KR-20260066730-A - Preparation of hydrophobic, mechanically flexible, and optically transparent polyimide aerogels

Abstract

The present invention relates to a method for producing physically crosslinked polyimide (PCPI) aerogels with significantly improved physical properties without using chemical crosslinking agents. The produced PCPI aerogels exhibit high moisture resistance, hydrophobicity, ultra-low density, ultra-high porosity, excellent thermal stability, enhanced mechanical strength, and high mechanical flexibility. Furthermore, samples in the form of thin films with high mechanical flexibility and controlled thickness were successfully produced. Moreover, some of the produced aerogel films exhibit enhanced optical transparency of over 80%, which is the highest level of transparency reported for organic polyimide aerogels.

Inventors

• 나기브 하니
• 아가바바에이 타프레쉬 오미드
• 가파리-모사넨자데 샤리아르
• 사다트니아 지아

Assignees

• 더 가버닝 카운슬 오브 더 유니버시티 오브 토론토

Dates

Publication Date

20260512

Application Date

20240909

Priority Date

20230908

Claims (20)

1. In a polyimide aerogel comprising a polyimide-based polymer of Formula 1: Equation 1 A polyimide aerogel characterized in that n is an integer greater than or equal to 10, the polyimide-based polymer is physically cross-linked through polymer chain entanglement and formed by a process including initial gelation for 1 to 10 minutes, and the polyimide aerogel is not a major source of polyamic amide polymer, or the polyimide aerogel does not contain polyamic amide polymer.
2. The polyimide aerogel according to claim 1, characterized in that the pore size of the polyimide aerogel is 2 nanometers to 100 nanometers.
3. A polyimide aerogel according to claim 1 or 2, characterized in that the pore size of the polyimide aerogel is less than 2 nanometers.
4. A polyimide aerogel characterized in that, in any one of claims 1 to 3, the porosity of the polyimide aerogel is 85% to 99%.
5. A polyimide aerogel characterized in that, in any one of claims 1 to 4, the polyimide aerogel does not have a chemical crosslinking agent.
6. In any one of claims 1 to 5, the density of the polyimide aerogel is 0.07 g/cm³ inside Polyimide aerogel characterized by having a g/cm³ of 0.25 g.
7. A polyimide aerogel characterized in that, in any one of claims 1 to 6, the thermal conductivity of the polyimide aerogel is 15 to 50 mW/(m·K).
8. A polyimide aerogel according to any one of claims 1 to 7, characterized in that the polyimide aerogel has hydrophobicity in a water contact angle range of 90 to 140 degrees.
9. A polyimide aerogel characterized in that, in any one of claims 1 to 8, the water absorption rate of the polyimide aerogel is 1%.
10. A polyimide aerogel characterized in that, in any one of claims 1 to 9, the thermal decomposition initiation temperature of the polyimide aerogel is 500°C to 700°C.
11. A polyimide aerogel characterized in that, in any one of claims 1 to 10, the dielectric constant of the polyimide aerogel is 1.5 to 3.
12. A polyimide aerogel according to any one of claims 1 to 11, characterized in that the polyimide aerogel is in the form of a film with a thickness of 80 microns or more and has a light transparency of 60% to 99%.
13. A polyimide aerogel characterized in that, in any one of claims 1 to 12, the compressive modulus of the polyimide aerogel is 17 to 25 megapascals (MPa).
14. A polyimide aerogel characterized in that, in any one of claims 1 to 13, the tensile modulus of the polyimide aerogel is 1 to 5 megapascals (MPa).
15. A polyimide aerogel characterized in that, in any one of claims 1 to 14, the integer n is in the range of 10 to 60, 10 to 50, or 30 to 50.
16. A method for manufacturing a polyimide aerogel according to any one of claims 1 to 15: - A step of forming a polymer of Formula A by reacting a diamine monomer (DIAM) and a dianhydride monomer (DIAH) in a reaction solution containing a dipolar aprotic solvent to form a wet gel (n is an integer greater than or equal to 10); Formula A; - Step of imidizing the formed polymer; - A step of gelling the formed polymer for 1 to 10 minutes; - A step of replacing the aprotic solvent with a dry solvent; and - A method characterized by including the step of removing a drying solvent from a formed wet gel.
17. A method according to claim 16, characterized in that the step of imidizing the formed polymer is performed through thermal imidization or chemical imidization.
18. A method according to claim 16 or 17, further comprising the step of aging the wet gel obtained by initial gelation to increase the polymerization yield and improve the degree of physical crosslinking.
19. A method according to any one of claims 16 to 18, characterized in that the aprotic solvent is N-methylpyrrolidinone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or a mixture of NMP and tetrahydrofuran (THF).
20. A method characterized in that, in any one of claims 16 to 19, the step of reacting the DIAM monomer and the DIAH monomer is performed without using a chemical crosslinking agent.

Description

Preparation of hydrophobic, mechanically flexible, and optically transparent polyimide aerogels The present invention relates to the synthesis of a physically cross-linked polyimide (PCPI) aerogel that is hydrophobic, mechanically flexible, and optically transparent. Aerogel is a material created by removing the liquid portion without damaging the solid network of the gel. Thanks to its mesoporous structure and high porosity of over 80%, aerogel exhibits ultra-low thermal conductivity (as low as 4 mW/m· K), it exhibits unique properties such as extremely low density, high porosity, high compressive strength, and a large surface area. These characteristics suggest the potential for aerogels to be utilized in a wide range of industrial fields, including ultra-thermal insulation, optics, soundproofing, airborne nanoparticle filtration, oil/organic solvent-water separation, energy harvesting, energy storage devices, electromagnetic shielding, and catalysts. Aerogels can be made from a wide range of materials capable of forming a gel. Among these, silica has been the most studied. However, due to its high brittleness and hydrophobicity, its use in industrial applications has been significantly limited. Organic polyimide (PI) aerogels have attracted the attention of scientists over the past decade due to their potential for improved ductility and high operating temperatures. Generally, PI gels are prepared by crosslinking the formed polymer chains with a chemical crosslinking agent after the stepwise polymerization of at least one diamine and dianhydride monomer[1]-[4]. Next, the formed gel is converted into an aerogel using supercritical drying or freeze-drying techniques. Based on this method, most research focuses on improving properties by modifying the aerogel's framework by changing the monomer composition or the type of chemical crosslinking agent, with the exception of a few studies ([5],[6]) that control properties by adjusting the aerogel's morphology. In this context, H. Guo used octa(aminophenyl)silses-quioxane (OAPS) chemical crosslinking agent, which has a silsesquioxane cage structure composed of a silicon and oxygen backbone and eight aminophenyl groups, to bond various monomers including bisaniline-p-xylidene (BAX), 2,2'-dimethylbenzidine (DMBZ), p-phenylenediamine (PPDA), and 4,4'-oxydianiline (ODA) diamine with 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) monomer through reaction [2], [4]. As a result, the OAPS crosslinked PI aerogel had slightly lower shrinkage rate and density compared to a previously reported 1,3,5-triaminophenoxybenzene (TAB) crosslinked aerogel with a similar backbone. In addition, OAPS crosslinked PI aerogels containing more than 50% DMBZ mol% in the framework showed improved moisture resistance. However, OAPS is not commercially available and is a very expensive chemical crosslinking agent. In contrast to OAPS, TAB-crosslinked PI aerogels have been reported to have improved mechanical properties but poor moisture resistance. According to MAB Meador, the idea of replacing 50 mol% of the diamine content with polypropylene glycol (PPG) to improve the moisture resistance of TAB-crosslinked PI aerogels was proposed [7]. According to this study, replacing at least 50 mol% of the ODA content with PPG resulted in an increase in the water contact angle to approximately 80° and a very low water absorption rate. Another study reported that compared to OAPS-crosslinked aerogels, TAB-crosslinked PI aerogels prepared with DMBZ diamine had a larger surface area and a fourfold increase in elastic modulus while increasing density by only 26% [3]. Due to their low cost and commercial availability, 1,3,5-benzenetricarbonyl trichloride (BTC) crosslinking agents have recently been widely used in PI aerogel research. Experimental results showed that the BTC cross-linked aerogel had a similar or higher compressive modulus and a larger surface area compared to OAPS cross-linked aerogel of similar density. However, the problem with the BTC cross-linked PI aerogel is that it has poor moisture resistance. Even the strategy of replacing 100% diamine content with hydrophobic DMBZ monomers was not successful in improving the moisture resistance of BTC-crosslinked PI aerogels. Subsequent research investigated Desmodur N3300A, a triisocyanate, for the crosslinking of PI aerogels as a cost-effective alternative [8]. Chemical crosslinking using triisocyanates has been reported to exhibit mechanical properties equivalent to or higher than those of OAPS, TAB, and BTC. However, triisocyanates have a low decomposition onset temperature, which lowers the operating temperature of the aerogel and may limit its applications. Additionally, some studies have reported that PI aerogels prepared without chemical crosslinking agents are limited to those derived from pyromellitic acid dianhydride (PMDA). These aerogels have been reported to exhibit very high shrinkage behavior and/or high mechanical brittl