claims 1 to 6, wherein the pH of the solution A is adjusted to 2 to 6 in step 1.
8. The method according to claim 7, wherein the pH of the solution A is adjusted to 3.5 to 5 in the step 1.
9. A polysaccharide polyelectrolyte self-supporting film obtained by the production method as claimed in any one of claims 1 to 8, the film having a thickness of 0.2mm to 2mm, wherein the film has a gradient structure, one side of which is loose and the other side of which is dense.
10. The polysaccharide polyelectrolyte self-supporting film according to claim 9, wherein the film is responsive to external stimuli including temperature, ionic strength and pH.
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