CN114773601A - high-Tg and high-modulus shape memory flame-retardant polyimide and preparation method and application thereof - Google Patents
high-Tg and high-modulus shape memory flame-retardant polyimide and preparation method and application thereof Download PDFInfo
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1057—Polyimides containing other atoms than carbon, hydrogen, nitrogen or oxygen in the main chain
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1042—Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
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- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1067—Wholly aromatic polyimides, i.e. having both tetracarboxylic and diamino moieties aromatically bound
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
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- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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- C08G2280/00—Compositions for creating shape memory
Abstract
The invention provides a high-Tg, high-modulus shape memory flame-retardant polyimide, a preparation method and application thereof, wherein the high-Tg, high-modulus shape memory flame-retardant polyimide is prepared from diamine and biphenyl dianhydride; the diamine comprises imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine, the mass ratio of the imidazole-containing aromatic heterocyclic diamine to the phosphorus-containing diamine is 0.9:0.1, and the mass ratio of the diamine to the biphenyl dianhydride is 1: 1-1.01. According to the invention, the polyimide is prepared from imidazole-containing aromatic heterocyclic diamine and biphenyl dianhydride, has shape memory performance, higher shape fixing rate and shape recovery rate, and flame retardant property reaching UL94VTM-0 level, and remarkably improves the application prospect of the polyimide in the fields of deformable flexible electrodes, high-temperature actively deformed aerospace devices and deployable structures.
Description
Technical Field
The invention relates to the technical field of functional polymers, in particular to high-Tg and high-modulus shape memory flame-retardant polyimide and a preparation method and application thereof.
Background
Shape Memory Polymer (SMP) is an intelligent material capable of responding to external stimuli such as heat, light, electricity, magnetism or chemistry, and the Polymer with Shape Memory effect can keep a certain temporary Shape after shaping and return to the original Shape before deformation under the external stimuli. Shape memory materials have begun to attract the attention of researchers since the first proposal by Mather of 1940 for "elastic memory", SMP has become a further area of intense research beyond Shape Memory Alloys (SMA) due to its unique shape memory function. Compared with SMA, SMP has the advantages of light weight, low production cost, easy processing, easy performance regulation, large recovery strain, wide response temperature range and the like, and can respond to various stimulation modes.
The polyimide material has the advantages of excellent high and low temperature resistance, high strength and modulus, high creep resistance, high dimensional stability, low thermal expansion coefficient, high electrical insulation, low dielectric constant and loss, irradiation resistance, corrosion resistance and the like, and has the characteristics of space materials such as low vacuum volatile matter, less volatile condensable matter and the like. The polyimide material can be processed into a plurality of material forms such as polyimide films, high-temperature-resistant engineering plastics, basic resin for composite materials, high-temperature-resistant adhesives, fibers and the like, and has wide application prospect and great commercial value in the high and new technical fields such as aerospace, aviation, space, microelectronics, precision machinery, medical instruments and the like.
Polyimide (SMPI) having a Shape Memory function has excellent Shape Memory effect, thermal stability, radiation resistance, and good mechanical properties, and can be applied to the fields of sensors, expandable structures, and the like. 0-8 wt% of cage-shaped polysilsesquioxane is grafted to an SMPI matrix synthesized by hexafluoro dianhydride and 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl by the Shuyanlei of the university of Compound Dan, and the like, so that light-color transparent organic-inorganic hybrid SMPI with the shape memory transition temperature of 320-380 ℃ is obtained, and the SMPI film is the currently known SMPI film with the highest shape memory transition temperature. In addition, the storage modulus of a general SMPI film is greatly reduced in the shape memory transition process, and most of the storage modulus is lower than 400 MPa.
In addition, in order to meet the application of the SMPI in a high-temperature fire-resistant environment, a fire retardant is often doped in the SMPI, and a phosphorus fire retardant is a very effective environment-friendly fire retardant. However, the physical blending of the flame retardant is easy to cause the problems of uneven dispersion, easy precipitation, easy formation of stress concentration points and the like, thereby causing the reduction of the mechanical properties of the SMPI. In order to further improve the application prospect of the SMPI, the SMPI with higher shape memory transition temperature, better performance and stronger flame retardant capability needs to be developed.
Disclosure of Invention
The invention solves the problem of how to provide a polyimide film with higher shape memory transition temperature, better performance and stronger flame retardant capability.
In order to solve at least one aspect of the above problems, the present invention provides a high Tg, high modulus shape memory flame retardant polyimide prepared from diamine and biphenyl dianhydride; the diamine comprises imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine, the mass ratio of the imidazole-containing aromatic heterocyclic diamine to the phosphorus-containing diamine is 0.9:0.1, and the mass ratio of the diamine to the biphenyl dianhydride is 1: 1-1.01.
Preferably, the imidazole-containing aromatic heterocyclic diamine comprises 2- (4-aminophenyl) -5-aminobenzimidazole; the phosphorus-containing diamine comprises bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide.
Preferably, the biphenyl dianhydride comprises 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride.
Preferably, the molecular structure of the polyimide is represented by formula (1):
wherein the value range of n is 122-175.
According to the invention, the polyimide is prepared from imidazole-containing aromatic heterocyclic diamine, phosphorus-containing diamine and biphenyl dianhydride, the polyimide has a storage modulus of more than 4GPa, a storage modulus of not less than 475MPa in a shape recovery stage, a glass transition temperature (Tg) of more than 400 ℃, and has shape memory performance, higher shape fixing rate and shape recovery rate, in addition, the prepared polyimide is an intrinsic flame retardant SMPI, the problems that a physical blending flame retardant is not uniform in dispersion, easy to precipitate, easy to form stress concentration points and the like can be solved, the obtained polyimide has better mechanical properties, the flame retardant performance reaches UL94VTM-0 level, and the application prospect of the polyimide in the fields of deformable flexible electrodes, high-temperature actively deformed aerospace devices and deployable structures is remarkably improved.
The invention also aims to provide a preparation method of the high-Tg and high-modulus shape memory flame-retardant polyimide, which is used for preparing the high-Tg and high-modulus shape memory flame-retardant polyimide and comprises the following steps:
step S1, dissolving imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine in a solvent to obtain a diamine solution;
step S2, adding biphenyl dianhydride into the diamine solution under a protective atmosphere, and reacting for 96-120h to obtain a polyamic acid solution;
step S3, pouring the polyamic acid solution onto a substrate, placing the substrate in a vacuum oven for vacuum drying treatment, and removing bubbles in the polyamic acid solution to obtain a polyamic acid solution substrate without bubbles;
step S4, placing the polyamic acid solution substrate without bubbles in a high-temperature oven, and performing thermal imidization by gradient temperature rise to obtain a substrate containing a polyimide film;
and step S5, placing the substrate containing the polyimide film in water for 1-2h, demolding, and drying to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
Preferably, the solvent comprises dimethyl sulfoxide.
Preferably, in the step S2, the concentration of the polyamic acid in the polyamic acid solution is 6 to 16 wt%.
Preferably, in step S3, the step of casting the polyamic acid solution onto a substrate and placing the substrate in a vacuum oven for vacuum drying includes:
pouring the polyamic acid solution onto a substrate, placing the substrate in a vacuum oven, controlling the temperature of the oven to be 45-55 ℃, keeping the temperature for 4.5-5.5h, then heating to 75-85 ℃, keeping the temperature for 4.5-5.5h, and vacuumizing.
Preferably, in step S4, the step of increasing the temperature gradient for thermal imidization includes:
the heating rate is 1-2 ℃/min, the temperature is raised to 115 ℃ and 125 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 155-165 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 195-plus-205 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 245 ℃ and 255 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 295-305 ℃, and the temperature is maintained for 1.5-2.5 h.
Compared with the prior art, the preparation method of the high-Tg and high-modulus shape memory flame-retardant polyimide provided by the invention has the same beneficial effects as the high-Tg and high-modulus shape memory flame-retardant polyimide, and is not repeated here.
The invention further aims to provide application of the polyimide in the fields of deformable flexible electrodes, high-temperature actively deformed aerospace devices and deployable structures.
Compared with the prior art, the application of the high-Tg and high-modulus shape memory flame-retardant polyimide provided by the invention has the same beneficial effect as the high-Tg and high-modulus shape memory flame-retardant polyimide, and is not repeated herein.
Drawings
FIG. 1 is a diagram illustrating the mechanism of shape memory effect of polyimide in an embodiment of the present invention;
FIG. 2 is a flow chart of a method for preparing a high Tg, high modulus shape memory flame retardant polyimide in an embodiment of the invention;
FIG. 3 is a synthetic route for a high Tg, high modulus shape memory flame retardant polyimide in an embodiment of the invention;
FIG. 4 is a plot of the storage modulus of a high Tg, high modulus shape memory flame retardant polyimide in example 1 of the present invention;
FIG. 5 is a graph of dissipation factor for a high Tg, high modulus shape memory flame retardant polyimide in example 1 of the present invention;
fig. 6 is a representation of the thermally driven shape memory process for a high Tg, high modulus shape memory flame retardant polyimide in example 1 of the invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments of the present invention are described in detail below.
It should be noted that the features of the embodiments of the present invention may be combined with each other without conflict. The terms "comprising," "including," "containing," and "having" are intended to be inclusive, i.e., that additional steps and other ingredients may be added without affecting the result. The above terms encompass the terms "consisting of … …" and "consisting essentially of … …". Materials, equipment and reagents are commercially available unless otherwise specified. Also, it is noted that the terms "first," "second," and the like in the description and claims of the present invention and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.
The embodiment of the invention provides high-Tg and high-modulus shape memory flame-retardant polyimide which is prepared from diamine and biphenyl dianhydride; the diamine comprises imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine, the mass ratio of the imidazole-containing aromatic heterocyclic diamine to the phosphorus-containing diamine is 0.9:0.1, and the mass ratio of the diamine to the biphenyl dianhydride is 1: 1-1.01.
The phosphorus flame retardant is a very effective environment-friendly flame retardant. In the condensed phase, the phosphorus-containing flame retardant can generate polyphosphoric acid with strong dehydration property by combustion, organic matters are quickly dehydrated and carbonized, and the generated carbide has a compact structure of a three-dimensional space and is not easy to combust; in the gas phase, the phosphorus-containing flame retardant decomposes nonflammable gas to reduce the concentration of combustible gas, and radicals such as P, PO. and the like released during combustion of the phosphorus-containing flame retardant can quench high-activity H and HO radicals generated by pyrolysis of polymers, so that the chain reaction of combustion is interrupted, and the flame retardant effect is achieved.
The phosphorus-containing diamine has good flame retardant ability, can obtain intrinsic flame retardant SMPI after the phosphorus-containing diamine is subjected to polycondensation reaction with imidazole-containing aromatic heterocyclic diamine and biphenyl dianhydride, has good mechanical property, and ether bond groups contained in the phosphorus-containing diamine can increase the flexibility of polyimide molecular chains and improve the shape memory property of the film; in addition, when polyimide prepared from imidazole-containing aromatic heterocyclic diamine, phosphorus-containing diamine and biphenyl dianhydride is combusted in air, relatively inert gases (such as carbon dioxide, water and a small amount of nitrogen oxides) released from imidazole groups on a molecular chain can also improve the flame retardant property. Therefore, different groups on the high-Tg and high-modulus shape memory flame-retardant polyimide molecular chain prepared by the embodiment of the invention can generate mutual synergistic action, and the shape memory performance and the flame retardant performance of the polyimide are improved together.
The polyimide is prepared from imidazole-containing aromatic heterocyclic diamine, phosphorus-containing diamine and biphenyl dianhydride, the storage modulus of the polyimide is over 4GPa at normal temperature, the storage modulus of the polyimide is not lower than 475MPa at the shape recovery stage, the glass transition temperature (Tg) is over 400 ℃, the polyimide has shape memory performance and higher shape fixing rate and shape recovery rate, in addition, the prepared polyimide is an intrinsic flame-retardant SMPI, the problems that a physical blending flame retardant is not uniform in dispersion, easy to precipitate, easy to form stress concentration points and the like can be solved, the mechanical property of the obtained polyimide is better, the flame-retardant performance reaches the UL94VTM-0 level, and the application prospect of the polyimide in the fields of deformable flexible electrodes, high-temperature actively deformed space devices and deployable structures is remarkably improved.
Illustratively, the imidazole-containing aromatic heterocyclic diamine includes 2- (4-aminophenyl) -5-aminobenzimidazole (DAPBI), the phosphorus-containing diamine includes bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide (M-BAPPO), and the biphenyl dianhydride includes 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride (BPDA). The molecular structural formula of the polyimide is shown as formula (1):
wherein the value range of n is 122-175.
In principle, the polyimide has a shape memory effect because the molecular chain segments form a stationary phase and a reversible phase in a physical crosslinking mode, wherein the stationary phase is a physical crosslinking network (namely a rigid chain) formed by pi-pi interaction and hydrogen bond interaction among aromatic rings and molecular chain entanglement, the stationary phase has the function of ensuring that the molecular chain does not slide integrally and realizes the memory function of a permanent shape, the reversible phase is a movable phase (namely a flexible chain) capable of generating reversible transformation, the transformation is provided by glass transition, and the molecular chain segments can be frozen under specific conditions and can be reactivated under external stimulation, so that the fixation of a temporary shape is realized and the driving energy is provided for shape recovery movement. As shown in fig. 1, when the temperature is raised to be higher than Tg (glass transition temperature), the micro brownian motion of the reversible phase molecular chain segment is intensified, while the stationary phase is still in a solidified state, and a certain external force is applied to deform the polymer, so that a temporary shape of ∈ 0+ Δ L' is obtained; when the temperature rises above Tg again, the reversible phase softens, the stationary phase is still solidified, the molecular chain segment of the reversible phase moves to be unfrozen, and the reversible phase gradually reaches a thermodynamic equilibrium state under the action of the restoring stress of the stationary phase, namely, the reversible phase is macroscopically represented as a restored shape Eporec.
For the high-Tg and high-modulus shape memory flame-retardant polyimide prepared by the embodiment of the invention, the molecular chain contains asymmetric imidazole groups, so that the rigidity is kept, the flexibility is certain, and the high rigidity is kept while the shape is restored to the original shape from the temporary shape in the shape restoring process, so that the load can be borne, and the application scene of the polyimide is expanded; in addition, the ether bond on the molecular chain also increases the flexibility of the molecular chain, and provides conditions for the shape memory performance of the polyimide.
Another embodiment of the present invention provides a method for preparing a high Tg, high modulus shape memory flame retardant polyimide, which is used for preparing the high Tg, high modulus shape memory flame retardant polyimide, as shown in fig. 2, and comprises the following steps:
step S1, dissolving imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine in a solvent to obtain a diamine solution;
step S2, adding biphenyl dianhydride into the diamine solution under a protective atmosphere, and reacting for 96-120h to obtain a polyamic acid solution;
step S3, pouring the polyamic acid solution onto a substrate, placing the substrate in a vacuum oven for vacuum drying treatment, and removing bubbles in the polyamic acid solution to obtain a polyamic acid solution substrate without bubbles;
step S4, placing the polyamic acid solution substrate without bubbles in a high-temperature oven, and performing thermal imidization by gradient temperature rise to obtain a substrate containing a polyimide film;
and step S5, placing the substrate containing the polyimide film in water for 1-2h, demolding, and drying to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
In step S1, the solvent includes dimethyl sulfoxide (DMSO), and the DSMO has good solubility for imidazole-containing aromatic heterocyclic diamine and phosphorous-containing diamine, and is soluble at room temperature, and particularly when 2- (4-aminophenyl) -5-aminobenzimidazole (DAPBI) is selected as a precursor, N-dimethylacetamide, N-methylpyrrolidone, or N, N-dimethylformamide cannot be dissolved at room temperature, and if the solvent is dissolved by heating, the reaction temperature is increased, thereby affecting the polycondensation reaction of diamine and biphenyl dianhydride.
In step S2, the polyamic acid solution has a polyamic acid concentration of 6 to 16 wt%. Wherein the protective atmosphere comprises a nitrogen protective atmosphere, and the reaction is carried out at normal temperature.
Specifically, biphenyl dianhydride is added into a diamine solution for 3-5 times according to the proportion, the adding step is completed within 30min, and the reaction is carried out for 96-120h at the rotation speed of 200-500r/min in the nitrogen protection atmosphere at normal temperature, so as to obtain a polyamic acid solution, wherein the concentration of the polyamic acid is 6-16 wt%. The reaction time is 96-120h, so that the performance of the obtained polyimide can be ensured, if the reaction time is too short, the polyamic acid has low molecular weight, and is fragmented in the subsequent thermal imidization step, so that a plurality of cracks are caused, and finally, the film forming failure is caused, and if the reaction time is too long, the polyamic acid formed by condensation polymerization is hydrolyzed, and the molecular weight is also reduced, so that the film forming property is influenced.
Illustratively, when the imidazole-containing aromatic heterocyclic diamine is 2- (4-aminophenyl) -5-aminobenzimidazole (DAPBI), the phosphorus-containing diamine is bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide (M-BAPPO), and the biphenyl dianhydride is 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride (BPDA), the synthesis pathway of the high Tg, high modulus shape memory flame retardant polyimide is shown in fig. 3.
In step S3, the polyamic acid solution is poured onto a substrate, placed in a vacuum oven, the temperature of the oven is controlled to be 45-55 ℃, kept for 4.5-5.5h, then heated to 75-85 ℃, kept for 4.5-5.5h, and then vacuumized to remove bubbles in the polyamic acid. Illustratively, the substrate is a glass plate.
In step S4, the polyamic acid solution substrate without bubbles is placed in a high-temperature oven, and heated in a gradient manner to perform thermal imidization, thereby obtaining a substrate containing a polyimide film.
Specifically, the gradient temperature rise is used for thermal imidization, and comprises the following steps:
the heating rate is 1-2 ℃/min, the temperature is raised to 115 ℃ and 125 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 155-165 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 195-plus-one temperature of 205 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 245 ℃ and 255 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 295-305 ℃, and the temperature is kept for 1.5-2.5 h.
If the gradient temperature rise rate is too high, that is, the temperature span is too large, the internal stress shrinkage in the thermal imidization process is uneven, and the obtained SMPI film is uneven, even has the problems of cracks, curls, fragments and the like.
The invention further provides application of the polyimide in the fields of actively deformed flexible electrodes, high-temperature actively deformed aerospace devices and deployable structures.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.
Example 1
1.1, completely dissolving 2.7mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.3mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 20mL of dimethyl sulfoxide to obtain a diamine solution;
1.2, 3.0mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride is added into the diamine solution for 3 times, and the feeding step is completed within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
1.3, pouring polyamic acid on a glass plate, placing the glass plate in a vacuum oven at 50 ℃, and keeping the temperature for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
1.4, placing the polyamide acid glass plate without bubbles in a high-temperature oven, and performing thermal imidization by gradient heating, wherein the thermal imidization step comprises the steps of heating at a heating rate of 2 ℃/min to 120 ℃ and keeping for 2 hours; the heating rate is 2 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is raised to 200 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 300 ℃, and the temperature is kept for 2 h;
1.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at 100 ℃ for 2 hours to complete demoulding;
1.6, placing the demolded film material in an oven at 100 ℃, keeping the temperature for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
Wherein, fig. 4 is a graph of storage modulus of the polyimide prepared in this example, and fig. 5 is a graph of loss factor of the polyimide prepared in this example; FIG. 6 is a diagram illustrating a shape memory process of the polyimide prepared in this example.
As can be seen from FIG. 4, the storage modulus of the polyimide prepared by the present example is 4.19GPa, and the minimum storage modulus of the polyimide in the shape recovery stage is 480 MPa; as can be seen from FIG. 5, the glass transition temperature (Tg) of the polyimide prepared in this example is 418.8 deg.C, i.e., the shape memory transition temperature is 418.8 deg.C; as can be seen from FIG. 6, under the thermal environment of 450 ℃, external force is applied to shape the polyimide, the temperature is reduced to normal temperature, the bent temporary shape is still kept after the external force is removed, and after the polyimide is heated to the thermal environment of 450 ℃ again, the original shape can be recovered by the polyimide, wherein the shape fixing rate is 94%, the shape recovery rate is 96%, and the flame retardant property reaches the UL94VTM-0 level.
Example 2
2.1, completely dissolving 2.7mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.3mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 20mL of dimethyl sulfoxide to obtain a diamine solution;
2.2, 3.02mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride is added into the diamine solution for 4 times, and the feeding step is completed within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
2.3, pouring the polyamic acid on a glass plate, and placing the glass plate in a vacuum oven at 50 ℃ for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
2.4, placing the polyamide acid glass plate without air bubbles in a high-temperature oven, and performing thermal imidization by gradient temperature rise, wherein the thermal imidization step is that the temperature rise rate is 2 ℃/min, the temperature rises to 120 ℃, and the temperature is kept for 2 hours; the heating rate is 2 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is raised to 200 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 300 ℃, and the temperature is kept for 2 h;
2.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at the temperature of 100 ℃ for 2 hours to finish demoulding;
2.6, placing the demolded film material in an oven at 100 ℃, keeping for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
The polyimide prepared by the embodiment has the storage modulus of 4.18GPa at normal temperature, the glass transition temperature (Tg) of 418.0 ℃, the storage modulus of 478MPa at the lowest in the shape recovery stage, the shape fixing rate of 93 percent and the shape recovery rate of 94.5 percent, and the flame retardant property of UL94VTM-0 grade.
Example 3
3.1, completely dissolving 2.7mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.3mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 20mL of dimethyl sulfoxide to obtain a diamine solution;
3.2, 3.03mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride is added into the imidazole-containing aromatic heterocyclic diamine solution for 5 times, and the feeding step is completed within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
3.3, pouring the polyamic acid on a glass plate, and placing the glass plate in a vacuum oven at 50 ℃ for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
3.4, placing the polyamide acid glass plate without bubbles in a high-temperature oven, and performing thermal imidization by gradient heating, wherein the thermal imidization step comprises the steps of heating at the speed of 1 ℃/min to 120 ℃ and keeping for 2 hours; the heating rate is 1 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; heating to 200 ℃ at a heating rate of 1 ℃/min, and keeping for 2 h; the heating rate is 1 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; heating to 300 ℃ at a heating rate of 1 ℃/min, and keeping for 2 h;
3.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at 100 ℃ for 2 hours to finish demoulding;
3.6, placing the demolded film material in an oven at 100 ℃, keeping the temperature for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
The polyimide prepared by the embodiment has the storage modulus of 4.17GPa at normal temperature, the glass transition temperature (Tg) of 417.5 ℃, the storage modulus of 475MPa at the lowest in the shape recovery stage, the shape fixation rate of 93.4 percent and the shape recovery rate of 94.6 percent, and the flame retardant property of the polyimide reaches the UL94VTM-0 level.
Example 4
4.1, completely dissolving 4.5mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.5mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 26mL of dimethyl sulfoxide to obtain a diamine solution;
4.2, 5.02mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride is added into the diamine solution for 5 times, and the feeding step is completed within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
4.3, pouring the polyamic acid on a glass plate, and placing the glass plate in a vacuum oven at 50 ℃ for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
4.4, placing the polyamide acid glass plate without bubbles in a high-temperature oven, and performing thermal imidization by gradient heating, wherein the thermal imidization step comprises the steps of heating at the speed of 1 ℃/min to 120 ℃ and keeping for 2 hours; the heating rate is 1 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; heating to 200 ℃ at a heating rate of 1 ℃/min, and keeping for 2 h; the heating rate is 1 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; heating to 300 ℃ at a heating rate of 1 ℃/min, and keeping for 2 h;
4.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at the temperature of 100 ℃ for 2 hours to finish demoulding;
4.6, placing the demolded film material in an oven at 100 ℃, keeping the temperature for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
The polyimide prepared by the embodiment has the storage modulus of 4.18GPa at normal temperature, the glass transition temperature (Tg) of 418.0 ℃, the storage modulus of 475MPa at the lowest in the shape recovery stage, the shape fixation rate of 93.9 percent and the shape recovery rate of 95.3 percent, and the flame retardant property reaches the UL94VTM-0 grade.
Example 5
5.1, completely dissolving 4.5mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.5mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 30mL of dimethyl sulfoxide to obtain a diamine solution;
5.2, adding 5.03mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride into the diamine solution for 5 times, and finishing the feeding step within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
5.3, pouring the polyamic acid on a glass plate, and placing the glass plate in a vacuum oven at 50 ℃ for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
5.4, placing the polyamide acid glass plate without air bubbles in a high-temperature oven, and performing thermal imidization by gradient temperature rise, wherein the thermal imidization step is that the temperature rise rate is 1 ℃/min, the temperature rises to 120 ℃, and the temperature is kept for 2 hours; the heating rate is 1 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; the heating rate is 1 ℃/min, the temperature is raised to 200 ℃, and the temperature is kept for 2 h; the heating rate is 1 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; heating to 300 ℃ at a heating rate of 1 ℃/min, and keeping for 2 h;
5.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at 100 ℃ for 2 hours to finish demoulding;
and 5.6, placing the demolded film material in an oven at 100 ℃, keeping the temperature for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
The polyimide prepared by the embodiment has the storage modulus of 4.19GPa at normal temperature, the glass transition temperature (Tg) of 418.2 ℃, the minimum storage modulus of 478MPa at the shape recovery stage, the shape fixing rate of 92.8 percent and the shape recovery rate of 95.5 percent, and the flame retardant property of UL94VTM-0 grade.
Example 6
6.1, completely dissolving 4.5mmol of 2- (4-aminophenyl) -5-aminobenzimidazole and 0.5mmol of bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide in 30mL of dimethyl sulfoxide to obtain a diamine solution;
6.2, 5.05mmol of 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride is added into the diamine solution for 5 times, and the feeding step is completed within 30 min; reacting for 120 hours at normal temperature in a nitrogen atmosphere at the rotating speed of 250r/min to obtain a polyamic acid solution;
6.3, pouring the polyamic acid on a glass plate, and placing the glass plate in a vacuum oven at 50 ℃ for 5 hours; keeping the temperature at 80 ℃ for 5h, vacuumizing, and removing bubbles to obtain a polyamide acid solution glass plate without bubbles;
6.4, placing the polyamide acid glass plate without bubbles in a high-temperature oven, and performing thermal imidization by gradient heating, wherein the thermal imidization step comprises the steps of heating at a heating rate of 2 ℃/min to 120 ℃ and keeping for 2 hours; the heating rate is 2 ℃/min, the temperature is increased to 160 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is raised to 200 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 250 ℃, and the temperature is kept for 2 h; the heating rate is 2 ℃/min, the temperature is increased to 300 ℃, and the temperature is kept for 2 h;
6.5, closing the high-temperature oven, naturally cooling to room temperature, taking out the glass plate, and placing the glass plate in deionized water at 100 ℃ for 2 hours to finish demoulding;
6.6, placing the demolded film material in an oven at 100 ℃, keeping for 12 hours, and volatilizing moisture to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
The polyimide prepared by the embodiment has the storage modulus of 4.19GPa at normal temperature, the glass transition temperature (Tg) of 418.0 ℃, the minimum storage modulus of 476MPa at the shape recovery stage, the shape fixation rate of 93.8 percent and the shape recovery rate of 96 percent, and the flame retardant property reaches the UL94VTM-0 grade.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the disclosure, and these changes and modifications are intended to fall within the scope of the invention.
Claims (10)
1. A high Tg, high modulus shape memory flame retardant polyimide, characterized by that, is prepared from diamine and biphenyl dianhydride; the diamine comprises imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine, the mass ratio of the imidazole-containing aromatic heterocyclic diamine to the phosphorus-containing diamine is 0.9:0.1, and the mass ratio of the diamine to the biphenyl dianhydride is 1: 1-1.01.
2. The high Tg, high modulus shape memory flame retardant polyimide according to claim 1, wherein said imidazole containing heteroaromatic diamine comprises 2- (4-aminophenyl) -5-aminobenzimidazole; the phosphorus-containing diamine comprises bis [4- (3-aminophenoxy) phenyl ] phenylphosphine oxide.
3. The high Tg, high modulus shape memory flame retardant polyimide according to claim 1, wherein said biphenyl dianhydride comprises 3,3 ', 4,4' -biphenyl tetracarboxylic dianhydride.
4. The high Tg, high modulus shape memory flame retardant polyimide according to any of claims 1 to 3 wherein the molecular structural formula of the polyimide is according to formula (1):
wherein the value range of n is 122-175.
5. A preparation method of a high Tg, high modulus shape memory flame retardant polyimide, which is used for preparing the high Tg, high modulus shape memory flame retardant polyimide as described in any one of claims 1-4, and is characterized by comprising the following steps:
step S1, dissolving imidazole-containing aromatic heterocyclic diamine and phosphorus-containing diamine in a solvent to obtain a diamine solution;
step S2, adding biphenyl dianhydride into the diamine solution under a protective atmosphere, and reacting for 96-120h to obtain a polyamic acid solution;
step S3, pouring the polyamic acid solution onto a substrate, placing the substrate in a vacuum oven for vacuum drying treatment, and removing bubbles in the polyamic acid solution to obtain a polyamic acid solution substrate without bubbles;
step S4, placing the polyamic acid solution substrate without bubbles in a high-temperature oven, and performing thermal imidization by gradient temperature rise to obtain a substrate containing a polyimide film;
and step S5, placing the substrate containing the polyimide film in water, keeping the substrate for 1-2 hours, completing demolding, and drying to obtain the high-Tg and high-modulus shape memory flame-retardant polyimide.
6. The method of claim 5, wherein the solvent comprises dimethyl sulfoxide.
7. The method for preparing high Tg, high modulus shape memory flame retardant polyimide according to claim 5, wherein in step S2, the polyamic acid concentration in the polyamic acid solution is 6-16 wt%.
8. The method for preparing high Tg, high modulus shape memory flame retardant polyimide according to claim 5, wherein in step S3, the polyamic acid solution is poured onto a substrate and placed in a vacuum oven for vacuum drying treatment, comprising:
pouring the polyamic acid solution onto a substrate, placing the substrate in a vacuum oven, controlling the temperature of the oven to be 45-55 ℃, keeping the temperature for 4.5-5.5h, then heating to 75-85 ℃, keeping the temperature for 4.5-5.5h, and vacuumizing.
9. The method for preparing high Tg, high modulus shape memory flame retardant polyimide according to claim 5, wherein in step S4, the gradient temperature rise is performed for thermal imidization comprising:
the heating rate is 1-2 ℃/min, the temperature is raised to 115 ℃ and 125 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 155 ℃ and 165 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 195-plus-one temperature of 205 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 245 ℃ and 255 ℃, and the temperature is kept for 1.5-2.5 h; the heating rate is 1-2 ℃/min, the temperature is raised to 295-305 ℃, and the temperature is maintained for 1.5-2.5 h.
10. The application of the polyimide prepared by the high Tg, high modulus shape memory flame retardant polyimide according to any one of claims 1 to 4 and the preparation method of the high Tg, high modulus shape memory flame retardant polyimide according to any one of claims 5 to 9 in the fields of deformable flexible electrodes, high temperature active deformation aerospace devices and deployable structures.
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