A convenient method for detecting the molecular weight of polymethylsilane
The molecular weight of polymethylsilane was determined by ultrasonic-assisted hydrolysis and sodium hydroxide titration, which solved the problems of expensive instruments and complicated operation of gel permeation chromatography, and realized a simple and low-cost molecular weight determination method suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PUYANG SHENGYUAN DONGCHEN TECHNOLOGY CO LTD
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-07
AI Technical Summary
The existing gel permeation chromatography method for determining the molecular weight of polymethylsilane has problems such as expensive instruments, complicated operation, and long time consumption. In addition, polymethylsilane has limited solubility in common chromatographic solvents.
By adding deionized water under vigorous stirring conditions and performing ultrasonic-assisted hydrolysis to form an aqueous solution of hydrogen chloride, the aqueous phase was titrated with a standard sodium hydroxide solution to calculate the content of hydrolyzable chlorine, and then the molecular weight of polymethylsilane was estimated.
This paper presents a simple, low-cost, and accurate molecular weight detection method, which is suitable for rapid detection in industrial production sites. It has good applicability, and the results are basically consistent with those of gel permeation chromatography.
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Figure CN122345690A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer material analysis technology, specifically a convenient method for detecting the molecular weight of polymethylsilane, which is particularly suitable for determining the molecular weight of polymethylsilane synthesized from sodium metal and dichloromethylsilane via the Woods reaction. Background Technology
[0002] Polymethylsilane is an important organosilicon polymer with unique structure and properties, and it has broad application prospects in ceramic precursors, functional materials, coating materials, and other fields. The molecular weight of polymethylsilane is one of the key parameters affecting its performance and applications; accurate determination of its molecular weight is of great significance for product quality control and application research.
[0003] Currently, the molecular weight determination of polymethylsilanes mainly employs gel permeation chromatography (GPC). This method requires expensive chromatographic instruments and specialized operators, and the process is time-consuming, making it unsuitable for rapid detection in industrial production settings. Furthermore, due to the unique structure of polymethylsilanes, their limited solubility in common chromatographic solvents also presents challenges for GPC determination.
[0004] Polymethylsilanes are typically synthesized via the Woods reaction, which involves a polycondensation reaction of sodium metal and dichloromethylsilane in an inert solvent. During this synthesis, a certain amount of chlorine is present at the ends or side chains of the polymethylsilane molecular chain. This chlorine can be converted into hydrogen chloride under hydrolytic conditions. Based on this characteristic, the molecular weight of the polymethylsilane can be estimated by determining the content of hydrolyzable chlorine.
[0005] Therefore, developing a simple, low-cost, and reliable method for detecting the molecular weight of polymethylsilane is of great practical value for the production and application of polymethylsilane. Summary of the Invention To address the shortcomings of existing technologies, this invention provides a convenient method for detecting the molecular weight of polymethylsilanes. The purpose is to provide a convenient method for detecting the molecular weight of polymethylsilanes, thereby solving the problems of expensive instruments, complex operation, and long time consumption in the existing gel permeation chromatography method for determining the molecular weight of polymethylsilanes.
[0006] To achieve the above objectives, the present invention provides the following technical solution: A convenient method for detecting the molecular weight of polymethylsilane, the method specifically includes the following steps: Step 1: Accurately weigh a certain mass of polymethylsilane sample, dissolve it in a solvent to obtain a polymethylsilane solution; Step 2: Add deionized water to the polymethylsilane solution obtained in Step 1, and perform ultrasonic-assisted hydrolysis under vigorous stirring to fully hydrolyze the chlorine element in the polymethylsilane to form an aqueous solution of hydrogen chloride. Step 3: Perform phase separation on the hydrolysate obtained in Step 2 and collect the aqueous phase; Step 4: Perform acid-base titration on the aqueous phase collected in Step 3 using a sodium hydroxide standard solution of known concentration, and record the volume of sodium hydroxide solution consumed; Step 5: Calculate the hydrogen chloride content based on the volume of sodium hydroxide solution consumed, and then estimate the amount of hydrolyzable chlorine in polymethylsilane. Step 6: Calculate the average molecular weight of polymethylsilane based on the mass of the polymethylsilane sample and the amount of hydrolyzable chlorine. Step 7: Perform three parallel determinations and take the average value as the result of the average molecular weight determination of polymethylsilane.
[0007] Further, in step 1, the polymethylsilane is a product synthesized by the Woods reaction using sodium metal and dichloromethylsilane as raw materials, and the mass ratio of the solvent to the polymethylsilane is 5:1 to 20:1. The solvent is at least one of benzene, toluene, xylene, tetrahydrofuran, n-hexane, chloroform, and dichloromethane. Through the above technical solution, the molecular structure of this type of polymethylsilane contains a certain amount of hydrolyzable chlorine, which serves as the basis for the application of the method of the present invention. As a specific solvent, it can fully dissolve the polymethylsilane, which is beneficial to the subsequent hydrolysis reaction. If the amount of solvent is too small, the polymethylsilane will not dissolve completely; if the amount is too large, it will dilute the sample and affect the measurement efficiency.
[0008] Furthermore, the mass ratio of deionized water to polymethylsilane added in step 2 is 10:1 to 50:1; The above technical solution ensures that a sufficient amount of water can fully dissolve the hydrogen chloride produced by hydrolysis, forming a homogeneous aqueous phase, which facilitates subsequent titration determination.
[0009] Furthermore, in step 2, the stirring speed is 500~2000 rpm, the hydrolysis time is 30~120 minutes, the ultrasonic power of the ultrasonic-assisted hydrolysis is 100~500W, and the ultrasonic frequency is 20~40kHz. Through the above technical solutions, vigorous stirring can increase the contact area between the organic phase and the aqueous phase, promote the hydrolysis reaction, and the cavitation effect of ultrasound can destroy the aggregation structure between polymethylsilane molecules, accelerate the hydrolysis process of chlorine, and improve the hydrolysis efficiency.
[0010] Furthermore, in step 4, the concentration of the sodium hydroxide standard solution is 0.01–0.5 mol / L; By employing the above technical solution, a suitable sodium hydroxide concentration can be selected based on the estimated range of chlorine content in the sample to ensure that the titration volume is within a reasonable range and improve the accuracy of the determination.
[0011] Furthermore, the amount of hydrolyzable chlorine in step 5 is calculated using the following formula: n (Cl) =C (NaOH) ×V (NaOH) ; Where C (NaOH） V represents the concentration of the sodium hydroxide standard solution. (NaOH） This represents the volume of sodium hydroxide standard solution consumed in the titration.
[0012] Furthermore, the average molecular weight of the polymethylsilane in step 6 is calculated using the following formula: M=2m / n (Cl) ; Where m is the mass of the polymethylsilane sample, n (Cl） This represents the amount of substance of chlorine that can be hydrolyzed.
[0013] This invention provides a convenient method for detecting the molecular weight of polymethylsilane. It has the following advantages: 1. This invention provides a convenient method for detecting the molecular weight of polymethylsilane. The method is simple, quick, and inexpensive. It does not require expensive chromatographic instruments; only conventional titration equipment and ultrasonic cleaner are needed to complete the determination. The method is simple to operate and has a short determination cycle, making it particularly suitable for rapid detection in industrial production sites. Furthermore, the reagents used in this method are conventional chemicals such as toluene and sodium hydroxide, which are inexpensive and readily available. The detection cost is far lower than that of gel permeation chromatography.
[0014] 2. This invention provides a convenient method for detecting the molecular weight of polymethylsilane. The method yields accurate and reliable results. By combining vigorous stirring with ultrasonic-assisted hydrolysis, the chlorine element in polymethylsilane is fully hydrolyzed, avoiding measurement errors caused by incomplete hydrolysis. The acid-base titration method for determining chlorine content has high accuracy and can obtain reliable molecular weight data.
[0015] 3. This invention provides a convenient method for detecting the molecular weight of polymethylsilanes, specifically for polymethylsilanes synthesized by the Woods reaction, making full use of their structural characteristics. The method is rationally designed and has good applicability. Attached Figure Description
[0016] Figure 1 This is a schematic flowchart of the method for detecting the molecular weight of polymethylsilane according to the present invention. Detailed Implementation
[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] Example 1: like Figure 1 As shown in the figure, this invention provides a convenient method for detecting the molecular weight of polymethylsilane, and the specific operation steps are as follows: Step 1: Accurately weigh 0.50 g of the polymethylsilane sample synthesized by the Woods reaction, place it in a 100 mL Erlenmeyer flask, add 10.0 g of toluene, shake to completely dissolve the sample, and obtain a colorless and transparent polymethylsilane solution; Step 2: Add 20.0g of deionized water to the above solution, place the conical flask in an ultrasonic cleaner, set the ultrasonic power to 300W and the ultrasonic frequency to 28kHz, and turn on the magnetic stirrer at 1000rpm. Hydrolyze at room temperature for 60 minutes. During the hydrolysis process, the chlorine in the organic phase gradually hydrolyzes, and the generated hydrogen chloride enters the aqueous phase. Step 3: Transfer the hydrolyzed mixture to a separatory funnel, allow it to stand and separate into layers, collect the lower aqueous phase in a 150 mL Erlenmeyer flask, wash the organic phase twice with a small amount of deionized water, 5.0 mL each time, and combine the washings in the Erlenmeyer flask. Step 4: Add 2-3 drops of phenolphthalein indicator to the collected aqueous phase, and titrate with a 0.10 mol / L sodium hydroxide standard solution until the solution changes from colorless to light red and does not fade within 30 seconds. The endpoint is recorded as 8.52 mL of sodium hydroxide standard solution consumed. Step 5: Calculate the amount of chlorine that can be hydrolyzed: n (Cl) =C (NaOH) *V (NaOH) = 0.10 * 8.52 * 10 -3 =8.52*10 -4 mol; Step 6: Calculate the average molecular weight of polymethylsilane: M = 2m / n (Cl) =2*0.50 / (8.52*10 -4 )≈1174; Step 7: The measurements were performed in parallel three times, and the results were 1174, 1184 and 1162, with an average value of 1173 and a relative standard deviation of 0.94%.
[0019] Example 2: like Figure 1As shown in the figure, this embodiment provides a convenient method for detecting the molecular weight of polymethylsilane. The specific operation steps are as follows: Step 1: Accurately weigh 1.0 g of the polymethylsilane sample synthesized by the Woods reaction, place it in a 250 mL Erlenmeyer flask, add 15.0 g of toluene, shake to completely dissolve the sample, and obtain a colorless and transparent polymethylsilane solution. Step 2: Add 30.0g of deionized water to the above solution, place the conical flask in an ultrasonic cleaner, set the ultrasonic power to 400W and the ultrasonic frequency to 40kHz, and turn on the magnetic stirrer at the same time, set the stirring speed to 1500rpm, and hydrolyze at room temperature for 90 minutes. During the hydrolysis process, the chlorine element in the organic phase gradually hydrolyzes, and the generated hydrogen chloride enters the aqueous phase. Step 3: Transfer the hydrolyzed mixture to a separatory funnel, allow it to stand and separate into layers, collect the lower aqueous phase in a 250 mL Erlenmeyer flask, wash the organic phase twice with a small amount of deionized water, 10.0 mL each time, and combine the washings in the Erlenmeyer flask. Step 4: Add 2-3 drops of phenolphthalein indicator to the collected aqueous phase, and titrate with a 0.20 mol / L sodium hydroxide standard solution until the solution changes from colorless to light red and does not fade within 30 seconds. The endpoint is recorded as 7.85 mL of sodium hydroxide standard solution consumed. Step 5: Calculate the amount of chlorine that can be hydrolyzed: n (Cl) =C (NaOH) *V (NaOH) =0.20 * 7.85 * 10 -3 =1.57*10 -3 mol; Step 6: Calculate the average molecular weight of polymethylsilane: M = 2m / n (Cl) =2*1.0 / (1.57*10 -3 = 1274; Step 7: The measurements were performed in parallel three times, and the results were 1274, 1290, and 1264, respectively. The average value was 1276, and the relative standard deviation was 1.03%.
[0020] Example 3: like Figure 1 As shown in the figure, this embodiment provides a convenient method for detecting the molecular weight of polymethylsilane. The specific operation steps are as follows: Step 1: Accurately weigh 0.30 g of the polymethylsilane sample synthesized by the Woods reaction, place it in a 100 mL Erlenmeyer flask, add 6.0 g of toluene, shake to completely dissolve the sample, and obtain a colorless and transparent polymethylsilane solution; Step 2: Add 15.0g of deionized water to the above solution. Place the conical flask in an ultrasonic cleaner, set the ultrasonic power to 200W and the ultrasonic frequency to 25kHz, and simultaneously turn on the magnetic stirrer at 800rpm. Perform hydrolysis at room temperature for 45 minutes. During the hydrolysis process, the chlorine in the organic phase gradually hydrolyzes, and the resulting hydrogen chloride enters the aqueous phase. Step 3: Transfer the hydrolyzed mixture to a separatory funnel, allow it to stand and separate into layers, and collect the lower aqueous phase in a 150 mL Erlenmeyer flask. Wash the organic phase twice with a small amount of deionized water, 5.0 mL each time, and combine the washings in the Erlenmeyer flask. Step 4: Add 2-3 drops of phenolphthalein indicator to the collected aqueous phase, and titrate with a 0.05 mol / L sodium hydroxide standard solution until the solution changes from colorless to light red and does not fade within 30 seconds. The endpoint is recorded as 11.23 mL of sodium hydroxide standard solution consumed. Step 5: Calculate the amount of chlorine that can be hydrolyzed: n (Cl) =C (NaOH) *V (NaOH) =0.05*11.23*10 -3 = 5.62*10 -4 mol; Step 6: Calculate the average molecular weight of polymethylsilane: M = 2m / n (Cl) =0.30 / (5.62*10 -4 = 1068; Step 7: The measurements were performed in parallel three times, and the results were 1068, 1080 and 1056, respectively. The average value was 1068 and the relative standard deviation was 1.12%.
[0021] Example 4 (Comparative Experiment): In this embodiment, to verify the accuracy of the method of the present invention, the molecular weight of the polymethylsilane samples in Examples 1-3 was determined by gel permeation chromatography, and the results were compared with those obtained by the method of the present invention. Gel permeation chromatography conditions: Styragel HR series column, differential refractive index detector, tetrahydrofuran mobile phase, flow rate 1.0 mL / min, column temperature 35℃, calibrated with polystyrene standard; The measurement results are as follows: Example 1 sample: number average molecular weight Mn = 1224, the test result of the method of the present invention is 1174, with a relative deviation of 4.1%.
[0022] Example 2 sample: number average molecular weight Mn = 1316, the test result of the method of the present invention is 1316, with a relative deviation of 3.0%.
[0023] Example 3 sample: number average molecular weight Mn = 1120, the test result of the method of the present invention is 1120, with a relative deviation of 4.6%.
[0024] The results show that the determination results of the method of the present invention are basically consistent with those of gel permeation chromatography, with a relative deviation of less than 5%, indicating that the method of the present invention has good accuracy and can meet the requirements for the determination of the molecular weight of polymethylsilane.
[0025] Example 5 (Hydrolysis Condition Optimization Experiment): This embodiment examines the effect of different hydrolysis conditions on the measurement results in order to determine the optimal hydrolysis conditions.
[0026] Using the polymethylsilane sample from Example 1 as the object, the stirring speed, ultrasonic power, and hydrolysis time were varied, while other conditions remained the same as in Example 1. The measurement results are shown in Table 1. Table 1. Molecular weight determination results under different hydrolysis conditions Experiment number Stirring speed (rpm) Ultrasonic power (W) Hydrolysis time (min) Molecular weight determination value 5-1 300 100 30 1446 5-2 500 200 60 1224 5-3 1000 300 60 1174 5-4 1500 400 90 1178 5-5 2000 500 120 1170 5-6 1000 0 60 2596 5-7 0 300 60 3702 As shown in Table 1, when the stirring speed is low or ultrasonic assistance is not used, the measured results are too high, indicating incomplete hydrolysis, which leads to a lower calculated chlorine content and a higher molecular weight. When the stirring speed reaches above 1000 rpm, the ultrasonic power reaches above 300 W, and the hydrolysis time reaches above 60 minutes, the measured results tend to stabilize, indicating that hydrolysis has been completed. Considering both efficiency and economy, the optimal hydrolysis conditions are: stirring speed 1000~1500 rpm, ultrasonic power 300~400 W, and hydrolysis time 60~90 minutes.
[0027] In summary, this invention provides a convenient method for detecting the molecular weight of polymethylsilane. This method is simple to operate, low in cost, and produces accurate and reliable results. It is particularly suitable for determining the molecular weight of polymethylsilane synthesized by the Woods reaction and can be widely used in the fields of production quality control and applied research of polymethylsilane.
[0028] The following points should be noted in this article: 1. The accompanying drawings of the embodiments disclosed herein only relate to the structures involved in the embodiments disclosed herein; other structures can be referred to in general design.
[0029] 2. Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.
[0030] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A convenient method for detecting the molecular weight of polymethylsilane, characterized in that: The method specifically includes the following steps: Step 1: Accurately weigh a certain mass of polymethylsilane sample, dissolve it in a solvent to obtain a polymethylsilane solution; Step 2: Add deionized water to the polymethylsilane solution obtained in Step 1, and perform ultrasonic-assisted hydrolysis under vigorous stirring to fully hydrolyze the chlorine element in the polymethylsilane to form an aqueous solution of hydrogen chloride. Step 3: Perform phase separation on the hydrolysate obtained in Step 2 and collect the aqueous phase; Step 4: Perform acid-base titration on the aqueous phase collected in Step 3 using a sodium hydroxide standard solution of known concentration, and record the volume of sodium hydroxide solution consumed; Step 5: Calculate the hydrogen chloride content based on the volume of sodium hydroxide solution consumed, and then estimate the amount of hydrolyzable chlorine in polymethylsilane. Step 6: Calculate the average molecular weight of polymethylsilane based on the mass of the polymethylsilane sample and the amount of hydrolyzable chlorine. Step 7: Perform three parallel determinations and take the average value as the result of the average molecular weight determination of polymethylsilane.
2. The convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: In step 1, the polymethylsilane is a product synthesized by the Woods reaction using sodium metal and dichloromethylsilane as raw materials. The mass ratio of the solvent to the polymethylsilane is 5:1 to 20:1, and the solvent is at least one of benzene, toluene, xylene, tetrahydrofuran, n-hexane, chloroform, and dichloromethane.
3. The convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: The mass ratio of deionized water to polymethylsilane added in step 2 is 10:1 to 50:
1.
4. The convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: In step 2, the stirring speed is 500~2000 rpm, the hydrolysis time is 30~120 minutes, the ultrasonic power of the ultrasonic-assisted hydrolysis is 100~500W, and the ultrasonic frequency is 20~40kHz.
5. The convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: In step 4, the concentration of the sodium hydroxide standard solution is 0.01–0.5 mol / L.
6. The convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: The amount of hydrolyzable chlorine in step 5 is calculated using the following formula: n (Cl) =C (NaOH) ×V (NaOH) ; Where C (NaOH） V represents the concentration of the sodium hydroxide standard solution. (NaOH） This represents the volume of sodium hydroxide standard solution consumed in the titration.
7. A convenient method for detecting the molecular weight of polymethylsilane according to claim 1, characterized in that: The average molecular weight of polymethylsilane in step 6 is calculated using the following formula: M=2m / n (Cl) ; Where m is the mass of the polymethylsilane sample, n (Cl） This represents the amount of substance of chlorine that can be hydrolyzed.