LIVING RADICAL POLYMERIZATION METHOD USING ZINC PHTHALOCYANINE DYE AS NEAR-INFRARED PHOTOCATALYST

Abstract

The invention provides a living radical polymerization method using a zinc phthalocyanine dye as a near-infrared photocatalyst, including subjecting a free radical polymerizable monomer to a near-infrared light-controlled polymerization reaction, in the presence of a chain transfer agent, a cocatalyst and a zinc phthalocyanine dye containing a carbon-carbon double bond, in a solvent at 0-30° C. under the air atmosphere, to obtain a living radical polymerization product. The free radical polymerizable monomer is an acrylate monomer, a methacrylate monomer, an acrylamide monomer or a methacrylamide monomer; the chain transfer agent includes a thiocarbonate; and the cocatalyst includes an organic amine with or without a carbon-carbon double bond. A near-infrared light-responsive functional zinc phthalocyanine dye is used as a near-infrared photocatalyst for the polymerization reaction, and after the polymerization is completed, the polymerizable zinc phthalocyanine dye remains on the polymer chain by polymerization, thereby realizing the cyclic utilization of the near-infrared photocatalyst.

Claims

1. A near-infrared light-controlled living radical polymerization method, comprising steps of: subjecting a free radical polymerizable monomer to a near-infrared light-controlled polymerization reaction, in the presence of a chain transfer agent, a cocatalyst and a zinc phthalocyanine dye with a carbon-carbon double bond as a catalyst, in a solvent at 0-30° C. under the air atmosphere, to obtain a living radical polymerization product after complete reaction, wherein the free radical polymerizable monomer is selected from an acrylate monomer, a methacrylate monomer, an acrylamide monomer or a methacrylamide monomer; the chain transfer agent comprises a thiocarbonate; the cocatalyst comprises an organic amine with a carbon-carbon double bond or an organic amine without a carbon-carbon double bond; and the living radical polymerization product has a structure of Formula (1) or (2): ##STR00017## in which R.sub.1 and R.sub.1′ are each independently selected from ##STR00018## R.sub.2 and R.sub.2′ are each independently selected from a C2-C12 alkyl group or a C2-C12 alkyl group substituted with carboxyl; R.sub.3, R.sub.3′, R.sub.5 and R.sub.5′ are each independently selected from hydrogen or methyl; R.sub.4 is selected from benzyl, a C1-C6 alkyl group, a C1-C6 alkyl group substituted with hydroxyl, a polyethylene glycol chain, a C1-C6 alkylene oxide, or a C1-C6 alkyl group substituted with dimethylamino; R.sub.6 and R.sub.6′ are each independently selected from ##STR00019## R.sub.7 and R.sub.7′ are each independently selected from hydrogen or methyl; R.sub.8 and R.sub.9 are each independently selected from hydrogen, a C1-C6 alkyl group, or a C1-C6 alkyl group substituted with hydroxyl; and X=3-1000; y is lower than 10; and z=0-20.

2. The living radical polymerization method according to claim 1, wherein when z=0, the cocatalyst is an organic amine without a carbon-carbon double bond; and the organic amine without a carbon-carbon double bond is triethylamine and/or tributylamine.

3. The living radical polymerization method according to claim 1, wherein when z=1-20, the cocatalyst comprises an organic amine with a carbon-carbon double bond; and the organic amine with a carbon-carbon double bond is dimethylaminoethyl acrylate and/or dimethylaminoethyl methacrylate.

4. The living radical polymerization method according to claim 1, wherein R.sub.2 and R.sub.2′ are each independently selected from ethyl, n-dodecyl, or —CH.sub.2CH.sub.2COOH.

5. The living radical polymerization method according to claim 1, wherein R.sub.4 is selected from a group having a structural formula below: —CH.sub.3, ##STR00020## in which n=5-22.

6. The living radical polymerization method according to claim 1, wherein R.sub.8 and R.sub.9 are each independently selected from hydrogen, methyl, ethyl, isopropyl or 2-hydroxypropyl.

7. The living radical polymerization method according to claim 1, wherein the molar ratio of the free radical polymerizable monomer to the zinc phthalocyanine dye is 1:0.00001-0.01.

8. The living radical polymerization method according to claim 1, wherein the molar ratio of the thiocarbonate to the cocatalyst is 1:0.5-20.

9. The living radical polymerization method according to claim 1, wherein the near-infrared light-controlled polymerization reaction takes place at a near-infrared light with a wavelength of 650-900 nm.

10. A living radical polymerization method prepared by the method according to claim 1, having a molecular weight of 1000-200000 g/mol and a molecular weight distribution of 1.07-1.5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 shows the test result of ZnTNPc by .sup.1H NMR;

[0055] FIG. 2 shows the test result of ZnTAPc by .sup.1H NMR;

[0056] FIG. 3 shows the test result of ZnTAPc-MAm by .sup.1H NMR;

[0057] FIG. 4 shows the test result of ZnTAPc-Am by .sup.1H NMR;

[0058] FIG. 5 shows the test result of ZnTAPc-A by .sup.1H NMR;

[0059] FIG. 6 shows a UV-visible absorption spectrum of polymer P (PEGA-co-DMAEA) in methanol as a solvent; and

[0060] FIG. 7 shows an elution curve by GPC of the polymer prepared by three-cycle of photocatalysis by a zinc phthalocyanine dye.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] The specific embodiments of the present invention will be described in further detail with reference to embodiments. The following embodiments are intended to illustrate the present invention, instead of limiting the scope of the present invention.

[0062] In the following examples of the present invention, the raw materials MMA, PEGMA, and PEGA used need to be passed through a neutral alumina column to remove the polymerization inhibitor, and then placed in the upper part of the refrigerator for storage. Other reagents can be used directly after they are obtained commercially. As a control, ZnTNPc is used as a catalyst, which has a structural formula below:

##STR00012##

[0063] In the present invention, the following test methods are used:

[0064] 1. The number average molecular weight (M.sub.n,GPC) and molecular weight distribution (M.sub.w/M.sub.n) of the obtained polymer are measured by TOSOH HLC-8320 gel permeation chromatograph equipped with a refractive index detector (TOSOH). The guard column used is TSK gel Super MP-N (4.6×20 mm). The detection column is TSK gel Super HZ-N (4.6×150 mm), DMF (with 0.1 wt % LiBr added as a co-solvent) is used as an eluent, the test temperature is 40° C., the flow rate is 0.35 mL.Math.min.sup.−1, and the molecular weight is in the range of 5×10.sup.2-5×10.sup.5 g.Math.mol.sup.−1. The TOSOH plus autosampler is used to inject the sample for gel permeation chromatography, and the standard PS sample purchased from TOSOH is used to calibrate the test result of the polymer. The sample for GPC test is prepared as follows. The polymer is dissolved in DMF (with 0.1 wt % LiBr added as a co-solvent) to give a concentration of 1-5 mg/mL. The polymer solution is passed through a small column of neutral alumina and a syringe fitted with 0.45 m filter. Finally, the neat polymer solution is injected into a test vial.

[0065] 2. The NMR spectra of the obtained products and polymers are measured by Bruker 300 MHz NMR machine, where CDCl.sub.3 or DMSO-d.sub.6 is used as a deuterated reagent, the test occurs at room temperature (25° C.), and tetramethylsilane (TMS) is used as an internal standard.

[0066] 3. UV-vis is measured by Shimadzu UV-2600 ultraviolet-visible spectrophotometer, where water or toluene is used as a solvent.

Example 1. Synthesis of Polymerizable Zinc Phthalocyanine Dye Near-Infrared Photocatalyst ZnTAPc-MAm

[0067] A zinc tetraaminophthalocyanine dye (ZnTAPc) (0.32 g, 0.50 mmol) was dissolved in DMF (20 mL), added with TEA (83.4 μL, 0.60 mmol), and stirred on a magnetic stirrer. Then a mixed solution of methacryloyl chloride (44.8 μL, 0.55 mmol) and anhydrous dichloromethane (10 mL) was added dropwise, and stirred at room temperature overnight. Then the reaction solution was poured into water (150 mL), and the solid product was separated and collected by filtration under suction, and further purified by washing with 1.0 M hydrochloric acid and 1.0 M sodium hydroxide, respectively. Finally, the product was precipitated by washing with deionized water and centrifuged at a speed of 10000 r.Math.min.sup.−1. The resulting dark blue-black product was dried in a vacuum drying oven before use. The reaction route was as follows:

##STR00013##

Example 2. Synthesis of Polymerizable Zinc Phthalocyanine Dye Near-Infrared Photocatalyst ZnTAPc-Am

[0068] ZnTAPc (0.32 g, 0.50 mmol) was dispersed in DMF (20 mL), added with TEA (83.4 μL, 0.60 mmol), and stirred on a magnetic stirrer. Then a mixed solution of acryloyl chloride (53.2 μL, 0.55 mmol) and anhydrous dichloromethane (10 mL) was added dropwise, and stirred at room temperature overnight. Then the reaction solution was poured into water (150 mL), and the solid product was separated and collected by filtration under suction, and further purified by washing with 1.0 M hydrochloric acid and 1.0 M sodium hydroxide, respectively. Finally, the product was precipitated by washing with deionized water and centrifuged at a speed of 10000 r.Math.min.sup.−1. The resulting dark blue-black product was a zinc phthalocyanine dye monomer-acrylamide (ZnTAPc-Am), which was dried in a vacuum drying oven, and the yield of the product was 80.2%. The reaction route was as follows:

##STR00014##

Example 3. Synthesis of Polymerizable Zinc Phthalocyanine Dye Near-Infrared Photocatalyst ZnTAPc-A

[0069] (1) Synthesis of acid chloride compound (acrylic acid-3-chloro-3-oxopropyl ester): 3-(acryloyloxy)propionic acid (79.30 mg, 0.55 mmol) was reacted with thionyl chloride (5.0 mL), and then two drops of DMF was dripped as a catalyst and stirred for 30 min. Excess thionyl chloride was removed by rotary evaporation, and the residue was left and sealed directly for the next reaction. The reaction route was as follows:

##STR00015##

[0070] (2) Synthesis of ZnTAPc-A: ZnTAPc (0.32 g, 0.50 mmol) was dissolved in DMF (20 mL), added with TEA (83.4 μL, 0.60 mmol), and stirred on magnetic stirrer. Then a mixed solution of acrylic acid-3-chloro-3-oxypropyl ester (89.40 mg, 0.55 mmol) and anhydrous dichloromethane (10.0 mL) was added dropwise, and stirred at room temperature overnight. Then the reaction solution was poured into water (150 mL), and the solid product was separated and collected by filtration under suction, and further purified by washing with 1.0 M hydrochloric acid and 1.0 M sodium hydroxide, respectively. Finally, the product was precipitated by washing with water and centrifuged at a speed of 10000 r.Math.min.sup.−1. The resulting dark blue-black product was a zinc phthalocyanine dye monomer-acrylate (ZnTAPc-A), which was dried in a vacuum drying oven, and the yield of the product was 85.6%. The reaction route was as follows:

##STR00016##

Example 4: Preparation of Polymethyl Methacrylate

[0071] According to Table 1, with various polymerizable monomers and catalysts, RAFT polymerization was carried out under the same reaction conditions under near-infrared light of 730 nm. Taking No. 7 as an example, the reaction steps were as follows:

[0072] The zinc phthalocyanine dye ZnTAPc-MAm synthesized above was used as the near-infrared photocatalyst. At a molar ratio of [PEGMA].sub.0/[CDSPA].sub.0/[TEA].sub.0/[ZnTAPc-MAm].sub.0=15/1/1/0.01, PEGMA (177.0 mg, 0.354 mmol), CDSPA (9.50 mg, 0.0236 mmol), TEA (1.7 μL, 0.0236 mmol), and zinc phthalocyanine monomer ZnTAPc-MAm (0.18 mg, 0.237 μmol) were added to a dried 2.0 mL ampoule fitted with a stir bar, and 0.5 mL of DMSO was added as a polymerization solvent. Then the mouth of the ampoule was sealed with plastic wrap to prevent volatilization of monomer and pollution. The ampoule was positioned in a magnetic stirrer and the content was polymerized at room temperature under irradiation with near-infrared LED light (66.3 mW.Math.cm.sup.−2) having a center wavelength of 730 nm for a set period of time. After the polymerization reaction, the reaction mixture was taken out and dissolved in THF (2.0 mL), and then petroleum ether (180 mL) was added for precipitation. The polymer product was collected by filtration and dried to a constant weight at 30° C. under vacuum. Then, the polymerization conversion rate was calculated according to the gravimetric method.

[0073] The polymerization results are shown in Table 1.

TABLE-US-00001 TABLE 1 RAFT polymerization under near-infrared light of 730 nm in the air.sup.a Time Conversion M.sub.n, th.sup.c M.sub.n, GPC No. Molar ratio Monomer Catalyst (h) rate (%).sup.b (g .Math. mol.sup.−1) (g .Math. mol.sup.−1) M.sub.w/M.sub.n 1 200/1/1/0.01 MMA ZnTAPc 5 84.6 17300 28700 1.07 .sup. 2.sup.d 200/1/1/0.01 MMA ZnTNPc 5 68.0 14000 24900 1.07  3.sup.e 164/1/1/0.01 MMA ZnTAPc 21 85.6 14500 11700 1.34 4 164/1/1/0.01 MMA ZnTAPc 5 66.7 11400 8600 1.35 7  15/1/1/0.01 PEGMA ZnTAPc-MAm 21 70.1 5700 9600 1.35  8.sup.f  70/1/1/0.01 NIPAAm ZnTNPc-MAm 21 63.4 5300 8100 1.12  9.sup.f  75/1/1/0.01 NIPAAm ZnTNPc-A 5 74.7 6700 9200 1.13 .sup.aPolymerization conditions: Molar ratio = [polymerizable monomer].sub.0/[CDSPA].sub.0/[TEA].sub.0/[zinc phthalocyanine catalyst].sub.0, V.sub.polymerizable monomer = 0.5 mL, V.sub.DMSO = 0.5 mL, and polymerization under near-infrared LED light sourcce(λ.sub.max = 730 nm, 66.3 mW .Math. cm.sup.−2) in the air at 25° C. .sup.bD conversion rate calculated by the weighing method. .sup.cM.sub.n, th = [Monomer].sub.0/[CDSPA].sub.0 × M.sub.w, Monomer × Conv. % + M.sub.w, CDSPA .sup.dreaction under argon atmosphere. .sup.eV.sub.DMI = 0.5 mL. .sup.fmolar ratio = [polymerizable monomer].sub.0/[CDCT].sub.0/[TEA].sub.0/[zinc phthalocyanine catalyst].sub.0

[0074] Although a polymerization product is also obtained in the experimental group No. 1-No. 4, because the catalyst zinc phthalocyanine dye used does not contain a carbon-carbon double bond and is not polymerizable, the polymerization product obtained in the experimental group No. 1-No. 4 cannot be used again as a photocatalyst for subsequent reactions. In the experimental group No. 7-No. 9, a polymerizable zinc phthalocyanine dye is used as a catalyst, and the molecular structure of the zinc phthalocyanine dye is introduced into the polymerization product, which can be used as a macromolecular chain transfer reagent for subsequent polymerization reactions by using its photocatalytic performance.

Example 5: Cyclic Polymerization Experiment Catalyzed with Zinc Phthalocyanine Dye Catalyst of Example 2

[0075] The polymerizable zinc phthalocyanine dye ZnTAPc-Am synthesized above was used as a near-infrared photocatalyst, and the organic amine structure-containing monomer DMAEA was used as a cocatalyst. At a molar ratio of [PEGA].sub.0/[CEPTA].sub.0/[DMAEA].sub.0/[ZnTAPc-Am].sub.0=20/1/2/0.02, PEGA (0.50 mL, 1.11 mmol), CEPTA (14.7 mg, 0.0557 mmol), DMAEA (16.9 μL, 0.111 mmol), and the zinc phthalocyanine dye monomer ZnTAPc-Am (0.77 mg, 1.11 μmol) were added to a dried 2.0 mL ampoule fitted with a stir bar, and 0.5 mL of DMSO was added as a polymerization solvent. Then the mouth of the ampoule was sealed with plastic wrap to prevent volatilization and pollution. The ampoule was positioned in a magnetic stirrer and the content was polymerized at room temperature under irradiation with near-infrared LED light (66.3 mW.Math.cm.sup.−2) having a center wavelength of 730 nm for 24 h. After the polymerization reaction, the reaction mixture was taken out and dissolved in THF (2.0 mL), and then anhydrous diethyl ether (180 mL) was added for precipitation. The polymer product was collected by filtration and dried to a constant weight at 30° C. under vacuum. The reaction results are shown in Table 2.

TABLE-US-00002 TABLE 2 RAFT polymerization under near-infrared light of 730 nm in the air Conv. (%).sup.b M.sub.n, th.sup.c(g .Math. mol.sup.−1) M.sub.n, GPC(g .Math. mol.sup.−1) M.sub.w/M.sub.n 80.5 8000 7800 1.30

[0076] The polymer obtained by the above polymerization is designated as P(PEGA-co-DMAEA). The polymer has good water solubility. To verify that the vinyl zinc phthalocyanine monomer ZnTAPc-Am was successfully polymerized and the catalyst molecules were retained and immobilized in a small amount of polymer chains, the obtained polymer was more rigorously purified. The prepared P(PEGA-co-DMAEA) polymerization reaction solution was dialyzed in an aqueous solution for 48 h, and then centrifuged to collect the upper liquid, which was freeze-dried to obtain the purified polymer P(PEGA-co-DMAEA). Through this process, the ZnTAPc-Am catalyst monomer that has not been polymerized into the polymer chain was removed. In the polymer P(PEGA-co-DMAEA), the organic amine cocatalyst was also immobilized and retained. Similarly, the purified polymer was characterized by ultraviolet-visible absorption spectroscopy. As shown in FIG. 6, Obvious absorption appears around 700 nm, confirming the existence of zinc phthalocyanine dye structure.

[0077] To verify that P(PEGA-co-DMAEA) has reusable catalytic performance and polymerization activity, P(PEGA-co-DMAEA) was used as a macromolecular chain transfer reagent in a living chain extension experiment to prepare a block polymer. During the process, no zinc phthalocyanine dye and organic amine cocatalyst were added again. The reaction steps were as follows.

[0078] NiPAAm or PEGA was used as the polymerization monomer for the second polymerization reaction. P(PEGA-co-DMAEA) and the polymerization monomer was dissolved in a solvent, and the polymerization reaction was carried out in a sealed tube in the air at room temperature under near-infrared light for a certain period of time. The solution was removed and precipitated with diethyl ether to obtain a polymer. The results are shown in Table 3. As shown in Table 3, P(PEGA-co-DMAEA) can be used to synthesize a block copolymer in DMSO or water solvent, confirming the secondary catalytic effect of the zinc phthalocyanine dye catalyst.

TABLE-US-00003 TABLE 3 Chain extension and polymerization of different monomers using P(PEGA-co-DMAEA) as macromolecular chain transfer reagent M.sub.n, GPC Molar Solvent Time (g .Math. No. ratio Monomer (mL) (h) mol.sup.−1) M.sub.w/M.sub.n 1 110/1  NiPAAm DMSO (0.40) 1.0 28100 1.60 2 25/1 PEGA DMSO (0.40) 2.0 26200 1.58 3 25/1 PEGA H.sub.2O (0.40) 2.0 19200 1.44
.sup.aPolymerization conditions: Molar ratio=[polymerizable monomer].sub.0/[P(PEGA-co-DMAEA)].sub.0, and polymerization under near-infrared LED light source (λ.sub.max=730 nm, 66.3 mW.Math.cm.sup.−2) in the air at 25° C. m.sub.P(PEGA-co-DMAEA)=0.17 g, P(PEGA-co-DMAEA) (M.sub.n,GPC=7800 g.Math.mol.sup.−1, M.sub.w/M.sub.n=1.30).

[0079] The block copolymer P(PEGA-co-DMAEA)-b-PPEGA obtained in the experimental group No. 3 in Table 3 was used as a macromolecular chain transfer reagent, and PEGA was used as the polymerization monomer for the third polymerization reaction. Following the same process, the chain extension and polymerization was performed again to verify the tertiary catalytic effect of the zinc phthalocyanine dye catalyst. The reaction conditions are shown in Table 4. A triblock polymer is also obtained in the reaction. The elution curves by GPC of the polymerization products P(PEGA-co-DMAEA), P(PEGA-co-DMAEA)-b-PPEGA, and P(PEGA-co-DMAEA)-b-PPEGA-b-PPEGA obtained by using the zinc phthalocyanine dye in the first and following cyclic catalysis are shown in FIG. 7.

TABLE-US-00004 TABLE 4 Chain extension and polymerization using P(PEGA-co-DMAEA)- b-PPEGA as macromolecular chain transfer reagent Molar ratio Solvent (mL) Time (h) M.sub.n, GPC (g .Math. mol.sup.−1) M.sub.w/M.sub.n 20/1 H.sub.2O (0.40) 12 23800 1.44

[0080] .sup.aPolymerization conditions: Molar ratio=[PEGA].sub.0/[P(PEGA-co-DMAEA)-b-PPEGA].sub.0, polymerization under near-infrared LED light source (λ.sub.max=730 nm, 66.3 mW.Math.cm.sup.−2) in the air at 25° C., V.sub.PEGA=0.10 mL, P(PEGA-co-DMAEA)-b-PPEGA (M.sub.n,GPC=19200 g.Math.mol.sup.−1, M.sub.w/M.sub.n=1.44).

[0081] In the present invention, the polymerization monomer used may also be other methacrylate monomers than those in the above examples, and the same results and conclusions can be obtained by using the same polymerization method.

[0082] In summary, a new polymerizable zinc phthalocyanine dye structure of the present invention is used as a near-infrared photocatalyst to realize the near-infrared light-controlled polymerization of (meth)acrylate monomers and (meth)acrylamide monomers by direct polymerization in the air without oxygen removal. As a result, a variety of polymer structures with a controllable molecular weight and a molecular weight distribution of 1.07-1.5 are obtained. In the present invention, a near-infrared light-responsive functional zinc phthalocyanine dye is used as a near-infrared photocatalyst for the polymerization reaction, with which polymers of a variety of structures can be directly prepared in the air without oxygen removal. The polymerization process has the characteristics of “living” radical polymerization. At the same time, the polymerizable zinc phthalocyanine dye remains on the polymer chain by polymerization, thereby realizing the cyclic utilization of the near-infrared photocatalyst.

[0083] While preferred embodiments of the present invention have been described above, the present invention is not limited thereto. It should be appreciated that some improvements and variations can be made by those skilled in the art without departing from the technical principles of the present invention, which are also contemplated to be within the scope of the present invention.