CN103804658A - Polymerizable polyfluorene macromonomer and synthesis method thereof - Google Patents

Abstract

The invention discloses a polymerizable polyfluorene macromonomer, the structure of which is shown in formula (I). In formula (I), R ¹ and R ² are independently selected from C ₁ -C ₁₀ alkyl groups; R ² is H or C ₁ -C ₅ alkyl; n is 1-20. The polymerizable polyfluorene macromonomer has high fluorescence quantum efficiency and can carry out radical copolymerization with various monomers. The present invention also provides a synthesis method of the polymerizable polyfluorene macromonomer, through Suzuki coupling reaction at a reaction temperature of 0°C to 200°C for 12 hours to 3 days, then reducing with sodium borohydride, and then reacting with formazan Acryloyl chloride or acryloyl chloride reaction, the polymerizable polyfluorene macromonomer obtained by this synthesis method has a narrow distribution.

Description

A kind of polymerizable polyfluorene macromonomer and its synthesis method

technical field

The invention belongs to the field of polymer monomer preparation, and in particular relates to a synthesis method of a novel polyfluorene macromonomer-polyfluorene methacrylate or polyfluorene methyl acrylate macromonomer.

Background technique

In the early 1990s, when scientists were studying fluorene derivatives in optoelectronic devices, they discovered for the first time that fluorene polymers have blue light-emitting properties. Since then, polyfluorene, as an important semiconductor conjugated polymer material, has been widely used in many fields such as flat panel display, biological or chemical sensing, nonlinear optics and solar cells.

The structure of fluorene is shown in Figure 1, which is a planar biphenyl structure, so polyfluorene is highly conjugated and rigid. It is precisely because of the special structure of polyfluorene and its derivatives that many excellent photoelectric and biological properties have been gradually discovered. Firstly, the photochemical stability and thermal stability of polyfluorene are relatively good, and the decomposition temperature can exceed 400 ° C [Polymer International, 2006, 55(5): 473]; secondly, polyfluorene has a large conjugated absorption wavelength in the molecule , the central maximum is about 380 nanometers (3.25eV), which has almost no relationship with the substituent at position 9; third, polyfluorene has electroluminescence and photoluminescence phenomena. In electroluminescence, polyfluorene exhibits a highly sensitive vibrational emission spectrum with a high-energy spacing of about 180eV, and its 0-0 electronic transition center is about 420 nanometers (2.9eV) [Physical Status Solidi A-Applied Research, 2004, 201(6): 1132]. In the solid state, its fluorescence quantum efficiency can reach 80%, the energy band is about 3.0eV, and the optical absorption bandgap is 2.95eV [Journal of Polymer Science Part A: Polymer Chemistry, 2001, 39(17): 2867]; fourth, the 2 It is easy to carry out structural modification on the carbons at the 1, 7 and 9 positions, a series of reactions can occur, and a variety of functional groups can be introduced. The 9-position substitution of fluorene has little effect on the electronic structure of the polyfluorene main chain, but it can affect the interchain interaction, solubility and thermal stability of the polymer. Therefore, polyfluorene and its derivatives have great potential in application. Great flexibility; fifth, fluorene can be separated from coal tar, the output is large, and it is cheap and easy to get.

Regarding the polymerization of fluorene-containing monomers, the earliest polyfluorene synthesis method reported in the literature [Journal of Applied Physics Part1-Regular Papers Short Notes & Review Papers, 1991, 30: 1941] is the _FeCl3 oxidation method. In chloroform solution, the resulting poly9 , The maximum luminescence position of 9-hexylfluorene is 470 nanometers, which is considered to be the beginning of the research on the preparation of soluble polyfluorene based on polymer light-emitting diodes. The synthesis process of this method is divided into two steps: 1) introducing an alkyl group on the 9-position carbon of fluorene to obtain 9,9-dialkylfluorene; 2) polymerizing 9,9-dialkylfluorene. Usually anhydrous treated ferric chloride is used as an oxidant in a chloroform solution and stirred at room temperature for about 70 hours. This preparation method is simple and the reaction conditions are mild. However, the obtained polyfluorene has a low molecular weight. At the same time, due to the connection of the 2 or 7 position, the molecular chain will be branched and affect the regularity and stability of the polyfluorene structure. Conjugate length [Advanced Materials, 2000, 12(23): 1737]. In recent years, the method of synthesizing polyfluorene through Yamamoto reaction and Suzuki reaction has been greatly developed.

The Yamamoto reaction [Chinese Journal of Luminescence, 2003, 24 (6): 612] (such as formula 2) is the reductive coupling reaction between two aryl halides, because the halogen atoms can be determined at No. 2 and No. 7 of fluorene in the reaction In this way, it can be strictly guaranteed that the connection of the fluorene unit is at the 2 and 7 positions, thereby ensuring the structural regularity of the polymer.

The Suzuki reaction [Journal of Materials Chemistry, 2003, 13:807] (such as formula 3) is a cross-coupling reaction of aryl boronic acid or boronic acid ester and aryl halide, and is currently the most widely used preparation method. Similar to the Yamamoto reaction, since the 2-position carbon and 7-position carbon of the fluorene monomer are first changed into bromine or boric acid (ester), and then polymerized, polyfluorene with a relatively clear molecular structure can be obtained. The improved Suzuki reaction can even control the degree of polymerization of polyfluorene [Macromolecules, 2004, 37:8897].

Both of the above two methods can obtain polyfluorene with relatively large molecular weight and relatively long chain links, and the Suzuki polymerization method, because it can control the sequence structure of the molecular chain more clearly, is more widely used. For the alternating copolymerization and embedding of polyfluorene Segment copolymerization generally adopts the Suzuki polymerization method.

The polymerization methods of fluorene-containing monomers introduced above are all step-by-step polymerization methods, mainly for the polymerization of fluorene-based monomers without double bonds, and the 2 and 7 positions of fluorene are substituted. The yoke effect, that is, the synthesis of polyfluorene in the traditional sense.

In 2000, Professor Hogen-Esch [Macromolecules, 2000, 33: 9176] synthesized a vinyl monomer with fluorene as a side group, 9,9-dimethyl-2-vinylfluorene (DMVF) (such as Formula 4), and its structural characteristics and polymerization properties were studied. Although the hydrogen on the 9-position carbon atom of the monomer has certain acidity, as long as the appropriate conditions are controlled, the acidity can be prevented and controllable anionic polymerization can be realized. The anionic polymerization operation is shown in formula 5. The resulting polymers had a narrow molecular weight distribution between 1.07 and 1.12.

This polymerization method provides a new idea for the polymerization of fluorene-containing monomers, so for fluorene monomers with double bonds, anionic polymerization can be used to achieve its controllable polymerization. However, in the actual application process, it can be found that the anionic polymerization has strict requirements on the polymerization conditions, and the range of applicable monomers is relatively limited, which limits the further expansion of this polymerization method in the research of polyfluorene. Considering the mild conditions of free radical polymerization and the wide application range of monomers, combining the advantages of the two to realize controllable free radical polymerization will bring the research and application of polyfluorene to a new height.

Contents of the invention

The invention provides a polymerizable polyfluorene macromonomer and a synthesis method thereof. The polymerizable polyfluorene macromonomer can carry out radical copolymerization with various monomers to obtain different functional materials.

A polymerizable polyfluorene macromonomer, the structure of which is shown in formula (I):

In formula (I), R ¹ and R ² are independently selected from C ₁ -C ₁₀ alkyl groups;

R ³ is H or C ₁ -C ₅ alkyl;

n is 1-20.

The polymerizable polyfluorene macromonomer obtained in the present invention contains an acrylate structure, and can carry out free radical copolymerization with various monomers, so that it can be used to prepare various functional materials; and contains a polyfluorene structure. According to the records in the literature, it has Compounds of this type of structure basically have higher fluorescence quantum efficiency (Holmes AB; Chemical Review, 2009; 109:897; Lin YP, Zheng ZC, Hogen-Esch TE, Ling J, Shen ZQ; Journal of Colloid and Interface Science, 2013, 390: 105.), is an excellent blue light material.

As a preference, said R ¹ and R ² are nC ₆ H ₁₃ ;

R ³ is methyl or H;

n is 1-10, at this time, the polymerizable polyfluorene macromonomer is easy to prepare and has good fluorescence quantum efficiency.

A kind of synthetic method of described polymerizable polyfluorene macromonomer comprises the steps:

(1) In the presence of a palladium catalyst and a base, the monomer is subjected to a Suzuki coupling reaction with p-formaldehyde phenylboronic acid as the end group, and after a period of reaction, bromobenzene is added to the reaction solution for capping to obtain a capped intermediate ;

The monomer is 9,9-di-n-hexyl-2-pinacol borate-7-bromofluorene (DBHBF), the structure of which is shown in formula (II):

The structure of the p-formaldehyde phenylboronic acid is shown in formula (Ⅲ):

(2) After reducing the capped intermediate obtained in step (1) with sodium borohydride, the obtained reduced product is acylated with methacryloyl chloride or acryloyl chloride to obtain the polymerizable polyfluorene macromonomer. The polymerizable polyfluorene macromonomer obtained by the synthesis method has narrow distribution and high preparation efficiency.

As preferably, the molar ratio of the monomer, p-formaldehyde phenylboronic acid and bromobenzene is 1:1:1～20:1:5, and the molar ratio of the obtained polymerizable polyfluorene macromonomer can be controlled by the molar ratio of the raw materials. The magnitude of the n value.

Preferably, in step (1), the temperature of the Suzuki coupling reaction is 0°C to 200°C, and the coupling reaction can occur within this temperature range; as a further preference, the Suzuki coupling reaction The temperature is 0°C to 100°C, at this time, the reaction yield is high and side reactions are few. The time of the Suzuki coupling reaction is 10-24 hours.

As a preference, in step (1), the palladium catalyst is tetrakis(triphenylphosphine)palladium;

Described alkali is sodium carbonate. The palladium catalyst and base have high reactivity to the substrate of the present invention.

Preferably, in step (2), the reduction temperature is 0°C to 80°C. The amount of sodium borohydride used is not particularly strict, and it only needs to be in excess relative to the reduced substrate.

Preferably, in step (2), the temperature of the acylation reaction is -20°C to 20°C. In the acylation reaction, triethylamine is added as an acid-binding agent.

In step (2), the reduction and acylation reactions are carried out in an ether solvent, and the ether solvent is preferably tetrahydrofuran (THF). Wherein, after the reduction is completed, the reduced product is obtained by precipitation in methanol, and then dissolved in an appropriate amount of solvent to carry out subsequent acylation reaction.

Compared with the prior art, the beneficial effect of the present invention is that the polyfluorene macromonomer functionalized with methacrylate or acrylate groups is synthesized for the first time, and the polyfluorene macromonomer can carry out free radical reaction with various monomers. Polymerization, so as to obtain a variety of functional materials; and such monomers have not appeared in the prior art and are used for free radical polymerization.

Description of drawings

Fig. 1 is the proton magnetic spectrum of methacrylate polyfluorene macromonomer.

Detailed ways

The present invention will be further described in conjunction with specific implementation below.

Example 1

Dissolve 0.5g of DBHBF in 1mL of toluene, add 1mL of 2mol/L sodium carbonate aqueous solution, and blow argon for 20-30min; dissolve 0.1g of tetrakis(triphenylphosphine)palladium in 7.5mL of toluene and add to the above reaction system, then add 4- Formylphenylboronic acid 0.1g, react at 0°C for 24h; add bromobenzene 0.1mL and react for 24h; cool to room temperature, precipitate in 300mL of methanol, and dry the product (yield: 44%) in a vacuum oven at 50°C 24h. Dissolve 0.1g of the above product and _0.15g NaBH in 15mL THF, react at 0°C for 12h, and precipitate in methanol after the reaction to obtain the reduced product; dissolve 0.1g of the reduced product in 1mL THF and add triethylamine and Methacryloyl chloride was reacted overnight at room temperature, and finally a light yellow solid was obtained (90% yield).

Example 2

Dissolve 2.5g of DBHBF in 2mL of toluene, add 2mL of 2mol/L sodium carbonate aqueous solution, and blow argon for 20-30min; dissolve 0.2g of tetrakis(triphenylphosphine)palladium in 7.5mL of toluene and add to the above reaction system, then add 4-methyl Acylphenylboronic acid 0.3g, react at 40°C for 24h; add bromobenzene 0.1mL and react for 24h; cool to room temperature, precipitate in 300mL of methanol, and dry the product (50% yield) in a vacuum oven at 50°C for 24h . Dissolve 0.2g of the above product and 0.2g NaBH ₄ in 15mL THF, react at 40°C for 12h, and precipitate in methanol after the reaction to obtain the reduced product; dissolve 0.15g of the reduced product in 2mL THF, add triethylamine and propylene respectively at 0°C Acyl chloride was reacted overnight at room temperature, and finally a light yellow solid was obtained (yield 89%).

Example 3

Dissolve 5g of DBHBF in 3mL of toluene, add 3mL of 2mol/L sodium carbonate aqueous solution, and blow argon for 20-30min; dissolve 0.3g of tetrakis(triphenylphosphine)palladium in 7.5mL of toluene and add to the above reaction system, then add 4-methyl Acylphenylboronic acid 0.45g, reacted at 80°C for 24h; added bromobenzene 0.1mL and reacted for 24h; cooled to room temperature, precipitated in 300mL of methanol, and dried the obtained product in a vacuum oven at 50°C for 24h (yield: 54% ). Dissolve 0.3g of the above product and 0.35g NaBH ₄ in 15mL THF and react at 80°C for 12h. After the reaction is completed, precipitate in methanol to obtain the reduced product; dissolve 0.25g of the reduced product in 3mL THF and add triethylamine and formazan respectively Acryloyl chloride was reacted overnight at room temperature, and finally a light yellow solid was obtained (yield 85%). The proton nuclear magnetic spectrum (CDCl ₃ ) of the obtained product is shown in FIG. 1 , and the n value can be obtained as 6 by integration. All signal peaks in Figure 1 are assigned, and the characteristic structure of fluorene units and double bonds can be clearly seen, indicating that the polymerization product is a methacrylate polyfluorene macromonomer.

Application example 1

Using the RAFT polymerization method, successively add 6 mg of chain transfer agent trithioester, 2 mg of initiator azobisisobutyronitrile, 5 mL of solvent anisole, 0.12 g of polyfluorene macromonomer obtained in Example 3 and tertiary acrylic acid 0.26mL of butyl ester, freeze pumping cycle three times, the polymerization temperature is 60°C, the time is 24h, the precipitant is a mixed solvent of methanol and water (1:1 by volume), the yield is 30%, and the molecular weight of the polymer is 33,000. Molecular weight distribution 1.26.

Claims (8)

1. A polymerizable polyfluorene macromonomer, characterized in that the structure is as shown in formula (I):

In formula (I), R ¹ and R ² are independently selected from C ₁ -C ₁₀ alkyl groups; R ³ is H or C ₁ -C ₅ alkyl; n is 1-20. 2. polymerizable polyfluorene macromonomer according to claim 1, is characterized in that, described R ¹ and R ² are nC ₆ H ₁₃ ; R ³ is methyl or H; n is 1-10. 3. a synthetic method of the polymerizable polyfluorene macromer described in claim 1 or 2, is characterized in that, comprises the steps: (1) In the presence of a palladium catalyst and a base, the monomer is subjected to a Suzuki coupling reaction with p-formaldehyde phenylboronic acid as the end group, and after a period of reaction, bromobenzene is added to the reaction solution for capping to obtain a capped intermediate ; The monomer is 9,9-di-n-hexyl-2-pinacol borate-7-bromofluorene, the structure of which is shown in formula (II):

The structure of the p-formaldehyde phenylboronic acid is shown in formula (Ⅲ):

(2) After reducing the capped intermediate obtained in step (1) with sodium borohydride, the obtained reduced product is acylated with methacryloyl chloride or acryloyl chloride to obtain the polymerizable polyfluorene macromonomer. 4. the synthetic method of polymerizable polyfluorene macromonomer according to claim 3 is characterized in that, the mol ratio of described monomer, p-formaldehyde group phenylboronic acid and bromobenzene is 1:1:1～20: 1:5. 5 . The synthesis method of polymerizable polyfluorene macromonomer according to claim 3 , characterized in that, in step (1), the temperature of the Suzuki coupling reaction is 0° C. to 200° C. 6 . 6. the synthetic method of polymerizable polyfluorene macromonomer according to claim 3 is characterized in that, in step (1), described palladium catalyst is tetrakis (triphenylphosphine) palladium; Described alkali is sodium carbonate. 7 . The method for synthesizing polymerizable polyfluorene macromonomer according to claim 3 , characterized in that, in step (2), the reduction temperature is 0-80° C. 7 . 8 . The synthesis method of polymerizable polyfluorene macromonomer according to claim 3 , characterized in that, in step (2), the temperature of the acylation reaction is -20-20° C.

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