High-thermal-conductivity shape memory nano composite material as well as preparation method and application thereof

Abstract

The invention relates to a high-thermal-conductivity shape memory nano composite material and a preparation method and application thereof, and the preparation method comprises the following steps: functionalizing a graphene nanosheet by using phenylphosphonic acid to obtain PPA (at) GNPs; the preparation method comprises the following steps: combining cellulose nanocrystals and PPA (at) GNPs through non-covalent interaction in an environment with the pH value of 6-8, so as to form a CNC-PPA (at) GNPs nanosheet; and uniformly dispersing the CNC-PPA-coated GNPs nanosheets in a polypropylene carbonate (PPC) solution, and then carrying out curtain coating and drying to obtain the shape memory nano composite material with high thermal conductivity. The preparation method comprises the following steps: anchoring a PPA functionalized graphene nanosheet GNPs by CNC (computer numerical control) to form a CNC-PPA coated GNPs nanosheet; the nanosheets are dispersed in a polypropylene carbonate (PPC) matrix, and the composite material is prepared through a solution casting method. According to the invention, a bridging heat conduction network is constructed in PPC through the CNC-PPA-GNPs nanosheets, so that the heat conductivity, the mechanical property and the shape memory function of the composite material are remarkably improved, and the composite material has biodegradability; the material can reduce the temperature of a CPU of a smart phone to 17.9 DEG C under real operation conditions, and balance of thermal insulation and heat dissipation is achieved.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials technology, specifically relating to a high thermal conductivity shape memory nanocomposite material, its preparation method and application, which is particularly suitable for thermal management, biodegradable packaging and shape memory materials for 5G electronic devices. Background Technology

[0002] With the rapid development of 5G technology and the miniaturization and high power of electronic devices, the problem of internal heat accumulation is becoming increasingly prominent, leading to decreased device stability, reduced efficiency, and shortened lifespan. Traditional thermal management materials such as epoxy resin and polyimide films have problems such as non-biodegradability and easy generation of electronic waste pollution. Polypropylene carbonate (PPC), as a biodegradable polymer, has shape memory properties, but its inherent defects, such as low thermal conductivity (approximately 0.059 W·m), are problematic. -1 ·K -1 Low mechanical strength (tensile strength 5.7 MPa) and poor thermal stability (T0). max Its application in high-performance electronic devices is limited by its temperature of approximately 251.5°C.

[0003] Graphene nanosheets (GNPs) possess high theoretical thermal conductivity (5000 W·m). -1 ·K -1 GNPs (Glycol Nanoparticles) are ideal fillers for enhancing the thermal properties of polymers, but they are prone to aggregation, leading to interfacial defects and performance degradation. Cellulose nanocrystals (CNCs) can serve as bio-based reinforcing agents, improving dispersibility through hydrogen bonding, but traditional methods cannot effectively address the issues of GNP aggregation and interfacial compatibility. Therefore, developing a composite material that combines high thermal conductivity, mechanical strength, biodegradability, and thermal stability is an urgent need in the field. Summary of the Invention

[0004] Based on the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a high thermal conductivity shape memory nanocomposite material, its preparation method and application. By anchoring PPA-functionalized GNPs with CNC, CNC-PPA@GNPs nanosheets are formed, and a bridging thermal conduction network is constructed in the PPC matrix, thereby synergistically improving thermal conductivity, mechanical properties and shape memory function.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a high thermal conductivity shape memory nanocomposite material includes the following steps: (1) PPA@GNPs were obtained by functionalizing graphene nanosheets GNPs with phenylphosphonic acid (PPA); (2) In an environment with pH 6 to 8, cellulose nanocrystals CNC and PPA@GNPs are combined through non-covalent interactions (such as hydrogen bonding and π-π stacking) to form CNC-PPA@GNPs nanosheets; (3) CNC-PPA@GNPs nanosheets were uniformly dispersed in polypropylene carbonate (PPC) solution, and then cast and dried to obtain high thermal conductivity shape memory nanocomposite material.

[0006] As a preferred embodiment, in step (1), PPA is dissolved in water, GNPs powder is added, and after ball milling, it is freeze-dried under vacuum to obtain PPA@GNPs; The ball milling process involves a rotation speed of 300-500 rpm and a time of 24-72 hours. The ball milling process described above ensures that PPA uniformly modifies the surface of GNPs through π-π stacking and van der Waals forces, thus inhibiting agglomeration.

[0007] As a preferred embodiment, the mass ratio of PPA to GNPs powder is (3-5):1.

[0008] As a preferred embodiment, in step (2), CNC and PPA@GNPs are mixed in a dispersion medium with a pH of 6 to 8, treated with an ultrasonic cell disruptor, and then centrifuged, the precipitate is collected and freeze-dried to obtain CNC-PPA@GNPs nanosheets. The ultrasonic cell disruptor has a power of 800-1200W, a pulse mode that is on for 5-10 seconds and off for 5-10 seconds, and the entire process takes 1-2 hours.

[0009] As a preferred embodiment, the mass ratio of CNC to PPA@GNPs is 1:(0.5-1.5). At this mass ratio, the hydroxyl groups of CNC and the phosphoryl groups (P=O) of PPA form a hydrogen bond network, while the steric hindrance effect of CNC effectively prevents the aggregation of GNPs.

[0010] As a preferred embodiment, in step (3), the solid-liquid ratio of the PPC solution is 1:(5-7), and the drying temperature is 60-80°C.

[0011] The present invention also provides a high thermal conductivity shape memory nanocomposite material prepared by the preparation method described in any of the preceding embodiments, wherein the mass fraction of CNC-PPA@GNPs nanosheets in the high thermal conductivity shape memory nanocomposite material is 1-10%.

[0012] As a preferred option, the thermal conductivity of the high thermal conductivity shape memory nanocomposite is 1.81-3.2 W·m. -1 ·K -1The shape fixation rate Rf≥90%, the shape recovery rate Rr≥90%, and the deformation recovery is completed within 30 seconds.

[0013] As a preferred option, the high thermal conductivity shape memory nanocomposite material exhibits a biodegradation rate of 15-20% in soil after 120 days.

[0014] The present invention also provides the application of high thermal conductivity shape memory nanocomposites as described in any of the preceding embodiments in the thermal management of electronic devices, for use in smartphone CPU heat dissipation or electronic packaging.

[0015] Compared with the prior art, the beneficial effects of this invention are: (1) The high thermal conductivity shape memory nanocomposite material of the present invention constructs a bridging thermal conduction network in PPC through CNC-PPA@GNPs nanosheets, which significantly improves the thermal conductivity, mechanical properties and shape memory function of the composite material, while also being biodegradable; (2) By constructing a unique nanosheet bridging network, the composite material achieves a breakthrough in thermal management performance, significantly improving heat dissipation efficiency and effectively controlling the core temperature of electronic devices; in terms of mechanical properties, the material exhibits excellent rigidity enhancement and stress transmission capabilities, completely overcoming the inherent mechanical strength deficiency of the matrix material; thermal stability achieves a qualitative leap, enabling the material to adapt to a wider operating temperature range; it also possesses intelligent shape memory characteristics, allowing it to quickly recover its original shape under thermal triggering; in terms of environmental friendliness, the material maintains excellent biodegradability, effectively reducing electronic waste pollution; through innovative interface design theory, it achieves precise control of the material's microstructure; the entire production process is simple and efficient, with significant potential for industrial application, providing a comprehensive and sustainable solution for next-generation electronic devices; (3) Under real operating conditions, the present invention can reduce the CPU temperature of smartphones by up to 17.9°C and achieve a balance between thermal insulation and heat dissipation. Attached Figure Description

[0016] Figure 1 This is a comparison chart of the thermal stability of pure PPC, Example 1, Comparative Example 2, and Comparative Example 3 of the present invention. Figure 2 This is a comparison diagram of the shape memory performance of pure PPC, Example 1, and Comparative Example 3 of the present invention; Figure 3 This is a comparison diagram of the CPU heat dissipation effect of pure PPC and Example 1 as heat conduction fluid in this invention; Figure 4 This is a comparison chart of the heat dissipation effects of a smartphone using a pure PPC, Example 1, and a blank group. Detailed Implementation

[0017] The following provides a detailed description of the high thermal conductivity shape memory nanocomposite material of the present invention, its preparation method, and its application.

[0018] The method for preparing the high thermal conductivity shape memory nanocomposite material of the present invention includes the following steps: (1) PPA@GNPs were obtained by functionalizing graphene nanosheets GNPs with phenylphosphonic acid (PPA); Specifically, PPA is dissolved in water, GNPs powder is added, and after ball milling, it is freeze-dried under vacuum to obtain PPA@GNPs; The mass ratio of PPA to GNPs powder is (3-5):1, and the specific mass ratio can be determined according to the actual application requirements. The ball milling process described above involves a rotation speed of 300-500 rpm and a time of 24-72 hours. The ball milling process ensures that PPA uniformly modifies the surface of GNPs through π-π stacking and van der Waals forces, thereby inhibiting agglomeration.

[0019] (2) In an environment with pH 6 to 8, cellulose nanocrystals CNC and PPA@GNPs are bonded together through non-covalent interactions to form CNC-PPA@GNPs nanosheets; Specifically, CNC and PPA@GNPs were mixed in a dispersion medium with a pH of 6-8, treated with an ultrasonic cell disruptor, centrifuged, and the precipitate was collected and freeze-dried to obtain CNC-PPA@GNPs nanosheets. The ultrasonic cell disruptor has a power of 800-1200W, a pulse mode of 5-10s on / off, and a total processing time of 1-2 hours. The specific operating parameters of the ultrasonic cell disruptor can be determined according to the actual application requirements. The mass ratio of CNC to PPA@GNPs is 1:(0.5-1.5). Within this mass ratio range, the hydroxyl groups of CNC and the phosphoryl groups (P=O) of PPA form a hydrogen bond network, while the steric hindrance effect of CNC effectively prevents the aggregation of GNPs. The aforementioned non-covalent interactions include hydrogen bonds and π-π stacking; among them, hydrogen bonds are formed between the hydroxyl groups of CNC, the P=O groups of PPA, and the polar chains of PPC, constructing a three-dimensional bridging interface; The dispersion medium with a pH of 6 to 8 is either water or ethanol, and the specific choice depends on the actual application requirements.

[0020] (3) CNC-PPA@GNPs nanosheets were uniformly dispersed in polypropylene carbonate (PPC) solution, and then cast and dried to obtain high thermal conductivity shape memory nanocomposite material. The solid-liquid ratio of the above PPC solution is 1:(5-7) to ensure that the solution viscosity is suitable for film formation; the drying temperature is 60-80°C to avoid high-temperature degradation of the PPC molecular chain; the solvent of the PPC solution can be a solvent that can dissolve PPC, such as chloroform.

[0021] In addition, the high thermal conductivity shape memory nanocomposite material prepared by the above preparation method has a mass fraction of CNC-PPA@GNPs nanosheets of 1-10%. Within this range, the composite material achieves optimal performance while maintaining processability. The specific mass fraction can be determined according to the actual application requirements.

[0022] The thermal conductivity of the aforementioned high thermal conductivity shape memory nanocomposite material is 1.81-3.2 W·m. -1 ·K -1 The shape fixation rate (Rf) is ≥90%, the shape recovery rate (Rr) is ≥90%, and the deformation recovery is completed within 30 seconds. Furthermore, the biodegradation rate of the aforementioned high thermal conductivity shape memory nanocomposite material in soil is 15-20% after 120 days.

[0023] The application of the high thermal conductivity shape memory nanocomposite material of the present invention in the thermal management of electronic devices, such as for heat dissipation of smartphone CPUs or electronic packaging.

[0024] The mechanism of action of this invention is explained below: (a) The mechanism of action of PPA on GNPs; Phenylephrine (PPA), as a functional modifier for GNPs, achieves efficient dispersion and interface optimization of GNPs through a dual action: Inhibition of aggregation: PPA molecules bind tightly to the surface of GNPs through π-π stacking and van der Waals forces. The phenyl groups in its molecular structure form a strong interaction with the aromatic ring structure of GNPs, effectively shielding the strong hydrophobic interaction on the surface of GNPs. This prevents GNPs from agglomerating due to their large specific surface area and strong van der Waals forces, ensuring that GNPs remain uniformly dispersed in the subsequent compounding process. Interface bridging effect: The phosphoryl group (P=O) in the PPA molecule can form stable hydrogen bonds with the hydroxyl groups on the CNC surface, and at the same time interact with the polar groups in the PPC molecular chain, constructing an interface connection bridge between GNPs and CNC and PPC, reducing interfacial thermal resistance and mechanical stress concentration, and laying the foundation for the formation of thermal conduction network and physical cross-linking network.

[0025] (II) Mechanism of bridging heat conduction network construction; CNC-PPA@GNPs nanosheets form a continuous bridging thermal conduction network in the PPC matrix through multi-level interactions: CNC and PPA@GNPs are bonded through hydrogen bonds (the hydroxyl groups of CNC and the P=O groups of PPA) and π-π stacking interactions to form structurally stable CNC-PPA@GNPs nanosheets. The steric hindrance effect of CNC further prevents GNPs from agglomerating, ensuring the uniformity of nanosheet dispersion. The CNC-PPA@GNPs nanosheets dispersed in the PPC matrix intertwine to form a three-dimensional continuous thermal conduction pathway. GNPs, as high thermal conductivity fillers, provide efficient thermal conduction channels, while CNC, as a "thermal bridge," connects adjacent GNPs, reducing the interfacial thermal resistance between GNPs and the PPC matrix. At the same time, the 3D hydrogen bond network (the P=O-PPC polar chain of CNC hydroxyl group-PPA) further optimizes the interfacial heat transfer efficiency, resulting in a breakthrough improvement in the thermal conductivity of the composite material compared to pure PPC.

[0026] (III) Ultra-fast shape memory mechanism; The ultrafast shape memory function of composite materials stems from the synergistic effect of molecular chain motion regulation and physical cross-linking networks: The immobilization effect of the physical cross-linking network: The physical cross-linking points of the 3D hydrogen bond network formed between CNC-PPA@GNPs nanosheets and the PPC matrix restrict the free slippage of PPC molecular chains; during deformation, this cross-linking network can stabilize the deformation state, giving the composite material a high shape fixation rate (Rf≥90%). Thermally responsive molecular chain recovery: When the temperature rises above the glass transition temperature (Tg) of PPC, the mobility of PPC molecular chain segments is enhanced, and physical cross-linking points such as hydrogen bonds are temporarily broken, allowing the molecular chains to recover from the stretched state after deformation to the original coiled state. At the same time, the rigid network formed by CNC-PPA@GNPs nanosheets provides guidance for molecular chain recovery, accelerating the shape recovery process, enabling the composite material to complete deformation recovery within 30 seconds, with a shape recovery rate (Rr≥90%).

[0027] Example 1: The preparation method of the high thermal conductivity shape memory nanocomposite material in this embodiment includes the following steps: (1) Graphene nanosheets (GNPs) were obtained from graphite powder; Specifically, 1g of graphite sheet and 50mL of formic acid were sonicated at room temperature for 2 hours to produce a GNP / HCOOH dispersion, which was then filtered and washed with acetone until the pH was approximately 7. The final step was to dry the mixture overnight in a vacuum oven. (2) Functionalizing graphene nanosheets (GNPs) using phenylphosphonic acid (PPA); Specifically, 8g of PPA was dissolved in 90mL of water and magnetically stirred for 30 minutes until completely dissolved; 2g of GNPs powder was slowly added and ultrasonically dispersed (500W power, 40kHz frequency) for 30 minutes to ensure uniform suspension; the mixture was transferred to a planetary ball mill jar and ball-milled at 400rpm for 48 hours at a controlled temperature of 25°C; the mixture after ball milling was freeze-dried at -80°C and 10Pa vacuum for 24 hours to obtain PPA@GNPs powder; (3) Cellulose nanocrystals CNC and PPA@GNPs are bonded together through non-covalent interactions to form CNC-PPA@GNPs nanosheets; 5g of CNC (prepared by hydrolyzing microcrystalline cellulose in a mixture of 3M citric acid and 6M hydrochloric acid for 6 hours, details can be found in existing technology and will not be elaborated here) was mixed with 6g of PPA@GNPs (mass ratio 1:1.2) in 200mL of ethanol; the mixture was treated with an ultrasonic cell disruptor (1000W power, pulse mode on 5s / off 5s) for 1 hour to promote hydrogen bonding and π-π stacking; the unbound components were removed by centrifugation (10000rpm, 15min), the precipitate was collected and freeze-dried to obtain CNC-PPA@GNPs nanosheets; (4) CNC-PPA@GNPs nanosheets were uniformly dispersed in a PPC-chloroform solution with a solid-liquid ratio of 1:6 (PPC number-average molecular weight of 130,000) and magnetically stirred for 12 hours; then cast and coated (wet film thickness of 500 μm) and dried (in a ventilated oven at 60°C for 24 hours) to obtain high thermal conductivity shape memory nanocomposite PCPG. 1:1.2 The mass fraction of CNC-PPA@GNPs is 3%.

[0028] The composite material PCPG in this embodiment 1:1.2 The thermal conductivity is 3.20 W·m. -1 ·K -1 The shape fixation rate Rf≥95.0%, the shape recovery rate Rr≥93.4%, the deformation recovery is completed within 30 seconds, and the biodegradation rate in soil after 120 days is 18.9%.

[0029] Example 2: The preparation method of the high thermal conductivity shape memory nanocomposite material in this embodiment differs from that in Example 1 in that: In step (2), the mass ratio of PPA to GNPs is adjusted to 3:1; In step (3), the mass ratio of CNC to PPA@GNPs is adjusted to 1:0.5; In step (4), the solid-liquid ratio of the PPC solution is adjusted to 1:5, and the film is dried at 70°C for 20 hours after casting to obtain the composite material PCPG. 1:0.5 ; The remaining steps are the same as in Example 1; The mass fraction of CNC-PPA@GNPs is 7%.

[0030] Results: The composite material PCPG in this embodiment 1:0.5 The thermal conductivity is 1.81 W·m. -1 ·K -1 However, it is lower than that of Example 1 due to insufficient continuity of the filler network. The shape fixation rate Rf≥90.0%, the shape recovery rate Rr≥79.2%, the deformation recovery is completed within 40 seconds, and the biodegradation rate in soil after 120 days is 15.0%.

[0031] Example 3: The preparation method of the high thermal conductivity shape memory nanocomposite material in this embodiment differs from that in Example 1 in that: In step (2), the ball mill speed is increased to 500 rpm; In step (3), the mass ratio of CNC to PPA@GNPs is adjusted to 1:1.5. In step (3), the solid-liquid ratio of the PPC solution is adjusted to 1:7. After casting and coating, the mixture is dried at 80°C for 12 hours to obtain the composite material PCPG. 1:1.5 ; The remaining steps are the same as in Example 1; The mass fraction of CNC-PPA@GNPs is 10%.

[0032] Results: The composite material PCPG in this embodiment 1:0.5 Thermal stability was further improved, but mechanical properties decreased slightly due to excessive aggregation of filler. The biodegradability rate in soil after 120 days was 16.8%, higher than pure PPC, and the thermal conductivity was 3.09 W·m. -1 ·K -1 The shape fixation rate Rf≥92.0%, the shape recovery rate Rr≥85.6%, and the deformation recovery is completed within 40 seconds.

[0033] Example 4: The preparation method of the high thermal conductivity shape memory nanocomposite material in this embodiment differs from that in Example 1 in that: In step (2), the PPA concentration is adjusted to 7%, and the ball milling time is shortened to 36 hours; In step (3), the mass ratio of CNC to PPA@GNPs is adjusted to 1:1.0, and the dispersion medium is changed to a chloroform-water mixed solvent (volume ratio 1:1). In step (4), the drying temperature is controlled at 65°C for 18 hours to obtain the composite material PCPG. 1:1.0 ; The remaining steps are the same as in Example 1; Results: The interfacial hydrogen bond fraction was increased in this embodiment, and the thermal conductivity was 2.97 W·m. -1 ·K -1 The shape fixation rate Rf≥92.5%, the shape recovery rate Rr≥89.8%, the deformation recovery is completed within 30 seconds, and the biodegradation rate in soil after 120 days is 17.4%.

[0034] Comparative Example 1: The method for preparing the composite material in this comparative example differs from that in Example 1 in that: Without using PPA to functionalize GNPs, GNPs were directly mixed with CNC and dispersed in PPC solution, with other steps the same as in Example 1; The resulting composite material is labeled as PPC-GNPs / CNC; Results: GNPs showed severe aggregation, resulting in limited improvement in thermal conductivity. SEM revealed significant phase separation. The thermal conductivity in this example was 0.54 W·m. -1 ·K -1 The shape fixation rate Rf≥87.5%, the shape recovery rate Rr≥78.2%, the deformation recovery is completed within 60 seconds, and the biodegradation rate in soil after 120 days is 12.6%.

[0035] Comparative Example 2: The method for preparing the composite material in this comparative example differs from that in Example 1 in that: To verify the key impact of hydrogen bonding on material properties: an acidic environment protonates the hydroxyl group -OH of CNC, destroying the hydrogen bond network between CNC and PPA, resulting in a weakened interfacial bond, therefore, in the preparation of CNC-PPA@GNPs, the pH value was adjusted to 5 with hydrochloric acid, and other steps were the same as in Example 1. The resulting composite material was labeled PCPG-pH5; Results: Insufficient hydrogen bonding and weak interfacial adhesion led to a significant decrease in thermal conductivity and mechanical properties. The thermal conductivity of the composite material in this embodiment was 0.79 W·m. -1 ·K -1 The shape fixation rate Rf≥89.5%, the shape recovery rate Rr≥81.2%, the deformation recovery is completed within 60 seconds, and the biodegradation rate in soil after 120 days is 14.3%.

[0036] Comparative Example 3: The method for preparing the composite material in this comparative example differs from that in Example 1 in that: Without going through the steps of "PPA functionalization of GNPs" and "CNC combined with PPA@GNPs to form nanosheets", the three raw materials GNPs, PPA and CNC were directly added to a PPC-chloroform solution with a solid-liquid ratio of 1:6 in the proportion of Example 1 (2g of GNPs, 8g of PPA and 5g of CNC). After magnetic stirring for 12 hours, a film was cast (wet film thickness 500μm) and dried in a ventilated oven at 60°C for 24 hours to obtain the composite material PPC-GNPs-PPA-CNC. Performance testing: GNPs showed severe aggregation, with a thermal conductivity of 0.83 W·m. -1 ·K -1 The shape fixation rate was 72.1%, the recovery rate was 68.6%, and the biodegradation rate in soil after 120 days was 10.3%, with significant deterioration in all properties. The reason is that it was not functionalized and compounded stepwise, and could not form stable nanosheets and bridging networks. The filler was unevenly dispersed and the interfacial bonding was weak.

[0037] In addition, the thermal conductivity of pure PPC is 0.059 W·m. -1 ·K -1 .

[0038] like Figure 1 As shown, pure PPC has poor thermal stability (T0 = 243.1℃, T...). max =251.5℃), the T0 of Example 1 (hereinafter referred to as Example 1) increased by 55.6℃, T max The temperature increase was 58.7℃, while the increases in Comparative Examples 2 and 3 were limited. The synergistic effect of the barrier formed by the 3D hydrogen bond network, carbon layer, and GNPs led to filler agglomeration, which disrupted the protective structure and weakened thermal stability.

[0039] like Figure 2 As shown, pure PPC has poor shape memory performance (Rf=85.0%, Rr=41.2%), Example 1 (PCPG) 1:1.2 With an Rf of 95.0% and an Rr of 93.4%, it can complete deformation recovery within 30 seconds; the physical cross-linking network inhibits molecular chain slippage, improving shape memory stability and response speed.

[0040] like Figure 3 As shown, the car was in motion. During the test, the sample was attached to the heat-generating area of ​​the car. The highest temperature of the bottom of the blank group reached 44.0℃, while the highest temperature of the bottom of the Example 1 group was only 32.6℃, with a temperature difference controlled at 11.4℃ and a more uniform heat distribution. The integrated functional heat-conducting network can promote rapid heat diffusion and effectively suppress local overheating, which confirms the application value of this composite material in the passive thermal management scenario of vehicles.

[0041] like Figure 4As shown, the temperature of the mobile phone CPU was tested while the phone was running. The peak temperature of the blank group's mobile phone CPU was 38.0℃, while the peak temperature of Example 1 group was 33.5℃, with a temperature difference of more than 17.9℃ between the blank group and the blank group. The bridging network enables rapid heat absorption and diffusion, avoids local overheating, and adapts to the thermal management requirements of smartphones.

[0042] Given the numerous embodiments of the present invention and the vast amount of experimental data for each embodiment, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here.

[0043] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity shape memory nanocomposite material, characterized in that, Includes the following steps: (1) PPA@GNPs were obtained by functionalizing graphene nanosheets GNPs with phenylphosphonic acid (PPA); (2) In an environment with pH 6 to 8, cellulose nanocrystals CNC and PPA@GNPs are bonded together through non-covalent interactions to form CNC-PPA@GNPs nanosheets; (3) CNC-PPA@GNPs nanosheets were uniformly dispersed in polypropylene carbonate (PPC) solution, and then cast and dried to obtain high thermal conductivity shape memory nanocomposite material.

2. The preparation method according to claim 1, characterized in that, In step (1), PPA is dissolved in water, GNPs powder is added, and after ball milling, it is freeze-dried under vacuum to obtain PPA@GNPs. The ball milling process involves a rotation speed of 300-500 rpm and a time of 24-72 hours.

3. The preparation method according to claim 2, characterized in that, The mass ratio of PPA to GNPs powder is (3-5):

1.

4. The preparation method according to claim 1, characterized in that, In step (2), CNC and PPA@GNPs are mixed in a dispersion medium with a pH of 6 to 8, treated with an ultrasonic cell disruptor, then centrifuged, the precipitate is collected and freeze-dried to obtain CNC-PPA@GNPs nanosheets. The ultrasonic cell disruptor has a power of 800-1200W, a pulse mode that is on for 5-10 seconds and off for 5-10 seconds, and the entire process takes 1-2 hours.

5. The preparation method according to claim 4, characterized in that, The mass ratio of CNC to PPA@GNPs is 1:(0.5-1.5).

6. The preparation method according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the PPC solution is 1:(5-7), and the drying temperature is 60-80°C.

7. The high thermal conductivity shape memory nanocomposite material prepared by the preparation method according to any one of claims 1-6, characterized in that, The mass fraction of CNC-PPA@GNPs nanosheets in the high thermal conductivity shape memory nanocomposite is 1-10%.

8. The high thermal conductivity shape memory nanocomposite material according to claim 7, characterized in that, Thermal conductivity is 1.81-3.2 W·m -1 ·K -1 The shape fixation rate Rf≥90%, the shape recovery rate Rr≥90%, and the deformation recovery is completed within 30 seconds.

9. The high thermal conductivity shape memory nanocomposite material according to claim 7, characterized in that, The biodegradation rate in soil after 120 days is 15-20%.

10. The application of the high thermal conductivity shape memory nanocomposite material as described in any one of claims 7-9 in the thermal management of electronic devices, characterized in that, Used for heat dissipation of smartphone CPUs or electronic packaging.

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