A polymer in-situ characterization method based on conductive two-dimensional material

Abstract

This invention discloses an in-situ polymer characterization method based on conductive two-dimensional materials. First, conductive two-dimensional material films and polymer films are prepared. Then, a composite material is constructed based on the conductive two-dimensional material films and the polymer films, such that the conductive two-dimensional material films act as electrical probes, uniformly and orderly dispersed within different polymer matrices, and forming continuous conductive pathways within the composite material. The composite material is used as a platform-based test unit to measure its resistance, obtaining resistance change curves. Analysis and processing of these resistance change curves reveal the structural changes of the polymer matrix during thermal transition and degradation processes, and the glass transition temperature and melting point of the polymer matrix are calculated. This method can be applied to important fields such as polymer thermal property characterization, polymer degradation process research, and polymer degradability evaluation.

Description

Technical Field

[0001] This invention relates to the field of polymer material characterization, and more particularly to an in-situ polymer characterization method based on two-dimensional materials. Background Technology

[0002] Polymer characterization is crucial for understanding their chemical composition, molecular weight, molecular weight distribution, and other physical properties, providing significant guidance for polymer processing and applications. Although various reliable techniques have been established to characterize diverse polymer properties, several challenges remain: First, the lack of a universal characterization platform necessitates different sample states and complex equipment for studying different polymer properties, making the process time-consuming, labor-intensive, and costly. Furthermore, rapid in-situ characterization of processed macroscopic polymer materials, such as their thermal transitions and degradation processes, is difficult to achieve. These issues severely limit the development and application of multifunctional polymer materials, as well as the in-depth understanding and control of polymer degradation processes, representing a significant challenge to current polymer science development. Therefore, developing a low-cost, platform-based in-situ polymer characterization technique is a pressing technical problem that needs to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide an in-situ polymer characterization and testing technique to address the shortcomings of existing polymer characterization technologies.

[0004] The objective of this invention is achieved through the following technical solution: an in-situ polymer characterization method based on conductive two-dimensional materials, the method comprising the following steps:

[0005] (1) Prepare conductive two-dimensional material thin films and polymer thin films, and construct composite materials based on conductive two-dimensional material thin films and polymer thin films, so that the conductive two-dimensional material thin films are electrical probes and are uniformly and orderly dispersed in different polymer matrices, and form continuous conductive pathways inside the composite materials.

[0006] (2) The composite material constructed in step (1) is used as a platform test unit. The resistance of the composite material is measured to obtain the resistance change curve. The structural changes of the polymer matrix during the thermal transformation and degradation process are obtained by analyzing and processing the resistance change curve of the composite material. The glass transition temperature and melting point of the polymer matrix are calculated.

[0007] Furthermore, the conductive two-dimensional material film includes graphene, two-dimensional metal materials, two-dimensional covalent organic framework materials, two-dimensional metal-organic framework materials, and two-dimensional conductive polymers.

[0008] Furthermore, the processing method of the conductive two-dimensional material thin film includes chemical vapor deposition, epitaxial growth, inkjet printing, filtration, solvent evaporation, interface growth, hydrothermal synthesis, or electrochemical synthesis, and the thickness of the conductive two-dimensional material thin film is less than 100 nm.

[0009] Furthermore, the polymer matrix is ​​a polymer material with thermal transformation behavior including glass transition and melting, or a polymer material that can be degraded by environmental factors.

[0010] Further, the polymer matrix includes thermoplastic plastics, polyolefin materials, or polyester materials; the thermoplastic plastics include polycarbonate, polystyrene, or polymethyl methacrylate; the polyolefin materials include polyethylene, polypropylene, or polyolefin thermoplastic elastomers; the polyester materials include polyethylene terephthalate, polybutylene adipate terephthalate, polycaprolactone, and polyamides and polyimides.

[0011] Furthermore, the process for preparing the polymer film includes: hot pressing, spin coating, blade coating or solvent evaporation to prepare the polymer film, wherein the thickness of the polymer film is 0.5-30 μm.

[0012] Furthermore, the process of constructing composite materials based on conductive two-dimensional material films and polymer films includes: transferring a continuous two-dimensional conductive material film to the surface of a polymer film to construct a composite film, and then further processing the composite film into vortex fibers by a transverse shearing and rolling method to obtain the composite material.

[0013] Furthermore, the process of measuring the resistance of the composite material includes: partially etching the polymer layer at both ends of the spiral fiber using a solvent that is compatible with the polymer matrix, and applying a conductive adhesive coating at the etched area to achieve conduction between the internal conductive two-dimensional material and the external circuit.

[0014] Furthermore, the structural changes in the thermal transition process of polymers include chain movement and chain breakage during glass transition and melting. The glass transition temperature and melting point of the polymer matrix can be quantitatively calculated by analyzing the resistance change curves. The structural changes in the degradation process of polymers include chain breakage and free radical generation during photodegradation, thermal degradation, and microbial degradation. The degradation process of polymers can be analyzed and the degradation rate of polymers can be evaluated by analyzing the resistance change curves.

[0015] Furthermore, the process of quantitatively calculating the glass transition temperature and melting point of the polymer matrix by analyzing the resistance change curve includes: for the glass transition, the differential of the resistance change curve is calculated, and the temperature corresponding to the maximum value of the differential is the glass transition temperature of the polymer matrix; for the melting phase transition, the resistance change curves of the initial and final stages of the melting limit are fitted with straight lines, and the intersection of the straight lines corresponding to the initial and final stages is the melting point of the polymer matrix.

[0016] The beneficial effects of this invention are: This invention provides a platform-based method for in-situ characterization testing of polymers. Based on a fast, non-destructive, simple-equipment electrical testing technology that is easy to integrate with other devices, it can utilize the same composite structure to achieve in-situ characterization of different polymers during different structural changes. It can be applied to the characterization of polymer thermal properties and the study of degradation processes. Attached Figure Description

[0017] Figure 1 For example, in Example 1, the PS matrix T g The test results;

[0018] Figure 2 For example, in Example 2, the POE 8003 matrix T m The test results;

[0019] Figure 3 This is a comparison between the characterization results in Examples 1-2 and the DSC test;

[0020] Figure 4 This is a monitoring of the photodegradation process of PBAT at different temperatures in Examples 3-4. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0022] This invention proposes an in-situ polymer characterization method based on conductive two-dimensional materials, the method specifically including the following steps:

[0023] (1) Prepare conductive two-dimensional material thin films and polymer thin films, and construct composite materials based on conductive two-dimensional material thin films and polymer thin films, so that the conductive two-dimensional material thin films are electrical probes and are uniformly and orderly dispersed in different polymer matrices, and form continuous conductive pathways inside the composite materials.

[0024] Among them, conductive two-dimensional material thin films include two-dimensional conductor materials such as graphene, two-dimensional metal materials, two-dimensional covalent organic framework materials (COF), two-dimensional metal-organic framework materials (MOF), and two-dimensional conductive polymers.

[0025] The processing methods for the aforementioned conductive two-dimensional material thin films include, but are not limited to, chemical vapor deposition, epitaxial growth, inkjet printing, filtration, solvent evaporation, interface growth, hydrothermal synthesis, and electrochemical synthesis. The thickness of the conductive two-dimensional material thin film is less than 100 nm. In the embodiments of the present invention, chemical vapor deposition is preferred for preparing continuous single-layer or few-layer two-dimensional conductive material thin films.

[0026] The polymer matrix is ​​a polymer material exhibiting thermal transformation behaviors, including glass transition and melting, or a polymer material that can be degraded by environmental factors. Specifically, the polymer matrix includes thermoplastics, polyolefins, or polyesters; the thermoplastics include polycarbonate (PC), polystyrene (PS), or polymethyl methacrylate; the polyolefins include polyethylene, polypropylene, or polyolefin thermoplastic elastomers (POE); and the polyesters include polyethylene terephthalate, polybutylene adipate terephthalate (PBAT), polycaprolactone (PCL), and polyamides and polyimides.

[0027] In this example, the process of preparing the polymer film includes: dissolving PC, PS, PBAT, PCL, etc. in an organic solvent such as chloroform to prepare a 2-3 wt% polymer solution, which is then spin-coated into a film; POE is not easy to process in solution, so hot pressing is used to form the film.

[0028] The process of constructing a composite material from a conductive two-dimensional material thin film and a polymer thin film includes: transferring a continuous two-dimensional conductive material thin film onto the surface of a polymer thin film to form a composite film; further processing the composite film into spiral fibers using a transverse shearing and rolling method to obtain the composite material; and completely encapsulating the two-dimensional conductive material thin film within the polymer layer to avoid interference from other impurities in the air. The composite material (spiral fibers) enables the conductive two-dimensional material thin film to act as an electrical probe, uniformly and orderly dispersed within different polymer matrices, and forming a continuous conductive pathway within the composite material. The processing methods for the polymer thin film include, but are not limited to, hot pressing, spin coating, blade coating, and solvent evaporation; the thickness of the polymer thin film is 0.5-30 μm.

[0029] In this example, the transfer of the two-dimensional conductive material thin film is as follows: For polymer materials such as PC, PS, PBAT, and PCL, the polymer solution can be directly spin-coated onto a substrate on which the two-dimensional material has been grown. Then, the substrate is etched and washed to achieve the transfer of the two-dimensional material. For POE films, the two-dimensional material is first transferred to a PMMA film using the same spin-coating and etching method, and then transferred to the surface of the POE hot-pressed film to construct a composite film. Conductive silver paste (2mm wide, with a length consistent with the film length) is coated at both ends of the film, and wires are fixed to achieve conductivity between the conductive two-dimensional material thin film and the external circuit (i.e., the circuit for measuring the resistance of the composite material). All the above composite films are then processed into Archimedean spiral fibers through transverse shearing and rolling.

[0030] (2) The composite material constructed in step (1) is used as a platform test unit. The resistance of the composite material is measured to obtain the resistance change curve. The structural changes of the polymer matrix during the thermal transformation and degradation process are obtained by analyzing and processing the resistance change curve of the composite material. The glass transition temperature and melting point of the polymer matrix are calculated.

[0031] The process of measuring the resistance of the composite material includes: partially etching the polymer layers at both ends of the spiral fiber using a solvent that is compatible with the polymer matrix; and applying a conductive adhesive coating to the etched areas to achieve conductivity between the internal conductive two-dimensional material and the external circuit. The conductive coating includes, but is not limited to, conductive silver paste, epoxy silver paste, and metal electrodes.

[0032] The structural changes during the thermal transition of polymers include chain movement and chain breakage during glass transition and melting. Thermal properties such as the glass transition temperature and melting point of the polymer matrix can be quantitatively calculated by analyzing relative electrical resistance curves. The structural changes during polymer degradation include chain breakage and free radical generation during photodegradation, thermal degradation, and microbial degradation. The degradation process and degradation rate of polymers can be evaluated by analyzing electrical resistance curves.

[0033] The analysis and processing of the resistance change curve includes: first, plotting the resistance change curve with temperature; for the glass transition, calculating the differential of the resistance change curve, and finding the temperature corresponding to the maximum value of the differential, which is the glass transition temperature of the corresponding polymer matrix; for the melting phase transition, fitting straight lines to the resistance change curves of the initial and final melting stages, and the intersection of the straight lines corresponding to the initial and final stages is the melting point of the polymer matrix.

[0034] The present invention is illustrated by the following specific embodiments, but the scope of the present invention is not limited to the following embodiments.

[0035] In the DSC comparative test, the glass transition temperature (Tg) and melting point (Tm) of the polymer were determined by TA Instruments Q200. 6.0–8.0 mg of polymer sample was weighed, heated to 200 °C at 30 °C / min, held for 5 min to eliminate thermal history, then cooled to -90 °C at 10 °C / min, held for 3 min, and then heated to 200 °C at 10 °C / min. The glass transition temperature or melting point of the polymer was obtained from the second heating curve.

[0036] Electrical tests on the composite material were performed using a Keithley 4200A-SCS semiconductor parameter analyzer. A fixed voltage of 1V was applied across the composite material, and the current passing through the composite material was monitored in situ during heating or illumination.

[0037] Example 1

[0038] The synthesis process of CVD monolayer graphene as the conductive two-dimensional material layer is as follows: A copper foil (2.0 cm × 2.0 cm) is placed in a tube furnace (2 inch in diameter). The tube furnace is evacuated and heated to 1060 °C under a 300 sccm H2 gas flow. After annealing for 30 minutes, a 1 sccm CH4 gas flow is introduced, and the temperature inside the tube is maintained for 30 minutes under a 10 sccm H2 gas flow. Heating is then stopped, and the copper foil with the grown monolayer graphene is removed after the system cools to room temperature.

[0039] A prepared PS / chloroform solution (2 wt%) was directly spin-coated onto the surface of a copper foil with graphene grown on it at a speed of 2700 rpm for 1 min. After drying under ambient conditions for 15 min, the PS / graphene / copper foil was placed in a sodium persulfate aqueous solution (10 wt%) and etched at room temperature for 10 h. The PS / graphene was then transferred to deionized water and washed four times, 10 min each time. The washed PS / graphene composite film was processed into Archimedes spiral fibers using a transverse shearing and rolling method. The fibers were then placed in a vacuum oven for 12 h to remove internal moisture. Finally, the PS portions at both ends of the fibers were removed using chloroform, and an epoxy silver paste was coated to connect with the internal graphene.

[0040] PS / graphene fibers were placed inside a probe stage (YB-V4) equipped with a heating platform. A test probe (10μm tungsten tip) was used to contact the epoxy silver paste at both ends of the fiber from above. Heating and current testing began simultaneously, with a heating range of 30-130℃. Starting at 30℃, the temperature was maintained at 10℃ for 5 minutes at intervals of 10℃. The resistance at each temperature was calculated from the current curve, and a curve showing the relative resistance change versus temperature was plotted. (See attached diagram.) Figure 1 At the onset of the glass transition, the resistivity of the composite material rises rapidly, indicating that the chain motion and volume expansion of the polymer matrix lead to the destruction of the graphene structure. However, in the later stages of the glass transition, before the temperature reaches the melting point or thermal decomposition temperature of the polymer matrix, the resistivity change of the composite material tends to level off, indicating that the energy at this point is insufficient to completely destroy the polymer chain entanglement, and its structure remains stable. Taking the derivative of this resistivity curve, the temperature at which the resistance changes most rapidly, corresponding to the maximum derivative, is the glass transition temperature T of the corresponding PS matrix. g In this example, the temperature was 95.8°C, and the DSC test of the sample was 91.8°C.

[0041] Example 2

[0042] The conductive two-dimensional material film was made of CVD monolayer graphene, and the synthesis steps were the same as in Example 1.

[0043] ENGAGE 8003 (POE brand name) particles were placed in a hot-press mold and hot-pressed at 160°C and 1300 psi for 10 min to obtain a 25 μm thick POE film. Photoresist SU8 (PMMA anisole solution) was spin-coated onto the surface of a copper foil with graphene grown on it at 2700 rpm for 1 min. Following the same method as in Example 1, the copper substrate was etched and cleaned, and the PMMA / graphene was transferred to the surface of the POE (2.0 cm × 2.0 cm) hot-press film. The PMMA was then removed with acetone to achieve the transfer of CVD graphene to the POE film. Conductive silver paste (2 mm wide, length consistent with the film length) was then coated onto both ends of the film, dried, and silver wires were fixed to its surface. The cleaned PS / graphene composite film was processed into Archimedes spiral fibers using a transverse shearing and rolling method. Conductivity between the fibers and the internal graphene was achieved at both ends using epoxy silver paste, silver wires, and conductive silver paste.

[0044] POE / graphene fibers were placed in the cavity of a probe station (YB-V4) equipped with a heating stage. The test probe (a 10μm tungsten probe with a tip diameter) contacted the epoxy silver paste at both ends of the fiber from above. Heating and current testing began simultaneously. The heating range was 30-90℃. Starting at 30℃, the temperature was maintained for 5 minutes at 10℃ intervals. Within the melting limit (70-80℃ in this example), the temperature was increased by 1℃ and maintained for 5 minutes at each interval. The resistance at this temperature was calculated from the current curve, and a curve showing the relative resistance change versus temperature was plotted. (See attached diagram.) Figure 2 As can be seen from the resistance change curve, within the polymer melting range, the intense movement of polymer chains and volume changes cause severe damage to the graphene structure, resulting in a sharp increase in resistance. Fitting straight lines were plotted at three points at the initial and final stages of the melting limit. The intersection of the two lines corresponds to the melting point Tm of ENGAGE 8003, which is 76.5℃ in this example. The DSC test value of the sample is 79.5℃.

[0045] Figure 3 For the comparison between the characterization results in Examples 1-2 and the DSC test, by Figure 3 It can be seen that the T of the polymer measured by the method proposed in this invention g With T m Similar to existing DSC testing methods, the method of this invention has high accuracy and has certain application prospects.

[0046] Example 3

[0047] The conductive two-dimensional material film was made of CVD monolayer graphene, and the synthesis steps were the same as in Example 1.

[0048] Polybutylene adipate terephthalate (PBAT) was used as the polymer matrix, and a 3% PBAT chloroform solution was prepared. PBAT / graphene spool fibers were prepared using the method described in Example 1, and the internal graphene was made conductive to the external circuit.

[0049] PBAT / graphene spools were placed in an aging chamber, using a xenon lamp as the light source and a standard solar filter to simulate sunlight, and continuously irradiated at 45°C to induce photodegradation of PBAT. During the first 10 hours, the resistivity of the composite fiber was measured every 2 hours, then every 20 hours, for a total of 200 hours. The curve showing the change in composite fiber resistivity with irradiation time was obtained. Figure 4 Within 120 hours, the resistance of the composite material decreased continuously with the extension of light exposure time. This corresponds to the degradation of the butylene oxalate chain segment and the generation of free radicals in the PBAT chain structure. The generated macromolecular stable free radicals containing benzene rings doped the graphene surface, increasing the carrier concentration of the graphene plane, which in turn caused the resistance of the composite material to decrease continuously.

[0050] Example 4

[0051] The operating temperature of the aging chamber was changed to 60°C, while the rest remained the same as in Example 3. The curve showing the change in the resistivity of the composite fiber with irradiation time is attached. Figure 4 As shown. By Figure 4 It can be seen that under the operating conditions of 60℃, the resistance of the composite material decreases significantly faster than that under the conditions of 45℃, indicating that the degradation rate of PBAT increases with increasing temperature.

[0052] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0053] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A method for in-situ characterization of polymers based on conductive two-dimensional materials, characterized in that, The method specifically includes the following steps: (1) Prepare conductive two-dimensional material thin films and polymer thin films, and construct composite materials based on conductive two-dimensional material thin films and polymer thin films, so that the conductive two-dimensional material thin films are electrical probes and are uniformly and orderly dispersed in different polymer matrices, and form continuous conductive pathways inside the composite materials; (2) The composite material constructed in step (1) is used as a platform test unit. The resistance of the composite material is measured to obtain the resistance change curve. The structural changes of the polymer matrix during the thermal transformation and degradation process are obtained by analyzing and processing the resistance change curve of the composite material. The glass transition temperature and melting point of the polymer matrix are calculated. The process of constructing composite materials based on conductive two-dimensional material films and polymer films includes: transferring a continuous two-dimensional conductive material film to the surface of a polymer film to construct a composite film, and then further processing the composite film into vortex fibers by transverse shearing and rolling to obtain the composite material. The process of measuring the resistance of the composite material includes: partially etching the polymer layer at both ends of the spiral fiber using a solvent that is compatible with the polymer matrix, and applying a conductive adhesive coating at the etched area to achieve conduction between the internal conductive two-dimensional material and the external circuit.

2. The polymer in-situ characterization method based on conductive two-dimensional materials according to claim 1, characterized in that, The conductive two-dimensional material film includes graphene, two-dimensional metal materials, two-dimensional covalent organic framework materials, two-dimensional metal-organic framework materials, and two-dimensional conductive polymers.

3. The polymer in-situ characterization method based on conductive two-dimensional materials according to claim 2, characterized in that, The processing method of the conductive two-dimensional material thin film includes chemical vapor deposition, epitaxial growth, inkjet printing, filtration, solvent evaporation, interface growth, hydrothermal synthesis or electrochemical synthesis, and the thickness of the conductive two-dimensional material thin film is less than 100 nm.

4. The polymer in-situ characterization method based on conductive two-dimensional materials according to claim 1, characterized in that, The polymer matrix is ​​a polymer material with thermal transformation behavior including glass transition and melting, or a polymer material that can be degraded by environmental factors.

5. The polymer in-situ characterization method based on conductive two-dimensional materials according to claim 4, characterized in that, The polymer matrix includes thermoplastics, polyolefin materials, or polyester materials; the thermoplastics include polycarbonate, polystyrene, or polymethyl methacrylate; the polyolefin materials include polyethylene, polypropylene, or polyolefin thermoplastic elastomers; the polyester materials include polyethylene terephthalate, polybutylene adipate terephthalate, polycaprolactone, and polyamides and polyimides.

6. The in-situ polymer characterization method based on conductive two-dimensional materials according to claim 1 or 5, characterized in that, The process of preparing polymer films includes: hot pressing, spin coating, blade coating or solvent evaporation to prepare polymer films, wherein the thickness of the polymer film is 0.5-30 μm.

7. The polymer in-situ characterization method based on conductive two-dimensional materials according to claim 1, characterized in that, The structural changes in the thermal transition process of polymers include chain motion and chain breakage during processes such as glass transition and melting. The glass transition temperature and melting point of the polymer matrix can be quantitatively calculated by analyzing the resistance change curves. The structural changes in the degradation process of polymers include chain breakage and free radical generation during processes such as photodegradation, thermal degradation, and microbial degradation. The degradation process of polymers can be analyzed and the degradation rate of polymers can be evaluated by analyzing the resistance change curves.

8. The in-situ polymer characterization method based on conductive two-dimensional materials according to claim 1 or 7, characterized in that, The process of quantitatively calculating the glass transition temperature and melting point of the polymer matrix by analyzing the resistance change curve includes: for the glass transition, the differential of the resistance change curve is calculated, and the temperature corresponding to the maximum value of the differential is the glass transition temperature of the polymer matrix; for the melting phase transition, the resistance change curves of the initial and final stages of the melting limit are fitted with straight lines, and the intersection of the straight lines corresponding to the initial and final stages is the melting point of the polymer matrix.

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