CN113480773A

CN113480773A - Aerogel, conductive nanofiber, preparation method and application thereof

Info

Publication number: CN113480773A
Application number: CN202110718640.6A
Authority: CN
Inventors: 周剑; 范俊呈; 李恒瑞; 彭柏霖; 金炫利
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2021-06-28
Filing date: 2021-06-28
Publication date: 2021-10-08
Anticipated expiration: 2041-06-28
Also published as: CN113480773B

Abstract

The invention provides aerogel, conductive nanofiber, and a preparation method and application thereof. The conductive polymer PBP is adopted to modify the aerogel, so that the using amount of the conductive polymer in the preparation process of the aerogel can be reduced, and the conductivity of the aerogel is obviously improved. The inner wall of the aerogel prepared by slow freezing is smooth; the aerogel prepared by adopting quick freezing has a nanofiber structure inside and high conductivity.

Description

Aerogel, conductive nanofiber, preparation method and application thereof

Technical Field

The invention belongs to the technical field of nano materials, and particularly relates to aerogel, conductive nanofiber, a preparation method and application thereof.

Background

Aerogels are the least dense materials with densities approaching that of air, and are also porous materials with porosities in excess of 99%, and therefore these properties are the most unique properties in many potential applications.

Aerogel materials are an ideal alternative to insulation materials, being less expensive and readily available than other insulation materials, driving the need for such materials in a variety of end-user applications and industries. Increased globalization and urbanization have led to the development of infrastructure in developed and developing countries, another key factor driving the growth of the global aerogel market. The increasing demand for aerogels has driven the growth of the global aerogel market due to their light diffusing, thermal insulating, and high surface area properties in architectural applications. Furthermore, advances and innovations in materials, increased awareness of product benefits, and the use of aerogels in new application areas are expected to promote growth in the global aerogel market over the projected period. A major and growing trend in the market is the increased awareness of global warming and the increasing need for more environmentally friendly and efficient insulation materials in the construction field, especially in developing countries.

However, the current aerogel still has the defects of high density or high resistance, and the wide application of the aerogel is limited.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art described above. To this end, the first aspect of the present invention provides an aerogel that can reduce the amount of raw material used and significantly improve the electrical conductivity thereof.

The second aspect of the invention provides a preparation method of the aerogel.

The third aspect of the invention provides an application of the aerogel.

A fourth aspect of the present invention proposes a sensor comprising the aerogel described above as a conductive layer.

According to a first aspect of the present invention, there is provided an aerogel comprising an electrically conductive polymer and a polyethylene-block-poly (ethylene glycol).

In the invention, Polyethylene-block-poly (ethylene glycol) (PBP) is a conductive polymer, so that the consumption of the conductive polymer in the preparation process of the aerogel can be reduced, the conductivity of the aerogel is obviously improved, and the long-chain block structure in the PBP also increases the mechanical strength of the prepared aerogel precursor solution, so that the frame structure of the aerogel can be well maintained in the subsequent sublimation process and is in a relatively ordered state, and the conductivity of the aerogel is greatly improved.

In some embodiments of the invention, the mass of the polyethylene-block-poly (ethylene glycol) comprises 10% to 70% of the sum of the masses of the conductive polymer and the polyethylene-block-poly (ethylene glycol).

In some preferred embodiments of the invention, the conductive polymer comprises a mixture of poly (3, 4-ethylenedioxythiophene) (PEDOT) and poly (styrenesulfonic acid) (PSS).

In some preferred embodiments of the present invention, the conductive polymer comprises poly (3, 4-ethylenedioxythiophene) and poly (styrenesulfonic acid) in a mass ratio of 1: (1-10).

According to a second aspect of the present invention, there is provided a method for preparing the aerogel, comprising the steps of: freezing a solution containing a conductive polymer and polyethylene block-poly (ethylene glycol) and then carrying out vacuum drying to prepare the aerogel.

In some embodiments of the invention, the freezing comprises slow freezing and/or fast freezing, the freezing temperature of the slow freezing is-20 ℃ to-50 ℃, and the time of the slow freezing is preferably 6h to 72 h; the freezing temperature of the quick freezing is-90 ℃ to-220 ℃, and the quick freezing time is preferably 3min to 10 min; further preferably, the temperature of the quick freezing is-150 ℃ to-200 ℃, and the time of the quick freezing is 3min to 10 min. In the invention, the low-density, high-porosity and high-conductivity aerogel can be obtained by modifying the PBP by adopting slow freezing or quick freezing. Among them, the freezing temperature of slow freezing is high, the freezing rate is slow, the radial cross section of the prepared aerogel shows pores of hundreds of microns width, and the wall of the formed aerogel is ultra-thin and smooth due to the slow freezing rate and long time.

In some preferred embodiments of the present invention, the freezing is fast freezing, the freezing temperature of the fast freezing is-90 ℃ to-220 ℃, and the time of the fast freezing is preferably 3min to 10 min. Use quick freezing to the aerogel to freeze, the aquogel can be at extremely low temperature (for example under the liquid nitrogen) the coagulation for the solid, this process freezing speed is fast, it is extremely short to duration, can not cause too big influence to the frame construction of aquogel, can fine maintain the original frame construction of aquogel and form the aerogel, for the aerogel that slowly freezes and make, the aerogel mechanical properties that quick freezing made is strong, and gas content is few in the system, and actual frame composition is more, and solid content is more, therefore its electric conductivity is strong.

In some more preferred embodiments of the present invention, the temperature of the vacuum drying is 20 ℃ to 90 ℃, and preferably, the time of the vacuum drying is 24h to 72 h.

In some more preferred embodiments of the present invention, the method for preparing the aerogel further comprises: and carrying out steam annealing treatment on the aerogel.

In some more preferred embodiments of the present invention, the steam is any one of water vapor, methanol vapor, ethylene glycol vapor, sulfolene vapor.

In some more preferred embodiments of the present invention, the temperature of the annealing treatment is 150 ℃ to 170 ℃; preferably, the time of the annealing treatment is 15min to 120 min.

According to a third aspect of the present invention, there is provided a use of an aerogel in an electrically conductive material, wherein the aerogel is the aerogel or is prepared by the aerogel preparation method.

According to a fourth aspect of the present invention, a sensor is presented, the conductive layer of which comprises the aerogel described above.

The invention has the beneficial effects that:

1. according to the invention, the conductive polymer PBP is adopted to modify the aerogel, so that on one hand, the consumption of the conductive polymer in the preparation process of the aerogel can be reduced, and the conductivity of the aerogel is obviously improved; on the other hand, the long-chain block structure in the PBP also enables the mechanical strength of the prepared aerogel precursor solution to be increased, so that the frame structure of the aerogel can be well maintained in the subsequent sublimation process and is in a relatively ordered state, and the conductivity of the aerogel is greatly improved.

2. The aerogel prepared by slow freezing has smooth inner wall; the aerogel prepared by adopting quick freezing has a nanofiber structure inside and high conductivity.

3. According to the invention, the steam annealing treatment is carried out on the aerogel, so that the conductivity of the aerogel can be obviously improved.

Drawings

The invention is further described with reference to the following figures and examples, in which:

FIG. 1 is an SEM image of aerogel sample A of example 1 of the present invention.

FIG. 2 is an SEM image of aerogel sample A of example 1 of the present invention.

FIG. 3 is an SEM image of aerogel sample A of example 1 of the present invention.

FIG. 4 is an SEM image of aerogel sample B of example 2 according to the invention.

FIG. 5 SEM image of aerogel sample B of example 2 of the invention.

FIG. 6 SEM image of aerogel sample B of example 2 of the invention.

FIG. 7 SEM image of aerogel sample B of example 2 of the invention.

FIG. 8 SEM image of comparative example 1 aerogel sample D of the present invention.

FIG. 9 SEM image of inventive comparative example 1 aerogel sample D.

FIG. 10 SEM image of inventive comparative example 1 aerogel sample D.

FIG. 11 SEM image of comparative example 2 aerogel sample E of the invention.

FIG. 12 SEM image of comparative example 2 aerogel sample E of the invention.

FIG. 13 SEM image of comparative example 2 aerogel sample E of the invention.

FIG. 14 SEM image of inventive comparative example 2 aerogel sample F.

FIG. 15 SEM image of inventive comparative example 2 aerogel sample F.

FIG. 16 SEM image of inventive comparative example 2 aerogel sample F.

FIG. 17 XRD pattern of aerogel sample A, inventive example 1.

FIG. 18 XRD pattern of aerogel sample B, example 2 of the invention.

FIG. 19 XRD pattern of comparative example 1 aerogel sample D of the present invention.

FIG. 20 XRD pattern of comparative example 2 aerogel sample F of the present invention.

Detailed Description

The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Example 1

This example prepared an aerogel, and the concrete process was:

s1: adding a certain amount of PBP into 5g of PEDOT/PSS aqueous solution (the solid mass ratio of the PBP to the PEDOT/PSS is 1:1), then adding water into the PEDOT/PSS/PBP aqueous solution to dilute the solution to 0.25 wt%, and stirring for 30 minutes;

s2: 2mL of the solution prepared in S1 was put into a centrifuge tube, sealed (the cover of the centrifuge tube was perforated with small holes to allow air to pass during freeze-drying), frozen in a freezing area of a refrigerator (about-20 ℃) for 6 hours, taken out and put into a freeze-dryer for drying for about 48 hours to obtain aerogel sample A.

Example 2

This example prepared an aerogel, and the concrete process was:

s2: and (3) putting 2mL of the solution prepared in the step (S1) into a centrifuge tube, sealing the centrifuge tube (the cover of the centrifuge tube needs to be provided with a plurality of small holes so as to be breathable during freeze drying), vertically putting the centrifuge tube into liquid nitrogen for about 5min, taking the centrifuge tube out of the liquid nitrogen, quickly opening the cover of the centrifuge tube, sealing the centrifuge tube by using roll paper and a rubber band (the sample can be prevented from being flushed out during freeze drying), and then putting the centrifuge tube into a freeze dryer for drying for about 48h to prepare an aerogel sample B.

The above steps were repeated to produce aerogel sample C.

Comparative example 1

The aerogel prepared in this example is different from the aerogel prepared in example 1 in that PBP modification is not adopted, and the specific process is as follows:

s1: 5g of PEDOT/PSS (1.1 wt%) solution was diluted to 0.25 wt% with water and stirred for 15 min;

s2: 2mL of the solution obtained in S1 was put into a centrifuge tube, sealed (the cover of the centrifuge tube was perforated with small holes to allow air to pass during freeze-drying), frozen in a freezing area of a refrigerator (about-20 ℃) for 6 hours, taken out and put into a freeze-dryer for drying for about 48 hours to obtain aerogel sample D.

Comparative example 2

This comparative example prepared an aerogel, which differs from example 2 in that PBP modification was not employed, and the specific procedure was:

s1: : 5g of PEDOT/PSS (1.1 wt%) solution was diluted to 0.25 wt% with water and stirred for 15 min;

s2: and (3) putting 2mL of the solution prepared in the step (S1) into a centrifuge tube, sealing the centrifuge tube (the cover of the centrifuge tube needs to be provided with a plurality of small holes so as to be breathable during freeze drying), vertically putting the centrifuge tube into liquid nitrogen for about 5min, taking the centrifuge tube out of the liquid nitrogen, quickly opening the cover of the centrifuge tube, sealing the centrifuge tube by using roll paper and a rubber band (the sample can be prevented from being flushed out during freeze drying), and then putting the centrifuge tube into a freeze dryer for drying for about 48h to prepare an aerogel sample E.

The above steps were repeated to produce aerogel sample F.

Example 3

Correspondingly preparing aerogel samples G to L according to the preparation methods of the embodiments 1 to 2 and the comparative examples 1 to 2, respectively, placing the aerogel samples G to L in a closed glass bottle containing glycol, and heating the glass bottle at 150 ℃ for 30 minutes in vacuum. After ethylene glycol steam annealing, the aerogels were left at 150 ℃ for 30 minutes to remove ethylene glycol residues.

Test example 1

The irregularly shaped aerogel was sawn off with a sharp utility knife or blade, and the size, mass, and resistance of the aerogel samples a to G were measured and the density was calculated, and the results are shown in table 1.

TABLE 1

From table 1, it can be seen that in the general trend, the density of the aerogel samples B, C and E, F obtained using fast freezing was greater than that of the slow freezing sample A, D for the same formulation, and the resistance of the fast freezing aerogel was slightly lower than that of the slow freezing aerogel. The liquid in the hydrogel is condensed into a solid in a short time at extremely low temperature by quick freezing, so that the frame structure of the hydrogel is not greatly influenced, the original frame structure can be maintained well, and the finally prepared aerogel has low resistance; and slow freezing is longer owing to reach the consuming time of sample frozen state, therefore hydrogel frame structure is more easily destroyed at the freezing in-process, probably lead to the collapse of original structure, lead to aerogel mechanical properties to worsen, lead to the inside gas of aerogel system that prepares to increase, therefore the whole density is freezing relatively low fast, and simultaneously because the system is interior gaseous more, actual frame composition is less, the solid content is low, because inside has more gas to exist during the measurement resistance, electronic transmission is difficult, and lead to measuring the faster sample of freezing of resistance and be slightly higher.

From table 1, it can also be seen that, after PBP is added, the density of the aerogel does not change much, but the resistance value changes significantly, and the resistance value of the aerogel sample prepared by adding PBP is significantly smaller than that of the aerogel sample without PBP, that is, the electrical conductivity of the aerogel can be improved by adding PBP during the preparation of the aerogel.

Test example 2

The morphology of the aerogel sample A, B, D, E, F was observed under SEM and the aerogel structure formed was analyzed, with the results shown. Wherein, SEM images of aerogel sample A are shown in figure 1 (1000X), figure 2 (2000X), and figure 3 (5000X); SEM pictures of aerogel sample B are shown in fig. 4(1000 ×), fig. 5(2000 ×), fig. 6(5000 ×), fig. 7(14500 ×); SEM images of aerogel sample D are shown in fig. 8(1000 ×), fig. 9(2000 ×), fig. 10(5000 ×); SEM images of aerogel sample E are shown in fig. 11(1000 ×), fig. 12(2000 ×), fig. 13(5000 ×); the SEM images of aerogel sample F are shown in fig. 14(1000 ×), fig. 15(2000 ×), and fig. 16(5000 ×).

As can be seen from fig. 1 to 16, regardless of whether PBP is added, the aerogel with a better pore structure can be prepared by fast freezing rather than slow freezing, and the aerogel is easier to have a fiber structure, while the aerogel prepared by slow freezing tends to have a smooth lamellar structure; while aerogel sample A, B with added PBP exhibited a more pronounced fibrous structure than aerogel sample D, E, F without added PBP, the aerogel body portion was comprised of fibers, essentially no porous structure, but rather formed an aggregate of intertwined fibers; whereas aerogel sample E, F, made without the addition of PBP and with fast freezing, exhibited very high porosity and a uniform pore structure, which is a very good aerogel structure. It can be seen that PBP, as a block copolymer, has a high impact on PEDOT: the PSS polymer structure affects the formation of fibers, and can promote the formation of fibers from the polymer. Thus, the degree of fiberization of the aerogel material can be controlled by controlling the amount of PBP added for a particular application.

The crystalline morphology of the aerogel sample A, B, D, F nanofiber material was characterized by XRD and the results are shown in fig. 17, fig. 18, fig. 19 and fig. 20, respectively.

As can be seen from fig. 17 to 20, XRD diffraction results of the four aerogel samples all appear as "steamed bread peaks", reflecting that their main structures are amorphous and amorphous. The slow frozen aerogel sample A, D had a relatively sharp peak at approximately 2 θ at 3.2 °, which reflects the relatively ordered arrangement of atoms in the aerogel framework and higher crystallinity of the slow frozen aerogel sample. This and the following diffraction peak at approximately 2 θ ═ 26 ° may correspond to the alternating stacking of thin layers in the PEDOT/PSS fibers, and the interchain pi-pi stacking in the PEDOT segments. Aerogel sample A, B with added PBP exhibited a small diffraction peak at approximately 21.8 ° 2 θ, which may be related to the relative ordering of the PBP and PEDOT/PSS fibers or to the increased degree of ordering and crystallinity of the PEDOT/PSS arrangement caused by the PBP. The relative intensity of a diffraction peak of the PBP modified fiber at 26 degrees 2 theta is increased, which shows that PEDOT fragments have better crystallization accumulation, so that the conductivity of the PEDOT/PSS fiber is improved after PBP is added. The quinoid planar structure will facilitate the alignment of PEDOT fragments. Meanwhile, after PBP modification, the proportion of quinoid structures in the fiber is increased, which leads to flattening of PEDOT chains, thus leading to reduction of pi-pi stacking distance, which reduces electron paths on and between chains, thus leading to higher conductivity of the fiber.

Test example 3

The resistance of the aerogels of example 3 before and after treatment with ethylene glycol steam was measured and the results are shown in table 2:

TABLE 2

Sample (I)	Resistance before treatment (k omega)	Post-treatment resistance (omega)	Rate of change of resistance
				Aerogel sample G	0.863	32.925	96.185％
Aerogel sample H	0.88	14.311	98.374％
				Aerogel sample I	0.336	29.084	91.344％
Aerogel sample J	13.22	28.066	99.788％
				Aerogel sample K	4.308	153.916	96.427％
Aerogel sample L	9.86	10.768	99.891％

Remarking: the sizes of the aerogel samples G to L are slightly different from those of the aerogel samples A to F, so that the resistances before treatment are slightly different, but the total resistances are similar.

As can be seen from Table 2, the resistance value of the aerogel sample after being treated with ethylene glycol is greatly reduced, which indicates that the ethylene glycol treatment can significantly improve the conductivity of the aerogel.

The embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments, and various changes can be made without departing from the gist of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

Claims

1. An aerogel, characterized by: including conductive polymers and polyethylene-block-poly (ethylene glycol).

2. Aerogel according to claim 1, characterized in that: the mass of the polyethylene-block-poly (ethylene glycol) accounts for 10-70% of the sum of the mass of the conductive polymer and the mass of the polyethylene-block-poly (ethylene glycol).

3. Aerogel according to claim 1, characterized in that: the conductive polymer includes a mixture of poly (3, 4-ethylenedioxythiophene) and poly (styrenesulfonic acid).

4. Aerogel according to claim 1, characterized in that: the conductive polymer comprises poly (3, 4-ethylenedioxythiophene) and poly (styrenesulfonic acid) according to a mass ratio of 1: (1-10).

5. A method for preparing an aerogel according to any of claims 1 to 4, wherein: the method comprises the following steps: freezing a solution containing a conductive polymer and polyethylene block-poly (ethylene glycol) and then carrying out vacuum drying to prepare the aerogel.

6. Method for the preparation of aerogels according to claim 5, characterized in that: the freezing comprises slow freezing and/or fast freezing; the freezing temperature of the slow freezing is-20 ℃ to-50 ℃, and the freezing temperature of the fast freezing is-90 ℃ to-220 ℃.

7. Method for the preparation of aerogels according to claim 5, characterized in that: the freezing is quick freezing, the freezing temperature of the quick freezing is-90 ℃ to-220 ℃, and the quick freezing time is 3min to 10 min.

8. Method for the preparation of aerogels according to claim 5, characterized in that: the preparation method of the aerogel also comprises the following steps: and carrying out steam annealing treatment on the aerogel.

9. Use of an aerogel as claimed in any one of claims 1 to 4 or prepared by a method of preparing an aerogel as claimed in any one of claims 5 to 8 in an electrically conductive material.

10. A sensor, the conductive layer of the sensor comprises the aerogel of any one of claims 1 to 4 or the aerogel prepared by the preparation method of the aerogel of any one of claims 5 to 8.