A method for real-time detecting the conformation of polymer chains grafted on a surface in a flow field by using non-radiative energy transfer technology

Abstract

The purpose of the present invention is to provide a method for obtaining conformational information of polymers on particle surfaces in a flow field. This method utilizes nonradiative fluorescence energy transfer from fluorescent groups on polymer chains to achieve real-time detection of the conformation of polymer chains grafted onto particle surfaces in a shear field, with detection accuracy reaching the order of 10000. This method can be used to derive general patterns in how the conformation of polymer chains on the surfaces of nanoparticles of varying molecular weights and grafting ratios changes with shear rate. Therefore, in scenarios where the polymer chains on the nanoparticle surface are required to maintain a specific conformation at a specific shear rate, parameters such as the chain length and grafting density of the polymer grafted onto the target nanoparticle surface can be determined based on these patterns, providing a guarantee for achieving precise nanomanufacturing.

Description

Technical Field

[0001] The method of the invention belongs to the field of basic research on polymer physics and polymer processing, and is suitable for real-time measurement of the conformation of polymer chains grafted on the surface of particles in a shear flow field. Background Art

[0002] Grafting polymer chains onto the surface of nanoparticles is a common method for improving the compatibility and dispersibility of nanoparticles in a matrix. Nanoparticle composites with surface-grafted polymer chains can be used as a dispersed phase to enhance the mechanical properties of composite materials or used independently to achieve specialized functions such as stimulus-responsiveness and targeted drug delivery. Nanoparticles during processing and application are often exposed to flow fields. For example, nanoparticles with surface-grafted polymer chains in a shear field undergo a change in conformation. As the shear rate changes, the conformation of the polymer chains on the particle surface changes, potentially collapsing closer to the particle surface or relaxing away from it. This conformational shift in the surface polymer chains significantly impacts the performance of nanomaterials. Soft Matter magazine notes that leveraging the conformational shifts in polymer chains on the nanoparticle surface induced by changes in shear rate could potentially enable shear-responsive drug release, shear-induced self-assembly, and shear-enhanced material dispersibility and compatibility.

[0003] In existing reports, when designing the chain length and grafting density of polymer chains grafted onto the surface of nanoparticles, only a small amount of preparation experiments were performed to obtain materials with different chain lengths and grafting densities, and the optimal chain length and grafting density parameters were selected based on the material properties. Obviously, such tentative methods cannot meet the requirements of large-scale nanomanufacturing based on specific processing or application needs, such as maintaining a specific conformation at a specific shear rate and accurately designing the polymer grafted onto the surface of nanoparticles. Therefore, it is necessary to perform real-time detection of the conformation of the polymer grafted onto the surface of nanoparticles in a shear field and explore the changes in the dynamic behavior of the polymer chain on the particle surface with the shear rate. This is not only of great research significance in the field of basic research in polymer physics, but also provides support for promoting the progress of nanomanufacturing and has great application value in the field of polymer processing.

[0004] Previous studies have deduced through simulations that shear flow fields can cause linear polymer chains to squeeze and shrink. Related articles have also pointed out that within a certain shear rate range, linear chains will adopt a relatively stable conformation as the shear rate increases. However, experimental methods for real-time monitoring of conformational changes in polymers grafted onto nanoparticle surfaces in shear fields are still lacking.

[0005] Existing technologies face the following challenges: First, the detection method is limited in scale. The polymers grafted onto the nanoparticle surface are extremely small. For example, a polystyrene chain with a molecular weight of 10,000 has a mean square end-to-end distance of only 10 nanometers. Changes in mean square end-to-end distance caused by shear are even smaller, at sub-nanometer levels. Conventional optical microscopes have a resolution limit of 200 nanometers, making it impossible to directly observe the size of polymer chains on the particle surface. Secondly, there is the challenge of in-situ detection of polymer chains grafted onto nanoparticles in a flow field. Dynamic light scattering and electron microscopy techniques can be used to observe the particle size of nanoparticles with surface-grafted polymer chains in a static state, but they cannot measure the temporal changes in the conformation of polymer chains grafted onto the surface of nanoparticles in a shear flow field. Although the polymer microrheological spectrometer developed using patented technologies (application publication numbers CN105699344A, CN111337469B, and CN106645070A) can obtain real-time spectral information of a single free polymer chain in a shear field, it is not suitable for nanoparticles with multiple polymer chains grafted onto their surfaces due to the requirement for extremely dilute concentrations of the system.

[0006] In summary, due to the limitations of surface observation, in-situ detection, and molecular chain scale, the industry currently lacks a method that can achieve real-time detection of conformational changes of polymer chains grafted onto the particle surface in a shear flow field. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for obtaining conformational information of polymers on particle surfaces in a flow field. This method utilizes the non-radiative fluorescence energy transfer of fluorescent groups on polymer chains to achieve real-time detection of the conformation of polymer chains grafted on the particle surface in a shear field. The detection accuracy can reach Level. Through this method, the general law of the change of the conformation of the polymer chain on the surface of nanoparticles with different molecular weights and different grafting ratios with shear rate can be obtained, providing a guarantee for realizing precise nanomanufacturing. For example, for the precise nanomanufacturing demand that requires the polymer chain on the surface of nanoparticles to maintain a specific conformation within a given shear rate range, the parameters such as the chain length and grafting density of the polymer grafted on the surface of the target nanoparticle can be determined based on the information law of the conformational change of the polymer on the particle surface in different flow fields provided by the present invention. Another object of the present invention is to provide a method for predicting the conformational change of the polymer chain grafted on the surface of the nanoparticle by directly using the conformational change detection data of the free polymer chain. The accuracy of this prediction method is very small compared with the true value, has the advantages of high accuracy and the ability to significantly reduce the experimental amount.

[0008] To achieve the above object, the present invention takes the following steps:

[0009] A method for real-time detection of the conformation of polymer chains grafted onto a surface in a flow field using non-radiative energy transfer technology comprises the following steps:

[0010] Step 1: Bonding a fluorescent acceptor group and a fluorescent donor group to both ends of a polymer chain, and then grafting one end of the polymer chain to the surface of the nanoparticle;

[0011] Step 2: Disperse the polymer chain grafted with nanoparticles obtained in step 1 in a solvent, apply shear force, and emit excitation light to the dispersion through a fluorescence spectrometer. The fluorescence emission spectrum is received by a receiver, and the change in the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group reflects the trend of the chain end distance of the polymer chain grafted on the surface of the nanoparticles with the shear rate.

[0012] In the step 2, the concentration of the polymer chains grafted with nanoparticles in the solvent is in the range of 0.001-0.05 g / L.

[0013] In step 2, the angle between the excitation light source and the receiver of the fluorescence spectrometer ranges from 60° to 120°.

[0014] In the step 2, the excitation wavelength range is 190-1100 nm.

[0015] In step 2, the shear rate range is 0-10 4 s -1 .

[0016] In the step 2, the polymer chain is dispersed in a solvent and then added to a quartz cuvette, and sheared by rotating a quartz rotor placed in the quartz cuvette. The excitation light source and the detector are respectively located outside the quartz cuvette and at a certain angle.

[0017] An excitation monochromator and a polarizer are also provided between the excitation light source and the quartz cuvette.

[0018] A fluorescence monochromator and a polarizer are also provided between the detector and the quartz cuvette.

[0019] In the step 1, the molecular weight range of the polymer chain is 10 3 -10 6 g / mol.

[0020] In step 1, the nanoparticles can be inorganic oxides, metals, graphene-like materials, etc.

[0021] The step 1 includes the following steps:

[0022] Step 1-1, synthesizing an initiator with a fluorescent group: introducing a halogen atom into a fluorescent molecule through a substitution reaction, and then obtaining an organic halide initiator with a fluorescent group;

[0023] Step 1-2, synthesizing a polymer chain with a desired molecular weight and a fluorescent group as the terminal group: mixing an initiator, a ligand, a catalyst, and a monomer with a fluorescent group, and conducting active polymerization in an inert gas. After a period of reaction, a reaction terminator is added, and the polymer is precipitated and washed to obtain a monodisperse polymer chain with a desired molecular weight and a fluorescent group as the terminal group;

[0024] Steps 1-3, inserting an azide group at the other end of the polymer chain with a fluorescent group as the terminal group: the polymer with a fluorescent group as the terminal group and sodium azide are added to an organic solvent, reacted in an inert gas, and the product is precipitated in methanol and washed to obtain a polymer chain with a fluorescent group at one end and an azide group at the other end;

[0025] Steps 1-4, introducing another fluorescent group capable of forming non-radiative energy transfer with the fluorescent group into the alkyne-modified coupling agent through a chemical reaction; the two fluorescent groups are respectively selected from one of a fluorescent donor group and a fluorescent acceptor group, and are different from each other.

[0026] Step 1-5, attaching the coupling agent to the polymer chain: reacting the aforementioned terminally azidated polymer chain with the aforementioned alkyne-modified coupling agent via a click chemistry reaction to obtain a polymer chain with a fluorescent donor and a fluorescent acceptor group attached to both ends, and a coupling group attached thereto;

[0027] Step 1-6, grafting polymer onto the surface of nanoparticles: nanoparticles and polymer chains with fluorescent groups at both ends and connected to coupling agents are dispersed in an organic solvent, refluxed, and the product is washed to obtain nanoparticles with polymer chains grafted onto the surface.

[0028] The two ends of the polymer chain are respectively connected to a fluorescent donor and a fluorescent acceptor group.

[0029] In the step 1-1, the reaction conditions are stirring in an ice-water bath for 5-20 hours.

[0030] In the step 1-2, the reaction conditions are 100-120° C. for 1-5 hours.

[0031] In the steps 1-3, the reaction conditions are 50-100° C. for 5-20 h.

[0032] In the steps 1-4, the first reaction condition is 70-100° C. for 5-20 h, and the second reaction condition is 50-90° C. for 1-15 h. Adjusting to acidic refers to adjusting the pH to 2-4.

[0033] In the steps 1-5, the reaction time is 20-60h.

[0034] In the steps 1-6, the reaction conditions are 70-100° C. for 5-20 hours.

[0035] A method for predicting the conformational relationship of a polymer chain grafted with nanoparticles in a flow field comprises the following steps:

[0036] Step a, dissolving free monodisperse polymer chains in a solvent to form a polymer solution of a certain concentration, applying shear force, and emitting excitation light into the solution using a fluorescence spectrometer, receiving the fluorescence emission spectrum using a receiver, and reflecting the change in the chain end distance of the free polymer chain with shear rate through the change in the ratio of the characteristic peak intensity of the fluorescent acceptor group and the fluorescent donor group;

[0037] Step b: Calculate the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the polymer chain grafted on the surface of the nanoparticles at different flow field shear rates using the following relationship:

[0038]

[0039] in is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the polymer chain grafted on the surface of the nanoparticles, It is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the free polymer chain. is the shear rate; is a parameter that characterizes the degree of overlap of polymer chains grafted on the particle surface, which can be obtained by calculating the ratio of twice the mean square rotation radius of the polymer chains to the interchain distance; χ is a parameter that characterizes the interaction between chains, and τ is the polymer relaxation time.

[0040] A method for real-time detection of polymer chain conformation through non-radiative energy transfer technology, wherein both ends of the polymer chain are modified with a fluorescent acceptor group and a fluorescent donor group respectively; when the fluorescent acceptor group is an anthracene group and the fluorescent donor group is carbazole, the polymer chain is synthesized by atom transfer radical polymerization.

[0041] Beneficial effects

[0042] The method of the present invention chemically bonds a fluorescent group pair to a polymer chain and grafts it onto the particle surface. The non-radiative energy transfer efficiency of the fluorescent group pair on the molecular chain is detected in real time in a shear flow field, thereby reflecting the conformational changes of the polymer chain grafted onto the particle surface in the shear field. This method fills the gap in the experimental method of real-time detection of the conformational evolution of surface-grafted polymers in a flow field, and can be used to measure the relationship between the conformational transition of the polymer chain on the particle surface and the shear rate. The accuracy of the conformational changes detected by the method of the present invention can reach class. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the device structure of the method of the present invention

[0044] Figure 2 This is the measurement principle diagram of the method of the present invention

[0045] Figure 3 The data of the fluorescence signal of the particle surface changes with the shear rate (0.005g / L PS-SiO2 solution and PS solution I A / I C Variation with shear rate)

[0046] The symbols in the figure are as follows: flow field application unit 1, quartz rotor 2, quartz cuvette 3, sample stage 4, temperature control unit 5, excitation light source 6, excitation monochromator 7, polarizer 8, polarizer 9, fluorescence monochromator 10, detector 11

[0047] Figure 4 This is the infrared image of PS grafted on the surface of SiO2 nanoparticles and free PS chains. DETAILED DESCRIPTION

[0048] The following describes in detail the measurement process of the method of the present invention for real-time detection of the conformation of polymer chains grafted onto the surface of particles in a shear flow field through specific examples.

[0049] A polymer chain of the desired molecular weight (i.e., chain length) is obtained through a living polymerization method, and a pair of fluorescent groups is bonded to both ends of the polymer chain. This pair of fluorescent groups can undergo non-radiative energy transfer. The specific synthesis route is as follows: an initiator with a fluorescent group is synthesized; a polymer chain is obtained by living polymerization using the initiator; the obtained polymer chain is then linked to another fluorescent group at the other end of the chain through an azide reaction and a click reaction. One end of the polymer chain bonded with the fluorescent group pair is connected to a silane coupling agent, and then the polymer chain is bonded to the surface of the nanoparticle through a silane coupling reaction to obtain nanoparticles with surface-grafted polymer chains.

[0050] The sample solution to be tested is a suspension of synthesized surface-grafted polymer nanoparticles dispersed in an organic solvent;

[0051] The sample to be tested is placed in a detection device combined with a fluorescence spectrometer and a shear flow field application device;

[0052] The measurement system used is composed of a fluorescence spectrometer and a flow field application device, including: a transparent sample stage unit for placing the sample to be tested and forming a shear flow field, a temperature control unit for monitoring and controlling the temperature of the sample to be tested, a flow field application unit for applying a shear flow field to the sample to be tested, and a fluorescence signal measurement unit for exciting the sample to be tested and detecting its fluorescence signal.

[0053] The test principle is: for the polymer grafted on the surface of the nanoparticles and in the shear flow field, its conformation will change with the shear rate, and its chain end distance will also change accordingly; for the fluorescent group pair bonded to the two ends of the polymer chain, when the distance between the groups is less than 10 nanometers, non-radiative energy transfer can occur between the fluorescent group pairs, and the fluorescence energy transfer efficiency satisfies the formula Where E is the non-radiative energy transfer efficiency between fluorescent groups, R0 is the Forster characteristic distance, and R is the spacing between fluorescent groups. The sample to be tested is placed in a detection device that combines a fluorescence spectrometer with a shear flow field application device. While shear is applied to the sample, the excitation light of the fluorescence spectrometer illuminates the sample cell, exciting the donor fluorescent groups in the sample. The excited donors then excite the fluorescent acceptor groups. The fluorescence emission spectrum of the sample is received and read by the spectral detector. Therefore, the change pattern of the fluorescence signal of the terminal fluorescent group pair of the polymer chain grafted on the surface of the nanoparticle with the shear rate under shear can be obtained, thereby obtaining the change pattern of the chain end distance with the shear rate. Further analysis and processing of the data measured by the detection device can obtain the change pattern of the non-radiative energy transfer efficiency of the fluorescent group pair at both ends of the polymer chain grafted on the surface of the nanoparticle with the shear rate.

[0054] Example 1

[0055] To obtain conformational transition information of polystyrene (PS) chains grafted onto the surface of silica particles at different shear rates, anthracene and carbazole were selected as the fluorescent group pair. The specific process was as follows:

[0056] 1. Sample preparation:

[0057] 1) Synthesis of an anthracene-containing initiator: 9-Anthracene alcohol, 4-dimethylaminopyridine (DMAP), 2-bromopropionic acid, and dicyclohexylcarbodiimide (DCC) were dissolved in ultra-dry dichloromethane (DCM) at a ratio of 10:11:1:10, and the mixture was stirred in an ice-water bath for 12 h to obtain an anthracene-containing initiator.

[0058] 2) Synthesis of polystyrene chains with an anthracene end by atom transfer radical polymerization: An anthracene initiator, bipyridine ligand, cuprous bromide catalyst, and styrene monomer were added in a specific ratio and reacted at 110°C under an argon atmosphere for 2 hours. After the reaction, the product was added dropwise to a large amount of methanol for precipitation and washing. The dried sample (denoted as An-PS-Br) had a molecular weight of 7900 g / mol as determined by gel permeation chromatography.

[0059] 3) Terminal azidation of the synthesized An-PS-Br: An-PS-Br and sodium azide were added at a molar ratio of 1:5 in ultra-dry dimethylformamide (DMF) under argon at 70°C for 12 hours. After the reaction, the solution was added dropwise to a large amount of methanol to precipitate the product, which was then repeatedly washed and dried, designated An-PS-N3.

[0060] 4) Synthesis of carbazole- and alkynyl-modified silane coupling agents: Carbazole, sodium hydroxide, and 3-bromopropionic acid were added to dimethyl sulfoxide (DMSO) in a ratio of 1:1.2:3 and reacted at 85°C for 12 hours. After the reaction, the solution was poured into a large amount of deionized water and filtered to remove insoluble impurities. The resulting filtrate was adjusted to a pH of 2-4 with hydrochloric acid, resulting in a large amount of white precipitate. The filtrate was filtered again and the filter cake was washed with deionized water until neutral. The mixture was then dried in a vacuum oven at 80°C to obtain 3-carbazolepropionic acid. Propargylamine and KH560 were dissolved in isopropanol in a ratio of 1:1, refluxed at 70°C for 6 hours, and rotary evaporated to obtain the alkynyl-modified silane coupling agent. The modified silane coupling agent, carbazolepropionic acid, DMAP, and DCC were dissolved in ultra-dry DCM in a ratio of 10:11:1:10. The mixture was stirred in an ice-water bath for 30 minutes. The ice bath was removed and the mixture was allowed to return to room temperature and react for 12 hours. The product after the reaction is purified through the steps of filtering, washing, rotary evaporation, chromatography and the like to obtain a silane coupling agent modified with a carbazole group and an alkynyl group.

[0061] 5) Attach the modified silane coupling agent to the termini of An-PS-N3 using click chemistry. Dissolve An-PS-N3, the modified silane coupling agent, cuprous bromide, and pentamethyldiethylenetriamine (PMDETA) in ultra-dry DMF at a ratio of 2:3:1:1 and react in a vacuum glove box at room temperature for 36 hours. The resulting solution is added dropwise to a large amount of methanol to precipitate the product. The solid is then washed repeatedly and dried to yield a PS polymer chain with fluorescent groups at both ends and attached to the silane coupling agent, designated PS-KH560.

[0062] 6) Synthesis of PS-SiO2: 0.15 g of nano-silica was ultrasonically dispersed in 5 mL of 2-butanone. 1.5 g of PS-KH560 was dissolved in 7.5 mL of 2-butanone. The PS-KH560 solution was added to the dispersed nano-silica solution. The mixture was refluxed at 90°C under a nitrogen atmosphere for 12 h. After the reaction, the solution was added dropwise to a large amount of methanol and repeatedly washed to obtain the product, designated PS-SiO2.

[0063] 2. Testing

[0064] 1) Ultrasonic dispersion of PS-SiO2 in cis-decalin was performed to obtain a PS-SiO2 / cis-decalin suspension with a concentration of 0.005 g / L, which was the sample to be tested.

[0065] 2) Place the sample to be tested in the quartz cuvette of the detection device and build the concentric cylindrical shear chamber;

[0066] 3) In the computer software, set the sample cell temperature to 11.5°C, the excitation wavelength of the fluorescence spectrometer to 254 nm, and the scanning wavelength range to 300-500 nm. After the temperature control component reports that the sample cell temperature has reached the set temperature, start the servo motor and set the shear rate.

[0067] 4) After stabilization, click "Start" on the software to start the fluorescence spectrum scan and obtain the fluorescence spectrum of the sample at the shear rate;

[0068] 5) Extract the ratio of the peak intensity at 414 nm to that at 361 nm from the obtained spectrum and record it as I A / I C ;

[0069] 6) Change the shear rate and repeat steps 4 and 5;

[0070] 7) The fluorescence emission spectra of the samples at various shear rates are shown in the attached figure. Figure 2 As shown, I A / I C It can represent the non-radiative energy transfer efficiency of the fluorescent groups grafted on the polymer chain on the particle surface, I A / I C As the shear rate changes, Figure 3 shown.

[0071] 3. Data Analysis

[0072] according to Figure 3 The pattern shown is that the conformation of PS with a molecular weight of 7900 grafted on the surface of silica particles shows a trend of gradually approaching the two ends as the shear rate increases. When the shear rate is between 400-800s -1 Range, I A / I C The appearance of a platform area indicates that in this shear rate range, the conformation of the grafted chain is stable and does not change with the change of shear rate.

[0073] Example 2

[0074] To obtain conformational transition information of free PS chains at different shear rates, anthracene and carbazole were selected as the fluorescent group pair. The specific process is as follows:

[0075] 1. Sample preparation:

[0076] 1) Synthesis of an anthracene-containing initiator: 9-Anthracene alcohol, 4-dimethylaminopyridine (DMAP), 2-bromopropionic acid, and dicyclohexylcarbodiimide (DCC) were dissolved in ultra-dry dichloromethane (DCM) at a ratio of 10:11:1:10, and the mixture was stirred in an ice-water bath for 12 h to obtain an anthracene-containing initiator.

[0077] 2) Synthesis of polystyrene chains with an anthracene end by atom transfer radical polymerization: An anthracene-containing initiator, bipyridine, cuprous bromide, and styrene were added in a specific ratio and reacted at 110°C under an argon atmosphere for 2 hours. After the reaction, the product was added dropwise to a large amount of methanol for precipitation and washing. The dried sample (denoted as An-PS-Br) had a molecular weight of 7900 g / mol as determined by gel permeation chromatography (GPC).

[0078] 3) Terminal azidation of the synthesized An-PS-Br: An-PS-Br and sodium azide were added at a molar ratio of 1:5 in ultra-dry dimethylformamide (DMF) under argon at 70°C for 12 hours. After the reaction, the solution was added dropwise to a large amount of methanol to precipitate the product, which was then repeatedly washed and dried, designated An-PS-N3.

[0079] 4) Alkyne-modification of 9-carbazoleethanol: 9-carbazoleethanol, 4-pentynoic acid, DMAP, and DCC were dissolved in ultra-dry DCM at a ratio of 10:11:1:10. Stir and dissolve in an ice-water bath for 30 minutes. Remove the ice bath, return to room temperature, and react for 12 hours. The reaction product was purified by filtration, washing, rotary evaporation, and chromatography to obtain the alkynyl-modified carbazole molecule.

[0080] 5) Click chemistry was used to attach the modified carbazole to the termini of An-PS-N3. An-PS-N3, modified carbazole, cuprous bromide, and pentamethyldiethylenetriamine (PMDETA) were dissolved in ultra-dry DMF at a ratio of 2:3:1:1 and reacted in a vacuum glove box at room temperature for 36 hours. The resulting solution was added dropwise to a large amount of methanol to precipitate the product. The solid was then washed repeatedly and dried to yield a PS polymer chain with fluorescent groups attached to its ends.

[0081] 2. Testing

[0082] 1) PS was dissolved in cis-decalin to obtain a PS / cis-decalin solution with a concentration of 0.005 g / L, which was the sample to be tested.

[0083] 2) Place the sample to be tested in the quartz cuvette of the detection device and build the concentric cylindrical shear chamber;

[0084] 3) In the computer software, set the sample cell temperature to 11.5°C, the excitation wavelength of the fluorescence spectrometer to 254 nm, and the scanning wavelength range to 300-500 nm. After the temperature control component reports that the sample cell temperature has reached the set temperature, start the servo motor and set the shear rate.

[0085] 4) After stabilization, click "Start" on the software to start the fluorescence spectrum scan and obtain the fluorescence spectrum of the sample at the shear rate;

[0086] 5) Extract the ratio of the peak intensity at 414 nm to that at 361 nm from the obtained spectrum and record it as I A / I C ;

[0087] 6) Change the shear rate and repeat steps 4 and 5;

[0088] 7) The fluorescence emission spectrum of the sample at each shear rate is obtained and calculated A / I C , I A / I C As the shear rate changes, Figure 3 shown.

[0089] 3. Data Analysis

[0090] according to Figure 3 The law shown is that the conformation of the PS linear chain with a molecular weight of 7900 shows a trend of gradually approaching the two ends as the shear rate increases. Among them, when the shear rate is between 500-900s -1 Range, I A / I C The appearance of a platform area indicates that in this shear rate range, the PS chain conformation is stable and does not change with the change of shear rate.

[0091] This study differs from Example 1 in that the relationship between chain conformation and shear rate in a shear field was studied directly using non-radiative energy transfer technology. The shear rate behavior of free PS chains with a molecular weight of 7900 g / mol was compared with that of PS chains grafted onto nanoparticle surfaces. Compared to free chains, the onset of conformational stability for PS chains grafted onto nanoparticle surfaces occurred at lower shear rates.

[0092] Furthermore, in order to reduce the workload of synthesizing polymer chains grafted onto nanoparticles, the present invention also conducted research on the prediction of conformational data of polymer chains grafted onto nanoparticles. By comparing the conformational changes of polymer chains grafted onto the surface of nanoparticles and free polymer chains with shear rate, the data analysis revealed that the conformational changes of polymer chains grafted onto the surface of nanoparticles and free polymer chains were significantly different. A / I CThe ratio of the values shows a specific functional relationship with the change of shear rate. According to the principle of molecular rheology, the following relationship is established to predict the I of the polymer chain with the same molecular weight after being grafted on the surface of the nanoparticles: A / I C Value:

[0093]

[0094] is the shear rate, is the ratio of 2 times the mean square rotation radius to the chain spacing, indicating the degree of overlap of the polymer chains grafted on the particle surface, χ is the parameter representing the interaction between the chains, and τ represents the relaxation time. is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the PS chain grafted on the surface of the silica nanoparticles, is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the free PS chain; in this case, χ and τ are 1.13381, -0.08826, and 0.00159, respectively.

[0095] exist Figure 3 The predicted values, true values and relative errors of the data are shown in the following table (In this experiment, when calculating the predicted values, the I of the PS free chain A / I C The values are obtained by interpolation based on the shear rate abscissa of SiO2-PS)

[0096]

[0097] Error analysis shows that the prediction errors of the present method are generally within 3% compared to the experimentally measured true values, demonstrating the high accuracy of the prediction method. This method can effectively predict the conformational changes of the polymer chains grafted onto the nanoparticle surface from the conformational changes of the free polymer chains, significantly reducing the experimental workload associated with the grafting step.

[0098] The above embodiments are only used to illustrate the method of the present invention. Any equivalent transformations and improvements based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

[0099] To obtain monodisperse polymer samples of a specific molecular weight, a living polymerization method is required. Reversible addition fragmentation chain transfer polymerization (RAFT) is a polymerization method that offers milder reaction conditions than ATRP. As shown in Table 1, different living polymerization methods can yield PS samples of varying molecular weights.

[0100] Table 1 Comparison of molecular weight and dispersion of PS chains obtained by different polymerization methods and different reaction times

[0101]

[0102] Comparative Example 1:

[0103] PS chains labeled with fluorescent donor and acceptor groups at both ends were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The conformational transitions of the chains at different shear rates were detected using non-radiative energy transfer technology.

[0104] 1. Preparation of PS chain by RAFT method: First, a chain transfer agent 4-cyano-4-(N-carbazole dithioester)-pentanoic acid anthracene methanol ester containing both carbazole and anthracene groups was synthesized. Then, styrene, chain transfer agent, and azobisisobutyronitrile (AIBN) were added into the reaction flask at a molar ratio of 72:1:0.625. Argon was passed through the reaction system to strictly remove oxygen. After reacting in an oil bath at 70°C for 48 hours, the product was dropped into a large amount of methanol for precipitation. After being dissolved in tetrahydrofuran, it was precipitated again in methanol. The dissolution and reprecipitation process was repeated three times. Finally, the PS linear chain with anthracene and carbazole grafted at both ends was obtained by drying. The molecular weight measured by GPC was 6200 g / mol.

[0105] 2. Test: The same test method as in Example 2 was used. The fluorescence emission spectrum of the sample did not contain the characteristic peak of anthracene, and it was impossible to obtain the I A / I C , resulting in the inability to obtain chain conformation information.

[0106] 3. Analysis: The dithioester group prevents non-radiative energy transfer between the fluorescent groups carbazole and anthracene. Therefore, the polymer chain labeled with the fluorescent donor and acceptor group pair carbazole and anthracene prepared by the RAFT method cannot be detected by non-radiative energy transfer methods.

[0107] Therefore, not all polymers prepared by living polymerization methods can be used to obtain chain conformation information using non-radiative energy transfer methods. It is necessary to select an appropriate fluorescent donor and acceptor group pair based on actual needs. On this basis, an appropriate living polymerization method that can maintain the fluorescent properties of the sample should be selected to prepare a polymer chain of a specified molecular weight.

Claims

1. A method for real-time detection of the conformation of polymer chains grafted onto the surface of nanoparticles in a flow field using non-radiative energy transfer technology, characterized in that: The steps include: Step 1: Bonding a fluorescent acceptor group and a fluorescent donor group to both ends of a polymer chain, and then grafting one end of the polymer chain to the surface of the nanoparticle; Step 2: Dispersing the polymer chain-grafted nanoparticles obtained in Step 1 in a solvent, applying shear, and emitting excitation light to the dispersion using a fluorescence spectrometer. The fluorescence emission spectrum is received by a receiver, and the change in the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group reflects the trend of the chain end distance of the polymer chain grafted on the surface of the nanoparticles as a function of the shear rate. The method also includes the steps of predicting the relationship between the conformation of the polymer chains grafted onto the surface of the nanoparticles and the shear rate in the flow field, including the following steps: Step a, dissolving the free polymer chain in a solvent, applying shear, and emitting excitation light into the solution using a fluorescence spectrometer, receiving the fluorescence emission spectrum using a receiver, and reflecting the change in the chain end distance of the free polymer chain with the shear rate through the change in the ratio of the characteristic peak intensity of the fluorescent acceptor group and the fluorescent donor group; Step b: Calculate the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the polymer chain grafted on the surface of the nanoparticles under different flow field shear forces using the following relationship: is the shear rate, is a parameter that characterizes the degree of overlap of polymer chains grafted on the particle surface; χ is a parameter that characterizes the interaction between chains; τ is the polymer relaxation time, is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the polymer chain grafted on the surface of the nanoparticles, It is the ratio of the characteristic peak intensities of the fluorescent acceptor group and the fluorescent donor group of the free polymer chain.

2. The method according to claim 1, characterized in that In the step 2, the concentration of the polymer chains grafted onto the surface of the nanoparticles in the solvent is 0.001-0.05 g / L.

3. The method according to claim 1, characterized in that In step 2, the angle between the excitation light source and the receiver of the fluorescence spectrometer is in the range of 60-120°.

4. The method according to claim 3, characterized in that In the step 2, the excitation wavelength of the excitation light source is in the range of 190-1100 nm; in the step 2, the shear rate is in the range of 0-10 4 s -1 .

5. The method according to claim 1, wherein In the step 2, after the polymer chains are dispersed in the solvent, It is added to a quartz cuvette and sheared by the rotation of a quartz rotor placed in the quartz cuvette. The excitation light source and detector are respectively located outside the quartz cuvette and at a certain angle.

6. The method according to claim 1, characterized in that An excitation monochromator and a polarizing plate are provided between the excitation light source and the quartz cuvette, and a fluorescence monochromator and a polarizing plate are provided between the detector and the quartz cuvette.

7. The method according to claim 1, characterized in that In the step 1, the molecular weight range of the polymer chain is 10 3 -10 6 g / mol; In step 1, the nanoparticles are selected from one or more of TiO2, SiO2, Al2O3, ZrO2, ZnO, RuO2, Fe2O3, Fe3O4, WO3, SnO2, graphene, graphene oxide, MXene, MoS2, carbon black, gold powder, silver powder, and copper powder.

8. The method according to claim 1, characterized in that The step 1 includes the following steps: Step 1-1, synthesizing an initiator with a fluorescent group: introducing a halogen atom into a fluorescent molecule through a substitution reaction, and then obtaining an organic halide initiator with a fluorescent group; Step 1-2, synthesizing a polymer chain with a desired molecular weight and a fluorescent group as the terminal group: mixing an initiator, a ligand, a catalyst, and a monomer with a fluorescent group, and conducting active polymerization in an inert gas. After a period of reaction, a reaction terminator is added, and the polymer is precipitated and washed to obtain a monodisperse polymer chain with a desired molecular weight and a fluorescent group as the terminal group; Steps 1-3, inserting an azide group at the other end of the polymer chain with a fluorescent group as the terminal group: the polymer with a fluorescent group as the terminal group and sodium azide are added to an organic solvent, reacted in an inert gas, and the product is precipitated in methanol and washed to obtain a polymer chain with a fluorescent group at one end and an azide group at the other end; Step 1-4, introducing another fluorescent group capable of forming non-radiative energy transfer with the aforementioned fluorescent group into the alkyne-modified coupling agent through a chemical reaction; Step 1-5, attaching the coupling agent to the polymer chain: reacting the aforementioned terminally azidated polymer chain with the aforementioned alkyne-modified coupling agent via a click chemistry reaction to obtain a polymer chain with a fluorescent donor and a fluorescent acceptor group attached to both ends, and a coupling group attached thereto; Steps 1-6, grafting polymers onto the surface of nanoparticles: Nanoparticles and polymer chains with fluorescent groups at both ends and connected to a coupling agent are dispersed in an organic solvent, refluxed, and the product is washed to obtain nanoparticles with polymer chains grafted on the surface, wherein the two ends of the polymer chain are connected to a fluorescent donor and a fluorescent acceptor group, respectively.

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