A method for determining phenyl ladder polyphenylsilsesquioxane based on SEC-MALS method

Abstract

The application discloses a method for determining phenyl ladder polysilsesquioxane based on SEC-MALS method. The method for determining phenyl ladder polysilsesquioxane comprises the following steps: (1) preparing a standard solution of phenyl ladder polysilsesquioxane and determining the refractive index increment d n / d c ; (2) dissolving Ph-LPSQ in a mobile phase to obtain a solution to be measured; and (3) detecting the molecular weight and distribution of phenyl ladder polysilsesquioxane in the solution to be measured by using the SEC-MALS method. The method for determining the molecular weight and distribution of Ph-LPSQ based on the SEC-MALS method can accurately characterize the influence law of reaction time on the molecular weight and distribution of prepared Ph-LPSQ, and is a reliable way for accurately evaluating the rigid special polymer.

Description

Technical Field

[0001] This invention relates to the field of polymer material analysis and characterization technology, specifically to a method for determining phenyl ladder polysilsesquioxane (Ph-LPSQ) based on the SEC-MALS method. Background Technology

[0002] Ladder-like polysilsesquioxanes (LPSQs), with their unique Si-O-Si double-chain rigid inorganic framework, exhibit significantly superior thermal stability and functionality compared to traditional linear polysiloxanes. For any polymer material, molecular weight and its distribution are the most crucial parameters determining its macroscopic physicochemical properties. The molecular weight and distribution of LPSQs directly and profoundly influence the material's solubility, film-forming properties, processing rheological properties, and the reliability of the final product. Therefore, finding an analytical method that can accurately characterize and monitor the true molecular weight and distribution of LPSQs is a prerequisite for the controllable preparation, quality evaluation, and practical engineering applications of this type of high-performance organosilicon material.

[0003] Currently, gel permeation chromatography (GPC) is commonly used to characterize the molecular weight and distribution of ladder-shaped polysilsesquioxanes (LPSQs). However, the standards used in GPC (such as polystyrene) exhibit a flexible random coil conformation in solution, while LPSQs exhibit a rigid rod-like conformation. This conformational mismatch leads to extremely inaccurate LPSQ relative molecular mass measurements obtained by traditional GPC. The currently known multi-angle laser light scattering coupled with gel permeation chromatography (SEC-MALS) technique can eliminate dependence on standards and is unaffected by polymer topology, allowing for accurate characterization of the molecular weight and distribution of polymers (such as ladder-shaped PPSQs). However, when using SEC-MALS to accurately determine the molecular weight of a specific polymer, the refractive index increment (d) of that polymer in a specific solvent must be accurately obtained beforehand. n / d c However, since there is currently no information regarding the d-type of phenyl ladder polysilsesquioxanes... n / d c The reports on this topic also lack information on standardized SEC-MALS detection processes. Therefore, there is an urgent need to develop a precise detection method for special rigid polymers such as Ph-LPSQ. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for determining phenyl ladder polysilsesquioxane (Ph-LPSQ) based on the SEC-MALS method. This method can completely eliminate the dependence on standards and determines the physical parameter of Ph-LPSQ, the refractive index increment (d). n / d cThis allows for the accurate determination of the molecular weight and distribution of Ph-LPSQ.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for determining phenyl ladder polysilsesquioxane (Ph-LPSQ) includes the following steps: (1) Prepare Ph-LPSQ standard solution and measure the refractive index increment d. n / d c ; The structural formula of the phenyl ladder-shaped polysilsesquioxane (Ph-LPSQ) is shown in Formula I below: Formula I Where n is 4-500; (2) Dissolve Ph-LPSQ in the mobile phase to obtain the test solution; The mobile phase is selected from one or more of tetrahydrofuran, trichloroethane, ethyl acetate, dioxane, xylene, toluene, benzene, dimethylformamide, dimethyl sulfoxide, chloroform, and trichlorobenzene, preferably toluene; (3) The molecular weight and distribution of phenyl ladder polysilsesquioxane in the test solution were determined by the SEC-MALS method; In the SEC-MALS method, the stationary phase of the chromatographic column is highly cross-linked polystyrene / divinylbenzene.

[0006] According to an embodiment of the present invention, in Formula I, n is 4, 6, 8, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, or a range between any two of the above values. Preferably, n is 8-200.

[0007] According to an embodiment of the present invention, the Ph-LPSQ standard solution includes a Ph-LPSQ standard sample and a mobile phase, wherein the concentration of the Ph-LPSQ standard sample is a gradient concentration with a concentration difference of 0.1-0.5 mg / mL, for example, the concentration of the Ph-LPSQ standard solution is 0.33 mg / mL, 0.66 mg / mL, 1 mg / mL, 1.33 mg / mL and 1.66 mg / mL.

[0008] According to an embodiment of the present invention, the linear fitting curve of the refractive index difference of the Ph-LPSQ standard solution with concentration is tested, and dn / dc is calculated.

[0009] For example, the Ph-LPSQ standard solution is a toluene solution of the Ph-LPSQ standard sample with concentrations of 0.33 mg / mL, 0.66 mg / mL, 1 mg / mL, 1.33 mg / mL, and 1.66 mg / mL; the dn / dc value of this Ph-LPSQ standard solution was measured to be -0.0653 mL / g, R 2 =0.9998.

[0010] According to an embodiment of the present invention, the mass concentration of phenyl ladder polysilsesquioxane in the test solution is 0.01-2 mg / mL, specifically such as 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.2, 1.4, 1.6, 1.8, 2 mg / mL, preferably 2 mg / mL.

[0011] According to an embodiment of the present invention, isocratic elution is used in the SEC-MALS method.

[0012] According to an embodiment of the present invention, in the SEC-MALS method, the column temperature is 20-50℃, specifically 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50℃, preferably 40℃.

[0013] According to an embodiment of the present invention, in the SEC-MALS method, the injection volume is 10-200 μL, specifically 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 μL, preferably 100 μL.

[0014] According to an embodiment of the present invention, in the SEC-MALS method, the flow rate is 0.1-5 mL / min, specifically such as 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 mL / min, preferably 0.5 mL / min.

[0015] According to an embodiment of the present invention, in the SEC-MALS method, the detector is selected from an 18-angle laser light scattering instrument, a differential refractive index detector, or a combination thereof.

[0016] For example, the detector is an 18-angle laser light scattering instrument cascaded with a differential refractive index detector.

[0017] According to an embodiment of the present invention, the detection method includes determining the molecular weight and distribution of phenyl ladder polysilsesquioxane (Ph-LPSQ). Beneficial effects

[0018] Traditional GPC analysis methods relying on single dRI signals and standard curves are completely ineffective for ladder-shaped polysiloxanes Ph-LPSQ. However, the method provided in this invention, based on SEC-MALS and using LS / dRI signal coupling to determine the molecular weight and distribution of Ph-LPSQ, can accurately characterize the effect of reaction time on the molecular weight and distribution of the prepared Ph-LPSQ, and is the only reliable approach for accurately evaluating this type of rigid specialty polymer. Attached Figure Description

[0019] Figure 1 The image shows the differential refractive index signal of Ph-LPSQ in toluene.

[0020] Figure 2 The figure shows the linear fitting curve of the refractive index difference of Ph-LPSQ in toluene as a function of concentration.

[0021] Figure 3 The chromatogram of Ph-LPSQ-30min prepared by reacting for 30 min is shown.

[0022] Figure 4 The chromatogram of Ph-LPSQ-1h prepared by reacting for 1 hour is shown.

[0023] Figure 5 The chromatogram of Ph-LPSQ-3h prepared by reacting for 3 hours is shown.

[0024] Figure 6 The chromatogram of Ph-LPSQ-6h prepared by reacting for 6 hours is shown.

[0025] Figure 7 The chromatogram of Ph-LPSQ-12h prepared by reacting for 12 hours is shown.

[0026] Figure 8 The chromatogram of Ph-LPSQ-24h prepared by reacting for 24 hours is shown.

[0027] Figure 9 The chromatogram of Ph-LPSQ-36h prepared by reacting for 36 hours is shown.

[0028] Figure 10 The chromatogram of Ph-LPSQ-48h prepared after 48 hours of reaction is shown. Detailed Implementation

[0029] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0030] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0031] The gel permeation chromatography (GPC) or size exclusion chromatography (SEC) described in this invention is a liquid chromatography method that relies on molecular physical size for separation. This technique primarily utilizes the porous structure of the stationary phase gel to create a "spatial exclusion" effect, where there is no substantial chemical interaction between the sample and the stationary phase. During elution, small-molecule solvents can freely enter and exit the gel pores. Since the hydrodynamic volume of polymers in solution typically increases with molecular weight, polymers of different sizes exhibit different penetration depths in the chromatographic column: solutes with relatively smaller molecular weights can penetrate deeper into the gel pores, resulting in a longer flow path, thus a larger elution volume and longer retention time; while solutes with relatively larger molecular weights are repelled by the micropores and can only pass through the gaps between gel particles, resulting in a smaller elution volume, shorter retention time, and being captured by the detector first.

[0032] In this invention, the term "Multi-Angle Laser Light Scattering Analyzer (MALS)" refers to a static light scattering detector that can measure the absolute molecular weight and mean square radius of rotation of a sample.

[0033] In this invention, the term "differential refractive index detector" refers to a general-purpose detector that detects sample concentration by continuously measuring the change in refractive index of the chromatographic column effluent, and can detect the vast majority of substances.

[0034] In this invention, the term "increment of refractive index (d)" is used. n / d c ")" represents the physical quantity that indicates the change in the refractive index of a polymer solution with its concentration.

[0035] In this invention, phenyl ladder polysilsesquioxane (Ph-LPSQ) can be prepared by the existing THF / H2O hydrolysis-condensation method.

[0036] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0037] Preparation Example 1 Ph-LPSQ was prepared using existing techniques (see Seung-Sock Choi et al., Structural Control of Fully Condensed Polysilsesquioxanes: Ladderlike vs Cage Structured Polyphenylsilsesquioxanes). Macromolecules Ph-LPSQ samples were prepared at different reaction times (30 min, 1 h, 3 h, 6 h, 12 h, 24 h, 36 h, 48 h) as test samples (2015, 48, 17, 6063–6070). Specifically, several 500 mL three-necked round-bottom flasks were prepared, and 0.2 g of anhydrous potassium carbonate (K2CO3), 24 g of deionized water, and 40 g of tetrahydrofuran (THF) were added sequentially to each flask. The mixture was stirred for 20 min to form a homogeneous system. 79.32 g (0.4 mol) of phenyltrimethoxysilane (PhTMS) was added dropwise to the reaction system in a 150 mL constant-pressure dropping funnel. The reaction temperature was 30 ℃, and the reaction times were 30 min, 1 h, 3 h, 6 h, 12 h, 24 h, 36 h, and 48 h. After the reaction was complete, stirring was stopped and the mixture was allowed to stand for 10 minutes to obtain a phase-separated system. The upper layer was a translucent liquid, and the lower layer was a white solid. The supernatant was poured off, and 250 g of dichloromethane was added to the lower layer. The mixture was stirred until the white solid was completely dissolved, and the system became slightly transparent. Subsequently, the organic phase was washed and extracted multiple times with deionized water until the pH of the aqueous phase was neutral. The bottom organic phase was collected by separation and dried overnight with an appropriate amount of anhydrous sodium sulfate. The clear solution was filtered, and most of the solvent was removed by rotary evaporation. The solution was then placed in a vacuum oven at 50 °C for 2 h to completely remove residual solvent. Finally, a white powder of phenyl ladder polysilsesquioxane (Ph-LPSQ) was collected. The yields of the products obtained at different reaction times are shown in Table 1 below.

[0038] Table 1. Yields of products obtained at different reaction times

[0039] The phenyl ladder polysilsesquioxanes (Ph-LPSQ) corresponding to the above different reaction times are respectively denoted as Ph-LPSQ-30min, Ph-LPSQ-1h, Ph-LPSQ-3h, Ph-LPSQ-6h, Ph-LPSQ-12h, Ph-LPSQ-24h, Ph-LPSQ-36h, and Ph-LPSQ-48h, for later use.

[0040] Example 1 Determine the dn / dc value of Ph-LPSQ: 1.1 Chromatographic conditions Instrument: Agilent Infinity II GPC; Detector: Multi-angle laser light scattering and gel permeation chromatography coupled detector (DAWN / OPTILAB); Column: Highly cross-linked polystyrene / divinylbenzene matrix (Plgel MIXED-C column, 7.5 mm × 300 mm). Mobile phase: Toluene; Isocratic elution was used, and the collection time was 30 minutes. Column temperature: 40℃; Flow rate: 0.5 mL / min; Injection volume: 100 μL; Workstation: Astra Analysis Workstation.

[0041] 1.2 Solution Preparation Calibration solution: Prepare a Ph-LPSQ standard solution by dissolving the Ph-LPSQ-3h from Preparation Example 1 in toluene to a concentration of 2 mg / mL, and use it as the stock solution.

[0042] d n / d c To test linear solutions: Dilute the stock solution using a concentration gradient and record the accurate concentrations. The specific dilution steps are as follows: Take 1 mL of stock solution, record the mass m1, add 5 mL of toluene solution, and record the mass M1; Take 2 mL of stock solution, record the mass m2, add 4 mL of toluene solution, and record the mass M2; Take 3 mL of stock solution, record the mass m3, add 3 mL of toluene solution, and record the mass M3; Take 4 mL of stock solution, record the mass m4, add 2 mL of toluene solution, and record the mass M4; Take 5 mL of stock solution, record the mass m5, add 1 mL of toluene solution, and record the mass M5. Differential refractive signal diagram as shown Figure 1 As shown, the linear fitting curve of the refractive index difference of Ph-LPSQ in toluene as a function of concentration is as follows: Figure 2 As shown, the results of detecting the dn / dc value of Ph-LPSQ are as follows: Detection conditions: wavelength 658.0 nm; Solvent: Toluene; Test results: dn / dc: 0.0653 mL / g, R 2 =0.9998.

[0043] The fitting results of the refractive index difference of Ph-LPSQ-3h in toluene, dn / dc and R, were used to determine the refractive index difference between Ph-LPSQ-3h and toluene. 2The value of 0.9998 indicates that the present invention uses Ph-LPSQ-3h to determine the high accuracy of dn / dc of Ph-LPSQ.

[0044] Example 2 Determination of the molecular weight and distribution of Ph-LPSQ: 2.1 Solution Preparation (1) Mobile phase: toluene (2) Ph-LPSQ-3h standard sample: Ph-LPSQ obtained when the reaction time is 3h is recorded as standard sample. In a 5mL sample bottle, add 6mg of standard sample and 3mL of mobile phase to prepare a 2mg / mL test solution. Prepare five portions in total. After standing for 2h, filter with a 0.22μm filter membrane for later use.

[0045] (3) Test solution: Add 6 mg of Ph-LPSQ test sample obtained at different reaction times (30 min, 1 h, 6 h, 12 h, 24 h, 36 h, 48 h) to a 5 mL sample bottle, add 3 mL of mobile phase to prepare a test solution of 2 mg / mL, let stand for 2 h and then filter with a 0.22 μm filter membrane for later use.

[0046] 2.2 Measurement The SEC-MALS method was used for detection, and the chromatographic conditions were the same as in Example 1, specifically: (1) Weigh the test solutions prepared above for different reaction times, inject them into the chromatograph, and record the chromatograms. The results for the test solutions with a reaction time of 30 min are as follows: Figure 3 The results of the test solution with a reaction time of 1 hour are shown below. Figure 4 The results of the test solution with a reaction time of 3 hours are shown below. Figure 5 The results for the test solution with a reaction time of 6 hours are shown below. Figure 6 The results for the test solution with a reaction time of 12 hours are shown below. Figure 7 The results of the test solution after a reaction time of 24 hours are shown below. Figure 8 The results for the test solution after a reaction time of 36 hours are shown below. Figure 9 The results for the test solution after a reaction time of 48 hours are shown below. Figure 10 .

[0047] Five Ph-LPSQ-3h standard samples of the same concentration from step (2) of 2.1 above were weighed and injected into the chromatograph and the chromatograms were recorded.

[0048] (2) During the same elution process, the acquired chromatographic signals were processed and calculated using an Astra analysis workstation: The SEC-MALS absolute quantitative mode of this invention: Simultaneously extracts the dual signals from the multi-angle laser light scattering (LS) detector and the differential refractive index (dRI) detector, and combines them with the refractive index increment d of Ph-LPSQ measured in Example 1. n / d c =-0.0653 mL / g, directly calculate the molecular weight and distribution of Ph-LPSQ obtained at different reaction times.

[0049] 2.3 Test Results (1) The repeatability test results of Ph-LPSQ-3h sample are shown in Table 2.

[0050] Table 2. Repeatability test results of Ph-LPSQ-3h

[0051] Five Ph-LPSQ-3h test solutions were analyzed by serial injection. The results showed that two molecular weight distributions were observed in different samples. The low molecular weight fraction was designated as oligomer (Peak 1), and the high molecular weight fraction as polymer (Peak 2). The relative standard deviations (RSDs) of the absolute number-average molecular weight measurements were 2.10% and 0.68%, respectively. These results are far below the conventional allowable deviation requirement of 5% in the field of instrumental analysis, fully demonstrating that the detection method has extremely high precision and repeatability.

[0052] (2) The molecular weight and distribution of Ph-LPSQ obtained at different reaction times are shown in Table 3. Peak1 is the peak with a retention time of 13-16 min, and Peak2 is the peak with a retention time of 16-19 min.

[0053] Table 3. Molecular weight data of Ph-LPSQ obtained by SEC-MALS method

[0054] Comparative Example 1 Referring to Example 2, the molecular weight and distribution of Ph-LPSQ obtained at different reaction times were determined, with the only difference being that: in the same elution process, the acquired chromatographic signals were processed and calculated using the conventional GPC relative quantification mode on an Astra analytical workstation. Only the single-channel signal from the differential refractive index (dRI) detector is extracted, and the relative molecular mass is converted based on the system's retention time and a pre-established calibration curve of a narrow-distribution polystyrene (PS) standard.

[0055] The molecular weight and distribution of Ph-LPSQ obtained at different reaction times are shown in Table 4. Peak1 is the peak with a retention time of 13-16 min, and Peak2 is the peak with a retention time of 16-19 min.

[0056] Table 4. Molecular weight data of Ph-LPSQ obtained by GPC method

[0057] As can be seen from the data in Table 3, the system exhibits a significant trend of "oligomery to polymer conversion" with increasing reaction time. During the first 3 hours of the reaction, the system is in a mild cyclization and short-chain growth phase, with the mass fraction of oligomer (Peak 1) remaining stable above 88%, and its number-average molecular weight being relatively low. M n <3000 g / mol). However, once the reaction time exceeds 3 h, the degree of condensation in the system intensifies significantly, and the oligomer, as a reaction intermediate, is largely consumed, its mass percentage rapidly decreasing until it disappears completely by 48 h; simultaneously, the absolute molecular weight of the polymer (Peak2) increases dramatically in a stepwise manner in the later stages of the reaction, reaching a peak at 48 h. M n Approaching 90,000 g / mol.

[0058] As can be seen from the data in Table 4, the number-average molecular weight of this oligomer measured by the traditional GPC method is much lower than that measured by the SEC-MALS method. This clearly shows that the traditional GPC mode relies solely on a single dRI signal to record retention time, essentially converting it based on the polymer's "hydrodynamic volume." Since the PS standard exhibits a flexible "random coil" conformation in solution, while Ph-LPSQ exhibits a rigid "trapezoidal / rod-like" conformation, at the same absolute mass, the rigid molecule has a smaller hydrodynamic volume, penetrates deeper into the chromatographic gel pores, and has a longer elution time. Therefore, the system incorrectly classifies it as an extremely low molecular weight product. This invention, by introducing a light scattering (LS) signal, directly measures the scattered light intensity of the macromolecule to calculate the absolute mass, successfully shielding the severe interference caused by the polymer's topological structure.

[0059] The test results above show that for rigid polymers such as Ph-LPSQ, even under the same chromatographic separation conditions, the traditional single-detector-based working mode will produce serious errors. Therefore, the present invention, which uses dual-detector signal coupling, is more accurate in testing the molecular weight and distribution of Ph-LPSQ.

[0060] Therefore, SEC-MALS can accurately characterize the effect of reaction time on the molecular weight and distribution of the prepared Ph-LPSQ. The above embodiments of the present invention fully demonstrate that the traditional GPC analysis mode relying on a single dRI signal and standard curve is completely ineffective for ladder-shaped polysiloxanes; the LS / dRI signal coupling and molecular weight calculation method provided by the present invention is the only reliable way to accurately evaluate this type of rigid special polymer.

[0061] The exemplary embodiments of the present invention have been described above. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining phenyl ladder polysilsesquioxanes, characterized in that, It includes the following steps: (1) Prepare a standard solution of phenyl ladder polysilsesquioxane and determine the refractive index increment d. n / d c The structural formula of the phenyl ladder-shaped polysilsesquioxane is shown in Formula I below: Formula I Where n is 4-500; (2) Dissolve Ph-LPSQ in the mobile phase to obtain the test solution; the mobile phase is selected from one or more of tetrahydrofuran, trichloroethane, ethyl acetate, dioxane, xylene, toluene, benzene, dimethylformamide, dimethyl sulfoxide, chloroform, and trichlorobenzene; (3) The molecular weight and distribution of phenyl ladder polysilsesquioxane in the test solution were determined by the SEC-MALS method; In the SEC-MALS method, the stationary phase of the chromatographic column is highly cross-linked polystyrene / divinylbenzene.

2. The method according to claim 1, characterized in that, In Equation I, n is 8-200.

3. The method according to claim 1, characterized in that, Ph-LPSQ standard solution includes Ph-LPSQ standard sample and mobile phase, wherein the concentration of Ph-LPSQ standard sample is a gradient concentration with a concentration difference of 0.1-0.5 mg / mL.

4. The method according to claim 1, characterized in that, The linear fitting curve of the refractive index difference of Ph-LPSQ standard solution with concentration was tested, and dn / dc was calculated.

5. The method according to claim 1, characterized in that, The mass concentration of phenyl ladder polysilsesquioxane in the test solution is 0.01-2 mg / mL.

6. The method according to claim 1, characterized in that, In the SEC-MALS method, isocratic elution is used.

7. The method according to claim 1, characterized in that, In the SEC-MALS method, the column temperature is 20-50℃; In the SEC-MALS method, the injection volume is 10-200 μL.

8. The method according to claim 1, characterized in that, In the SEC-MALS method, the flow rate is 0.1-5 mL / min.

9. The method according to claim 1, characterized in that, In the SEC-MALS method, the detector is selected from an 18-angle laser light scattering instrument, a differential refractive index detector, or a combination thereof.

10. The method according to claim 1, characterized in that, In the aforementioned detection method, the detection target includes determining the molecular weight and distribution of phenyl ladder polysilsesquioxane.

Images