CN106519228B - Polyimide aerogels and preparation method thereof - Google Patents

Polyimide aerogels and preparation method thereof Download PDF

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CN106519228B
CN106519228B CN201610987497.XA CN201610987497A CN106519228B CN 106519228 B CN106519228 B CN 106519228B CN 201610987497 A CN201610987497 A CN 201610987497A CN 106519228 B CN106519228 B CN 106519228B
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dianhydride
polyimide aerogels
anhydride
spiro
present
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CN106519228A (en
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韩宝春
吴作林
朱丹阳
张春华
杨正华
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Changchun Institute of Applied Chemistry of CAS
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    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • 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
    • 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
    • C08G73/1075—Partially aromatic polyimides
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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
    • 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
    • C08G73/1039—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors comprising halogen-containing substituents
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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
    • C08G73/1046—Polyimides containing oxygen in the form of ether bonds in the main chain
    • C08G73/105—Polyimides containing oxygen in the form of ether bonds in the main chain with oxygen only in the diamino moiety
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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
    • 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
    • C08G73/1046—Polyimides containing oxygen in the form of ether bonds in the main chain
    • C08G73/1053—Polyimides containing oxygen in the form of ether bonds in the main chain with oxygen only in the tetracarboxylic moiety
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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
    • C08G73/1075—Partially aromatic polyimides
    • C08G73/1078—Partially aromatic polyimides wholly aromatic in the diamino moiety
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    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
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    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
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    • C08J2205/00—Foams characterised by their properties
    • C08J2205/02—Foams characterised by their properties the finished foam itself being a gel or a gel being temporarily formed when processing the foamable composition
    • C08J2205/026—Aerogel, i.e. a supercritically dried gel
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    • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
    • C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C08J2379/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Abstract

The present invention provides a kind of polyimide aerogels, obtain the linear polyamidoamine acid of anhydride group sealing end through amidation by diamines, dianhydride, then crosslinked dose is crosslinked, dehydrating agent dehydration, is obtained by extraction；The crosslinking agent is 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino.The present invention is with 2,2 ', 7,7 '-tetramino -9,9 '-spiro-bisfluorenes react to obtain polyimide aerogels as crosslinking agent, due to the specific tetrahedral structure and good symmetry, stability, spatial extension of spiro-bisfluorene, in combination with acid anhydride end group polyamic acid oligomer object, finally make the aeroge shrinking percentage being prepared small, heat loss temperature is high, and porosity is high.

Description

Polyimide aerogels and preparation method thereof
Technical field
The present invention relates to a kind of method for producing polymer field more particularly to a kind of polyimide aerogels and its preparation sides Method.
Background technique
Aeroge is one kind using gas as the dry state gel rubber material of decentralized medium, and solid phase and pore structure are nanometer Magnitude.Aeroge is the smallest artificial solid material of current world's upper density.These features of aeroge allow to for heat Stability insulator, catalyst carrier, filtering material, so aeroge is in fields such as integrated circuit, energy conservation and environmental protection, aerospaces Have wide practical use.
The aerosil skeleton structure for being widely studied and using at present is brittleness, in order to improve silica gas Gel mechanical performance generallys use polymer coating and carries out toughening, but used toughened resin to silicon dioxide skeleton structure, Such as epoxy resin, isocyanates, cyanoacrylate, styrene use temperature most multipotency reach 100-150 DEG C.Aviation boat Its field requires used material strictly, such as in landing system, due to the spy of structure and environment in terms of heat resistance Different property determines that its heat-barrier material must have a high temperature resistance, and the flexibility that must have of material and foldability, convenient for big Amount gas, which can be wrapped in narrow space, forms lightweight heat-proof cover.
Polyimides has good thermal stability, excellent mechanical performance and higher glass transition temperature, so Polyimides high molecular material is the first choice of space industry high performance polymer material.In view of space industry to lightweight, it is high-strength every The specific demand of hot material, design synthesized high-performance polyimide aerogels material have important scientific value and are widely applied Prospect.Polyimide aerogels are to be made by polyamic acid weak solution through chemical imidization and gelation are then dry earliest.This The aeroge of kind method preparation has strong contraction tendency, shrinking percentage nearly 40%.Chidambareswarapattar C (Chidambareswarapattar C,Larimore Z,Sotiriou-Leventis C,Mang JT,Leventis N.J.Mater.Chem.2010；20:9666-9678.) et al. report using diisocyanate and tetracarboxylic acid dianhydride reaction preparation The method of polyimide aerogels, the polymer aerogel of this method preparation have a lesser contraction at room temperature, but thermal weight loss Analysis shows that having obvious weight loss or even imidization incomplete at 200 DEG C.
Summary of the invention
In view of this, the present invention provides the technical problem to be solved in the present invention is that providing a kind of polyimide aerogels Polyimide aerogels shrinking percentage it is small, heat loss temperature is high, and porosity is high.
The present invention provides a kind of polyimide aerogels, obtain the linear of anhydride group sealing end through amidation by diamines, dianhydride Polyamic acid, then crosslinked dose of crosslinking, dehydrating agent dehydration, be obtained by extraction；The crosslinking agent is 2,2 ', 7,7 '-four ammonia Base -9,9 '-spiro-bisfluorene.
Preferably, the diamines is aromatic diamine；The dianhydride is aromatic dianhydride.
Preferably, the aromatic diamine be selected from p-phenylenediamine, 2,2 '-bis trifluoromethyl -4,4 '-benzidines, 4,4 ' - One or more of diaminodiphenyl ether and 2,2 '-bis- -4,4 '-benzidines of methyl；The aromatic dianhydride is selected from 1,2, 4,5 ,-pyromellitic acid anhydride, 3,3 ', 4,4 '-bibenzene tetracarboxylic dianhydrides, 3,3 ', 4,4 '-diphenyl ether tetraformic dianhydrides and 4, One or more of 4'- (hexafluoro isopropyl alkene) two anhydride phthalic acids.
Preferably, the molar ratio of the diamines and dianhydride is n:n+1；1≤n≤100.
Preferably, the molal quantity of the crosslinking agent is 0.5 times of acid anhydride end group molal quantity in linear polyamidoamine acid.
Preferably, the dehydrating agent is selected from one or both of acetic anhydride and pyridine.
The present invention provides a kind of preparation methods of polyimide aerogels, comprising:
A) by diamines and two anhydride reactants, the linear polyamidoamine acid solution of anhydride group sealing end is obtained；
B) the linear polyamidoamine acid solution is reacted with crosslinking agent, the polyamic acid solution being crosslinked；The crosslinking Agent is 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino；
C the polyamic acid solution of crosslinking is reacted with dehydrating agent), obtains polyimides gel；
D) polyimides gel is extracted, and obtains polyimide aerogels.
Preferably, the step B) reaction temperature be 10~25 DEG C；Reaction time is 15~25min；The step A) it is anti- Answering temperature is 10~25 DEG C；Reaction time is 20~30h.
It preferably, further include immersion treatment after the step C, the immersion treatment specifically: use acetone and N- methyl Pyrrolidones mixed solvent impregnates polyimides gel；The mass percent of mixed solvent shared by the acetone is gradually incremented by.
Preferably, the extraction is specially to use carbon dioxide supercritical extraction；The extracting pressure is 12~30Mpa；Institute Stating extraction temperature is 30~50 DEG C.
Compared with prior art, the present invention provides a kind of polyimide aerogels, are obtained by diamines, dianhydride through amidation The linear polyamidoamine of anhydride group sealing end is sour, then crosslinked dose is crosslinked, dehydrating agent dehydration, is obtained by extraction；The crosslinking agent is 2, 2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino.The present invention is reacted with 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino as crosslinking agent Polyimides gel is obtained, due to the specific tetrahedral structure of spiro-bisfluorene and good symmetry, stability, spatially extended Property, in combination with acid anhydride end group polyamic acid oligomer object, finally make the aeroge shrinking percentage being prepared small, heat loss temperature Height, porosity are high.
Detailed description of the invention
The infrared spectrogram for the polyimide aerogels that Fig. 1 embodiment of the present invention 1 is prepared；
Fig. 2 is the scanning electron microscope diagram for the polyimide aerogels that the embodiment of the present invention 1 is prepared；
Fig. 3 is thermal weight loss (TGA) curve for the polyimide aerogels that the embodiment of the present invention 1 is prepared；
Fig. 4 is the dielectric constant curve for the polyimide aerogels that the embodiment of the present invention 1 is prepared；
Fig. 5 is the N for the polyimide aerogels that the embodiment of the present invention 1 is prepared2The attached curve of absorption-desorption.
Specific embodiment
The present invention provides a kind of polyimide aerogels, obtain the linear of anhydride group sealing end through amidation by diamines, dianhydride Polyamic acid, then crosslinked dose crosslinking, dehydrating agent dehydration, be obtained by extraction；The crosslinking agent is 2,2 ', 7,7 '-tetraminos- 9,9 '-spiro-bisfluorenes.
Polyimide aerogels provided by the invention obtain the linear poly- of anhydride group sealing end through amidation by diamines, dianhydride first Amic acid；Dehydrating agent dehydration, polyimides is obtained by extraction in crosslinked dose of crosslinking of linear polyamidoamine acid of the anhydride group sealing end Gel.
In the present invention, the diamines is aromatic diamine or alicyclic diamine；The aromatic diamine is preferably selected from pair Phenylenediamine, 2,2 '--4,4 '-benzidines of bis trifluoromethyl (TFDB), 4,4 '-diaminodiphenyl ethers (4,4 '-ODA) and 2,2 ' - One or more of double -4,4 '-benzidines of methyl；The alicyclic diamine is preferably selected from two amido dicyclohexyl methyl hydrides.
The dianhydride is aromatic dianhydride or alicyclic dianhydride；The aromatic dianhydride is preferably selected from 1,2,4,5 ,-equal benzene Tetracarboxylic acid dianhydride, 3,3 ', 4,4 '-bibenzene tetracarboxylic dianhydrides (BPDA), 3,3 ', 4,4 '-diphenyl ether tetraformic dianhydrides (ODPA) and One or more of 4,4'- (hexafluoro isopropyl alkene) two anhydride phthalic acids (6FDA)；The alicyclic dianhydride is preferably selected from 1,2,3,4 ,- Cyclobutane tetracid dianhydride (CBDA), bicyclic [2.2.1] heptane -2,3,5,6- tetracid dianhydride, 1,2,4,5- hexamethylene tetracid dianhydride One or more of.
In the present invention, the molar ratio of the diamines and dianhydride is preferably n:n+1；1≤n≤100.Preferred 2≤n ≤60；Preferred 5≤n≤40；Most preferably 5≤n≤40.
In the present invention, the molal quantity of the crosslinking agent is preferably 0.5 times of acid anhydride end group molal quantity in linear polyamidoamine acid.
In the present invention, the dehydrating agent is selected from one or both of acetic anhydride and pyridine.
In the present invention, the polyimide aerogels preferably have structure shown in formula (I):
Wherein,
Above-mentioned is the chemical structure of spiro-bisfluorene, it is characterized in that two fragrant fluorenes rings are mutually perpendicular to, forms spirane structure, Four amino are introduced in its 2,2 ', 7,7 '-position, amino is just tetrahedral four vertex in the position in space, and symmetry is non- Chang Hao.Spiro-bisfluorene chemical property is highly stable, using it as high molecular structural unit, not only stable structure, and spatial extension Well, it is easier to constitute spacial framework.
1≤n≤100；
Amino residue group is removed for aromatic diamine or alicyclic diamine；
Anhydride group residue group is removed for aromatic dianhydride or alicyclic dianhydride.
In the present invention, 1≤n≤100 n is the number of repetitive unit, chooses integer；Preferred 2≤n≤ 60；Preferred 5≤n≤40；Most preferably 5≤n≤40.
In the present invention, describedAmino residue group is removed for aromatic diamine or alicyclic diamine；It is preferred that Including but not limited to structure shown in (a-1)~formula (a-4):
In the present invention, describedAnhydride group residue group is removed for aromatic dianhydride or alicyclic dianhydride, preferably Including but not limited to structure shown in formula (b-1)~formula (b-4):
The present invention provides a kind of polyimide aerogels, obtain the linear of anhydride group sealing end through amidation by diamines, dianhydride Polyamic acid, then crosslinked dose crosslinking, dehydrating agent dehydration, be obtained by extraction；The crosslinking agent is 2,2 ', 7,7 '-tetraminos- 9,9 '-spiro-bisfluorenes.It is solidifying that the present invention with 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino reacts to obtain polyimides as crosslinking agent Glue, due to the specific tetrahedral structure and good symmetry, stability, spatial extension of spiro-bisfluorene, in combination with acid anhydride End group polyamic acid oligomer object finally makes the aeroge shrinking percentage being prepared small, and heat loss temperature is high, and porosity is high.
The present invention provides a kind of preparation methods of polyimide aerogels, comprising:
A) by diamines and two anhydride reactants, the linear polyamidoamine acid solution of anhydride group sealing end is obtained；
B) the linear polyamidoamine acid solution is reacted with crosslinking agent, the polyamic acid solution being crosslinked；The crosslinking Agent is 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino；
C the polyamic acid solution of crosslinking is reacted with dehydrating agent), obtains polyimides gel；
D) polyimides gel is extracted, and obtains polyimide aerogels.
The present invention by diamines and two anhydride reactants, obtains the linear polyamidoamine acid solution of anhydride group sealing end first.It is preferred that being specially Diamines and dianhydride are mixed in a solvent, reacted, the linear polyamidoamine acid solution of anhydride group sealing end is obtained.The reaction is preferably stirred Reaction is mixed, the reaction is preferably reacted in the environment of being passed through nitrogen.
In the present invention, the diamines is aromatic diamine or alicyclic diamine；The aromatic diamine is preferably selected from pair Phenylenediamine, 2,2 '--4,4 '-benzidines of bis trifluoromethyl (TFDB), 4,4 '-diaminodiphenyl ethers (4,4 '-ODA) and 2,2 ' - One or more of double -4,4 '-benzidines of methyl；The alicyclic diamine is preferably selected from two amido dicyclohexyl methyl hydrides.
The dianhydride is aromatic dianhydride or alicyclic dianhydride；The aromatic dianhydride is preferably selected from 1,2,4,5 ,-equal benzene Tetracarboxylic acid dianhydride, 3,3 ', 4,4 '-bibenzene tetracarboxylic dianhydrides (BPDA), 3,3 ', 4,4 '-diphenyl ether tetraformic dianhydrides (ODPA) and One or more of 4,4'- (hexafluoro isopropyl alkene) two anhydride phthalic acids (6FDA)；The alicyclic dianhydride is preferably selected from 1,2,3,4 ,- Cyclobutane tetracid dianhydride (CBDA), Shuan Huan ﹝ 2.2.1) heptane -2,3,5,6- tetracid dianhydride, 1,2,4,5- hexamethylene tetracid dianhydride One or more of.
In the present invention, the molar ratio of the diamines and dianhydride is n:n+1；1≤n≤100.Preferred 2≤n≤ 60；Preferred 5≤n≤40；Most preferably 5≤n≤40.
By diamines and dianhydride with above-mentioned molar ratio reaction, what is obtained is the linear polyamidoamine acid solution of anhydride group sealing end, so as to In with cross-linking agents.
In the present invention, the reaction temperature is preferably 10~25 DEG C；More preferably 15~25 DEG C；Reaction time is preferably 20~30h；More preferably 24~30h.The reaction dissolvent be preferably selected from N-Methyl pyrrolidone, DMAC N,N' dimethyl acetamide and The one or more of dimethyl sulfoxide；More preferably one of N-Methyl pyrrolidone and DMAC N,N' dimethyl acetamide or several Kind.
Specific reaction is as follows:
After obtaining the linear polyamidoamine acid solution of anhydride group sealing end, the linear polyamidoamine acid solution is reacted with crosslinking agent, The polyamic acid solution being crosslinked；The crosslinking agent is 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino.
In the present invention, the crosslinking agent is preferably solved in solvent, and the solvent is N-Methyl pyrrolidone.Then again with Polyamic acid mixing, carries out amidation process.
The molal quantity of the crosslinking agent is preferably 0.5 times of acid anhydride end group molal quantity in linear polyamidoamine acid solution.The step Rapid B) reaction temperature is preferably 10~25 DEG C；More preferably 15~25 DEG C；The reaction time is preferably 15~25min；It is more excellent It is selected as 15~20min.
Specific reaction is as follows:
2,2 ', 7,7 '-tetramino -9,9 '-spiro-bisfluorenes are that two fragrant fluorenes rings are mutually perpendicular to, and spirane structure are formed, at it 2,2 ', 7,7 '-positions introduce four amino, and amino is just tetrahedral four vertex in the position in space, and symmetry is very good. Spiro-bisfluorene chemical property is highly stable, and using it as high molecular structural unit, not only stable structure, spatial extension is good, More easily constitute spacial framework.
After the polyamic acid solution being crosslinked, the polyamic acid solution of crosslinking is reacted with dehydrating agent, obtains polyamides Asia Amine gel.It is preferred that being specially that the polyamic acid solution of crosslinking and dehydrating agent are mixed, it is cast in mold and be dehydrated instead It answers, obtains gel.
In the present invention, the dehydrating agent is selected from one or both of acetic anhydride and pyridine.The dehydrating agent and dianhydride Molar ratio be preferably preferably (3.0~8.0): 1；More preferably (4.0~7.0): 1.The time of the mixing be 5~ 15min；More preferably 7~10min；The present invention for the agitating mode without limit, it is well known to those skilled in the art Agitating mode.The reaction time is preferably 1~3h；More preferably 1~2h.
In the present invention, the reaction time is the time to form gel, formed time of gel according to n it is different without Together, n value is bigger, and the gel time of formation is longer.
It in the present invention, further include immersion treatment after the step C, the immersion treatment is preferred specifically: uses acetone Polyimides gel is impregnated with N-Methyl pyrrolidone mixed solvent；The mass percent of mixed solvent shared by the acetone is gradually It is incremented by.
The immersion number is preferably 3~6 times；More preferably 4 times；The mass percent of mixed solvent shared by the acetone Gradually it is incremented by preferred specifically:
8~14h is impregnated for the first time with 20%~30% acetone and 70%~80% N-Methyl pyrrolidone；
8~14h is impregnated with 40%~60% acetone and second of 60%~40% N-Methyl pyrrolidone；
8~14h is impregnated with 70%~80% acetone and 20%~30% N-Methyl pyrrolidone third time；
With the 4th 8~14h of immersion of 100% acetone.
More preferably specifically:
10~12h is impregnated for the first time with 25%~30% acetone and 75%~80% N-Methyl pyrrolidone；
10~12h is impregnated with 50%~60% acetone and second of 60%~50% N-Methyl pyrrolidone；
10~12h is impregnated with 75%~80% acetone and 25%~30% N-Methyl pyrrolidone third time；
With the 4th 10~12h of immersion of 100% acetone.
Above-mentioned specific concentration gradient and specific solvent ratios cooperate specific soaking time, make it possible to preferably Solvent and the dehydrating agent etc. in gel are removed, while relative to remaining minimizing technologies such as directly overcritical removals, preferably being protected The structure and porosity of aeroge.
In the present invention, polyimides gel is extracted, and obtains polyimide aerogels.
In the present invention, the extraction is specially to use carbon dioxide supercritical extraction polyimides gel, obtains polyamides Asia Amine aeroge.The extracting pressure is preferably 12~30Mpa；More preferably 14~18Mpa；The extraction temperature is 30~50 ℃；More preferably 35~40 DEG C；The extraction time is preferably 4~6h, more preferably 5~6h.
In the present invention, by diamines, dianhydride monomer and 2,2 ', 7,7 '-tetramino -9,9 '-spiro-bisfluorenes are as crosslinking Agent prepares polyimides gel, and combines specific solvent minimizing technology, so that finally obtained aeroge porosity is high, density Low, large specific surface area, dielectric constant and dielectric loss are low, and shrinking percentage is small, and heat loss temperature is high.
Aeroge of the present invention can be applied to heat-barrier material, super large-scale integration interlevel dielectric material and In thermal insulation material.Wherein, the application concretely anti-heat insulating member such as aerospace, such as emit equipment thermostabilization thermal insulation layer, Planetary landing system, following robot and manned spaceship component.
The present invention preferably carries out performance measurement to the polyimide aerogels being prepared in the following manner:
N2The attached curve of absorption-parsing is using ASAP2000 surface area and pore-size distribution analysis-e/or determining, adsorbed gas It is N2, through 80 DEG C of Fruit storage 10h before the test of sample.
Dielectric constant and dielectric loss are tested using Agilent vector analysis instrument, measure sample having a size of cylindrical length, width and height 50mm × 30mm × 10mm, and two faces apply electrode layer (silver paste) above and below cylinder, 100 DEG C of drying.Test frequency 0- 0.35MHz。
Thermal weight loss (TGA) is measured using U.S. TA company Q-50 thermal analyzer, and heating rate is 20 DEG C/min, tests environment For nitrogen atmosphere.
In order to further illustrate the present invention, with reference to embodiments to polyimide aerogels provided by the invention and its system Preparation Method is described in detail.
Embodiment 1
As n=30,1.9274g is added in a there-necked flask equipped with mechanical stirring, temperature and nitrogen inlet The N-Methyl pyrrolidone (NMP) that (9.625mmol) 4,4 '-diaminodiphenyl ether (ODA) and 10ml newly distill is passed through nitrogen. 3.0857g (9.946mmol) 4,4 '-bibenzene tetracarboxylic dianhydride (BPDA) and 30ml NMP are added after TFDB is completely dissolved, in 25 DEG C of progress condensation polymerization reactions for 24 hours, obtain the polyamic acid solution of anhydride group sealing end.
(the crosslinking of -9,9 '-spiro-bisfluorene crosslinking agent of 0.0604g (0.016mmol) 2,2 ', 7,7 '-tetramino is added in system Agent is first dissolved in 10ml NMP, then will be in lysate addition system), in 25 DEG C of progress amidation process 20min, it is crosslinked Polyamic acid solution.
6.091g (0.077mol) pyridine and 7.854g (0.077mol) are added in the polyamic acid solution of gained crosslinking Acetic anhydride stirs 10min, is cast in mold and carries out dehydration, system is in 2h inner gel.
Obtained polyimides gel is removed from the molds, impregnates 4 repeatedly with acetone and N- pyrrolidones mixed solution It is secondary, specifically: 12h is impregnated with 25% acetone and the mixing of 75% N-Methyl pyrrolidone for the first time, for the second time with 50% Acetone and 50% N-Methyl pyrrolidone into mixing impregnate 12h, for the third time with 75% acetone and 25% N- methylpyrrole Alkanone mixing impregnate 12h, the 4th time with 100% acetone soak 12h.It will obtain polyimides gel and be added to overcritical dioxy Change and be dried in carbon reaction kettle, dry 5h, obtains polyimide aerogels under the conditions of 35 DEG C, 16Mpa.
The infrared spectrum measurement for the aeroge that embodiment 1 is prepared, as a result as shown in FIG. 1, FIG. 1 is the present invention to implement The infrared spectrogram for the polyimide aerogels that example 1 is prepared, from the foregoing, it will be observed that the aerogel structure is correct.
The aerogel material that the present invention is prepared is scanned electron microscope, N2Absorption-desorption is attached, thermal weight loss (TGA), dielectric constant and dielectric loss are tested, as a result respectively as shown in Fig. 2, Fig. 3, Fig. 4, Fig. 5.Wherein, Fig. 2 is that the present invention is real Apply the scanning electron microscope diagram for the polyimide aerogels that example 1 is prepared；Fig. 3 is what the embodiment of the present invention 1 was prepared Thermal weight loss (TGA) curve of polyimide aerogels；Fig. 4 is the polyimide aerogels that the embodiment of the present invention 1 is prepared Dielectric constant curve；Fig. 5 is the N for the polyimide aerogels that the embodiment of the present invention 1 is prepared2The attached curve of absorption-desorption.
Above-mentioned test result can be seen that the aerogel structure that is prepared of the present invention be it is nanometer fibrous, nano-pore is straight For diameter between 10nm~50nm, aeroge porosity is 92%.
The density of the aeroge is 0.110g/cm3, 5% thermal weight loss temperature is 527.226 DEG C, in 0-0.35MHz frequency model Enclosing interior dielectric constant is 1.575, dielectric loss 0.0015.
Embodiment 2
As n=30,0.8999g is added in a there-necked flask equipped with mechanical stirring, temperature and nitrogen inlet The N-Methyl pyrrolidone that (2.81mmol) -4,4 '-benzidine of 2,2 '-bis trifluoromethyl (TFDB) and 8ml newly distill (NMP) it is passed through nitrogen.0.8599g (2.92mmol) 4,4 '-bibenzene tetracarboxylic dianhydride (BPDA) is added after TFDB is completely dissolved And 6mlNMP for 24 hours in 25 DEG C of progress condensation polymerization reactions obtains the polyamic acid solution of anhydride group sealing end.
(the crosslinking of -9,9 '-spiro-bisfluorene crosslinking agent of 0.0212g (0.057mmol) 2,2 ', 7,7 '-tetramino is added in system Agent is first dissolved in 4mlNMP, then will be in lysate addition system), in 25 DEG C of progress amidation process 20min, what is be crosslinked is poly- Amide acid solution.
1.849g (23.38mmol) pyridine and 2.387g are added in the polyamic acid solution of gained crosslinking (23.38mmol) acetic anhydride stirs 10min, is cast in mold and carries out dehydration, system is in 2h inner gel.
Obtained polyimides gel is removed from the molds, is mixed with acetone with N- pyrrolidones (acetone is incremented by step by step) Solution impregnates 4 times repeatedly.Specifically: 12h is impregnated with 25% acetone and the mixing of 75% N-Methyl pyrrolidone for the first time, the It is secondary to impregnate 12h into mixing with 50% acetone and 50% N-Methyl pyrrolidone, for the third time with 75% acetone and 25% N-Methyl pyrrolidone mixing impregnate 12h, the 4th time with 100% acetone soak 12h.It will obtain the addition of polyimides gel It is dried into supercritical carbon dioxide reaction kettle, dry 5h, obtains polyimide aerogels under the conditions of 35 DEG C, 16Mpa.
It is surveyed using the polyimide aerogels that the embodiment of the present invention 2 is prepared in method same as Example 1 It is fixed, the results showed that for nanometer bore dia between 10nm~100nm, aeroge porosity is 86.2%.The density of the aeroge is 0.113g/cm3, 5% thermal weight loss temperature is 480.923 DEG C, and glass transition temperature is 538.82 DEG C in 0-0.35MHz frequency model Enclosing interior dielectric constant is 1.861, dielectric loss 0.0019.
Embodiment 3
As n=30,1.4867g is added in a there-necked flask equipped with mechanical stirring, temperature and nitrogen inlet The N-Methyl pyrrolidone (NMP) that (7.425mmol) 4,4 '-diaminodiphenyl ether (ODA) and 10ml newly distill is passed through nitrogen. After TFDB is completely dissolved be added 2.3802g (7.672mmol) 3,3 ', 4,4 '-diphenyl ether tetraformic dianhydride (ODPA) and 17mlNMP for 24 hours in 25 DEG C of progress condensation polymerization reactions obtains the polyamic acid solution of anhydride group sealing end.
- 9,9 '-spiro-bisfluorene crosslinking agent of 0.0466g (0.0124mmol) 2,2 ', 7,7 '-tetramino is added in system (to hand over Connection agent is first dissolved in 10ml NMP, then will be in lysate addition system), in 25 DEG C of progress amidation process 20min, it is crosslinked Polyamic acid solution.
4.849g (61.38.mmol) pyridine and 6.260g are added in the polyamic acid solution of gained crosslinking (61.38mmol) acetic anhydride stirs 10min, is cast in mold and carries out dehydration, system is in 2h inner gel.
Obtained polyimides gel is removed from the molds, is mixed with acetone with N- pyrrolidones (acetone is incremented by step by step) Solution impregnates 4 times repeatedly.Specifically: 12h is impregnated with 25% acetone and the mixing of 75% N-Methyl pyrrolidone for the first time, the It is secondary to impregnate 12h into mixing with 50% acetone and 50% N-Methyl pyrrolidone, for the third time with 75% acetone and 25% N-Methyl pyrrolidone mixing impregnate 12h, the 4th time with 100% acetone soak 12h.It will obtain the addition of polyimides gel It is dried into supercritical carbon dioxide reaction kettle, dry 5h, obtains polyimide aerogels under the conditions of 35 DEG C, 16Mpa.
It is surveyed using the polyimide aerogels that the embodiment of the present invention 3 is prepared in method same as Example 1 It is fixed, the results showed that for nanometer bore dia between 10nm~100nm, aeroge aperture rate is 82.61%.The density of the aeroge For 0.119g/cm3, 5% thermal weight loss temperature is 460.458 DEG C, and glass transition temperature is 502.44 DEG C in 0-0.35MHz frequency Dielectric constant is 1.965 in range, dielectric loss 0.0022.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For member, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also answered It is considered as protection scope of the present invention.

Claims (7)

1. a kind of polyimide aerogels, which is characterized in that obtain the linear polyamides of anhydride group sealing end through amidation by diamines, dianhydride Amino acid, then crosslinked dose crosslinking, dehydrating agent dehydration, be obtained by extraction；The crosslinking agent is 2,2 ', 7,7 '-tetramino -9, 9 '-spiro-bisfluorenes；Aromatic diamine is selected from p-phenylenediamine, 2,2 '--4,4 '-benzidines of bis trifluoromethyl, 4,4 '-two amidos two One or more of phenylate and 2,2 '-bis- -4,4 '-benzidines of methyl；Aromatic dianhydride is selected from 1,2,4,5 ,-equal benzene tetramethyl Acid dianhydride, 3,3 ', 4,4 '-bibenzene tetracarboxylic dianhydrides, 3,3 ', 4,4 '-diphenyl ether tetraformic dianhydrides and 4,4'- (hexafluoro isopropyl alkene) One or more of two anhydride phthalic acids；The molal quantity of the crosslinking agent is 0.5 times of acid anhydride end group molal quantity in linear polyamidoamine acid.
2. polyimide aerogels according to claim 1, which is characterized in that the molar ratio of the diamines and dianhydride is n: n+1；1≤n≤100.
3. polyimide aerogels according to claim 1, which is characterized in that the dehydrating agent is selected from acetic anhydride and pyridine One or both of.
4. a kind of preparation method of polyimide aerogels, comprising:
A) by diamines and two anhydride reactants, the linear polyamidoamine acid solution of anhydride group sealing end is obtained；
B) the linear polyamidoamine acid solution is reacted with crosslinking agent, the polyamic acid solution being crosslinked；The crosslinking agent is 2,2 ', 7,7 '--9,9 '-spiro-bisfluorenes of tetramino；
C the polyamic acid solution of crosslinking is reacted with dehydrating agent), obtains polyimides gel；
D) polyimides gel is extracted, and obtains polyimide aerogels.
5. the preparation method according to claim 4, which is characterized in that the step B) reaction temperature be 10~25 DEG C；Instead It is 15~25min between seasonable；The step A) reaction temperature be 10~25 DEG C；Reaction time is 20~30h.
6. the preparation method according to claim 4, which is characterized in that it further include immersion treatment after the step C, it is described Immersion treatment specifically: impregnate polyimides gel with acetone and N-Methyl pyrrolidone mixed solvent；It is mixed shared by the acetone The mass percent of bonding solvent is gradually incremented by.
7. preparation method according to claim 6, which is characterized in that the extraction is specially to be extracted with CO 2 supercritical It takes；The extracting pressure is 12~30Mpa；The extraction temperature is 30~50 DEG C.
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