Terpolymers containing bicyclo[1.1.1]pentane and their use as optical resins

Abstract

The application discloses a terpolymer containing bicyclo[1.1.1]pentane and an optical resin use thereof. The structure of the terpolymer is shown in formula I, wherein R1 and R2 form a ring or are independent of each other, at least one of R1 and R2 contains an electron-withdrawing group, R3 is a hydrogen atom, an alkyl group or a hydroxyalkyl group, R4 is an electron-withdrawing group and contains a sulfur element, and x and y represent polymerization degrees. The alternating copolymer containing the bicyclo[1.1.1]pentane structure in the main chain is obtained by copolymerizing [1.1.1]spiropropyl with two electron-deficient olefin monomers, the 'head-head' structure is eliminated, and the thermal stability is significantly improved; the copolymer has a relatively high refractive index and Abbe number, good transparency, and the glass transition temperature can be adjusted by changing the structure of the olefin monomer and the relative proportion of the two olefin monomers, and is a good transparent optical resin material.

Description

Technical Field

[0001] This invention relates to optical resins and their preparation methods, specifically to a terpolymer containing bicyclic [1.1.1]pentane prepared by copolymerization reaction. This terpolymer can be used as an optical resin and belongs to the field of polymer chemistry and physics. Background Technology

[0002] Polymethyl methacrylate (PMMA), commonly known as plexiglass, is a commercially available optical resin with good transparency in the visible light region. However, PMMA prepared by ordinary free radical polymerization often exhibits poor thermal stability due to its low dissociation energy "head-to-head" structure [Kashiwagi, T. et al. Macromolecules 1986, 19, 2160-2168.], and also has a low refractive index. Preparing polymer blends or adding nanoparticles can improve the thermal stability of PMMA to some extent, but these methods can lead to problems such as poor polymer compatibility and nanoparticle agglomeration [Parameswaranpillai, J. et al. J. Appl. Polym. Sci. 2016, 133, 43628.]. Introducing aliphatic rings (such as adamantane) into the polymer side groups is also an effective strategy to improve polymer thermal stability, but this method has very limited effect on improving thermal stability [Zhong, F. et al. Colloid Surface A 2019, 578, 123594.]. Introducing sulfur-containing groups into the side groups of PMMA can improve the refractive index, but it significantly reduces the Abbe number [Do, JY et al. React. Funct. Polym. 2015, 91-92, 28-34.]. Polymers with bridged ring structures in the main chain synthesized via thiol-ene reaction have good thermal stability and optical properties, but highly toxic monomers are used in their synthesis [Ueda, M. et al. Macromolecules 2012, 45, 3402-3408.]. Therefore, these methods are difficult to apply in practice. Summary of the Invention

[0003] The present invention aims to efficiently and controllably prepare transparent optical resins with good thermal stability, high refractive index and Abbe number using readily available raw materials.

[0004] In a first aspect of the invention, a polymer containing a bicyclic [1.1.1]pentane structure is provided, the structure of which is shown in Formula I below:

[0005]

[0006] In Formula I, R1 and R2 can be cyclic or independent, and at least one of R1 and R2 is an electron-withdrawing group (e.g., ester group); R3 is a hydrogen atom, alkyl or hydroxyalkyl, and R4 is an electron-withdrawing group (e.g., ester group) and contains sulfur; x and y represent the degree of polymerization, and x / y represents the ratio of two different structural units in the copolymer.

[0007] Preferably, when R1 and R2 are independent, R1 can be a hydrogen atom, an alkyl group, or a hydroxyalkyl group, preferably a hydrogen atom, a C1-C6 alkyl group, or a C1-C6 hydroxyalkyl group; R2 is an electron-withdrawing group, typically an ester group, an acyl group, a sulfone group, or a cyano group, for example: ester group -COOR, acyl group -C(=O)-R, sulfone group -S(=O)2-R, wherein R is preferably a C1-C6 alkyl group or a phenyl group.

[0008] When R1 and R2 form a ring, they can be selected from one of the following groups (the wavy line represents the connecting bond):

[0009]

[0010] R3 is selected from hydrogen atoms, C1-C6 alkyl groups, and C1-C6 hydroxyalkyl groups, such as methyl, ethyl, hydroxymethyl, and hydroxyethyl.

[0011] Preferably, R4 can be selected from one of the following groups: -COO-(CH2) m -SC n H 2n+1 -COO-(CH2) m -S(=O)2-C n H 2n+1 -S(=O)2-C n H 2n+1 -S(=O)2-Ph, where m and n are each independent integers from 1 to 6, and Ph is a phenyl group; or one of the following groups:

[0012]

[0013] Preferably, x / y is 0.1 to 10.

[0014] In a second aspect of the invention, a method is provided for the ternary copolymerization of [1.1.1]spiroalkyl with two electron-deficient alkene monomers to form the polymer shown in Formula I above, as follows:

[0015]

[0016] As mentioned above, R1, R2, R3, and R4 are different from monomer 1 and monomer 2.

[0017] Monomer 1 can be selected from one of the following compounds, whose basic characteristic is the presence of an electron-deficient double bond:

[0018]

[0019] Monomer 2 can be selected from one of the following compounds, whose basic characteristics are the presence of an electron-deficient double bond and sulfur:

[0020]

[0021] Two electron-deficient olefin monomers are copolymerized with [1.1.1]spiroalkyl, and the polymerization reaction is stopped when all three monomers are present in excess, resulting in a terpolymer with an alternating structure. Generally, the polymerization reaction does not require an initiator, the polymerization temperature range is 20–40°C, preferably 35°C, and the polymerization time is 6–24 hours. If monomer 1 is an acyclic monomer, the polymerization time is preferably 7 hours; if monomer 1 is a cyclic monomer, the polymerization time is preferably 24 hours.

[0022] In a third aspect of the present invention, based on the good thermal stability, high refractive index and Abbe number of the polymer of Formula I, the polymer of Formula I, as a transparent optical resin material, can be used in the manufacture of lenses, camera lenses, lenses, prisms, waveguides, diffraction gratings, touch screens, displays and so on.

[0023] Compared with the prior art, the present invention has the following technical advantages:

[0024] 1. By copolymerizing [1.1.1]spiroline with two olefin monomers, an alternating copolymer with a bicyclic [1.1.1]pentane structure in the main chain was obtained, which eliminated the "head-to-head" structure and significantly improved the thermal stability of the polymer.

[0025] 2. Two different olefin monomers were copolymerized with [1.1.1] propeller alkane to obtain two amorphous polymers with random repeating unit sequences. The copolymers have good transparency, and the glass transition temperature can be adjusted by changing the structure of the olefin monomers and the relative ratio of the two olefin monomers.

[0026] 3. By using olefin monomers containing heavy elements (such as sulfur), polymers with higher refractive indices were obtained while maintaining a high Abbe number. Detailed Implementation

[0027] The preparation process of the optical resin of the present invention is described in detail below through examples, but this does not limit the scope of the present invention in any way.

[0028] For ease of description, in this invention, [1.1.1]propellane is abbreviated as P, methyl methacrylate as M, ethyl 2-(methylthio)acrylate as A, the cyclic allyl sulfide monomer 6-methylene-1,4-oxathiophene-7-one as B, bicyclo[1.1.1]pentane as BCP, and 4-(dimethylamino)pyridine p-toluenesulfonate as DPTS. M is used respectively... a A b P and B a A b P is used to identify terpolymers. The subscripts a and b in the polymer name represent the feed equivalents of olefin monomers when synthesizing the polymer (with monomer P being 1 equivalent).

[0029] Example 1: Preparation of monomer A

[0030]

[0031] A 250 mL round-bottom flask equipped with a magnetic stir bar was connected to a vacuum line and evacuated and purged with nitrogen three times. 5 mL of 2-(methylthio)ethanol (57.5 mmol, 1 equiv), 9.7 mL of triethylamine (69 mmol, 1.2 equiv), and 60 mL of dichloromethane (DCM) were added. The reaction flask was placed in an ice-water bath, and 4.7 mL of acryloyl chloride (57.5 mmol, 1 equiv) was added. The ice-water bath was removed, and the reaction was allowed to proceed at room temperature for 2 hours. After adding saturated sodium chloride solution, the mixture was separated; the aqueous phase was extracted with dichloromethane. The combined organic phases were dried over anhydrous Na₂SO₄. The solvent was removed by rotary evaporation, and the mixture was separated by column chromatography (petroleum ether / ethyl acetate = 19 / 1, v / v) to give 7.48 g of product (89% yield). 1 H NMR (400MHz, CDCl3, δ): 6.42 (dd, J=17.3, 1.4Hz, 1H), 6.12 (dd, J=17.3, 10.4Hz, 1H), 5 .84(dd,J=10.5,1.4Hz,1H),4.32(t,J=6.9Hz,2H),2.76(t,J=6.9Hz,2H),2.16(s,3H).

[0032] Example 2: Preparation of monomer B

[0033]

[0034] A 250 mL round-bottom flask equipped with a magnetic stir bar was connected to a vacuum line and evacuated and purged with nitrogen three times. 5 mL of 2-mercaptoethanol (72 mmol, 1 equiv), 10 mL of triethylamine (72 mmol, 1 equiv), and 70 mL of dichloromethane were added. 10 mL of ethyl 2-(bromomethyl)acrylate (72 mmol, 1 equiv) was added dropwise with stirring, and the reaction was allowed to proceed for 20 minutes. After adding water, the mixture was separated, and the aqueous phase was extracted with dichloromethane. The combined organic phases were dried over anhydrous Na₂SO₄, and the solvent was removed by rotary evaporation. The crude product was dissolved in 20 mL of methanol and transferred to a 250 mL round-bottom flask, where a magnetic stir bar was added. 3.2 g of sodium hydroxide (79.2 mmol, 1.1 equiv) was dissolved in 100 mL of water and added to the reaction flask with stirring. The reaction solution was acidified with hydrochloric acid to pH 2 and extracted with ethyl acetate. After drying the organic phase over anhydrous Na₂SO₄, the solvent was removed by rotary evaporation to obtain the crude hydroxy acid product. Weigh 6.2 g of EDC·HCl (32.1 mmol, 1.3 equiv) and 1.5 g of 4-(dimethylamino)pyridine p-toluenesulfonate (DPTS) (4.9 mmol, 0.2 equiv) into a 500 mL round-bottom flask, dissolve them in 100 mL of dichlorohexane, and add a magnetic stir bar. Dissolve 4 g of hydroxy acid (24.7 mmol, 1 equiv) in 50 mL of dichloromethane and add it dropwise to the reaction flask over 12 hours. After adding saturated sodium chloride solution, separate the layers; extract the aqueous phase with dichloromethane. Combine the organic phases, dry them with anhydrous Na₂SO₄, and remove the solvent by rotary evaporation. Separate by column chromatography (petroleum ether / ethyl acetate = 3 / 1, v / v) to give 2.08 g of product (overall yield of 58% for the three steps). 1 H NMR (400MHz, CDCl3, δ): 5.79 (s, 1H), 5.55 (d, J = 1.2Hz, 1H), 4.49–4.39 (m, 2H), 3.37–3.25 (m, 2H), 2.98–2.84 (m, 2H).

[0035] Example 3, terpolymer M 0.75 A 2.25 Synthesis of P

[0036]

[0037] Weigh 1.02 g of monomer A (6.975 mmol, 2.25 equiv) into a 25 mL Shrek tube equipped with a magnetic magnet. Connect the tube to a vacuum line and repeat the vacuum-nitrogen purging process three times. Under nitrogen protection, add 5 mL of [1.1.1] propeller alkyl ether solution (0.62 mol / L, 3.1 mmol, 1 equiv) and 247 μL of methyl methacrylate (M) (2.325 mmol, 0.75 equiv). Place the Shrek tube in an oil bath at 35 °C for polymerization for 7 hours. Add methanol dropwise to the reaction solution, centrifuge, discard the supernatant, dissolve the polymer in chloroform, add methanol dropwise to precipitate, and repeat the dissolution-precipitation process twice. Place the obtained polymer in a vacuum oven at 50 °C to remove residual solvent, obtaining M. 0.75 A 2.25 P is a white solid, 641 mg (yield 44%, not considering monomer conversion, yield calculated based on 100% conversion of all monomers). The proportion of different structural units in the polymer can be obtained by integrating the peak areas in the 1H NMR spectrum. The sum of the number of structural units derived from the two olefin monomers equals the number of structural units derived from [1.1.1]spiroalkyl, indicating that the terpolymer is composed of two alternating repeating units. By changing the feed amounts of monomers A and M, while keeping other conditions the same, different compositions of M were obtained. a A b P. Increasing the relative feed ratio of monomer M (increasing a / b) can yield a terpolymer with a higher content of methyl methacrylate structural units (larger x / y).

[0038] The thermal stability of the terpolymers was characterized using thermogravimetric analysis (TGA). All terpolymers exhibited good thermal stability, with 5% thermogravimetric temperatures ranging from 350 to 360 °C, significantly higher than PMMA (144 °C). All terpolymers were amorphous polymers; only a glass transition was observed in differential scanning calorimetry (DSC). Polymers containing a higher proportion of methyl methacrylate structural units exhibited higher glass transition temperatures. The amorphous terpolymers all possessed good transparency; UV-Vis absorption and transmission spectroscopy revealed no absorption peaks in the UV-Vis range, and a transmittance exceeding 91% at 550 nm. The refractive index and Abbe number of the terpolymers were measured using elliptic polarization spectroscopy. The refractive index of the sulfur-containing terpolymers was higher than that of PMMA. The sulfur content of the polymer depends on the relative proportions of the structural units corresponding to the two olefin monomers; incorporating more monomer A increases the sulfur content in the copolymer, resulting in a higher refractive index. Polymer M 2.25 A 0.75 P has a refractive index of 1.519 and an Abbe number of 51.9 at 589.3 nm; while M, with a higher sulfur content, has a higher refractive index of 1.519 and an Abbe number of 51.9. 0.75 A 2.25The refractive index of P is 1.534, and the Abbe number decreases to 41.1.

[0039] Example 4: Synthesis of terpolymer B1A2P

[0040]

[0041] Weigh 0.34 g of monomer A (2.4 mmol, 2 equiv) into a 10 mL Shrek tube equipped with a magnetic flux, and repeat the vacuum-nitrogen purging process three times. Weigh 0.18 g of monomer B (1.2 mmol, 1 equiv) into a vial, dissolve it in 2 mL of [1.1.1] propeller alkyl ether solution (0.6 mol / L, 1.2 mmol, 1 equiv), and add it to the Shrek tube. Place the Shrek tube in an oil bath at 35 °C for polymerization for 24 hours. Add methanol to the reaction solution, centrifuge, discard the supernatant, dissolve the polymer in chloroform, add methanol to precipitate, and repeat the dissolution-precipitation process twice. Place the obtained polymer in a vacuum oven at 50 °C to remove residual solvent, and obtain 255 mg of white solid B1A2P (yield 43%, monomer conversion not considered, yield calculated based on 100% conversion of all monomers). The proportion of different structural units in the polymer can be obtained by the peak area integration ratio in the proton NMR spectrum. The sum of the number of structural units derived from the two olefin monomers equals the number of structural units derived from [1.1.1]spiroalkyl, indicating that the terpolymer is composed of two alternating repeating units. Changing the feed amounts of monomers B and A, while keeping other conditions the same, yields B with different compositions. a A b P. Increasing the relative feed ratio of monomer B (increasing a / b) can yield terpolymers with a higher content of cyclic side groups.

[0042] The thermal stability of the terpolymers was characterized by thermogravimetric analysis (TGA). All terpolymers exhibited good thermal stability, with 5% thermogravimetric temperatures around 340°C, significantly higher than PMMA (144°C). All terpolymers were amorphous polymers; only glass transition was observed in differential scanning calorimetry (DSC). Increasing the incorporation ratio of monomer B increased the content of cyclic side groups, resulting in polymers with higher glass transition temperatures. Due to the presence of rigid lactone ring structures in the side groups, B... a A b P-series terpolymers compared to M a A bP-series terpolymers exhibit higher glass transition temperatures. The amorphous terpolymers all possess good transparency; UV-Vis absorption and transmission spectroscopy reveals no absorption peaks in the visible light band, and they exhibit transmittance exceeding 98% at 550 nm. The refractive index and Abbe number of the terpolymers were measured using elliptic polarization spectroscopy. The refractive index of sulfur-containing terpolymers is higher than that of PMMA. Due to the similar chemical compositions of monomers B and A, the terpolymers have a fixed sulfur content (15.2 wt%). Therefore, when the relative proportions of the structural units corresponding to the two olefin monomers change, the refractive index of the polymer remains essentially unchanged, around 1.55, higher than that of PMMA with lower sulfur content. a A b P series.

[0043] Table 1 Copolymer M a A b P and B a A b Thermal and optical properties of P

[0044]

[0045] a Tetrahydrofuran phase GPC determination; b x / y is the ratio of the two repeating units in the terpolymer, derived from... 1 The integral ratio of H NMR is obtained; c TGA assay, T d,5％ The temperature at which the sample mass loss is 5%; d T was measured by DSC. g This refers to the glass transition temperature during the second heating process. e Transmittance of the polymer film at 550 nm; f n was determined by elliptic polarization spectrometer D n F n C ν represents the refractive index of the polymer film at 589.3 nm, 486.1 nm, and 656.3 nm, respectively. D The Abbe number of the polymer film is given by the formula ν. D =(n D -1) / (n F -n C ) was calculated.

Claims

1. The polymer shown in Formula I: In Formula I, R1 and R2 are either cyclic or independent, and at least one of R1 and R2 is an electron-withdrawing group selected from ester, acyl, sulfone, and cyano groups; R3 is a hydrogen atom, alkyl, or hydroxyalkyl, and R4 is selected from one of the following groups: -COO-(CH2). m -SC n H 2n+1 -COO-(CH2) m -S(=O)2-C n H 2n+1 -S(=O)2-C n H 2n+1 , -S(=O)2-Ph, where m and n are each independent integers from 1 to 6, and Ph is a benzene ring; or, R4 is selected from one of the following groups: x and y represent the degree of aggregation.

2. The polymer of Formula I as described in claim 1, characterized in that, When R1 and R2 are independent, R1 is a hydrogen atom, an alkyl group, or a hydroxyalkyl group, and R2 contains an electron-withdrawing group selected from ester, acyl, sulfone, and cyano groups; when R1 and R2 form a ring, the group is selected from one of the following groups: 。 3. The polymer of formula I as described in claim 1, characterized in that, x / y ranges from 0.1 to 10.

4. The polymer of formula I as described in claim 1, characterized in that, Selected from one of the following polymers: 。 5. The method for preparing the polymer of Formula I according to claim 1, wherein the polymer is synthesized by ternary copolymerization of [1.1.1]spiroalkyl with two electron-deficient alkene monomers, as shown below: in, R1, R2, R3, and R4 are as described in claim 1, wherein monomer 1 and monomer 2 are not the same.

6. The preparation method according to claim 5, characterized in that, Monomer 1 is selected from one of the following compounds: 。 7. The preparation method according to claim 5, characterized in that, Monomer 2 is selected from one of the following compounds: 。 8. The preparation method according to claim 5, characterized in that, [1.1.1] The polymerization reaction of propane with the two monomers does not require an initiator. The polymerization temperature is 20~40℃ and the polymerization time is 6~24 hours.

9. Use of the polymer of Formula I as described in any one of claims 1 to 4 as an optical resin.

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