A polyester plastic composite based on aryl quaternary ammonium salt doping, plastic product and preparation and application thereof

Abstract

This invention relates to a polyester plastic composite material and plastic products based on aryl quaternary ammonium salt doping, comprising polyester plastic and a heterocyclic quaternary ammonium salt; the heterocyclic quaternary ammonium salt is prepared by introducing side-chain substituents onto the nitrogen atom through a quaternization reaction using a nitrogen-containing heterocyclic core; the nitrogen-containing heterocyclic core includes 2,3,3-trimethylindole, pyridine, quinoline, and their derivatives; the side-chain substituents are bromoalkanes. This invention constructs a dual-confined system through host-guest ion-dipole interactions, achieving efficient and high-brightness room-temperature phosphorescence emission, while also possessing excellent melt processability and mechanical properties. By designing heterocyclic cores and side-chain substituents with different degrees of conjugation, a wide range of emission wavelength modulation is achieved, realizing multicolor phosphorescence emission from blue to orange and a wide range of lifetime modulation (424~595 nm). The highest phosphorescence lifetime reaches 523.3 ms, with afterglow visible to the naked eye for several seconds; some samples still show clear phosphorescence under fluorescent light. It can be used in fields such as erasable and rewritable information encryption and anti-counterfeiting, and 3D printing.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials and plastic products, specifically to a polyester plastic composite material, plastic products, and their preparation and application based on aryl quaternary ammonium salt doping. Background Technology

[0002] Pure organic room-temperature phosphorescent materials are a class of functional materials that can achieve room-temperature triplet emission without the need for noble metal doping, relying solely on organic molecules. They possess characteristics such as large Stokes shift, long emission lifetime, and environmental responsiveness. Compared to traditional inorganic phosphorescent materials and organometallic complexes, they offer advantages such as low raw material cost, strong structural designability, good biocompatibility, and high process adaptability, making them a research hotspot in the field of luminescent materials in recent years.

[0003] However, the emission wavelength of pure organic light-emitting molecules is highly dependent on the conjugated backbone structure. Existing systems lack simple and systematic molecular regulation pathways, requiring complex synthetic modifications to achieve emission wavelength control. This makes it difficult to balance full-color tunability with low cost, resulting in poor color controllability. Most pure organic RTP materials emit light concentrated in the green band, making it difficult to achieve full-color emission control from blue to orange using simple and universal methods. Currently, crystal engineering relies on ordered molecular crystallization and cannot be processed by thermal melting. Furthermore, crystalline materials are inherently brittle, making it impossible to fabricate devices with complex structures. Crystalline RTP materials have extremely poor processability and brittle mechanical properties, making them unsuitable for industrial processing techniques such as melt extrusion, injection molding, and 3D printing, hindering large-scale applications. To improve luminescence performance, existing polymer-based RTP materials require increased matrix rigidity, leading to poor melt flowability, high processing difficulty, and material brittleness. Improving processability, on the other hand, weakens the confinement effect and reduces luminescence performance. Summary of the Invention

[0004] The purpose of this invention is to provide a polyester plastic composite material based on aryl quaternary ammonium salt doping, its preparation and application, to solve the problems existing in the prior art. This invention is a low-cost, high-performance, scalable, full-color tunable polylactic acid-based room-temperature phosphorescent composite material, which utilizes the strong ion-dipole interaction between the quaternary ammonium salt and the carbonyl group of the polyester plastic to achieve triplet confinement.

[0005] A polyester plastic composite material based on aryl quaternary ammonium salt doping comprises polyester plastic and heterocyclic quaternary ammonium salt; the heterocyclic quaternary ammonium salt is prepared by introducing side chain substituents on the nitrogen atom through a quaternization reaction with a nitrogen-containing heterocyclic core as the parent core; the nitrogen-containing heterocyclic core comprises 2,3,3-trimethylindole, pyridine and its derivatives, quinoline and its derivatives; the side chain substituents are bromoalkanes.

[0006] Preferably, the amount of the heterocyclic quaternary ammonium salt added is 0.01-1% of the mass of the polyester plastic.

[0007] Preferably, the polyester plastic comprises polylactic acid, polymethyl methacrylate, and polycarbonate; the bromoalkane comprises bromoethane, bromoethanol, and ethyl bromoacetate. This invention is based on the room-temperature phosphorescence mechanism of polyester plastics through ion-dipole interactions. A heterocyclic quaternary ammonium salt is used as a single-component luminescent guest and is incorporated into a polyester plastic matrix (PLA, PMMA, PC) via twin-screw melt blending. Utilizing the ion-dipole electrostatic interaction between the quaternary ammonium salt cations and the carbonyl groups of the polyester plastic, a dynamic physical cross-linking network is constructed within the matrix. Combined with the rigid confinement effect of the polyester plastic, efficient room-temperature phosphorescence emission is achieved. This strategy does not require covalent modification of the polyester plastic; room-temperature phosphorescence of the polyester plastic system can be activated simply through physical doping.

[0008] This invention utilizes quaternary ammonium salts at different concentrations to achieve excellent luminescence, melt processability, and mechanical properties. Quaternary ammonium salts act as both luminescent substrates and PLA plasticizers, significantly improving PLA melt flowability and adapting to various melt processing techniques such as injection molding and 3D printing. Simultaneously, the ion-dipole dynamic crosslinking network compensates for the strength reduction caused by plasticization, achieving a balance between luminescence, processability, and mechanical properties. Furthermore, the phosphorescence is high, with some samples clearly visible under fluorescent light.

[0009] The preparation method of the above-mentioned polyester plastic composite material includes the following steps: (1) Synthesizing heterocyclic quaternary ammonium salts by one-step quaternization reaction; (2) A polyester plastic composite material based on aryl quaternary ammonium salt doping was prepared by twin-screw melt extrusion process.

[0010] Preferably, the synthesis of heterocyclic quaternary ammonium salts includes: adding nitrogen-containing heterocyclic core material and bromoalkanes to a reaction solvent at a molar ratio of 1:1.2, heating and refluxing for 6-12 h; after the reaction is completed, cooling to room temperature, recrystallizing, washing, and vacuum drying.

[0011] Preferably, step (2) of preparing the aryl quaternary ammonium salt-doped polyester plastic composite material using a twin-screw melt extrusion process includes: ① Raw material pretreatment: The polyester plastic granules are vacuum dried at 60~80℃ for 6~12 h to remove residual moisture; then simply mixed with the heterocyclic quaternary ammonium salt obtained in step (1) to obtain a premix. ② Twin-screw melt blending: The premixed material is added to a twin-screw extruder, the extrusion temperature is set to 160~250℃, and the screw speed is 100~200 rpm; after the material is melt-sheared and mixed, it is extruded from the die head, and then water-cooled and pelletized.

[0012] The aforementioned polyester plastic composite materials are used for erasable information encryption and anti-counterfeiting, and 3D printing.

[0013] 1. Erasable and rewritable information encryption and anti-counterfeiting: The composite material is hot-pressed into a thin film, and patterned photolithography is achieved by using a mask in conjunction with ultraviolet irradiation; heating at 100℃ can accelerate oxygen penetration and quench phosphorescence to achieve pattern erasure; after vacuum drying, ultraviolet activation can rewrite the pattern, which has the ability to be erased and rewritten multiple times.

[0014] 2. FDM 3D Printing of Light-Emitting Structures: Polylactic acid composite masterbatch is prepared as 3D printing filament, and high-precision, complex three-dimensional light-emitting devices are prepared by FDM printing for personalized light-emitting decoration and multi-dimensional information anti-counterfeiting.

[0015] A plastic article for 3D printing comprising the aforementioned polyester plastic composite material.

[0016] 3D printing filament preparation: Polylactic acid masterbatch is extruded through a single screw extruder to obtain a continuous printing filament with a diameter of 1.75 mm, which is adapted to fused deposition modeling (FDM) 3D printers.

[0017] The post-processing molding method for the aforementioned polyester plastic composite material includes placing the polyester plastic composite material masterbatch in a mold, hot pressing at 160~250℃ for 3~5 min, and cold pressing to shape it into films or sheet samples of different thicknesses. Compared with the prior art, the present invention has the following beneficial effects: (1) This invention is a simple, low-cost, and high-performance heterocyclic quaternary ammonium salt-doped polylactic acid room temperature phosphorescent composite material. It constructs a dual confinement system through host-guest ion-dipole interaction to achieve efficient and high-brightness room temperature phosphorescence emission. At the same time, it has excellent melt processability and mechanical properties, and is compatible with various processing technologies such as hot pressing, injection molding, fused deposition modeling (FDM) 3D printing, thus expanding its application fields.

[0018] (2) Excellent luminescence performance and full-color tunability with simple control method. By designing heterocyclic cores and side chain substituents with different degrees of conjugation, a wide range of emission wavelength can be controlled. Combined with the intersystem crossing promotion effect of heteroatoms and bromide ions, full-color phosphorescence emission and lifetime can be controlled in a wide range from blue to orange, achieving emission of 424~595 nm, with the highest phosphorescence lifetime reaching 523.3 ms. The afterglow is visible to the naked eye for several seconds, and the phosphorescence of some samples is still clearly visible under fluorescent lamps.

[0019] (3) The preparation process of the present invention is simple and green, and can be mass-produced on a large scale. The composite masterbatch is prepared in one step by using a twin-screw melt blending process, without any organic solvents, which is green and environmentally friendly; the dopant is synthesized by a one-step quaternization reaction, the raw materials are cheap and readily available, and the process is suitable for industrial continuous production.

[0020] (4) The material is green and biodegradable with good biocompatibility. Unlike commonly used polymethyl methacrylate (PMMA) and polyvinyl alcohol (PVA) as polymer matrices, this invention uses biodegradable polylactic acid as the matrix and low-dopant quaternary ammonium salt. The overall material is green and environmentally friendly and can be extended to biomedical luminescence applications. Attached Figure Description

[0021] Figure 1 Phosphorescence spectra of polylactic acid composites doped with quaternary ammonium salts (0.1% mass fraction) by different heterocyclic cores and brominated alkanes are shown. Among them, the heterocyclic core of (A) is pyridine, the heterocyclic core of (B) is quinoline, the heterocyclic core of (C) is 2,3,3-trimethylindole, the heterocyclic core of (D) is 4-cyanopyridine, and the heterocyclic core of (E) is 4-dimethylaminopyridine.

[0022] Figure 2 Phosphorescence images of plastic products of polylactic acid doped with quaternary ammonium salts according to the present invention are shown; wherein (A) is a 3D printed product of 4-cyanopyridine-ethyl acetate, (B) is 4-cyanopyridine-ethyl acetate masterbatch, (C) is 2,3,3-trimethylindole-ethyl masterbatch, and (D) is pyridine-hydroxyethyl masterbatch. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0024] Example 1 A polyester plastic composite material based on aryl quaternary ammonium salt doping is composed of polylactic acid (PLA), polymethyl methacrylate (PMMA) and polycarbonate (PC) (main body) and heterocyclic quaternary ammonium salt dopant (guest body), wherein the mass fraction of heterocyclic quaternary ammonium salt dopant is 0.01~1.00%.

[0025] Dopant: Quaternary ammonium salts prepared by introducing different side-chain substituents onto the nitrogen atom through a quaternization reaction using a nitrogen-containing heterocyclic core. The heterocyclic cores include three main categories: 2,3,3-trimethylindole, pyridine, and quinoline. A wide range of emission wavelengths can be controlled by adjusting the size of the conjugated system and the substituents on the ring. Greater conjugation results in a higher electron-withdrawing degree on the ring and a more red-shifted emission wavelength. N-side-chain substituents include bromoethane, bromoethanol, and ethyl bromoacetate.

[0026] The preparation method includes the following steps: (1) A one-step quaternization reaction is used to synthesize heterocyclic quaternary ammonium salt dopants. This involves adding nitrogen-containing heterocyclic raw materials (2,3,3-trimethylindole, quinoline, pyridine and their derivatives) and bromoalkanes (bromoethane, bromoethanol, ethyl bromoacetate, etc.) to a reaction solvent (acetonitrile) at a molar ratio of 1:1.2, and heating under reflux for 6–12 h. After the reaction is complete, the mixture is cooled to room temperature, recrystallized from ethyl acetate, washed, and vacuum dried to obtain the purified heterocyclic quaternary ammonium salt product. This method uses inexpensive and readily available raw materials, and the reaction conditions are mild, making it suitable for large-scale preparation.

[0027]

[0028] (2) A twin-screw melt extrusion process was used to prepare polyester plastic composites based on aryl quaternary ammonium salt doping. The specific steps are as follows: ① Raw material pretreatment: Dry polylactic acid, polymethyl methacrylate or polycarbonate particles under vacuum at 60~80℃ for 6~12 h to remove residual moisture; weigh the dried plastic particles and the quaternary ammonium salt obtained in step (1) according to the design ratio, and simply mix them to obtain a premix.

[0029] ② Twin-screw melt blending: The premixed material is added to a twin-screw extruder, the extrusion temperature is set to 160~250℃, and the screw speed is 100~200 rpm; after the material is melt-sheared and mixed, it is extruded from the die head, and after water cooling and pelletizing, quaternary ammonium salt@PLA composite masterbatch is obtained.

[0030] The quaternary ammonium salt@PLA composite masterbatch can be further processed as follows: ③ Vacuum drying and deoxygenation: After the composite masterbatch is placed in the air for a long time, oxygen will cause triplet quenching and phosphorescence decay; by vacuum drying and deoxygenation combined with ultraviolet activation treatment, the phosphorescence intensity of the material can be effectively restored.

[0031] ④ Post-processing and molding: The obtained masterbatch can be processed into devices of different shapes through various processes: hot pressing molding: place the masterbatch in a mold, hot press at 160~250℃ for 3~5 min, and cold press to shape to obtain films or sheet samples of different thicknesses.

[0032] ⑤ 3D printing filament preparation: Polylactic acid masterbatch is extruded through a single screw extruder to obtain a continuous printing filament with a diameter of 1.75 mm, which is adapted to fused deposition modeling (FDM) 3D printers.

[0033] The application methods of the polyester plastic composite material based on aryl quaternary ammonium salt doping of the present invention include the following: 1. Erasable and rewritable information encryption and anti-counterfeiting: The composite material is hot-pressed into a thin film, and patterned photolithography is achieved by using a mask in conjunction with ultraviolet irradiation; heating at 100℃ can accelerate oxygen penetration and quench phosphorescence to achieve pattern erasure; after vacuum drying, ultraviolet activation can rewrite the pattern, which has the ability to be erased and rewritten multiple times.

[0034] 2. FDM 3D Printing of Light-Emitting Structures: Polylactic acid composite masterbatch is prepared as 3D printing filament, and high-precision, complex three-dimensional light-emitting devices are prepared by FDM printing for personalized light-emitting decoration and multi-dimensional information anti-counterfeiting.

[0035] Performance testing: 1. Photophysical properties Luminescence performance was characterized using steady-state fluorescence spectroscopy and phosphorescence spectroscopy; phosphorescence lifetime was calculated using time-resolved phosphorescence decay testing. Table 1 shows the phosphorescence color and wavelength (λem) of polylactic acid doped with quaternary ammonium salt at a mass fraction of 0.1%. Table 2 shows the phosphorescence lifetime (τ) of PLA doped with quaternary ammonium salt at a mass fraction of 0.1%. It can be seen that the phosphorescence emission and lifetime of the composite material change to varying degrees with the conjugation of the heterocyclic core. Increased conjugation of the heterocyclic core results in a significant redshift in phosphorescence; the more active sites of the side chain substituents (ethyl acetate > hydroxyethyl > ethyl), the greater the redshift. By designing heterocyclic cores and side chain substituents with different conjugation degrees, a wide range of emission wavelength modulation was achieved, realizing multi-color phosphorescence emission and lifetime modulation from blue to orange (424~595 nm emission), with a maximum phosphorescence lifetime of 523.3 ms. The afterglow of the plastic products made from the polylactic acid composite material doped with quaternary ammonium salt was visible to the naked eye for several seconds, and the phosphorescence of some samples remained clearly visible under fluorescent light. Figure 1 As shown.

[0036] Table 1. Phosphorescence color and emission wavelength (λem) of PLA doped with quaternary ammonium salt at a concentration of 0.1%.

[0037] Table 2. Phosphorescence lifetime (τ) of PLA doped with quaternary ammonium salt at a concentration of 0.1%.

[0038] This invention achieves multicolor modulation by changing the conjugation degree of the heterocyclic core and the side chain alkyl groups: In-Et@PLA emits blue light, Py-x@PLA emits green light, and Qn-EA@PLA emits orange-red light, covering the color gamut from blue to orange in the visible light region.

[0039] Electronic effect regulation by substituents: Introducing an electron-withdrawing cyano group onto the pyridine ring can increase the positive charge density of the cation, enhance the interaction with the polymer matrix, red-shift the emission and prolong the lifetime (4-cyanopyridinium compounds all show a red-shift in emission compared to pyridinium compounds); introducing an electron-donating dimethylamino group reduces the positive charge density, weakens the effect, and shortens the lifetime.

[0040] 2. Mechanical and Machining Properties The quaternary ammonium salt-doped polylactic acid composite material of the present invention has both excellent hot melt processing stability and melt flowability, and can be adapted to a variety of industrial-grade processing technologies such as twin-screw extrusion, hot pressing, injection molding, and fused deposition modeling (FDM) 3D printing. It solves the technical pain points of poor processability and inability to mass-produce existing pure organic room temperature phosphorescent materials.

[0041] Taking the Py-HE@PLA composite material of this invention as an example, the melt flow rate (MFR) was used to characterize the melt processing fluidity of the composite material. The test temperature was 190℃, and the nominal load was 2160 g. The melt flow rate of pure polylactic acid (PLA) was 6.6 g / 10 min. When the doping mass fraction was 0.10 wt%, the melt flow rate increased to 17.4 g / 10 min, indicating that heterocyclic quaternary ammonium salts can act as highly efficient plasticizers, significantly reducing the melt viscosity of PLA and improving processing fluidity.

[0042] Polylactic acid (PLA) and the Py-HE@PLA composite material of this invention were hot-pressed into I-beam tensile specimens with a thickness of 2 mm and a width of 4 mm. Tensile strength and elongation at break were tested on a universal testing machine at room temperature and a crosshead speed of 10 mm / min. The test results are shown in Table 3. Pure PLA exhibited typical brittle fracture characteristics with an elongation at break (ε) of 42.1%. The elongation at break of the Py-HE@PLA composite material with a mass fraction of 0.1 wt% significantly increased to 378.9%.

[0043] Table 3 Mechanical properties of Py-HE@PLA composite materials

[0044] Example 2 2,3,3-Trimethylindole (or 4-cyanopyridine, quinoline, pyridine) and bromoethane (optionally bromoethanol, ethyl bromoacetate) were each dissolved in anhydrous acetonitrile at a molar ratio of 1:1.2, then mixed and refluxed at 80°C for 8-12 h. The reaction was monitored by thin-layer chromatography (TLC). After the reaction was complete, the solvent was removed by rotary evaporation, and the residue was purified by slurrying with ethyl acetate (optionally n-hexane, petroleum ether, diethyl ether) to obtain the pure product.

[0045] Then, pyridine-hydroxyethyl, indole-ethyl, and 4-methylpyridine-ethyl acetate in different mass ratios (0.01wt%, 0.1wt%, 1wt%) were respectively mixed with PLA, PMMA, and PC, and polyester plastic composite materials based on aryl quaternary ammonium salt doping were prepared by one-step melt blending with PLA, PMMA, and PC.

[0046] Table 4. Performance Comparison of Polyester Plastic Composites Based on Aryl Quaternary Ammonium Salt Doping

[0047] It can be seen that among the aforementioned quaternary ammonium salt-doped polyester plastic composites, the composite with PLA as the polyester plastic exhibits a better afterglow time than PMMA and PC. When the polyester plastic is PMMA, there is a concentration dependence (between 0.01-1 wt%), with higher concentrations resulting in a greater redshift of the wavelength. In the case of PLA, there is no concentration dependence; 0.01-0.5 wt% cyanopyridine-ethyl acetate shows no phosphorescence in PLA, while 0.01-0.5 wt% cyanopyridine-ethyl acetate shows phosphorescence in PMMA.

[0048] Table 5. Phosphorescence emission wavelengths of quaternary ammonium salts doped in PLA and PMMA at different concentrations ( Lambda em )

[0049] As can be seen from Table 5, compared with quaternary ammonium salt-polylactic acid composites, the phosphorescence of quaternary ammonium salt-polymethyl methacrylate composites is basically red-shifted and has a certain concentration dependence. That is, as the concentration of quaternary ammonium salt increases, the wavelength of the composite material becomes more red-shifted.

Claims

1. A polyester plastic composite material based on aryl quaternary ammonium salt doping, characterized in that, It comprises polyester plastic and heterocyclic quaternary ammonium salt; the heterocyclic quaternary ammonium salt is prepared by introducing side chain substituents on the nitrogen atom through a quaternization reaction with a nitrogen-containing heterocycle as the parent core; the nitrogen-containing heterocycle parent core includes 2,3,3-trimethylindole, pyridine and its derivatives, quinoline and its derivatives; the side chain substituents are bromoalkanes.

2. The polyester plastic composite material according to claim 1, characterized in that, The amount of the heterocyclic quaternary ammonium salt added is 0.01-1% of the mass of the polyester plastic.

3. The polyester plastic composite material according to claim 1, characterized in that, The polyester plastic includes polylactic acid, polymethyl methacrylate and polycarbonate; the bromoalkane includes bromoethane, bromoethanol and ethyl bromoacetate.

4. The method for preparing the polyester plastic composite material according to claim 1, characterized in that, Includes the following steps: (1) Synthesizing heterocyclic quaternary ammonium salts by one-step quaternization reaction; (2) A polyester plastic composite material based on aryl quaternary ammonium salt doping was prepared by twin-screw melt extrusion process.

5. The preparation method according to claim 4, characterized in that, The synthesis of heterocyclic quaternary ammonium salts includes: adding nitrogen-containing heterocyclic core material and bromoalkanes to the reaction solvent at a molar ratio of 1:1.2, heating and refluxing for 6-12 h; after the reaction is completed, cooling to room temperature, recrystallizing, washing, and vacuum drying.

6. The preparation according to claim 4, characterized in that, Step (2) involves preparing aryl quaternary ammonium salt-doped polyester plastic composite materials using a twin-screw melt extrusion process, including: ① Raw material pretreatment: The polyester plastic granules are vacuum dried at 60~80℃ for 6~12 h; then mixed with the heterocyclic quaternary ammonium salt obtained in step (1) to obtain a premix; ② Twin-screw melt blending: The premixed material is added to a twin-screw extruder, the extrusion temperature is set to 160~250℃, and the screw speed is 100~200 rpm; after the material is melt-sheared and mixed, it is extruded from the die head, and then water-cooled and pelletized.

7. The application of the polyester plastic composite material according to claim 1, characterized in that, Used for erasable and rewritable information encryption and anti-counterfeiting, and 3D printing.

8. A plastic article for 3D printing, characterized in that, It includes the polyester plastic composite material of claim 1.

9. The post-processing molding method for the polyester plastic composite material according to claim 1, characterized in that, This involves placing polyester plastic composite masterbatch in a mold, hot-pressing at 160~250℃ for 3~5 minutes, and then cold-pressing to shape it into a film or sheet sample.

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