Preparation method of reversible addition fragmentation chain transfer reagent
By using tetrabutylammonium bromide as a phase transfer catalyst, the synthesis steps and conditions of RAFT reagents are simplified, solving the problems of complex synthesis and high cost in the prior art. This achieves efficient and low-cost preparation of RAFT reagents and controllable molecular weight of polymers.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XINXIANG RICHFUL LUBE ADDITIVE CO LTD
- Filing Date
- 2026-01-12
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for synthesizing RAFT reagents are cumbersome, require harsh reaction conditions, have high raw material costs, and are not suitable for large-scale production.
Using tetrabutylammonium bromide as a phase transfer catalyst, the RAFT reagent of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid was prepared by simplifying the reaction and purification process. The process includes steps such as adding alkaline solution, generating thiolate, neutralization, filtration and recrystallization, which avoids the complex steps and high temperature and pressure of traditional methods.
The preparation of RAFT reagents was achieved with high efficiency and low cost, with a yield of up to 93.74%, which is suitable for industrial production. The prepared RAFT reagents exhibit good controllability and narrow molecular weight distribution in polymerization reactions.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of RAFT reagent synthesis, specifically relating to a method for preparing a reversible addition-fragmentation chain transfer reagent. Background Technology
[0002] Polymer materials permeate our daily lives, ranging from commercial polymers used in packaging, paints, or structural materials to highly engineered polymers used in microelectronics and medicine. In existing polymerization techniques, traditional chain-growth polymerization involves irreversible chain termination reactions, making it impossible to precisely control the molecular weight, molecular weight distribution, chain end structure, and topology of the polymer, severely limiting the preparation of high-performance polymer materials.
[0003] To overcome this limitation, the field of polymer science has developed reversible deactivation radical polymerization (RDRP) technology. This technology, by reversibly switching growing chain radicals between active and dormant states, greatly suppresses irreversible termination reactions, enabling precise design of polymer structures. Among various RDRP technologies, reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most widely used due to its broad range of applicable monomers and mild reaction conditions.
[0004] The concept of RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) was first explicitly proposed by scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia in 1998.
[0005] The core mechanism of RAFT polymerization lies in a reversible activation-deactivation equilibrium. In the initial stage of polymerization, the growing chain radicals (Pn•) generated by traditional initiators (such as azo dyes) undergo an addition-fragmentation reaction with the RAFT reagent, producing a dormant polymer chain (Pn-SC(Z)=S) and a new re-initiating radical (R•). Subsequently, through rapid and reversible exchange between the growing chain radicals (Pn• / Pm•) and all dormant chains, all polymer chains grow synchronously, resulting in a polymer with a narrow molecular weight distribution. At the end of polymerization, the vast majority of polymer chains retain active RAFT end groups, which can be separated as stable products and used for subsequent chain extension.
[0006] CN104592072A discloses a RAFT polymerization method, introducing the main structure of RAFT reagents and many application examples. The preparation method uses isobutylthiol and 2-bromopropionic acid as main raw materials to prepare trithiocarbonate-type RAFT reagents. A batch of polymers with controllable molecular weights and narrow molecular weight distributions were synthesized using RAFT reagents.
[0007] CN102690217A discloses the basic principles and characteristics of RAFT polymerization. It introduces a method for preparing a trithiocarbonate-type RAFT reagent. The method uses dodecanethiol and 2-bromoisobutyric acid as main raw materials, and the product is prepared through post-processing steps such as vacuum distillation, dissolution, extraction, and washing. The methyltrioctylammonium chloride used in this patent is a relatively expensive phase transfer catalyst, and its catalytic efficiency in this multi-step continuous reaction system (involving multiple interfacial reaction steps such as thiolate formation, carbon disulfide addition, and chloroform addition) is low, resulting in various byproducts. The post-processing steps are cumbersome and unsuitable for large-scale production.
[0008] Known methods for synthesizing RAFT reagents typically suffer from one or more of the following drawbacks:
[0009] 1. The synthesis steps are cumbersome and the routes are long. Many known methods require multiple reaction steps, involving the separation and purification of intermediates, resulting in low overall yield and low production efficiency, making them unsuitable for industrial production.
[0010] 2. Harsh reaction conditions. Some methods require harsh conditions such as high temperature, anhydrous and oxygen-free environments, or high pressure, which place high demands on equipment, consume a lot of energy, and have poor operational safety.
[0011] 3. High raw material costs. The high cost of raw materials required for the synthesis of RAFT reagents results in expensive finished RAFT reagents, which limits their application in industrial production.
[0012] Therefore, there is an urgent need in this field to develop a new method that is easy to operate, has mild conditions, is low in cost, and especially has simple and efficient post-processing, suitable for the large-scale preparation of high-purity RAFT reagents. Summary of the Invention
[0013] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for the simple, mild, low-cost, and easily scalable preparation of high-purity RAFT reagents. The present invention aims to achieve efficient and economical synthesis of RAFT reagents by optimizing the catalyst system and simplifying the reaction and purification processes.
[0014] The inventors unexpectedly discovered that by using tetrabutylammonium bromide as a phase transfer catalyst, its molecular structure can migrate efficiently between an alkaline aqueous phase and an organic phase containing acetone and chloroform. This is particularly beneficial for the timely transfer of the in-situ generated thiolate intermediate to the organic phase to react with carbon disulfide and promote the subsequent addition reaction of chloroform, thereby achieving high efficiency throughout the process.
[0015] To achieve the above objectives, the present invention adopts the following technical solution:
[0016] This invention designs and discloses a method for preparing a reversible addition-fragmentation chain transfer reagent, wherein the reversible addition-fragmentation chain transfer reagent is 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, and the method for preparing the reversible addition-fragmentation chain transfer reagent includes the following steps:
[0017] S1: Dodecyl mercaptan, acetone and tetrabutylammonium bromide are mixed and reacted by adding an alkaline solution dropwise in an ice bath or at room temperature to form a thiolate; carbon disulfide is then added dropwise to the reaction system to form a trithiocarbonate; chloroform is then added under ice bath conditions, followed by the addition of an alkaline solution, and the reaction is completed by stirring in an ice bath or at room temperature to obtain a mixed solution;
[0018] S2: Add water to dilute the mixture obtained in S1, and acidify it by adding acidic solution dropwise under ice bath conditions until the solid is completely precipitated; then filter it, dissolve the obtained solid in petroleum ether and recrystallize it to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid.
[0019] In S1, the molar ratio of dodecyl mercaptan to tetrabutylammonium bromide is 100:(1~8).
[0020] In S1, the alkaline solution is a 50% (w / w) aqueous solution of sodium hydroxide or potassium hydroxide.
[0021] In S1, the molar ratio of dodecyl mercaptan to carbon disulfide is 1:(0.95~1.2).
[0022] In S1, the molar ratio of dodecyl mercaptan to chloroform is 1:(1~1.5).
[0023] In S1, chloroform is added under ice bath conditions, followed by the addition of alkaline solution over a period of 20–60 minutes.
[0024] In S1, the reaction is carried out under stirring in an ice bath or at room temperature for 12-36 hours.
[0025] In S2, the acidic solution is 12 mol / L concentrated hydrochloric acid.
[0026] The molar ratio of concentrated hydrochloric acid in S2 to dodecyl mercaptan in S1 is (1.1~2):1.
[0027] Compared with the prior art, the beneficial effects of this invention are as follows:
[0028] 1. This invention specifically selects tetrabutylammonium bromide as a phase transfer catalyst, and its dosage is only 1-8% of the molar amount of dodecyl mercaptan, significantly lower than that of conventional catalysts. Under the same reaction conditions, compared with other phase transfer catalysts (such as methyltrioctylammonium chloride), the catalyst system of this invention can achieve a higher product yield (the yield in Example 2 is as high as 93.74%), indicating that tetrabutylammonium bromide has better catalytic activity and selectivity in the reaction system.
[0029] 2. Tetrabutylammonium bromide is a commonly used and relatively inexpensive phase transfer catalyst. It is not only used in small quantities, but also widely available and inexpensive, which is conducive to the large-scale and economical preparation of RAFT reagents.
[0030] 3. This invention eliminates the cumbersome steps of nitrogen blowing, solvent replacement, multiple dissolutions and rotary evaporation in the traditional method (CN104861130A). After the reaction, a high-purity product can be obtained simply by diluting with water, acidifying to precipitate, filtration and recrystallization with petroleum ether. The process is simple and suitable for industrial production.
[0031] 4. The reaction is carried out at room temperature or in an ice bath, without the need for high temperature, high pressure or a strictly anhydrous and oxygen-free environment, which reduces equipment requirements and operational risks and improves the safety and controllability of the process.
[0032] 5. The RAFT reagent prepared by the method of this invention has high purity and can be directly used in RAFT polymerization reactions. As shown in Examples 5-7, it exhibits good controllability during polymerization and can prepare polymers with controllable molecular weight and narrow molecular weight distribution (PDI ≤ 1.21), indicating that the reagent has excellent chain transfer properties and wide applicability. Detailed Implementation
[0033] The technical solution of the present invention will be described in detail below with reference to embodiments, but this does not limit the present invention to the scope of the embodiments described. Process parameters not specified in the embodiments of this application can be performed according to conventional methods, and all raw materials used can be obtained through commercial channels.
[0034] Example 1: Preparation of RAFT reagent
[0035] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 0.64 g tetrabutylammonium bromide phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 5 °C. After 15 minutes, 8 g of 50% NaOH solution was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g of chloroform was added, followed by the dropwise addition of 40 g of 50% NaOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0036] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether by heating, and then filter again. Recrystallize the filtrate directly at low temperature to obtain 20.36 g (55.84%) of a bright yellow solid.
[0037] Example 2: Preparation of RAFT reagent
[0038] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 0.64 g tetrabutylammonium bromide phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 5 °C. After 15 minutes, 11.2 g KOH solution (50%) was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g chloroform was added, followed by the dropwise addition of 56 g 50% KOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0039] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether, filter, and recrystallize to obtain 34.20 g (93.74%) of bright yellow solid.
[0040] Example 3: Preparation of RAFT reagent
[0041] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 1.28 g tetrabutylammonium bromide phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 5 °C. After 15 minutes, 11.2 g KOH solution (50%) was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g chloroform was added, followed by the dropwise addition of 56 g 50% KOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0042] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether, filter, and recrystallize to obtain 30.04 g (82.36%) of bright yellow solid.
[0043] Example 4: Preparation of RAFT reagent
[0044] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 1.28 g tetrabutylammonium bromide phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 10 °C. After 15 minutes, 11.2 g KOH solution (50%) was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g chloroform was added, followed by the dropwise addition of 56 g 50% KOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0045] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether, filter and recrystallize to obtain 26.47 g (72.52%) of bright yellow solid.
[0046] Comparative Example 1
[0047] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 0.81 g methyltrioctylammonium chloride phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 5 °C. After 15 minutes, 8 g of 50% NaOH solution was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g of chloroform was added, followed by the dropwise addition of 40 g of 50% NaOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0048] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether, filter and recrystallize to obtain 15.74 g (43.26%) of bright yellow solid.
[0049] Comparative Example 2
[0050] (1) 20.24 g dodecyl mercaptan, 58 g acetone and 0.81 g methyltrioctylammonium chloride phase transfer catalyst were mixed and added to a 250 mL three-necked flask and stirred thoroughly at 5 °C. After 15 minutes, 11.2 g KOH solution (50%) was added dropwise using a constant pressure dropping funnel. After continuing the reaction for 15 minutes, carbon disulfide was added dropwise to the reaction flask. After stirring for 10 minutes, 14.32 g chloroform was added, followed by the dropwise addition of 56 g 50% KOH solution for 30 minutes. The entire reaction was then stirred at room temperature for 12 h.
[0051] (2) Add 150 ml of deionized water to the reaction system, followed by 50 mL of concentrated HCl (12 mol / L). After acidification, filter, dissolve in petroleum ether, filter and recrystallize to obtain 27.84 g (76.35%) of bright yellow solid.
[0052] Example 5:
[0053] 20.0 g toluene, 20.0 g dodecyl methacrylate, 0.733 g RAFT reagent (Example 4), and 76 mg azobisisobutyronitrile were added to a 100 mL three-necked flask, and the mixture was purged with nitrogen for 30 min. The reaction was carried out at 90 °C for 2 h. Poly(dodecyl methacrylate) was precipitated with methanol, dried in a vacuum oven to a constant temperature, and weighed. The yield was 94%. GPC analysis showed that Mn was 8273, Mw was 9526, and the molecular weight distribution was 1.15.
[0054] Example 6:
[0055] 20.0 g toluene, 20.0 g dodecyl methacrylate, 0.365 g RAFT reagent (Example 4), and 76 mg azobisisobutyronitrile were added to a 100 mL three-necked flask, and the mixture was purged with nitrogen for 30 min. The reaction was carried out at 90 °C for 2 h. Poly(dodecyl methacrylate) was precipitated with methanol, dried in a vacuum oven to a constant temperature, and weighed. The yield was 96%. GPC analysis showed that Mn was 16951, Mw was 19853, and the molecular weight distribution was 1.17.
[0056] Example 7:
[0057] 20.0 g toluene, 20.0 g dodecyl methacrylate, 0.548 g RAFT reagent (Example 4), and 76 mg azobisisobutyronitrile were added to a 100 mL three-necked flask, and the mixture was purged with nitrogen for 30 min. The reaction was carried out at 90 °C for 2 h. Poly(dodecyl methacrylate) was precipitated with methanol, dried in a vacuum oven to a constant temperature, and weighed. The yield was 94%. GPC analysis showed that Mn was 25841, Mw was 31255, and the molecular weight distribution was 1.21.
[0058] The results above demonstrate that the RAFT reagent of this invention possesses excellent performance and can be used for living controlled polymerization. The polymers synthesized using the RAFT reagent of this invention exhibit controllable molecular weight and a narrow molecular weight distribution, making it a universal RAFT reagent applicable to living controlled polymerization.
[0059] This invention is not limited to the above-described embodiments. Any changes in shape or structure are within the scope of protection of this invention. The scope of protection of this invention is defined by the appended claims. Those skilled in the art can make various changes, modifications, substitutions, combinations, and simplifications to these embodiments without departing from the principles and essence of this invention. All such changes and simplifications should be considered equivalent substitutions and fall within the scope of protection of this invention.
Claims
1. A method for preparing a reversible addition-fragmentation chain transfer reagent, wherein the reversible addition-fragmentation chain transfer reagent is 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, characterized in that, The preparation method of the reversible addition-fragmentation chain transfer reagent includes the following steps: S1: Dodecyl mercaptan, acetone and tetrabutylammonium bromide are mixed and reacted by adding an alkaline solution dropwise in an ice bath or at room temperature to form a thiolate; carbon disulfide is then added dropwise to the reaction system to form a trithiocarbonate; chloroform is then added under ice bath conditions, followed by the addition of an alkaline solution, and the reaction is completed by stirring in an ice bath or at room temperature to obtain a mixed solution; S2: Add water to dilute the mixture obtained in S1, and acidify it by adding acidic solution dropwise under ice bath conditions until the solid is completely precipitated; then filter it, dissolve the obtained solid in petroleum ether and recrystallize it to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid.
2. The preparation method according to claim 1, characterized in that, In S1, the molar ratio of dodecyl mercaptan to tetrabutylammonium bromide is 100:(1~8).
3. The preparation method according to claim 1, characterized in that, In S1, the alkaline solution is a 50% (w / w) aqueous solution of sodium hydroxide or potassium hydroxide.
4. The preparation method according to claim 1, characterized in that, In S1, the molar ratio of dodecyl mercaptan to carbon disulfide is 1:(0.95~1.2).
5. The preparation method according to claim 1, characterized in that, In S1, the molar ratio of dodecyl mercaptan to chloroform is 1:(1~1.5).
6. The preparation method according to claim 1, characterized in that, In S1, chloroform is added under ice bath conditions, followed by the addition of alkaline solution over a period of 20–60 minutes.
7. The preparation method according to claim 1, characterized in that, In S1, the reaction is carried out under stirring in an ice bath or at room temperature for 12-36 hours.
8. The preparation method according to claim 1, characterized in that, In S2, the acidic solution is 12 mol / L concentrated hydrochloric acid.
9. The preparation method according to claim 8, characterized in that, The molar ratio of concentrated hydrochloric acid in S2 to dodecyl mercaptan in S1 is (1.1~2):1.