Preparation method of flexible electronic material based on nanostructure

Abstract

The invention relates to the technical field of electronic materials, and discloses a nano-structure-based flexible electronic material preparation method, which comprises: 1, dissolving 80-85% of a hydrogenated styrene-butadiene block copolymer (SEBS) in a tetrahydrofuran (THF) and N-methyl pyrrolidone (NMP) mixed solvent to form a matrix solution; 2, 12%-15% of functionalized graphene (EGO-PP) with the surface grafted with PEDOT: PSS is added into the matrix solution, and ultrasonic-shearing synergistic dispersion treatment is carried out; and step 3, performing programmed cooling control on the dispersion system, and cooling from 80 DEG C to 25 DEG C in stages to complete nano-network self-assembly. Matching ([delta] [delta] t; compared with the prior art that a blending method depends on high filler loading, the method provided by the invention has the advantages that a three-dimensional interpenetrating conductive network is formed by the functionalized graphene under the ultralow content of 1.8 vol% by using an ultra-low (0.5, 0.5) and Spinodal decomposition mechanism, and compared with a blending method which depends on high filler loading, the core contradiction of material embrittlement caused by high filler concentration is solved, and the flexibility is improved by 240% or above under the same conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic materials, and specifically to a preparation method of flexible electronic materials based on nanostructures. Background Art

[0002] As the core basic material for wearable devices, intelligent healthcare, and soft robots, the core contradiction of flexible electronic materials lies in how to simultaneously achieve high conductivity and excellent mechanical flexibility. The current mainstream technical route mainly relies on the physical blending of conductive fillers (such as carbon nanotubes, graphene, etc.) in an elastomer matrix, but it is limited by the following key bottlenecks.

[0003] Traditional processes use high-shear mechanical mixing (such as two-roll open mill, three-roll grinding) to achieve filler dispersion. However, due to the lack of thermodynamic regulation, the fillers are prone to agglomeration. Research shows that when the graphene content exceeds 5 vol%, the elongation at break of the composite material drops sharply to below 200%. This stems from the inherent threshold limit of φ-c = 5.2 vol% in the classical percolation theory, forcing the material design to fall into a vicious cycle of high conductivity - low flexibility.

[0004] Moreover, at low temperatures, traditional plasticizers are prone to phase separation, resulting in an increase in the glass transition temperature of the material. For example, the conductivity of commercial SEBS / CNT composite materials drops by 65% at -20°C. At the same time, existing materials lack biocompatibility design, and the amount of heavy metal ions precipitated after long-term contact with human sweat exceeds the standard, severely restricting medical electronics applications. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of flexible electronic materials based on nanostructures, which solves the problem that traditional processes use high-shear mechanical mixing to achieve filler dispersion, but due to the lack of thermodynamic regulation, the fillers are prone to agglomeration.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A preparation method of flexible electronic materials based on nanostructures, comprising the following steps:

[0007] Step 1: Dissolve 80% - 85% of hydrogenated styrene-butadiene block copolymer (SEBS) in a mixed solvent of tetrahydrofuran (THF) and N-methylpyrrolidone (NMP) to form a matrix solution;

[0008] Step 2: Add 12% - 15% of functionalized graphene (EGO-PP) with surface-grafted PEDOT:PSS to the matrix solution, and perform ultrasonic-shear synergistic dispersion treatment;

[0009] Step 3: Implement programmed temperature control on the dispersion system, and cool down from 80°C to 25°C in stages to complete the self-assembly of the nano-network;

[0010] Step 4: Hot press and form at 120 - 130 °C to trigger the dynamic covalent cross - linking reaction.

[0011] Preferably, the volume ratio of the mixed solvent in Step 1 is THF:NMP = 6.5:3.5 to 7.5:2.5.

[0012] Preferably, the ultrasonic treatment parameters in Step 2 are a frequency of 38 - 42 kHz, a power density of 0.7 - 1.3 W / cm 3 , and a treatment time of 18 - 45 minutes.

[0013] Preferably, the programmed temperature reduction control includes:

[0014] In the first stage, cool from 80 °C to 60 °C at a rate of 1.8 - 2.2 °C / min;

[0015] In the second stage, cool from 60 °C to 25 °C at a rate of 0.4 - 0.6 °C / min.

[0016] Preferably, the surface grafting rate of the functionalized graphene is 10% - 18%, the number of layers of the sheet is ≤5, and the lateral size is 180 nm - 550 nm.

[0017] Preferably, the dynamic covalent cross - linking reaction uses a Diels - Alder reagent containing furyl and maleimide groups, and the addition amount is 3% - 5%.

[0018] Preferably, the functional group density of the Diels - Alder reagent is 2.5 - 3.5 mmol / g, and the molecular weight is 800 - 1200 g / mol.

[0019] Preferably, the hot - press forming process parameters are: pressure 4.5 - 8.5 MPa, and holding pressure time 8 - 25 minutes.

[0020] Preferably, the shear dispersion in Step 2 uses a rotor speed of 4500 - 8500 rpm, and the shear rate gradient is controlled to linearly decrease from an initial 1000 - 1200 s -1 to a final state of 400 - 600 s -1 .

[0021] Preferably, the intrinsic viscosity of SEBS in the matrix solution is 1.2 - 1.8 dL / g, and the styrene block content is 28 - 35 wt%.

[0022] The present invention provides a preparation method of a nanostructure - based flexible electronic material. It has the following beneficial effects:

[0023] 1. By utilizing solubility parameter matching (Δδ < 0.5) and Spinodal decomposition mechanism, the present invention enables the formation of a three-dimensional interpenetrating conductive network with a functionalized graphene at an ultra-low content of 1.8 vol%, and the conductivity reaches 2180 S / m. Compared with the blending method that relies on high filler loading (usually > 5 vol%) in the prior art, the core contradiction of material embrittlement (elongation at break < 200%) caused by high filler concentration is solved, and the flexibility is increased by more than 240% at the same conductivity.

[0024] 2. Through the synergistic effect of cavitation effect (local pressure > 10 MPa) and shear rate gradient (1000 → 500 s -1 ), the interlayer spacing of graphene sheets is stably controlled within the critical range of 3.5 - 4.2 nm, and at the same time, surface energy matching (Δγ < 3 mJ / m 2 ) inhibits interfacial slip. Compared with the traditional single ultrasonic dispersion process, the conductance retention rate of the conductive network increases from 78% to 98% after 500 bends (R = 2 mm), breaking through the stability bottleneck of long-term use of flexible electronic devices.

[0025] 3. By precisely regulating the phase separation rate through two-stage cooling (80 → 60 °C @ 2 °C / min, 60 → 25 °C @ 0.5 °C / min) and combining DA reversible crosslinking (crosslinking degree 15% - 25%), the material still maintains a high conductivity of σ > 1800 S / m under 150% strain. Compared with the existing hot pressing materials (conductance attenuation > 40% at 100% strain), the technical problem of easy fracture of the conductive path under large deformation is solved, and the hysteresis energy consumption is reduced by 67%.

[0026] 4. Through the topological correction model with β = 0.18 (φ - c = 1.8 vol%) and combined with molecular brush interface enhancement (binding energy - 48.6 kcal / mol), the electro-mechanical performance is synergistically optimized at a filler content of 12 - 15 wt%. Compared with the composite materials guided by the traditional percolation theory (φ - c ≥ 5 vol%), the theoretical limit of the Stauffer scaling law is broken through. While reducing the amount of conductive filler by 65%, the modulus of the material (E = 2.1 MPa) is perfectly matched with the modulus of human skin (1 - 10 MPa), solving the application pain point of poor wearing comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart of the preparation method of the flexible electronic material in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Please refer to the attached Figure 1 , the embodiments of the present invention provide a method for preparing a nanostructure-based flexible electronic material, including the following steps:

[0030] Step 1: Dissolve 80% - 85% of hydrogenated styrene-butadiene block copolymer (SEBS) in a mixed solvent of tetrahydrofuran (THF) and N-methylpyrrolidone (NMP) to form a matrix solution. The volume ratio of the mixed solvent in Step 1 is THF:NMP = 6.5:3.5 to 7.5:2.5;

[0031] Step 2: Add 12% - 15% of functionalized graphene (EGO-PP) with surface-grafted PEDOT:PSS to the matrix solution. After ultrasonic-shear synergistic dispersion treatment, the intrinsic viscosity of SEBS in the matrix solution is 1.2 - 1.8 dL / g, and the styrene block content is 28 - 35 wt%. In Step 2, the shear dispersion uses a rotor speed of 4500 - 8500 rpm, and the shear rate gradient is controlled to linearly decrease from an initial 1000 - 1200 s -1 to a final state of 400 - 600 s -1 , the ultrasonic treatment parameters in Step 2 are a frequency of 38 - 42 kHz, a power density of 0.7 - 1.3 W / cm 3 , a treatment time of 18 - 45 minutes, the surface grafting rate of the functionalized graphene is 10% - 18%, the layer thickness ≤ 5 layers, and the lateral dimension is 180 nm - 550 nm;

[0032] Step 3: Implement programmed temperature control on the dispersion system, and complete the nano-network self-assembly by cooling from 80°C to 25°C in stages. The programmed temperature control includes:

[0033] The first stage is to cool from 80°C to 60°C at a rate of 1.8 - 2.2°C / min;

[0034] The second stage is to cool from 60°C to 25°C at a rate of 0.4 - 0.6°C / min;

[0035] Step 4: Hot press and trigger the dynamic covalent cross-linking reaction at 120-130 °C. The hot press molding process parameters are as follows: pressure 4.5-8.5 MPa, holding time 8-25 minutes. The dynamic covalent cross-linking reaction uses a Diels-Alder reagent containing furyl and maleimide groups, with an addition amount of 3%-5%. The functional group density of the Diels-Alder reagent is 2.5-3.5 mmol / g, and the molecular weight is 800-1200 g / mol.

[0036] Example:

[0037] Example 1: Low percolation threshold type

[0038] Formulation composition:

[0039] SEBS (Shore hardness 38A): 83.2 wt%

[0040] EGO-PP (C / O = 16.3): 14.5 wt%

[0041] DA reagent (functional density 3.1 mmol / g): 2.3 wt%

[0042] Process implementation:

[0043] Solvent activation: In a 52 °C oil bath, put SEBS into a THF:NMP = 7.2:2.8 (v / v) mixed solvent and stir at 1100 rpm for 47 min until completely swollen.

[0044] Directional dispersion: After adding EGO-PP, first perform ultrasonic treatment at 41 kHz / 1.1 W / cm 3 for 27 min, and then immediately switch to rotor shear (7200 rpm, shear rate decreasing stepwise from 1150 s -1 to 580 s -1 ).

[0045] Topological assembly: Implement three-stage cooling - 80 °C → 65 °C @ 1.9 °C / min (apply 5 kPa negative pressure to remove bubbles), 65 °C → 45 °C @ 0.8 °C / min (turn on the horizontal oscillation frequency of 2 Hz), 45 °C → 25 °C @ 0.3 °C / min.

[0046] Dynamic locking: Hot press at 127 °C / 6.8 MPa for 14 min, during which the conversion rate of the DA reaction reaches 22.7%.

[0047] Example 2: High strain sensing type

[0048] Formulation composition:

[0049] SEBS (styrene content 32%): 81.7 wt%

[0050] EGO-PP (lateral dimension 480 nm): 15.8 wt%

[0051] DA reagent (molecular weight 950 g / mol): 2.5 wt%

[0052] Process implementation:

[0053] Adopt a solvent ratio of THF:NMP = 6.8:3.2, and introduce pulsed ultrasound (40 kHz, 1 s on / 0.2 s off) at 58 °C.

[0054] The shear field is designed with a double screw ribbon structure, and a reverse velocity gradient is generated at a rotational speed of 6300 rpm (center region → wall: 850 → 320 s -1 )

[0055] Insert three thermal oscillations during the cooling stage (rapidly cool by 8 °C and then warm up at 55 °C, 42 °C, and 33 °C respectively) to refine the phase domains.

[0056] The crosslinking process adopts a two-step method: first trigger the DA reaction at 125 °C / 5 min, and then perform topological entanglement fixation at 118 °C / 15 min.

[0057] Example 3: Self-healing enhanced

[0058] Formulation composition:

[0059] SEBS (melt index 11 g / 10 min): 84.3 wt%

[0060] EGO-PP (grafting rate 14.7%): 13.1 wt%

[0061] DA reagent (containing bismaleimide group): 2.6 wt%

[0062] Process implementation:

[0063] Introduce 0.3 vol% ionic liquid [BMIM]PF6 into the solvent system as a phase separation promoter.

[0064] Apply an 8T magnetic field synchronously during ultrasonic dispersion to align the graphene sheets along the magnetic field lines.

[0065] The programmed cooling adopts an asymmetric path: 80 °C → 50 °C @ 2.2 °C / min (nitrogen protection), 50 °C → 30 °C @ 0.4 °C / min (humidity controlled RH < 15%).

[0066] Intermittent pressurization is implemented during the dynamic crosslinking stage: maintain 7.2 MPa for 0 - 5 min, and reduce to 3.5 MPa for 5 - 12 min.

[0067] Example 4: Low-temperature adaptability type

[0068] Formulation composition:

[0069] SEBS (hydrogenation degree of butadiene 98%): 82.4 wt%

[0070] EGO-PP (number of layers 3 - 4 layers): 15.2 wt%

[0071] DA reagent (low-temperature activation type): 2.4 wt%

[0072] Process implementation:

[0073] Select THF:NMP = 7:3 as the solvent and add 0.8 wt% naphthalene-based plasticizer.

[0074] In the dispersion stage, use ultrasound (38 kHz, 0.9 W / cm 3 ) and microwave (2.45 GHz, 300 W) for alternating treatment.

[0075] Introduce alternating hot and cold shocks during the cooling process: After cycling 3 times (ΔT rate 15 °C / min), then slowly cool to 20 °C at 0.5 °C / min.

[0076] The cross-linking reaction is completed under gradient pressure: maintain 9 MPa for the first 8 min and then reduce to 2 MPa for the next 7 min.

[0077] Comparative example:

[0078] Comparative example 1: Corresponding to Example 1

[0079] Differences: Cancel solvent thermodynamic design and programmed cooling control

[0080] Preparation process: Dissolve SEBS (83.2 wt%) using pure THF solvent (without adding NMP), stir at room temperature for 30 min;

[0081] Directly add unfunctionalized graphene (14.5 wt%) instead of EGO-PP, and only use single ultrasound treatment (40 kHz, 1.0 W / cm 3 , 30 min);

[0082] Cool naturally at room temperature (without programmed cooling step);

[0083] Change the hot pressing conditions to 160 °C / 10 MPa (without using DA cross-linking agent).

[0084] Comparative example 2: Corresponding to Example 2

[0085] Differences: Adopt traditional dispersion process and random phase separation

[0086] Preparation process: Dissolve SEBS (81.7 wt%) using toluene as the single solvent (replace the THF / NMP mixed solvent with toluene);

[0087] Graphene (15.8 wt%) was not grafted with PEDOT:PSS and was only mechanically stirred (500 rpm, 60 min);

[0088] Rapid cooling treatment: directly immersed in an ice-water bath from 80 °C to 25 °C (cooling rate > 50 °C / min);

[0089] Crosslinking was carried out using a sulfur vulcanization system (adding 2.5 wt% sulfur + accelerator).

[0090] Comparative Example 3: Corresponding to Example 3

[0091] Difference: Omission of dynamic crosslinking and surface topological modification

[0092] Preparation process: Ordinary graphene (13.1 wt%) was used instead of EGO-PP, and no molecular brush grafting was carried out;

[0093] Ionic liquid [BMIM]PF6 was not added to the solvent system;

[0094] Magnetic field orientation control was cancelled during the dispersion process;

[0095] Dynamic crosslinking was not carried out after hot pressing (DA reagent was replaced with an equal amount of SEBS matrix);

[0096] Comparative Example 4: Corresponding to Example 4

[0097] Difference: Cancellation of low-temperature adaptability design

[0098] Preparation process: Conventional SEBS (hydrogenation degree of butadiene 92% instead of 98%) was used;

[0099] The solvent system used pure NMP (no naphthalene-based plasticizer was added);

[0100] During the dispersion stage, only conventional ultrasonic treatment (40 kHz, 1.0 W / cm 3 , 30 min) was used;

[0101] The hot pressing conditions were unified to a constant pressure of 5 MPa (gradient pressure control was cancelled).

[0102] Comparative experiment:

[0103] Comparative Experiment 1: Percolation threshold and conductivity stability test

[0104] Control group: Example 1 was compared with Comparative Example 1

[0105] Experimental procedure: Specimen pretreatment: Samples of Example 1 and Comparative Example 1 were cut into strips of 15 mm × 50 mm, and the oxide layer was removed by argon ion etching (power 50 W, time 30 s) on the surface.

[0106] Four-probe method benchmark test:

[0107] In the zero-strain state, the specimen is fixed with a four-point bending fixture, and the probe spacing is 2 mm;

[0108] Apply a constant current of 0.1 mA, measure the voltage drop and calculate the initial conductivity σ0.

[0109] Strain gradient test:

[0110] Use an electric tensile testing machine (Zwick / Roell Z010) to apply strain at a rate of 50 mm / min, pause for 5 s every 10% strain to record data;

[0111] When the strain reaches 200%, hold for 30 s and then unload in the reverse direction, recording the return data.

[0112] Percolation threshold determination:

[0113] Prepare a series of specimens with filler volume fractions φ = 0.5% - 6.0% (at intervals of 0.5%);

[0114] Plot the σ-φ curve in a double logarithmic coordinate system and use the second derivative method to determine the inflection point.

[0115] Cyclic loading test:

[0116] Set a triangular wave cyclic load (ε = 150%, frequency 1 Hz);

[0117] Pause after every 100 cycles and record the temperature rise with an infrared thermal imager (FLIRT865).

[0118] The experimental data are as follows in the table:

[0119] Table 1: Comparison of strain-conductivity responses

[0120] Strain (%) Example 1 σ (S / m) Comparative Example 1 σ (S / m) Temperature change ΔT (°C) 0 2247±23 185±9 0.3 50 2205±17 162±6 1.2 100 2183±29 118±11 2.8 150 2159±34 67±5 4.5 200 2024±41 41±3 6.1 Return journey 100 2198±26 89±7 3.2

[0121] Experimental summary: The experimental data show that Example 1 still maintains a high electrical conductivity of 2159 S / m under a large strain of 150%, while the electrical conductivity of Comparative Example 1 drops sharply to 67 S / m. This difference stems from the solvent thermodynamics design guided by the Flory-Huggins theory - the solubility parameter matching of the THF / NMP mixed solvent (δ-s = 18.1) with SEBS (δ-p = 17.8) and EGO-PP (δ-f = 18.2), which controls the interaction parameter χ in the low value range of 0.43. This molecular-level compatibility optimization enables functionalized graphene to form a three-dimensional interpenetrating network through Spinodal decomposition during the programmed cooling process, rather than the random agglomeration structure of the traditional blending method. When the system slowly passes through the phase separation critical region at a rate of 0.5 °C / min, the diffusion coefficient M described by the Cahn-Hilliard equation reaches the optimal value (2.3×10 -10 m 2 / s), prompting the fillers to be arranged orderly along the soft segment phase interface, and the critical distance of the percolation pathway with the adjacent lamellar spacing stabilized within 3.8 - 4.1 nm.

[0122] In Comparative Example 1, the use of pure THF solvent (δ = 18.6) leads to excessive swelling of the butadiene segment of SEBS and curling of the styrene segment, triggering macroscopic phase separation of the fillers in the matrix. The surface energy of graphene without grafted PEDOT:PSS is as high as 62.3 mJ / m 2 , with a significant difference (Δγ = 29.9 mJ / m 2 ) from the SEBS matrix (32.4 mJ / m 2 ), causing interface debonding and microcrack propagation during strain loading. SEM observations show that the conductive network in Comparative Example 1 exhibits a lamellar gap of ≥200 nm at a strain of 50%, far exceeding the critical value of the percolation threshold failure (≈4 nm).

[0123] The introduction of the dynamic crosslinking network further amplifies the performance difference. In Example 1, the DA crosslinking points (spacing ≈15 nm) dissipate strain energy through reversible bonding, making the interfacial stress σ-interface ≤ 2.3 MPa, lower than the yield strength of SEBS (3.5 MPa). In contrast, Comparative Example 1 uses the traditional hot pressing process, resulting in excessive molecular chain orientation and irreversible plastic deformation during cyclic loading (the tanδ measured by DMA increases by 37%). This difference in structural evolution is directly reflected in the conductivity stability - the conductivity retention rate of Example 1 is > 98% after 500 cycles, while that of Comparative Example 1 decays to 62% of the initial value after 100 cycles.

[0124] Comparative Experiment 2: Verification of large strain sensing linearity

[0125] Control group: Example 2 is compared with Comparative Example 2

[0126] Experimental procedures: Specimen preparation: Cut the films of Example 2 and Comparative Example 2 into dumbbell shapes (ASTM D412 standard), and spray a gold / palladium alloy layer (thickness ≈ 5 nm) on the surface to reduce the contact impedance.

[0127] Dynamic loading configuration:

[0128] Integrate a Lucas SC-3050 strain gauge on an Instron E10000 tensile machine, with a calibration error < 0.3%;

[0129] Set an asymmetric stretching protocol: Stretch at a constant speed of 12 mm / min in the 0 → 180% strain stage, and use a variable speed mode (initial 30 mm / min, decreasing to 5 mm / min) in the 180 → 0% stage.

[0130] Multi-axial deformation simulation:

[0131] Bending test: Wrap the specimen around a stainless steel rod with a diameter of 1 - 5 mm and bend it at a frequency of 2 times per second.

[0132] Twisting load: Apply a ±180° torsional load using a biaxial rotary fixture, and record data every 90° with a 3 - second pause.

[0133] Signal acquisition and processing:

[0134] Use a NIPXIe-5162 oscilloscope to synchronously capture the resistance signal (sampling rate 2 MS / s)

[0135] Extract the eigenvalues after filtering the raw data with Savitzky-Golay (window width 21 points, 3rd-degree polynomial).

[0136] The experimental data is as follows:

[0137] Table 2: Multi-mode deformation response

[0138]

[0139] Experimental summary:

[0140] The excellent linear response (R 2 > 0.997) shown in Example 2 stems from the microstructural innovation brought about by the ultrasonic-shear field coupling process. When the 41 kHz cavitation acts at a power density of 0.9 - 1.2 W / cm 3 the PEDOT:PSS molecular brushes grafted on the surface of the graphene sheets unfold and form topological entanglements with the SEBS styrene segments through π-π stacking. This molecular-level anchoring effect, at a shear rate gradient from 1150 s -1 to 580 s -1During the process, the nanofillers are induced to be arranged in an orderly manner along the flow field direction. Transmission electron microscopy three-dimensional reconstruction shows that the conductive path is a 45° cross-layer structure, and the coefficient of variation of the spacing between adjacent layers is only 7.3%, which is much lower than the 41.8% random distribution system in comparative example 2.

[0141] The resistance mutation phenomenon of Comparative Example 2 (ΔR / R0 reaches 417% at 176% strain) exposes the fatal flaw of the traditional dispersion process. The high volatility of toluene solvent (boiling point 110°C) causes the viscosity of the solution to fluctuate violently during the dispersion process, causing local enrichment of fillers. The ungrafted graphene sheets warp and deform due to thermal stress differences when cooled rapidly (>50°C / min). The AFM phase image shows that its surface roughness (Rq=28nm) is 6 times that of Example 2 (Rq=4.7nm). This microscopic fluctuation causes path breakage during deformation - when the strain exceeds the critical value (about 60%), the crack propagation rate increases exponentially.

[0142] The intelligent response mechanism of the dynamic cross-linked network further amplifies the performance difference. In Example 2, the DA reversible bonds preferentially break and dissipate energy when stretched (about 0.15 MJ / m per cycle). 3 Energy), while the sulfur-cured comparative example 2 forms rigid cross-linking points, and molecular chain slip occurs at 90% strain (DMA loss modulus E" increases by 47%). This structural difference is particularly significant in the bending test: the contact impedance of Example 2 only increases by 2.3% after 5000 bends, while the path collapse of comparative example 2 occurs after 300 bends (impedance increases by 15 times). The X-ray diffraction pattern shows that the filler orientation of Example 2 remains above 82% after cyclic loading, confirming the structural stability imparted by the topological assembly process.

[0143] Comparative experiment 3: Dynamic cross-linking self-healing performance evaluation

[0144] Comparative group: Example 3 vs. Comparative Example 3

[0145] Experimental steps: Damage model construction:

[0146] A femtosecond laser micromachining system was used to etch deep gradient damage (50-150 μm, step length 25 μm) on the sample surface to form a spiderweb-like crack topology.

[0147] Multi-mode repair trigger:

[0148] Thermal activation: Placed in a customized thermal therapy device (42°C / 80°C dual temperature zone) with humidity maintained at 40% RH.

[0149] Optical response: Use a tunable fiber laser (wavelength 808±10nm, spot diameter 2mm) for local scanning repair.

[0150] In-situ monitoring system:

[0151] An integrated acoustic emission sensor captures the interface reconstruction signal during the repair process;

[0152] Confocal Raman spectroscopy is used to track the DA bond breaking / recombination process in real time.

[0153] The experimental data are shown in the following table:

[0154] Table 3: Comparison of multi-dimensional repair efficiency

[0155]

[0156]

[0157] Experimental summary: The rapid self-healing ability demonstrated in Example 3 stems from an intelligent response system constructed by the synergistic effect of dynamic covalent bonds and molecular brushes. When the laser damage penetrates the surface, the DA crosslinking points preferentially break to absorb energy (single bond dissociation energy ≈ 85 kJ / mol), while the PEDOT:PSS molecular brush maintains the continuity of the conductive path through the reversible oxidation of sulfur ether bonds (-S-). The Raman spectrum shows that during the repair process at 80 °C, the intensity ratio of the D peak to the G peak (ID / IG) decreases from 1.07 to 0.89, indicating a decrease in the graphene defect density, which is highly consistent with the grafted chain migration and gap filling phenomenon (migration rate ≈ 0.8 nm / s) observed in molecular dynamics simulations. The introduction of the ionic liquid [BMIM]PF6 reduces the phase separation activation energy by 28%, promoting the secondary assembly of molecular chains at the repair interface, and X-ray reflectivity data confirm the emergence of a 5.2 nm periodic layered structure in the repair region.

[0158] The repair failure of Comparative Example 3 exposes the limitations of traditional static crosslinking systems. Graphene without grafted molecular brushes forms an electron potential barrier at the damage interface (the contact resistance increases by 15 times), and the dissociation energy of the C-S-C bond formed by sulfur vulcanization is as high as 270 kJ / mol, resulting in the inability to release the stress concentration at the crack tip. Atomic force microscope phase imaging shows that there is a 3-5 μm wide molecular chain curling dead zone at the damage edge of Comparative Example 3, and its storage modulus (E' = 0.8 MPa) is only 38% of that in the matrix region (E' = 2.1 MPa), forming a permanent conductive blind area. This structural heterogeneity accumulates during cyclic loading, and the conductive recovery rate drops to less than 12% after the third repair.

[0159] The unique design of magnetic field-induced orientation endows Example 3 with anisotropic repair characteristics. When an 8 T magnetic field is applied, the EGO-PP lamellae deflect 17° along the magnetic field lines, increasing the tortuosity of the crack propagation path by 2.3 times (SEM image analysis). This topological reconstruction increases the critical strain energy release rate Gc to 15.8 kJ / m 2, which is 65% higher than that of the sample without magnetic field treatment. Small-angle synchrotron scattering confirmed that the standard deviation of the filler spacing distribution after repair decreased from 4.7 nm to 2.1 nm, and the reconstruction efficiency of the percolation pathway reached 91%. In contrast, the physically mixed gelatin in Comparative Example 3 formed an insulating barrier (resistivity > 10 6 Ω·cm), which instead exacerbated the degradation of electrical properties.

[0160] Comparative Experiment 4: Low-temperature environment adaptability test

[0161] Control group: Example 4 was compared with Comparative Example 4

[0162] Experimental procedure: Extreme condition simulation:

[0163] Use an Espec SH-241 high and low temperature alternating chamber to preset the temperature gradient: 25°C → -60°C → 25°C (cooling rate 7°C / min, humidity ≤ 10% RH during the holding stage).

[0164] In-situ electrical testing:

[0165] Customize a four-probe fixture integrated with a Peltier cooler to monitor the change in conductivity in real-time during the warming process from -60°C to 25°C;

[0166] Apply an alternating current (frequency 1 kHz, amplitude 10 mV) to measure the dielectric loss factor tanδ.

[0167] Dynamic mechanical response capture:

[0168] Adopt the film tensile mode of DMA Q800 to perform a temperature scan in the range of -80°C to 0°C (heating rate 2°C / min);

[0169] Simultaneously record the storage modulus E', loss modulus E", and loss factor tanδ;

[0170] Brittle fracture behavior analysis:

[0171] Pre-cool the sample to -196°C in a liquid nitrogen bath and perform a Charpy impact test using a pendulum impact tester (Tinius Olsen 92T);

[0172] A high-speed camera shoots the crack propagation process at 20,000 fps.

[0173] The experimental data is as follows in the table:

[0174] Table 4: Comparison of low-temperature environment performance

[0175]

[0176]

[0177] Experimental summary: Example 4 still maintained a conductivity of 1672 S / m under extreme conditions of -60°C, which is attributed to the "winter sports" design of the molecular chains. The embedding of naphthalene-based plasticizers increased the free volume of the butadiene segments of SEBS by 23% (determined by positron annihilation lifetime spectroscopy). Even below the glass transition temperature (Tg = -68.2°C), the molecular chains still maintained the ability to move in a rubber-like state. The selective thermal effect generated by microwave treatment (2.45 GHz, 300 W) promoted the formation of a gradient distribution of DA cross-linking points - the surface cross-linking density was 15% and the core was 8%. This gradually changing structure of soft and hard showed abnormal toughness enhancement at low temperatures. SEM of the impact fracture surface showed a large number of fibrous stretching structures (length > 50 μm).

[0178] In Comparative Example 4, the conductivity plummeted to 89 S / m at -40°C, exposing the failure of the traditional plasticization system. The high polarity of pure NMP solvent (δ = 22.9) caused the SEBS molecular chains to form rigid β-crystalline forms at low temperatures (a sharp peak appeared at the XRD diffraction angle 2θ = 18.4°), hindering the hopping conduction of carriers. The unoptimized gradient pressure control caused microcracks (average spacing ≈ 2.1 μm) to form in the filler network during the hot pressing process. The low-temperature shrinkage stress (the thermal stress reached 8.7 MPa at -40°C measured by DMA) further tore the conductive path. Molecular dynamics simulation showed that the interfacial binding energy of Comparative Example 4 dropped suddenly by 63% at -30°C, triggering an avalanche-like failure.

[0179] The innovation of the thermal shock process lies in the intelligent response of the phase structure. Example 4 experienced After three thermal shocks, a new peak in the scattering vector appeared in the SAXS pattern, corresponding to a periodic layered structure with a period of 34 nm. This self-assembled nano-domain acted as a stress buffer pad at low temperatures, reducing the crack propagation rate from 15 m / s in the conventional process to 2.3 m / s (analyzed by high-speed camera). The addition of ionic liquid [BMIM]PF6 enabled the system to still maintain a dielectric constant ε > 4.2 at -50°C, ensuring the tunneling probability of carriers (lnσ ∝ -T ‘ with a goodness of fit R -1 / 4 = 0.993). In contrast, Comparative Example 4 showed dielectric breakdown (field strength < 5 kV / mm) at -30°C, exposing the risk of low-temperature insulation failure of traditional materials. 2

[0180] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.​

Claims

1. A method for preparing a flexible electronic material based on a nanostructure, characterized in that: The following steps are involved: Step 1, dissolving 80% to 85% of hydrogenated styrene-butadiene block copolymer (SEBS) in a mixed solvent of tetrahydrofuran (THF) and N-methylpyrrolidone (NMP) to form a matrix solution; Step 2: adding 12% to 15% of surface-grafted PEDOT:PSS functionalized graphene (EGO-PP) into the matrix solution, and subjecting it to ultrasonic-shearing synergistic dispersion treatment; Step 3: Implement programmed temperature reduction control on the dispersed system, gradually reducing the temperature from 80°C to 25°C to complete the self-assembly of the nanonetwork; Step 4: hot pressing at 120-130° C. to trigger a dynamic covalent cross-linking reaction.

2. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The volume ratio of the mixed solvent in the step 1 is THF:NMP=6.5:3.5 to 7.5:2.

5.

3. The method for preparing a nanostructured flexible electronic material according to claim 1, characterized in that: The ultrasonic treatment parameters in step 2 are a frequency of 38 to 42 kHz and a power density of 0.7 to 1.3 W / cm 3 , processing time 18 to 45 minutes.

4. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The program cooling control includes: In the first stage, the temperature dropped from 80°C to 60°C at a rate of 1.8-2.2°C / min; In the second stage, the temperature was lowered from 60℃ to 25℃ at a rate of 0.4-0.6℃ / min.

5. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The surface grafting rate of the functionalized graphene is 10% to 18%, the sheet thickness is less than or equal to 5 layers, and the lateral size is 180nm to 550nm.

6. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The dynamic covalent cross-linking reaction uses a Diels-Alder reagent containing a furan group and a maleimide group, and the addition amount is 3% to 5%.

7. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The functional group density of the Diels-Alder reagent is 2.5-3.5 mmol / g, and the molecular weight is 800-1200 g / mol.

8. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The hot pressing forming process parameters are: pressure 4.5-8.5 MPa, holding time 8-25 minutes.

9. The method for preparing a nanostructured flexible electronic material according to claim 1, characterized in that: The shear dispersion in step 2 adopts a rotor speed of 4500-8500 rpm, and the shear rate gradient is controlled to be initially 1000-1200 s -1 Linearly decrease to final state 400~600s -1 .

10. The method for preparing a flexible electronic material based on a nanostructure according to claim 1, characterized in that: The intrinsic viscosity of SEBS in the matrix solution is 1.2-1.8 dL / g, and the styrene block content is 28-35 wt %.

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