CN112210038B

CN112210038B - Degradable polymer, preparation method thereof and method for transferring graphene by using degradable polymer

Info

Publication number: CN112210038B
Application number: CN202010958591.9A
Authority: CN
Inventors: 马金鑫; 徐鑫; 余杰; 李昕; 姜浩; 史浩飞
Original assignee: Chongqing Graphene Technology Co Ltd
Current assignee: Chongqing Graphene Technology Co Ltd
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2022-05-20
Anticipated expiration: 2040-09-14
Also published as: CN112210038A

Abstract

The invention relates to a degradable polymer, a preparation method thereof and a method for transferring graphene by using the degradable polymer, which comprises the following steps: s100: mixing and reacting polyamine compounds and multi-aldehyde compounds in a solvent to obtain a compound with a Schiff base structure in a main chain; s200: and mixing the compound with a bifunctional monomer, and carrying out catalytic reaction by using an alkali catalyst to obtain a product. The degradable polymer prepared by the method has high enough molecular weight and glass transition temperature, so that the support strength of the resin film to graphene in the transfer process can be kept, and the integrity of the graphene can be ensured; at the same time, has enough alkali resistance; in an acidic aqueous environment, the degradable polymer can be rapidly degraded into small molecules and oligomers without heating, a high molecular chain is broken and unwound, the solubility is obviously improved, and meanwhile, polymer molecules coated on graphene defects and surface impurities are degraded to fall off and peel off, so that clean transfer of graphene is realized.

Description

Degradable polymer, preparation method thereof and method for transferring graphene by using degradable polymer

Technical Field

The invention belongs to the field of polymer chemistry, and particularly relates to a degradable polymer, a preparation method thereof and a method for transferring graphene by using the degradable polymer.

Background

Graphene, as one of the emerging two-dimensional nano materials, has excellent performance in aspects of force, heat, light, sound, electricity and the like, and has wide application prospects in high-precision technical fields of flexible display, touch, sensing, atomic films and the like.

At present, a relatively mature production process of high-quality graphene generally utilizes a chemical vapor deposition technology (CVD method) to grow a single-layer continuous graphene on a metal (such as copper, palladium, nickel and the like) catalytic substrate by a carbon source, then removes the metal substrate by a dissolving or stripping method, and transfers the graphene to a target substrate; graphene is typically transferred using a soluble thermoplastic resin as a transition support layer. However, the conventional technology for wet transfer of graphene by PMMA (polymethyl methacrylate) often has the problem that PMMA is difficult to completely remove, and a very small amount of residual PMMA exists on the surface of graphene in the form of stubborn impurities, thereby directly affecting the appearance and functional response of electrical elements and the like made of graphene.

In the context of "clean transfer of chemical vapor deposition graphene thin films", researchers have mentioned that PMMA is difficult to completely dissolve and remove in conventional organic solvents due to severe folding and entanglement of long-chain polymers; generally, in a certain range, the smaller the molecular weight of PMMA, or the lower the concentration, i.e., the thinner the film formed, the less PMMA remains on the graphene layer after removal with the organic solvent. In addition, the acting force formed between the graphene and the polymer is complex and various, and comprises electrostatic force, van der waals force, pi-pi bond, intermolecular hydrogen bond and the like, and some acting forces are strong, so that the polymer is difficult to remove.

In order to ensure sufficient support strength and toughness, PMMA resins used for transferring graphene generally have a high degree of polymerization, generally requiring a molar molecular weight of several hundred thousand or even millions; and has a certain thickness to form a continuous resin hard film. In the film forming process of the polymer resin with the long molecular chain, the physical entanglement of the polymer resin is more, the adsorption points of the polymer resin and graphene are more, the intermolecular force is strong, and the dissociation is difficult; and the graphene is easy to permeate, entangle or wrap at the growth defect or surface adhered impurity part of the graphene, so that an atomic-level film or an impurity point which is difficult to remove is formed.

Nevertheless, the method of transferring graphene with PMMA as an excessive support material is still the most commonly used method at present. The currently reported PMMA substitutes such as rosin, cellulose, pentacene, cyclododecane, polycarbonate, long-chain alkane and other compounds have the problems of low mechanical strength, high cost and the like, and are not suitable for large-scale production of large-area graphene.

In the prior art, a method for transferring graphene is described, and polylactic acid or polyglycolic acid mentioned is compounded with a graphene material and then degraded, but although the polymer can be degraded, the degradation speed is too slow and the conditions are harsh, and the method is not suitable for the actual production of graphene. The above problems are technical problems to be solved in the art.

Disclosure of Invention

In order to solve the technical problems, the invention provides a degradable polymer and a preparation method and application thereof.

The technical scheme for solving the technical problems is as follows: a method for preparing a degradable polymer, comprising the steps of:

s100: reacting a polyamine compound with a polyaldehyde compound to obtain a solution of a compound with a Schiff base structure in a main chain;

s200: and mixing the solution of the compound with a bifunctional monomer, and catalyzing by using an alkali catalyst to obtain a product.

The beneficial effect of this application is: on one hand, the degradable polymer prepared by the method has high enough molecular weight and glass transition temperature, so that the support strength of the resin film to graphene in the transfer process is kept, and the integrity of the graphene is ensured; on the other hand, the main chain of the polymer has a Schiff base structure, so that the polymer has enough alkali resistance; in an acidic aqueous environment, the degradable polymer can be rapidly degraded into small molecules and oligomers without heating, a high molecular chain is broken and unwound, the solubility is obviously improved, and meanwhile, polymer molecules coated on graphene defects and surface impurities are degraded to fall off and peel off, so that clean transfer of graphene is realized.

Further, after step S200, step S300 is further included: chain extension of the product is carried out.

Further, the step S100 further includes the steps of: adding a water absorbent in the reaction process;

the polyamine compound is diamine, the polyaldehyde compound is dialdehyde, the molar ratio of the diamine compound to the polyaldehyde is 10: 9-2: 1, the reaction temperature is 40-80 ℃, the reaction time is 1-2 h, the polyaldehyde and the polyamine react in a solvent, the solvent for the reaction can be DMF, acetone, ethyl acetate, butyl acetate and the like, and the concentration of the solvent is preferably 30-90 wt%; in the reaction process, a water absorbent can be added according to the requirement to promote the reaction.

According to the preparation method, diamine is reacted with dialdehyde, so that the formed Schiff base structure can be ensured to be positioned in the main chain, and the chain end still has reaction activity.

Further, the polyamine compound is at least one of aliphatic diamine, alicyclic diamine and aromatic diamine; the multi-aldehyde compound is at least one of aliphatic dialdehyde, alicyclic dialdehyde and aromatic dialdehyde; in a more specific embodiment, wherein the polyamine-based compound is at least one of ethylenediamine, 1, 3-propylenediamine, isophoronediamine, p-phenylenediamine, and m-phenylenediamine; the dialdehyde is at least one of succinaldehyde, glutaraldehyde, terephthalaldehyde and the like; the water absorbent is at least one of molecular sieve, calcium chloride, aluminum oxide and dicyclohexylcarbodiimide.

Further, in the step S200, the molar ratio of the bifunctional monomer to the compound is 1: 1-3: 1, the reaction time is 1-10 hours, the reaction temperature is 50-80 ℃, and the alkali catalyst is at least one of alkali metal hydroxide, sodium alkoxide, and tertiary amine; the bifunctional monomer is at least one of bifunctional acrylate monomers, isocyanate monomers, carboxyl-terminated acrylate monomers and hydroxyl-terminated acrylate monomers.

According to the method, the compound and the double-tube functionality monomer are subjected to addition reaction under the condition of alkali catalysis, and the product can be ensured to have a bifunctional active group, so that chain extension can be conveniently performed subsequently when the polymerization degree is insufficient.

Further, the step S200 further includes a step of mixing the solution of the compound with a monofunctional acrylate monomer for reaction, before mixing the solution of the compound with the bifunctional monomer;

the molar ratio of the monofunctional acrylate monomer to the compound is 1: 1-4: 1, and the reaction time is 1-3 h; the monofunctional acrylate monomer is at least one of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, norbornyl methacrylate and tetrahydrofurfuryl acrylate;

the bifunctional monomer adopts a bifunctional acrylate monomer, and the bifunctional acrylate monomer is at least one of 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, tripropylene glycol diacrylate, ethoxylated bisphenol A diacrylate and tricyclodecane dimethanol diacrylate;

the alkali catalyst is at least one of triethylamine, N' -dimethylaniline and triethanolamine

Before the addition reaction is carried out, the solution of the compound is firstly reacted with a proper amount of monofunctional acrylate monomer, partial primary amine can be consumed, and the reaction gel is prevented.

Further, in the step S300, the chain extension is performed by at least one of a radical polymerization, a urethanization reaction, and an epoxy ring-opening reaction.

Further, the step S300 of chain extension by radical polymerization specifically includes the steps of: mixing the product with an acrylate monomer, an initiator and a chain transfer agent in a solvent, heating to 60-100 ℃ under the condition of inert gas, wherein the reaction time is 2-20 h, the initiator is a free radical initiator, and the concentration of the initiator is 0.05-5 wt%; the chain transfer agent is a mercapto compound, the concentration of the chain transfer agent is preferably 0.5-20 wt%, and the molar ratio of the acrylate monomer to the product is 1: 1-100: 1.

Wherein the reaction solvent can be at least one of DMF, acetone, ethyl acetate and butyl acetate, and the content of the solvent is preferably 30-90 wt%; the acrylate monomer can be at least one of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, norbornyl methacrylate, tetrahydrofurfuryl acrylate and glycidyl methacrylate;

the initiator is at least one of azobisisobutyronitrile, azobisisoheptonitrile, dibenzoyl peroxide and tert-butyl hydroperoxide;

the chain transfer agent is at least one of dodecyl mercaptan, tetradecyl mercaptan, mercaptoethanol and mercaptoacetic acid.

The application also discloses a degradable polymer prepared by the method, wherein the polymerization degree is 500-5000, the weight average molecular weight is 100000-2000000, and the glass transition temperature is 90-110 ℃.

The degradable polymer prepared by the method has high enough molecular weight and glass transition temperature, so that the support strength of the resin film to graphene in the transfer process is kept, and the integrity of the graphene is ensured; meanwhile, the polymer has enough alkali resistance; in an acidic aqueous environment, the degradable polymer can be rapidly degraded into small molecules and oligomers without heating, a high molecular chain is broken and unwound, the solubility is obviously improved, and meanwhile, polymer molecules coated on graphene defects and surface impurities are degraded to fall off and peel off, so that clean transfer of graphene is realized.

The application also discloses a method for transferring graphene by using the degradable polymer, which comprises the following steps:

generating a graphene layer with a two-dimensional continuous structure on one side surface of the metal catalytic substrate; the metal catalyzed substrate may be, but is not limited to, a copper catalyzed substrate;

uniformly coating a degradable polymer solution on the surface of one side, away from the metal catalytic substrate, of the graphene layer, and drying to obtain a degradable layer, wherein the degradable polymer is a polymer with a Schiff base structure in a main chain; in more specific examples, the degradable polymer prepared herein may be diluted with a diluent such as, but not limited to, acetone, ethyl acetate, butyl acetate, etc. into a coating solution, and then coated on the surface of the graphene layer, the coating method including, but not limited to, spin coating, spray coating, roll coating, etc.; the drying temperature is preferably 40-150 ℃; the drying time is preferably 0.5-10 h.

Removing the metal catalytic substrate, and then compounding the surface of one side, away from the degradable layer, of the graphene layer with a target substrate; in a more specific embodiment, the graphene layer compounded with the degradable layer floats on the water surface, the graphene layer is positioned at the lower layer, the target substrate is operated to be fished up from the water and is fully dried, and the graphene and the target substrate are fully attached tightly by capillary force formed along with volatilization of moisture; the drying temperature is preferably 40-180 ℃; the drying time is preferably 1-50 h, so that the graphene layer can be transferred to a target substrate, and the obtained layered structure sequentially comprises a target substrate, the graphene layer and a degradable layer;

and soaking the product in an acidic aqueous solution, and decomposing the degradable layer into small molecules and oligomers under the acidic aqueous solution to obtain the target substrate compounded with the graphene layer. Wherein, the acidic aqueous solution can be, but is not limited to, an aqueous solution of hydrochloric acid, sulfuric acid, nitric acid or acetic acid; the concentration of the acidic aqueous solution is preferably 0.5-20 wt%; the soaking time is preferably 10 s-1 h. Rinsing in a solvent for a certain time after soaking, and cleaning residual glue to obtain a clean graphene layer transferred to a target substrate; wherein the rinsing solvent may be, but is not limited to, DMF, acetone, ethyl acetate, or butyl acetate; the rinsing time is preferably 1s to 10 min.

According to the metal catalytic substrate, the degradable polymer is used as the degradable layer, and the main chain of the degradable polymer contains a Schiff base structure, so that on one hand, the degradable layer has enough alkali resistance, the shape of the degradable layer can be kept and the transfer is completed in the process of electrochemically stripping and removing the metal catalytic substrate in an alkaline environment, and on the other hand, the degradable layer can be rapidly degraded into small molecules and oligomers in an acidic environment, so that the solubility is remarkably improved; particularly, the resin fragments coated on the growth defects and the adhered impurities of the graphene are damaged and broken chains are broken, the unwinding is realized, the complete dissolution can be realized, the structure of the graphene is not damaged, and the clean transfer of the graphene is realized

Further, the concentration of the degradable polymer solution is 1-10 wt%;

and removing the metal catalytic substrate by an electrochemical stripping method or an etching copper dissolving method under an alkaline condition.

The metal catalysis substrate is removed under alkaline conditions, the metal catalysis substrate has a Schiff base structure based on the degradable layer, the alkaline resistance is enough, the degradable layer can keep the shape in the process of removing the metal catalysis substrate in the alkaline environment through electrochemical stripping, and the graphene structure cannot be damaged after the metal catalysis substrate is removed.

Drawings

FIG. 1 is a 1000-fold microscope photograph of a conventional PMMA-transferred graphene in a control group of the present invention, with a short photoresist stripping time;

FIG. 2 is a 10000 times SEM photograph of the conventional PMMA-transferred graphene in the control group of the invention after short-time photoresist stripping;

FIG. 3 is a 1000-fold microscope photograph of a conventional PMMA-transferred graphene in a control group of the present invention after a long-time photoresist stripping;

FIG. 4 is a 1000-fold microscope photograph of the degradable layer transferred graphene in the first embodiment;

FIG. 5 is a 10000 times SEM photograph of the degradable layer transferred graphene in the first example;

FIG. 6 is a 1000-fold microscope photograph of the degradable layer transferred graphene in the second embodiment;

FIG. 7 is a 1000-fold microscope photograph of the degradable layer transferred graphene in the third embodiment;

FIG. 8 is a schematic flow chart of graphene transfer in an example;

FIG. 9 is a GPC chart of the product synthesized in example one;

FIG. 10 is a DSC of the product synthesized in the first example;

FIG. 11 is a GPC chart of the product synthesized in example two

FIG. 12 is a DSC spectrum of the product synthesized in example three;

FIG. 13 is a 1000-fold microscope photograph of resin III-4 transfer graphene synthesized in example four;

FIG. 14 is a 1000-fold micrograph of the thinner resin III-1 film transferred graphene of example six;

FIG. 15 is a 1000-fold microscope photograph of resin III-1 film-transferred graphene in example VII using an alkaline copper dissolution method.

Detailed Description

The principles and features of this application are described below in conjunction with the following drawings, the examples of which are set forth to illustrate the application and are not intended to limit the scope of the application.

In the description herein, reference to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

The terms used in the present specification are those general terms currently widely used in the art in consideration of functions related to the present disclosure, but they may be changed according to the intention of a person having ordinary skill in the art, precedent, or new technology in the art. Also, specific terms may be selected by the applicant, and in this case, their detailed meanings will be described in the detailed description of the present disclosure. Therefore, the terms used in the specification should not be construed as simple names but based on the meanings of the terms and the overall description of the present disclosure.

Flowcharts or text are used herein to illustrate the operational steps performed in accordance with embodiments of the present application. It should be understood that the operational steps in the embodiments of the present application are not necessarily performed in the exact order recited. Rather, the various steps may be processed in reverse order or simultaneously, as desired. Meanwhile, other operations may be added to the processes, or a certain step or several steps of operations may be removed from the processes.

The following discloses a variety of different implementation or examples implementing the subject technology. While specific examples of one or more arrangements of features are described below to simplify the disclosure, the examples should not be construed as limiting the present disclosure, and a first feature described later in the specification in conjunction with a second feature can include embodiments that are directly related, can also include embodiments that form additional features, and further can include embodiments in which one or more additional intervening features are used to indirectly connect or combine the first and second features to each other so that the first and second features may not be directly related.

In the embodiments of the present application, which disclose degradable polymers and methods for preparing the same, the following describes specific synthetic routes in the embodiments of the present application, taking diamines and dialdehydes as examples, in step S100, the synthetic routes are as follows:

in the step, the compound with Schiff base structure can be synthesized by using the reaction of amine and aldehyde, the subsequent reaction is carried out by using the compound as a monomer,

in step S200, taking bifunctional acrylate monomers as an example, the specific synthetic route is as follows:

step S300 is performed, taking the chain extension with acrylate monomers as an example, the specific synthetic route is as follows:

wherein R is₁Represents an in-chain molecular structure of an aliphatic, alicyclic or aromatic diamine such as ethylenediamine, 1, 3-propylenediamine, isophoronediamine, paraphenylenediamine, metaphenylenediamine or the like;

R₂it represents the molecular structure of aliphatic and aromatic dialdehyde, such as succinaldehyde, glutaraldehyde, terephthalaldehyde, etc.

R₃Represents a chain-in molecular structure of a difunctional acrylate monomer having a linear or cyclic skeleton, such as 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, tripropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, tricyclodecane dimethanol diacrylate, etc.;

R₄represents the in-chain molecular structure of the compound.

R₅Represents a chain molecular structure of a monofunctional acrylate monomer having a linear or cyclic side group, such as methyl methacrylate, butyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, norbornyl methacrylate, tetrahydrofurfuryl methacrylate, glycidyl methacrylate, etc.

R₆Representing the chain molecular structure of an aliphatic hydrocarbon thiol or a thiol having a hydrophilic group, e.g. dodecyl mercaptan, tetradecyl mercaptan, mercaptoethanol, mercaptoacetic acid, etc

To facilitate understanding of the present application, the present application provides example one and example two with the synthetic route example described above.

The first embodiment is as follows:

the preparation method of the hyperbranched polyacrylate resin as the synthetic degradable polymer comprises the following steps:

step S100: reacting 148 parts by mass of 1, 3-propane diamine with 134 parts by mass of terephthalaldehyde with 1128 parts by mass of ethyl acetate as a solvent and 333 parts by mass of anhydrous calcium chloride as a water absorbent at 60 ℃ for 1 hour, and synthesizing a product with primary amino groups at two ends through Schiff base reaction, wherein the product is marked as a compound I; filtering to remove the absorbed calcium chloride to obtain a solution of a compound I;

step S200: adding 200 parts of MMA (methyl methacrylate) into the solution of the compound I, and reacting at 60 ℃ for 1h by using 20 parts of triethylamine as a catalyst; then 608 parts of tricyclodecane dimethanol diacrylate ester is added to react for 2 hours at 70 ℃; synthesizing a compound with a bifunctional acrylate structure through a Michael addition reaction, and marking as a compound II;

step S300: adding 400 parts of MMA and 444 parts of IBOMA (norbornyl methacrylate) into a solution of a compound II-1, taking 6 parts of AIBN (azobisisobutyronitrile) as an initiator and 202 parts of dodecyl mercaptan as a chain transfer agent, supplementing 2040 parts of ethyl acetate solvent, reacting for 5 hours at 80 ℃ under a nitrogen atmosphere, and synthesizing a solution of a degradable polymer through free radical polymerization, wherein the degradable polymer is a hyperbranched polyacrylate resin with the concentration of 40 wt%.

The weight average molecular weight of the polymer was 335700 as characterized by GPC, as shown in FIG. 9; the glass transition temperature Tg of the polymer, as characterized by DSC, is 95 deg.C, as shown in FIG. 10.

The embodiment of transferring graphene by using the synthesized degradable polymer comprises the following steps:

step T100: generating a graphene layer with a two-dimensional continuous structure on a copper foil catalytic substrate;

step T200: diluting the 40 wt% degradable polymer solution to 5wt% by using butyl acetate to prepare a coating liquid, and marking as a coating liquid S-1;

step T300: coating liquid S-1 on the surface of the graphene layer, which is far away from the copper foil catalytic substrate, in a spin coating manner, and drying for 1h at 130 ℃ to form a film so as to obtain a degradable layer, thereby obtaining a structure which is composed of the degradable layer, the CVD graphene layer and the copper foil catalytic substrate in sequence and is marked as a structure T-II-1;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-1 by an electrochemical stripping method at a voltage of 3V, cleaning the negative electrode for 2-3 times by using pure water, and compositing the graphene layer with the degradable layer to be marked as a structure T-III-1;

step T500: floating the T-III-1 on the water surface, enabling the graphene layer to be positioned below, taking the silicon wafer as a target substrate, fishing the structure T-III-1 from the water surface by operating the silicon wafer substrate, drying and drying at 150 ℃ for 1h, and adhering tightly to obtain a structure which sequentially consists of a resin III-1 film, a CVD graphene layer and the silicon wafer and is marked as a structure T-IV-1;

step T600, preparing 5wt% of H₂SO₄Soaking the water solution with the structure T-IV-1 in acid liquor for 10-20 min, and fully decomposing into micromolecules and oligomers; and rinsing in butyl acetate for 1-2 min, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate, as shown in fig. 4 and 5.

Example two

The preparation method comprises the following steps:

step S100: reacting 340 parts by mass of isophorone diamine with 134 parts by mass of terephthalaldehyde by using 1896 parts by mass of DMF (N, N' -dimethylformamide) as a solvent and 333 parts by mass of anhydrous calcium chloride as a water absorbent at 60 ℃ for 1h, and reacting through Schiff base to synthesize a compound with primary amino groups at two ends, wherein the compound is marked as a compound I-2; filtering to remove the absorbed calcium chloride, and marking the obtained product as a solution of a compound I-2;

step S200: adding 200 parts of MMA and 252 parts of DMF (dimethyl formamide) into a solution of a compound I-2, and reacting at 60 ℃ for 1h by using 50 parts of triethylamine as a catalyst; then 304 parts of tricyclodecane dimethanol diacrylate ester is added to react for 5 hours at 70 ℃; chain extension is carried out through Michael addition reaction; a polymer having a solids content of 30% by weight was obtained.

The molecular weight of the polymer was 58,100 by GPC, as shown in FIG. 11.

This example utilizes the polymer transfer graphene synthesized above, including the following steps:

step T200: diluting the polymer solution with the weight percent of 30 to the weight percent of 5 by using butyl acetate to prepare a coating liquid, and marking as a coating liquid S-2;

step T300: spin-coating a coating liquid S-2 on the surface of the graphene layer, and drying at 130 ℃ for 1h to form a film, so as to obtain a structure which is formed by a degradable layer, a CVD graphene layer and a copper foil catalytic substrate in sequence and is marked as a structure T-II-2;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-2 by an electrochemical stripping method at a voltage of 3V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of a degradable layer and a CVD graphene layer, wherein the structure is marked as a structure T-III-2;

step T500: floating the structure T-III-2 with the graphene layer below on the water surface, fishing the structure T-III-2 from the water surface by operating the silicon wafer substrate, drying and drying at 150 ℃ for 1h and tightly adhering to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-2;

a step T600: preparation of 5wt% H₂SO₄Soaking the water solution with the structure T-IV-2 in acid liquor for 5-10 min, sufficiently decomposing the water solution into small molecules, rinsing the small molecules in clear water for 1-3 min, and then falling off to obtain a clean graphene layer transferred to a target substrate, as shown in FIG. 6.

In this example, since the chain extension of the synthesized product is not performed, the degree of polymerization of the degradable layer is difficult to reach high, which results in poor strength and toughness of the degradable layer relative to that of reference 1 in this example, and it is difficult to transfer graphene having a large size.

In addition, in some embodiments, the product of the synthesis of diisocyanate and the compound having schiff base and then the chain extension by diol can be used, and the synthetic route is as follows:

wherein R is₈Represents an in-chain molecular structure of a diisocyanate having a linear or cyclic skeleton,including but not limited to HDI (hexamethylene diisocyanate), TDI (toluene diisocyanate), IPDI (isophorone diisocyanate), MDI (diphenylmethane diisocyanate), and the like. The long chain diols include, but are not limited to, various polyether diols or polyester diols.

For ease of understanding, this application provides a third example for illustration.

EXAMPLE III

This example synthesizes a degradable polyurethane resin, including the following steps:

step S100: 340 parts of isophorone diamine and 134 parts of terephthalaldehyde in parts by mass are reacted for 1 hour at 60 ℃ by using 1896 parts of DMF as a solvent and 333 parts of anhydrous calcium chloride as a water absorbent, and a compound with primary amino groups at two ends is synthesized by Schiff base reaction and is marked as a compound I-3; filtering to remove the absorbed calcium chloride to obtain a solution of a compound I-3;

step S200: to the solution of the compound I-3, 444 parts of IPDI (isophorone diisocyanate) was added and reacted at 60 ℃ for 2 hours with 3 parts of diisobutyltin dilaurate as a catalyst.

S300: then 1000 parts of polyether glycol PTMEG-1000 and 930 parts of DMF are added for reaction for 4 hours at 60 ℃; and carrying out polyurethane reaction chain extension to obtain a polymer solution with the solid content of 40 wt%.

The glass transition temperature Tg of the polymer was 20 ℃ as characterized by DSC, as shown in FIG. 12.

step T200: diluting the 40 wt% polymer solution to 5wt% with butyl acetate to prepare coating liquid S-3;

step T300: spin coating a coating liquid S-3 on the surface of the graphene layer, and drying at 130 ℃ for 1h to form a film, so as to obtain a structure consisting of the degradable layer, the CVD graphene layer and the copper foil catalytic substrate in sequence, wherein the structure is marked as a structure T-II-3;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-3 by an electrochemical stripping method at a voltage of 3V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of a degradable layer and a CVD graphene layer, wherein the structure is marked as a structure T-III-3;

step T500: floating the structure T-III-3 below the graphene layer on the water surface, fishing the structure T-III-3 from the water surface by operating the silicon wafer substrate, drying and drying at 150 ℃ for 1h to be tightly attached to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-3;

step T600: preparation of 5wt% H₂SO₄Soaking the water solution with the structure T-IV-3 in acid liquor for 10-20 min, and fully decomposing the water solution into micromolecules and oligomers; and rinsing in ethyl acetate for 1-2 min, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate.

In this example, since the synthesized monomer is polyether glycol, compared with the degradable layer prepared in example 1, the degradable layer has a lower glass transition temperature, a softer texture and a lower rigidity, and graphene is prone to wrinkle or microcrack during the transfer process, as shown in fig. 7.

Example four

The degradable polymer synthesized by the embodiment is hyperbranched polyacrylate resin, and comprises the following steps:

step S100: reacting 92.5 parts by mass of 1, 3-propane diamine with 134 parts by mass of terephthalaldehyde with 906 parts by mass of ethyl acetate as a solvent and 222 parts by mass of anhydrous calcium chloride as a water absorbent at 40 ℃ for 2 hours, synthesizing a compound with primary amine groups at two ends by Schiff base reaction, marking as a compound I-4, and filtering to remove the calcium chloride absorbing water to obtain a solution of the compound I-4;

step S200: adding 213 parts of BMA (butyl methacrylate) into the solution of the compound I-4, and reacting at 50 ℃ for 3 hours by using 10 parts of triethylamine as a catalyst; adding 565 parts of HDDA, and reacting at 60 deg.C for 5 hr; synthesizing a compound with a bifunctional acrylate structure through a Michael addition reaction, and marking as a compound II-4; obtaining a solution of a compound II-4;

step S300: adding 600 parts of MMA and 426 parts of BMA into a solution of a compound II-4, taking 16 parts of AIBN as an initiator, 202 parts of dodecyl mercaptan as a chain transfer agent, supplementing 1306 parts of an ethyl acetate solvent, reacting for 40 hours at 65 ℃ under a nitrogen atmosphere, and carrying out free radical polymerization to synthesize a degradable polymer, namely hyperbranched polyacrylate resin, recording the degradable polymer as resin III-4, thereby obtaining a resin III-4 solution with the concentration of 50 wt%.

The embodiment of transferring graphene by using the synthesized resin III-4 comprises the following steps:

step T200: diluting 50 wt% of resin III-4 solution to 5wt% by using ethyl acetate to prepare coating liquid, and marking as coating liquid S-4;

step T300: spin-coating a coating liquid S-4 on the surface of the graphene layer, and drying at 110 ℃ for 0.5h to form a film, so as to obtain a structure which is formed by the degradable layer, the CVD graphene layer and the copper foil catalytic substrate in sequence and is marked as a structure T-II-4;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-4 by an electrochemical stripping method at a voltage of 3V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of the degradable layer and the CVD graphene layer, wherein the structure is marked as a structure T-III-4;

step T500: floating the structure T-III-4 with the graphene layer below on the water surface, fishing the structure T-III-4 from the water surface by operating the silicon wafer substrate, drying and drying at 120 ℃ for 1h to be attached tightly to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-4;

step T600: 10 wt% of H is prepared₂SO₄Soaking the water solution with the structure T-IV-4 in acid liquor for 5-10 min, and fully decomposing the water solution into micromolecules and oligomers; and rinsing in butyl acetate for 1-2 min, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate. Due to the longer pendant fatty chain of the monomer, the glass transition temperature of the polymer is lower than that of PMMA, so the transferred graphene still has fine wrinkles and cracks, as shown in fig. 13.

EXAMPLE five

step S100: 190 parts by mass of isophorone diamine, 134 parts by mass of terephthalaldehyde, 2916 parts by mass of butyl acetate as a solvent, 444 parts by mass of anhydrous calcium chloride as a water absorbent, reacting at 60 ℃ for 2 hours, and synthesizing a compound with primary amine groups at two ends through Schiff base reaction, wherein the compound is marked as a compound I-5; filtering to remove the absorbed calcium chloride to obtain a solution of a compound I-5;

step S200: adding 250 parts of MMA into the solution of the compound I-5, and reacting at 60 ℃ for 1hr by using 20 parts of triethylamine as a catalyst; adding 456 parts of tricyclodecane dimethanol diacrylate ester, and reacting at 70 ℃ for 2 hr; synthesizing a compound II-5 with a bifunctional acrylate structure through a Michael addition reaction; obtaining a solution of a compound II-5;

step S300: adding 600 parts of MMA and 222 parts of IB0MA into a solution of a compound II-5, taking 13 parts of AIBN as an initiator, taking 156 parts of 2-mercaptoethanol as a chain transfer agent, supplementing 3100 parts of a butyl acetate solvent, reacting for 2 hours at 95 ℃ under a nitrogen atmosphere, and carrying out free radical polymerization to obtain a synthetic degradable polymer which is hyperbranched polyacrylate resin, marked as resin III-5, so as to obtain a resin III-5 solution with the concentration of 25 wt%.

The embodiment of transferring graphene by using the synthesized resin III-5 comprises the following steps:

step T200: diluting 25 wt% of resin III-5 solution to 5wt% by using ethyl acetate to prepare coating liquid, and marking as coating liquid S-5;

step T300: spin-coating a coating liquid S-5 on the surface of the graphene layer, and drying at 130 ℃ for 1h to form a film, so as to obtain a structure which is formed by the degradable layer, the CVD graphene layer and the copper foil catalytic substrate in sequence and is marked as a structure T-II-5;

step T400: preparing 3 wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-5 by an electrochemical stripping method at a voltage of 2.5V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of a degradable layer and a CVD graphene layer, wherein the structure is marked as a structure T-III-5;

step T500: floating the structure T-III-5 below the graphene layer on the water surface, fishing the structure T-III-5 from the water surface by the silicon wafer substrate, drying and drying at 150 ℃ for 2h, and attaching the structure T-III-5 to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-5;

step T600: preparation of 3 wt% H₂SO₄Soaking the water solution with the structure T-IV-5 in acid liquor for 0.5-1 min, and fully decomposing into micromolecules and oligomers; and rinsing in butyl acetate for 10-20 s, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate.

In addition, the present application also prepares example six and example seven, and the following examples transfer graphene using the degradable polymer synthesized in example one.

EXAMPLE six

Transfer of graphene using the degradable polymer synthesized in example one, comprising the steps of:

step T200: diluting 40 wt% degradable polymer solution to 1 wt% by using butyl acetate to prepare a coating liquid, and marking as coating liquid S-1-2;

step T300: spin-coating a coating liquid S-1-2 on the surface of the graphene layer, and drying at 130 ℃ for 1h to form a film, so as to obtain a structure which is formed by a degradable layer, a CVD graphene layer and a copper foil catalytic substrate in sequence and is marked as a structure T-II-7;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on the negative electrode of the structure T-II-7 by an electrochemical stripping method at a voltage of 2V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of a degradable layer and a CVD graphene layer, wherein the structure is marked as a structure T-III-7;

step T500: floating a structure T-III-7 below the graphene layer on the water surface, fishing the structure T-III-1 from the water surface by the silicon wafer substrate, drying for 24h at 40 ℃ and drying for 0.5h at 150 ℃ and tightly adhering to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-7;

step T600: preparation of 5wt% H₂SO₄Soaking the water solution with the structure T-IV-7 in acid liquor for 1-2 min, and fully decomposing the water solution into micromolecules and oligomers; and rinsing in butyl acetate for 20-30 s, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate. Because the resin dry film is very thin, the degradation and the photoresist removal are fast; however, the strength was decreased, and the transferred graphene was damaged to some extent, as shown in fig. 14.

EXAMPLE seven

This example utilizes the degradable polymer synthesized in example one to transfer graphene, including the following steps:

step T200: diluting 40 wt% of degradable polymerization solution to 3 wt% by using butyl acetate to prepare a coating liquid, and marking as coating liquid S-1-3;

step T300: spin-coating a coating liquid S-1-3 on the surface of the graphene layer, and drying at 130 ℃ for 1h to form a film, so as to obtain a structure which is formed by a degradable layer, a CVD graphene layer and a copper foil catalytic substrate in sequence and is marked as a structure T-II-8;

step T400: according to CuCl₂：NH₄OH：H₂0-1: 19: 80, preparing alkaline copper dissolving liquid; floating the copper foil of the structure T-II-8 downwards on the copper-dissolved liquid level for 2-3 hours to completely dissolve the copper foil; cleaning with pure water for 2-3 times to obtain a structure consisting of the degradable layer and the CVD graphene layer, and marking as a structure T-III-8;

step T500: floating the structure T-III-8 below the graphene layer on the water surface, fishing the structure T-III-8 from the water surface by the silicon wafer substrate, drying for 24h at 40 ℃ and drying for 0.5h at 150 ℃ and tightly adhering to obtain a structure which sequentially consists of the degradable layer, the CVD graphene layer and the silicon wafer and is marked as a structure T-IV-8;

step T600: 1 wt% of H is prepared₂SO₄Soaking the water solution with the structure T-IV-8 in acid liquor for 50-60 min, and fully decomposing the water solution into micromolecules and oligomers; and rinsing in ethyl acetate for 1-2 min, and cleaning residual glue to obtain a clean graphene layer transferred to the target substrate, as shown in fig. 15.

Control group:

in addition, this application has also passed through a set of contrast group, and this contrast group transfers graphite alkene to the silicon chip through traditional PMMA wet process transfer technology, includes the following step:

step T200: diluting general PMMA resin with the weight average molecular weight of about 300,000 to 2 wt% by using butyl acetate to prepare a coating liquid, and marking the coating liquid as coating liquid S-0;

step T300: spin-coating a coating liquid S-0 on the surface of the graphene layer, which is far away from the copper foil catalytic substrate, and drying for 1h at 130 ℃ to form a film, so as to obtain a structure consisting of a PMMA resin film, a CVD graphene layer and the copper foil catalytic substrate in sequence, wherein the structure is marked as a structure T-II-0;

step T400: preparing 5wt% NaOH aqueous solution; removing copper foil on a negative electrode of the structure T-II-0 by an electrochemical stripping method at a voltage of 3V, and cleaning for 2-3 times by using pure water to obtain a structure consisting of a PMMA resin film and a CVD graphene layer, wherein the structure is marked as a structure T-III-0;

step T500: floating the structure T-III-0 below the graphene layer on the water surface, fishing the structure T-III-0 from the water surface by operating the silicon wafer substrate, drying at room temperature, drying at 150 ℃ for 1h, and adhering tightly to obtain a structure which sequentially consists of a PMMA resin film, a CVD graphene layer and a silicon wafer and is marked as the structure T-IV-0;

step T600: soaking in acetone for 5min to remove the photoresist to obtain a graphene layer transferred to a target substrate, wherein the existence of residual photoresist is obviously seen, as shown in fig. 1 and 2; if the graphene is soaked in acetone for more than 30min, it is obvious that the graphene is damaged in a large area, as shown in fig. 3.

By comparing the above embodiments with the control group, it can be found that the graphene transferred by the polymer prepared by the embodiments disclosed in the present application can be transferred more completely, and the graphene is cleaner, while the control group cannot achieve the effect, and in the present application, the effect of transferring the graphene by the first embodiment is the best.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a degradable polymer, which is characterized by comprising the following steps:

s100: reacting a polyamine compound with a polyaldehyde compound to obtain a solution of a compound with a Schiff base structure in a main chain; the polyamine compound is diamine, the polyaldehyde compound is dialdehyde, and the molar ratio of the diamine to the dialdehyde is 10: 9-2: 1;

s200: mixing the solution of the compound containing the Schiff base structure with a bifunctional monomer, and carrying out catalytic reaction by using an alkali catalyst to obtain a product, wherein the molar ratio of the bifunctional monomer to the compound containing the Schiff base structure is 1: 1-3: 1, and the bifunctional monomer is at least one of 1, 4-butanediol diacrylate, 1, 6-hexanediol diacrylate, tripropylene glycol diacrylate, ethoxylated bisphenol A diacrylate and tricyclodecane dimethanol diacrylate;

the preparation method comprises the following steps of mixing a solution of the compound with a bifunctional monomer, and reacting the solution of the compound containing the Schiff base structure with a monofunctional acrylate monomer in a molar ratio of 1:1 for 1-3 h, wherein the monofunctional acrylate monomer is at least one of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, lauryl acrylate, lauryl methacrylate, norbornyl acrylate, norbornyl methacrylate and tetrahydrofurfuryl acrylate;

s300: chain extension is carried out on the product, and chain extension is carried out through free radical polymerization, and the method comprises the following steps: mixing the product with an acrylate monomer, an initiator and a chain transfer agent in a solvent, heating to 60-100 ℃ under the condition of inert gas, wherein the reaction time is 2-20 h, the initiator is a free radical initiator, and the concentration of the initiator is 0.05-5 wt%; the polymerization degree of the degradable polymer is 500-5000, the weight average molecular weight is 100000-2000000, and the glass transition temperature is 90-110 ℃.

2. The method according to claim 1, wherein the step S100 further comprises the steps of: adding a water absorbent in the reaction process;

in the step S100, the reaction temperature is 40-80 ℃, and the reaction time is 1-2 h.

3. The method according to claim 2, wherein the diamine is at least one of an aliphatic diamine, an alicyclic diamine, and an aromatic diamine; the dialdehyde is at least one of aliphatic dialdehyde, alicyclic dialdehyde and aromatic dialdehyde; the water absorbent is at least one of molecular sieve, calcium chloride, aluminum oxide and dicyclohexyl carbodiimide.

4. The method according to claim 1, wherein in step S200, the base catalyst is at least one of triethylamine, N' -dimethylaniline, and triethanolamine.

5. The method according to claim 1, wherein in step S200, the solution of the compound having Schiff base structure is mixed with the bifunctional monomer for 1 to 10 hours at a reaction temperature of 50 to 80 ℃, and the base catalyst is at least one of alkali metal hydroxide, sodium alkoxide, and tertiary amine.

6. The method according to claim 1, wherein in step S300, the chain transfer agent is a mercapto compound, the concentration of the chain transfer agent is 0.5 to 20wt%, and the molar ratio of the acrylate monomer to the product is 1:1 to 100: 1.

7. A method for preparing degradable polymer transfer graphene by using the preparation method of any one of claims 1 to 6, wherein the method comprises the following steps:

generating a graphene layer with a two-dimensional continuous structure on one side surface of the metal catalytic substrate;

uniformly coating the degradable polymer solution on the surface of the graphene layer on the side away from the metal catalytic substrate, and drying to obtain a degradable layer attached to the graphene layer;

removing the metal catalytic substrate, and then compounding a target substrate on the surface of one side, far away from the degradable layer, of the graphene layer;

and decomposing the degradable layer in an acidic aqueous solution to obtain the target substrate compounded with the graphene layer.