CN118812863A - A Janus nanoparticle and a preparation method thereof and a bio-based polyester composition prepared therefrom - Google Patents

Abstract

The invention discloses a Janus nanoparticle, and the preparation method thereof comprises the following steps: (1) polypropylene carbonate diol (PPCD) reacts with lysine diisocyanate, and after the reaction is completed, a _TiO2 hollow sphere dispersion is added to the system to obtain a _TiO2 hollow sphere with PPCD grafted on the outer surface; (2) the _TiO2 hollow sphere with PPCD grafted on the outer surface is ultrasonically crushed to obtain _TiO2 -PPCD nanoparticles, and then reacted with a silane coupling agent and right-handed polylactic acid (PDLA) to obtain the Janus nanoparticles. The Janus nanoparticles are used to prepare a bio-based polyester composition, which comprises the following raw materials in parts by weight: 60-90 parts of polypropylene carbonate, 10-40 parts of left-handed polylactic acid, and 0.1-3 parts of Janus nanoparticles. The nanoparticles of the invention effectively improve the volume expansion efficiency of the composition, and at the same time, both the tensile strength and the elongation at break are improved.

Description

A Janus nanoparticle and a preparation method thereof and a bio-based polyester composition prepared therefrom

Technical Field

The invention relates to the technical field of functional materials, and in particular to a Janus nanoparticle, a preparation method thereof, and a bio-based polyester composition prepared therefrom.

Background Art

With the continuous advancement of science and technology, single-component polymers are difficult to meet the requirements of industrial production and the needs of life. Polymer blends can combine the advantages of single polymers and effectively solve this problem, so the technical development of polymer blending is extremely important. However, many polymer blends are incompatible, and their components exhibit large interfacial tension, resulting in rough phase structures and poor mechanical properties of these blends. Therefore, it is particularly important to improve the compatibility of blends. At present, the best choice to improve the compatibility of polymers is to add compatibilizers. With the development of compatibilization technology, people have put forward higher requirements for improving the compatibility of polymers. In addition to improving the compatibilization efficiency, multifunctionality should be introduced to expand its application in the field of materials.

Adding a compatibilizer is a relatively simple and efficient way to improve the compatibility of blend materials. Polypropylene carbonate PPC is a new type of biodegradable aliphatic biopolymer with good degradation performance, barrier properties, temperature sensitivity, transparency, non-toxicity and other characteristics. It has good application prospects in food packaging, medical materials, engineering plastics, adhesives and other fields. Polylactic acid PLA is a new type of biodegradable material with good processing properties. It can be used in extrusion, injection molding, film drawing, spinning and other fields. However, the compatibility of the two is poor, and the blend exhibits poor processing properties. Commonly used compatibilizers include block copolymers, graft copolymers, etc., but their capacity expansion efficiency is low, and they do not have other functionality and cannot meet the needs of processing materials.

Summary of the invention

In view of the above problems existing in the prior art, the present invention provides a Janus nanoparticle and a preparation method thereof and a prepared bio-based polyester composition. The present invention uses _TiO2 hollow spheres as templates to modify them and prepare PPCD/PDLAJanus nanoparticles, which are added to the matrix PPC/PLLA to be better dispersed at the interface between the two phases, thereby effectively improving the volume expansion efficiency of the blend. At the same time, the tensile strength and elongation at break of the blend are improved. At the same time, due to the characteristics of the _TiO2 template, the blend also has a certain anti-ultraviolet effect, which effectively broadens the application field of the blend.

The technical solution of the present invention is as follows:

The first object of the present invention is to provide a Janus nanoparticle, wherein the Janus nanoparticle uses a _TiO2 hollow sphere as a template, and polypropylene carbonate diol and dextrorotatory polylactic acid are respectively modified on both sides of the template.

A second object of the present invention is to provide a method for preparing Janus nanoparticles, comprising the steps of:

(1) polypropylene carbonate diol (PPCD) reacts with lysine diisocyanate, and after the reaction is completed, a _TiO2 hollow sphere dispersion is added to the system to prepare a _TiO2 hollow sphere with PPCD grafted on the outer surface;

(2) The TiO ₂ hollow spheres with PPCD grafted on the outer surface are ultrasonically crushed to obtain TiO ₂ -PPCD nanoparticles, which are then reacted with a silane coupling agent and dextrorotatory polylactic acid (PDLA) to obtain the Janus nanoparticles.

In one embodiment of the present invention, in step (1), the molar ratio of PPCD to lysine diisocyanate is 1:2-3.5.

In one embodiment of the present invention, the specific reaction process is: PPCD is dripped into lysine diisocyanate, and a catalyst dibutyltin dilaurate is added (the addition amount is 0.01-0.05% of the mass of PPCD), and the reaction is stirred at 60°C for 2 hours under nitrogen conditions; then, the _TiO2 hollow sphere dispersion is added to the reaction system, cooled to 40°C and stirred for 12 hours; then, the dispersion is washed with tetrahydrofuran and anhydrous ethanol and centrifuged and dried to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface.

In one embodiment of the present invention, in step (1), the _TiO2 hollow sphere dispersion is prepared by dispersing the _TiO2 hollow spheres in anhydrous ethanol; the concentration of the _TiO2 hollow sphere dispersion is 1-1.5 g/100 ml.

In one embodiment of the present invention, in step (1), the mass volume ratio of PPCD to _TiO2 hollow sphere dispersion is 0.3-0.5/100, g/ml.

In one embodiment of the present invention, in step (1), the specific method is: add 100 ml of _TiO2 hollow sphere dispersion to the product of polyurethane reaction, react at 40°C in a three-necked flask (nitrogen) for 12 hours, then centrifuge and wash with tetrahydrofuran and anhydrous ethanol respectively, and obtain _TiO2 hollow spheres with PPCD grafted on the outer surface after drying.

In one embodiment of the present invention, in step (2), the TiO ₂ hollow spheres with PPCD grafted on the outer surface are dispersed in anhydrous ethanol and subjected to ultrasonic treatment at 500W for 1 hour to break the hollow spheres into pieces, namely TiO ₂ -PPCD nanoparticles.

In one embodiment of the present invention, in step (2), the silane coupling agent is KH560; the mass ratio of TiO ₂ -PPCD nanoparticles, dextrorotatory polylactic acid and the silane coupling agent is 1:2-5:5-10.

In one embodiment of the present invention, in step (2), the reaction is carried out in nitrogen at 120° C. for 20 to 25 hours; then the free PDLA is removed by washing with chloroform and centrifugation to obtain the final Janus nanoparticles.

In one embodiment of the present invention, TiO ₂ -PPCD nanoparticles are dispersed in anhydrous ethanol, and then silane coupling agent KH560 is added to graft epoxy groups on the surface thereof, and then dextrorotatory polylactic acid PDLA is added to react the epoxy groups thereof, and finally the Janus nanoparticles are obtained after sufficient stirring, centrifugation and drying.

In one embodiment of the present invention, the ultrasonic power is 400-600 W, preferably 500 W, and the ultrasonic time is 1-2 h.

In one embodiment of the present invention, KH560 is added to anhydrous ethanol for alcoholysis, the temperature is raised to 40° C., and the reaction is carried out for 1-1.5 hours.

In one embodiment of the present invention, the mass ratio of TiO ₂ -PPCD nanoparticles to the silane coupling agent is 1:5-10; preferably 1:7-8.

The third object of the present invention is to provide an application of Janus nanoparticles for preparing a bio-based polyester composition.

The fourth object of the present invention is to provide a bio-based polyester composition containing Janus nanoparticles, comprising the following raw materials in parts by weight: 60-90 parts of polypropylene carbonate, 10-40 parts of L-polylactic acid, and 0.1-3 parts of Janus nanoparticles.

In one embodiment of the present invention, the bio-based polyester composition comprises the following raw materials in parts by weight: 70 parts of polypropylene carbonate, 30 parts of poly (L-lactic acid), and 0.3 parts of Janus nanoparticles.

In one embodiment of the present invention, the bio-based polyester composition comprises the following raw materials in parts by weight: 60 parts of polypropylene carbonate, 40 parts of L-polylactic acid, and 0.5 parts of Janus nanoparticles.

The fifth object of the present invention is to provide a bio-based polyester material containing Janus nanoparticles, which is obtained by melt blending 60-90 parts of polypropylene carbonate, 10-40 parts of L-polylactic acid, and 0.1-3 parts of Janus nanoparticles, and then molding.

In one embodiment of the present invention, melt blending is performed at 170-190°C by a torque rheometer.

In one embodiment of the present invention, melt blending is performed at 180°C by a torque rheometer.

During the melt blending process, molecular chains are entangled, and the grafted PDLA and the matrix PLLA form a stereocomposite structure.

A fifth object of the present invention is to provide an application of Janus nanoparticles or a bio-based polyester composition or a bio-based polyester material for use in food packaging, agriculture or aerospace fields.

The beneficial technical effects of the present invention are:

(1) The present invention obtains a strong bio-based polyester composition by synthesizing Janus nanoparticles, which can be used to prepare film materials and improve the physical and mechanical properties of polypropylene carbonate materials such as tensile strength and elongation at break.

(2) The present invention designs a Janus structure and adjusts its distribution morphology, so that the obtained bio-based polyester composition has high transparency, which is conducive to the expansion of its application in the packaging field.

(3) The present invention can significantly improve the interfacial interaction between PPC and PLLA by adding reactive compatibilizer Janus nanoparticles, reduce the average size of the dispersed phase, and enable the dispersed phase to have better toughening or other modification effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared spectrum of the Janus nanoparticles obtained in Example 1.

FIG. 2 is a schematic diagram of Janus nanoparticles at the interface between two phases.

FIG. 3 shows the distribution morphology of Janus nanoparticles at the interface between two phases in the thin film material in Application Example 1.

FIG. 4 shows the transparency of the thin film material in Application Example 1.

DETAILED DESCRIPTION

The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

The average particle size of the _TiO2 hollow microspheres selected in the embodiment of the present invention is 3 microns.

Figure 2 is a schematic diagram of Janus nanoparticles at the interface between two phases. During the melt blending process, under high temperature and shearing, the PPCD and PDLA molecular chains grafted on both sides of the Janus nanoparticles are entangled with the matrix, and during the mixing process, the PDLA molecular chain forms a stereocomposite structure with the PLLA of the matrix, so it can be stably anchored at the interface between the two phases, which helps to reduce the interfacial tension and significantly improve the compatibilization efficiency. The compatibility between PPC and PLLA has been significantly improved, while improving the overall performance of the blend.

Example 1

A method for preparing Janus nanoparticles comprises the following steps:

(1) 47.5 g of PPCD was used as a diol and distilled under reduced pressure at 110°C for 2 h. The mixture was then cooled to 60°C. The distilled PPCD was added dropwise to 11.3 g of lysine diisocyanate and 0.005 g of dibutyltin dilaurate as a catalyst. The mixture was stirred and reacted at 60°C for 2 h under nitrogen conditions. Then 200 ml of _TiO2 hollow sphere dispersion (1.5/100, g/ml) was added and the mixture was cooled to 40°C and stirred for 12 h. The mixture was then washed with tetrahydrofuran and anhydrous ethanol and centrifuged and dried to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface.

(2) dispersing the TiO ₂ hollow spheres grafted with PPCD on the outer surface in ethanol and treating them with ultrasound (500W) for 1 h to break them into pieces, thereby obtaining TiO ₂ -PPCD nanoparticles;

(3) 3 g of TiO ₂ -PPCD nanoparticles were dispersed in anhydrous ethanol, and then 15 ml of silane coupling agent KH560 was added to graft epoxy groups on the surface of the nanoparticles. Then 5 g of right-handed polylactic acid PDLA was added, and the mixture was reacted at 120° C. for 25 h in a three-necked flask (nitrogen). Finally, the mixture was fully stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanoparticles.

The KH560 is an alcoholysis product, which is added into anhydrous ethanol, heated to 40° C., and reacted for 1.5 h.

The infrared spectrum of the Janus particles prepared in this embodiment is shown in Figure 1. As can be seen from Figure 1, compared with _TiO2 , the infrared curve of _TiO2 -PPCD nanoparticles has additional peaks at 1748cm ^-1 and 1254cm ^-1 , which correspond to C=O bond and CO bond, which are characteristic groups of PPCD, respectively, indicating that the PPCD chain is successfully grafted. And the Ti-OH group peak is significantly reduced, indicating that the reaction consumes part of OH, further proving the occurrence of the reaction. The infrared curve of PPCD/PDLA Janus nanoparticles has a new peak at 2800-3000cm ^-1 , which is attributed to the symmetric and asymmetric stretching vibrations of the CH bond. In addition, the carbonyl peak at 1748cm ^-1 is significantly enhanced and is attributed to the carbonyl stretching vibration of the PDLA chain, thereby proving that the PPCD/PDLA Janus nanoparticles are successfully synthesized.

Example 2

A method for preparing Janus nanoparticles comprises the following steps:

(1) 47.5 g of PPCD was used as a diol and distilled under reduced pressure at 110°C for 2 h, then cooled to 60°C, and the distilled PPCD was dropped into 5.65 g of lysine diisocyanate, and 0.005 g of dibutyltin dilaurate as a catalyst was added. The mixture was stirred at 60°C for 2 h under nitrogen conditions; then 200 ml of _TiO2 hollow sphere dispersion (1.5/100, g/ml) was added, the temperature was lowered to 40°C, and stirred for 12 h; then the mixture was washed with tetrahydrofuran and anhydrous ethanol and centrifuged and dried to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface;

(2) dispersing the TiO ₂ hollow spheres grafted with PPCD on the outer surface in ethanol and treating them with ultrasound (500W) for 1 h to break them into pieces, thereby obtaining TiO ₂ -PPCD nanoparticles;

(3) 3 g of TiO ₂ -PPCD nanoparticles were dispersed in anhydrous ethanol, and then 15 ml of silane coupling agent KH560 was added to graft epoxy groups on the surface of the nanoparticles. Then 5 g of right-handed polylactic acid PDLA was added, and the mixture was reacted at 120° C. for 25 h in a three-necked flask (nitrogen). Finally, the mixture was fully stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanoparticles.

Example 3

A method for preparing Janus nanoparticles comprises the following steps:

(1) 23.75 g of PPCD was used as a diol and distilled under reduced pressure at 110°C for 2 h. The mixture was then cooled to 60°C and the distilled PPCD was added dropwise to 11.3 g of lysine diisocyanate. 0.005 g of dibutyltin dilaurate as a catalyst was added and stirred at 60°C for 2 h under nitrogen conditions. Then 200 ml of _TiO2 hollow sphere dispersion (1.5/100, g/ml) was added and the mixture was cooled to 40°C and stirred for 12 h. The mixture was then washed with tetrahydrofuran and anhydrous ethanol and centrifuged and dried to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface.

(2) dispersing the TiO ₂ hollow spheres grafted with PPCD on the outer surface in ethanol and treating them with ultrasound (500W) for 1 h to break them into pieces, thereby obtaining TiO ₂ -PPCD nanoparticles;

(3) 3 g of TiO ₂ -PPCD nanoparticles were dispersed in anhydrous ethanol, and then 15 ml of silane coupling agent KH560 was added to graft epoxy groups on the surface of the nanoparticles. Then 5 g of right-handed polylactic acid PDLA was added, and the mixture was reacted at 120° C. for 25 h in a three-necked flask (nitrogen). Finally, the mixture was fully stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanoparticles.

Example 4

A method for preparing Janus nanoparticles comprises the following steps:

(1) 47.5 g of PPCD was used as a diol and distilled under reduced pressure at 110°C for 2 h. The mixture was then cooled to 60°C. The distilled PPCD was added dropwise to 11.3 g of lysine diisocyanate and 0.005 g of dibutyltin dilaurate as a catalyst. The mixture was stirred and reacted at 60°C for 2 h under nitrogen conditions. Then 200 ml of _TiO2 hollow sphere dispersion (1.5/100, g/ml) was added and the mixture was cooled to 40°C and stirred for 12 h. The mixture was then washed with tetrahydrofuran and anhydrous ethanol and centrifuged and dried to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface.

(2) dispersing the TiO ₂ hollow spheres grafted with PPCD on the outer surface in ethanol and treating them with ultrasound (500W) for 1 h to break them into pieces, thereby obtaining TiO ₂ -PPCD nanoparticles;

(3) 3 g of TiO ₂ -PPCD nanoparticles were dispersed in anhydrous ethanol, and then 15 ml of silane coupling agent KH560 was added to graft epoxy groups on the surface of the nanoparticles. Then 5 g of right-handed polylactic acid PDLA was added, and the mixture was reacted at 60° C. for 25 h in a three-necked flask (nitrogen). Finally, the mixture was fully stirred, centrifuged, washed with chloroform, and dried to obtain the Janus nanoparticles.

Application Example 1

70 parts of PPC, 30 parts of PLLA, and 0.3 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Figure 3 shows the morphology of Janus nanoparticles at the interface of thin film materials. It can be seen that the Janus nanoparticles are anchored at the interface in a single or few-layer state, thus playing a role in efficient capacity expansion.

Figure 4 is the transparency test result of the film material obtained in this application example. Compared with the film material obtained from the pure PPC/PLLA blend in Comparative Example 1 (Figure 4a), the transparency of the film material formed by the blend after adding Janus nanoparticles did not decrease significantly (Figure 4b). Without sacrificing transparency, the compatibility and comprehensive performance of the blend were significantly improved, which was attributed to the anchoring of Janus nanosheets at the interface, and effective molecular chain entanglement and chemical reaction occurred. When only unmodified _TiO2 nanoparticles were added, the transparency was poor, and the comprehensive performance of the blend was also poor, which was attributed to the poor dispersibility of _TiO2 nanoparticles in the blend.

Application Example 2

70 parts of PPC, 30 parts of PLLA, and 0.7 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Application Example 3

70 parts of PPC, 30 parts of PLLA, and 1 part of the Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Application Example 4

60 parts of PPC, 40 parts of PLLA, and 0.3 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Application Example 5

70 parts of PPC, 30 parts of PLLA, and 0.3 parts of Janus nanoparticles prepared in Example 2 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Application Example 6

70 parts of PPC, 30 parts of PLLA, and 0.3 parts of Janus nanoparticles prepared in Example 3 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Application Example 7

70 parts of PPC, 30 parts of PLLA, and 0.3 parts of Janus nanoparticles prepared in Example 4 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Comparative Example 1

Compared with Application Example 1, Janus nanoparticles are not added, and other conditions remain unchanged, as follows:

70 parts of PPC and 30 parts of PLLA were fully dried and added into a torque rheometer at 180°C to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190°C.

Comparative Example 2

Compared with Application Example 1, the number of Janus nanoparticles added is changed to 5, and other conditions remain unchanged, as follows:

70 parts of PPC, 30 parts of PLLA, and 5 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Comparative Example 3

Compared with Application Example 1, the number of Janus nanoparticles added is changed to 10, and other conditions remain unchanged, as follows:

70 parts of PPC, 30 parts of PLLA, and 10 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Comparative Example 4

Compared with Application Example 2, the number of Janus nanoparticles added is changed to 5, and other conditions remain unchanged, as follows:

60 parts of PPC, 40 parts of PLLA, and 5 parts of Janus nanoparticles prepared in Example 1 were fully dried and added into a torque rheometer at 180° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Comparative Example 5

Compared with Application Example 2, the processing temperature is changed to 160°C, and other conditions remain unchanged, as follows:

60 parts of PPC, 40 parts of PLLA, and 0.5 parts of Janus nanoparticles prepared in Example 2 were fully dried and added into a torque rheometer at 160° C. to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190° C.

Comparative Example 6

Compared with Application Example 1, PPC, PPCD, PLLA, PDLA, and _TiO2 hollow microspheres (pure nanoparticles without any modification or grafting) were added together, and other conditions remained unchanged, as follows:

70 parts of PPC, 30 parts of PLLA, 1 part of PPCD, 1 part of PDLA, and 0.3 parts of _TiO2 hollow microspheres were fully dried and added into a torque rheometer at 180°C to prepare a tough bio-based polyester composition. Finally, a film material was obtained by a compression molding process at 190°C.

After being fully dried, the bio-based polyester composition obtained in the above application examples 1-7 was tested for tensile properties at room temperature according to the GB/T 10402006 standard method. The tensile rate was set to 10 mm/min. At least 5 specimens of the same sample were tested and the average value was taken. The size of the PLLA phase was counted by SEM at a magnification of 5000 for the sample after liquid nitrogen brittle fracture. The ultraviolet protection factor (UPF) was calculated according to the ultraviolet transmittance of the bio-based polyester composition in the range of 290 nm-400 nm, and the results are shown in Table 1.

Table 1

Application Examples Breaking strength(MPa) Elongation at break (%) PLLA phase size (μm) UPF Application Example 1 48 459 0.56 725 Application Example 2 45 432 0.81 655 Application Example 3 44 414 0.80 603 Application Example 4 46 471 0.77 599 Application Example 5 42 389 0.82 555 Application Example 6 40 402 0.76 581 Application Example 7 45 398 0.73 577

The bio-based polyester compositions obtained in the above comparative examples 1-6 were tested for their performance qualities using the same testing process. The results are shown in Table 2.

Table 2

Comparative Example Breaking strength(MPa) Elongation at break (%) PLLA phase size (μm) UPF Comparative Example 1 twenty two 44 4.51 2 Comparative Example 2 29 102 4.35 twenty one Comparative Example 3 26 58 4.43 19 Comparative Example 4 27 98 4.31 17 Comparative Example 5 20 49 4.49 8 Comparative Example 6 29 76 4.26 twenty two

Combining Table 1 and Table 2, it can be seen that the breaking strength and elongation at break of the blend of polylactic acid and polypropylene carbonate (Comparative Example 1) after adding Janus nanoparticles (Application Example 1) are significantly improved compared with direct blending, and the PLLA phase size is significantly reduced to below the micron level. It shows that at this time, the Janus nanoparticles are evenly dispersed at the interface of the two phases, playing a good compatibilizing effect, so the mechanical properties of the bio-based polyester composition, such as breaking strength and elongation at break, are improved. Unmodified _TiO2 hollow microspheres are added in Comparative Example 6, and the breaking strength and elongation at break are not significantly improved compared with the pure sample, and the phase size of PLLA is not significantly reduced. This shows that the compatibility of the two polymers is not good, and the addition of _TiO2 hollow microspheres does not play a good compatibilizing effect. It can be seen from the bio-based polyester compositions with different Janus nanoparticle addition contents (Application Examples 1-3) that with the addition of Janus nanoparticles, the compatibility is significantly improved, and the mechanical properties of the blend are also significantly improved. However, when the content of Janus nanoparticles is too much (Comparative Examples 2-4), the compatibility and mechanical properties of the bio-based polyester composition decrease to a certain extent. The reason is that the distribution of nanoparticles is uneven at this time, and too many nanoparticles accumulate at the interface of the two phases and are distributed in the two phases, which affects the mechanical properties of the blend. In addition, the temperature of melt blending also has a certain degree of influence on the compatibility of the material (Comparative Example 5). When the temperature of melt blending is lower than 180°C, PLLA is not fully melted, so the tensile strength and elongation at break of the material are not significantly improved, and the compatibility is not significantly improved. On the other hand, the Janus nanoparticles selected by the present invention are based on _TiO2 , which further improves its functionality, so that its bio-based polyester composition has good UV resistance (Application Example 1) far higher than the excellent level (UPF50+). In short, the present invention prepares a tough bio-based polyester composition film, which is simple and practical, easy to industrialize, and is expected to be used in film packaging materials, agricultural greenhouse film materials and other fields.

The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims (10)

1. A Janus nanoparticle, characterized in that the Janus nanoparticle uses _TiO2 hollow spheres as templates, and poly(propylene carbonate) diol and dextrorotatory polylactic acid are respectively modified on both sides of the template. 2. A method for preparing the Janus nanoparticles according to claim 1, characterized in that the preparation method comprises the following steps: (1) PPCD reacts with lysine diisocyanate, and after the reaction is completed, a _TiO2 hollow sphere dispersion is added to the system to obtain _TiO2 hollow spheres with PPCD grafted on the outer surface; (2) The TiO ₂ hollow spheres with PPCD grafted on the outer surface are ultrasonically crushed to obtain TiO ₂ -PPCD nanoparticles, which are then reacted with a silane coupling agent and dextrorotatory polylactic acid to obtain the Janus nanoparticles. 3. The preparation method according to claim 2, characterized in that, in step (1), the molar ratio of the polypropylene carbonate diol to lysine diisocyanate is 1:2-3.5. 4. The preparation method according to claim 2, characterized in that, in step (1), the _TiO2 hollow sphere dispersion is prepared by dispersing the _TiO2 hollow spheres in anhydrous ethanol; and the concentration of the _TiO2 hollow sphere dispersion is 1-1.5 g/100 ml. 5. The preparation method according to claim 2, characterized in that in step (1), the mass volume ratio of PPCD to _TiO2 hollow sphere dispersion is 0.3-0.5/100, g/ml. 6 . The preparation method according to claim 2 , characterized in that in step (2), the silane coupling agent is KH560; and the mass ratio of TiO ₂ -PPCD nanoparticles, dextrorotatory polylactic acid and the silane coupling agent is 1:2-5:5-10. 7. An application of the Janus nanoparticles according to claim 1, characterized in that they are used to prepare a bio-based polyester composition. 8. A bio-based polyester composition comprising the Janus nanoparticles according to claim 1, characterized in that it comprises the following raw materials in parts by weight: 60-90 parts of polypropylene carbonate, 10-40 parts of L-polylactic acid, and 0.1-3 parts of Janus nanoparticles. 9. A bio-based polyester material containing the Janus nanoparticles according to claim 1, characterized in that 60-90 parts of polypropylene carbonate, 10-40 parts of L-polylactic acid, and 0.1-3 parts of Janus nanoparticles are melt-blended and then molded to obtain the bio-based polyester material. 10. An application of the Janus nanoparticles according to claim 1, the bio-based polyester composition according to claim 8, or the bio-based polyester material according to claim 9, characterized in that it is used in food packaging, agriculture or aerospace fields.