Method for preparing a main-chain acetal-functionalized copolymer

Abstract

The present invention discloses a method for preparing a main-chain acetal-functionalized copolymer. Under an inert atmosphere, an aromatic dialdehyde compound and an epoxide are added to a three-component metal-free catalytic / initiating system for reaction to obtain a main-chain acetal-functionalized copolymer. The three-component metal-free catalytic / initiating system includes: a compound containing active hydrogen, an organic base, and an alkyl borane. The present invention discovers for the first time the ring-opening - ring-closing copolymerization reaction of an aromatic dialdehyde compound and an epoxide, and a main-chain acetal-functionalized copolymer with controllable structure can be prepared at room temperature. Meanwhile, the copolymer has a degradation behavior in dilute acid, which lays a foundation for the application of the main-chain acetal-functionalized copolymer in the field of degradable materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer synthesis, and particularly relates to a method for preparing a main-chain acetal-functionalized copolymer. Background Art

[0002] Acetals are an important class of organic groups, which are stable under alkaline conditions and can be hydrolyzed to aldehydes and alcohols under dilute acid conditions. This property makes polymers with acetal groups in the main chain become an important class of degradable polymers and find applications in many fields such as biomedicine. For example, acetal-functionalized polyethylene oxides loaded with drugs in the main chain or side chain can degrade when releasing drugs in the body, avoiding the accumulation of high-molecular-weight polymers in the kidneys and being unable to be metabolized.

[0003] The main synthesis methods of main-chain acetalized polymers are as follows:

[0004] 1. Chain addition homopolymerization of aldehyde compounds, chain addition copolymerization between aldehyde compounds, and chain addition copolymerization between aldehyde compounds and different monomers. Through anionic polymerization, cationic polymerization, coordination polymerization and other methods, chain addition homo / copolymerization of aldehyde compounds such as formaldehyde, C2-C aliphatic monoaldehydes, C4-C8 aliphatic dialdehydes, polyhaloacetaldehydes, glyoxylate esters, aromatic dialdehydes, etc. can be carried out to prepare polyacetals. In addition, polyacetals can also be obtained by cationic addition copolymerization of aldehyde compounds and vinyl ethers, and the obtained copolymers can be degraded to obtain small-molecule aldehydes with double bonds. Since aldehyde compounds generally have a low ceiling temperature of polymerization, the addition homo / copolymerization of most aldehyde compounds can only be carried out at low temperatures. 10 2. Chain addition homopolymerization of cyclic acetal compounds and chain addition copolymerization between cyclic acetal compounds and different monomers. For example: under the catalysis of strong Lewis acids, homo / copolymerization of cyclic acetal compounds such as trioxane, 1,3-dioxolane, 1,3-dioxepane, etc. can be carried out to prepare polyacetals. In addition, the above cyclic acetal compounds can also be copolymerized with epoxides such as ethylene oxide, epichlorohydrin, ethylene glycol diglycidyl ether, etc.

[0005] 3. Stepwise polycondensation of dialdehyde compounds and tetraols. The two compounds can undergo a condensation reaction under the catalysis of an acid to form a polymer with a main chain composed of cyclic acetals. Among them, the dialdehyde compounds include C2-C8 aliphatic dialdehydes, aromatic dialdehyde compounds, cyclohexanedimethanol, etc., and the tetraols include pentaerythritol, bis(trimethylol)propane, erythritol, etc. The cyclic rigid structure gives the polymer relatively high thermal stability.

[0006] 4. Stepwise polyaddition of alcohols and vinyl ethers. The earliest reported was in

[0007] 5. Under the catalysis of an acid, an equimolar polyaddition reaction occurs between a dihydroxy compound and a divinyl ether compound. The dihydroxy compounds include 1,4-cyclohexanedimethanol and bisphenol A, and the divinyl ether compounds include 1,4-butanediol vinyl ether and diethylene glycol divinyl ether. Subsequently, it was reported that hydroxy-vinyl ether difunctional compounds such as 4-hydroxybutyl vinyl ether can undergo self-polyaddition reactions. Compared with the stepwise polycondensation of aldehydes and alcohols, such reactions do not produce small molecule by-products. The main chain acetal-functionalized polyethers can be prepared by this method.

[0008] In addition, the synthetic methods of the main chain acetalized polymers also include acetal exchange reactions involving diacetal monomers, stepwise polymerization involving diols or diamines with acetal groups in the molecular skeleton, olefin metathesis reactions of dienes with acetal groups in the molecular skeleton, ring-opening polymerization of cyclic esters with acetal groups in the molecular skeleton, and ring-opening homo- / co-polymerization of epoxides initiated by paraformaldehyde diol, etc.

[0009] Among the main synthetic methods of the above-mentioned main chain acetal-functionalized copolymers, many proceed through cationic reaction pathways, require the catalysis of strong acids, and have an adverse impact on the reaction equipment. At the same time, due to the nature of cationic polymerization, chain transfer is inevitable, making it impossible to achieve controlled synthesis of the main chain acetal-functionalized copolymers.

[0010] In addition, as a compound with a wide source and low price, epoxides can be used to obtain polyethers through homopolymerization, or to prepare polyesters, polycarbonates, polythiocarbonates, etc. through copolymerization with cyclic anhydrides, CO2, COS, CS2, etc. However, up to now, epoxides have never been used for copolymerization with aldehyde compounds. Therefore, finding a suitable catalytic system to implement the copolymerization of aldehyde compounds and epoxides is of great significance for enriching the structure and properties of the main chain acetalized polymers. Summary of the Invention

[0011] To solve the drawbacks and deficiencies of the prior art, the purpose of the present invention is to provide a method for preparing a main chain acetal-functionalized copolymer.

[0012] The present invention uses a compound containing an active hydrogen group and a metal-free Lewis acid-base pair to construct a catalytic / initiating system, and implements ring-opening - ring-closing copolymerization of aromatic dialdehyde compounds and epoxides to synthesize a main chain acetal-functionalized copolymer.

[0013] The purpose of the present invention is achieved through the following technical solutions:

[0014] A method for preparing a main chain acetal-functionalized copolymer, comprising the following steps:

[0015] Under a nitrogen or inert atmosphere, an aromatic dialdehyde compound and an epoxide are added to a three-component metal-free catalytic / initiating system, and a polymerization reaction is carried out at -20 to 80 °C for 0.1 to 120 h to obtain a main-chain acetal-functionalized copolymer;

[0016] The three-component metal-free catalytic / initiating system consists of a hydrogen-containing active compound, an organic base, and an alkyl boron;

[0017] The molar ratio of the aromatic dialdehyde compound, the epoxide, the hydrogen-containing active compound, and the organic base is (1 to 1000):(20 to 5000):1:(0.01 to 10), and the molar ratio of the organic base to the alkyl boron is 1:(1 to 30).

[0018] Preferably, the aromatic dialdehyde compound is at least one of (1) phthalaldehyde, (2) polysubstituted phthalaldehyde, (3) 2-alkyl-5,6-dialdehyde-isoindoline-1,3-dione with 1 to 10 carbon atoms in the alkyl group, (4) 2-formylphenylacetaldehyde, (5) naphthalene-2,3-dicarbaldehyde, and (6) thiophene-2,3-dicarbaldehyde. The specific structural formulas are as follows:

[0019]

[0020] Among them, X 1 ~X 4 are the same or different and are the following groups, but X 1 ~X 4 cannot be H at the same time: *-H *-F *-Cl *-Br *-I *-CF3 *-CCl3 *-CBr3 *-Cl3 *-C≡N

[0021] More preferably, the aromatic dialdehyde compound is at least one of phthalaldehyde, 4,5-dichlorophthalaldehyde, 2-hexyl-5,6-dialdehyde-isoindoline-1,3-dione, and thiophene-2,3-dicarbaldehyde.

[0022] Preferably, the epoxide is at least one of (1) ethylene oxide, (2) straight-chain alkyl ethylene oxide with 1 to 20 carbon atoms in the alkyl group, (3) straight-chain alkyl glycidyl ether with 1 to 16 carbon atoms in the alkyl group, (4) isopropyl glycidyl ether, (5) tert-butyl glycidyl ether, (6) 2-ethylhexyl glycidyl ether, (7) phenyl glycidyl ether, (8) benzyl glycidyl ether, (9) 2-biphenyl glycidyl ether, (10) allyl glycidyl ether, (11) propargyl glycidyl ether, (12) straight-chain alkyl carboxylic acid glycidyl ester with 1 to 16 carbon atoms in the alkyl group, and (13) glycidyl methacrylate. The specific structural formulas are as follows:

[0023]

[0024] More preferably, the epoxide is at least one of ethylene oxide, propylene oxide, butylene oxide, n-butyl glycidyl ether, and 2-biphenyl glycidyl ether.

[0025] Preferably, the active hydrogen-containing compound is water and / or an organic compound containing at least one of the following groups: primary amino group, secondary amino group, hydroxyl group, mercapto group, carboxyl group, thiocarboxyl group, amide group, ureido group, carbamate group, sulfonic acid, phosphoric acid, terminal acetylenic hydrogen.

[0026] More preferably, the active hydrogen-containing compound is at least one of water, p-xylene glycol, benzoic acid, N-ethyl propionamide, and pentaerythritol.

[0027] Preferably, the organic base is at least one of a tertiary amine, an amidine, a guanidine, a triaminophosphine, and a phosphazene base; wherein, the tertiary amine is at least one of 1,4-diazabicyclo[2.2.2]octane (DABCO), pentamethyldiethylenetriamine (PMDETA), tris(2-dimethylaminoethyl)amine (ME6TREN), and (1S,9S)-3,11-diazabicyclo[7.3.1.0 3,8 trideca-5,7-dien-4-one (sparteine); the amidine is at least one of 1,8-diazabicycloundec-7-ene (DBU) and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN); the guanidine is at least one of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,1,3,3-tetramethylguanidine (TMG), and 1,1,2,3,3-pentamethylguanidine (PMG); the triaminophosphine is at least one of tris(dimethylamino)phosphine (HMTP), tris(diethylamino)phosphine (HETP), 2,8,9-trimethyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane (TMAP), and 2,8,9-triisopropyl-2,5,8,9-tetraaza-1-phosphabicyclo[3.3.3]undecane (TIPAP); the phosphazene base is tert-butylimino-tris(dimethylamino)phosphorane ( t BuP1), tert-octylimino-tris(dimethylamino)phosphorane ( t OctP1), tert-butylimino-tris(pyrrolidino)phosphorane (BTPP), 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP), 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2λ 5 ,4λ 5 -bis(phosphazene) ( tBuP2), 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2λ 5 ,4λ 5 -bis(phosphazene)(EtP2), 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylideneamino]-2λ 5 ,4λ 5 -bis(phosphazene)( t BuP4), 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylideneamino]-2λ 5 ,4λ 5 -bis(phosphazene)( t OctP4), or at least one of them. The specific structural formulas are as follows:

[0028]

[0029] More preferably, the organic base is t BuP1, t BuP2, t BuP4, DBU, DBN, MTBD, DABCO, HMTP, or TMAP, or at least one of them.

[0030] Preferably, the alkyl borane is at least one of tri-n-alkyl boranes (A3B) with a straight-chain alkane having 1-8 carbon atoms, tri-sec-butyl borane ( s Bu3B), and triisopropyl borane ( i Bu3B). The specific structural formulas are as follows:

[0031]

[0032] More preferably, the alkyl borane is at least one of triethyl borane, tributyl borane, and triisopropyl borane.

[0033] Preferably, the molar ratio of the aromatic dialdehyde compound, the epoxy compound, the active hydrogen-containing compound, and the organic base is (6 - 400):(40 - 1000):1:(0.05 - 2), and the molar ratio of the organic base to the alkyl borane is 1:(3 - 10).

[0034] Preferably, the polymerization reaction can be carried out in the bulk of the epoxy compound, or in at least one solvent selected from tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, ethyl acetate, cyclopentyl methyl ether, benzene, toluene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,3-dimethylpropylene urea and 1,3-dimethyl-2-imidazolidinone, more preferably in at least one solvent selected from tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, cyclopentyl methyl ether and ethyl acetate.

[0035] Preferably, the concentration of the epoxy compound at the beginning of the polymerization reaction is 1 to 18 mol / L.

[0036] Preferably, the polymerization reaction temperature is 20 to 80° C., and the reaction time is 2 to 72 hours.

[0037] The preparation method of the present invention uses a compound containing an active hydrogen group as an initiator, combines the synergistic catalytic effect of an organic base and an alkyl boron, and oxygen anions attack aromatic dialdehyde compounds to close the ring, and the formed hemiacetal anions combine with epoxy compounds to form a stable intermediate, and then the epoxy compounds open the ring to form alkoxy anions, and the cycle is repeated to achieve a copolymerization reaction of the aromatic dialdehyde compounds and the epoxy compounds at room temperature, and synthesize a main chain acetal functionalized copolymer.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] (1) The present invention is the first to copolymerize aromatic dialdehyde compounds with epoxy compounds to prepare a main chain acetal functionalized copolymer by anionic polymerization. Previously, the comonomers of aromatic dialdehyde compounds were aldehyde compounds or vinyl ether compounds, and the polymerization method was mostly cationic polymerization.

[0040] (2) The polymerization method provided by the present invention can completely convert monomers into polymers at room temperature. The polymerization conditions are mild and the resulting products are stable. This breaks through the limitation that the upper limit polymerization temperature of most aromatic dialdehyde compounds in the existing catalytic initiation system is far below room temperature, and simplifies the operation of synthesizing polymers.

[0041] (3) The present invention provides several new copolymer structures and can flexibly regulate the copolymer microstructure sequence by the monomer feed ratio. For example, when the amount of o-phthalaldehyde and the epoxy compound is equal, a copolymer with an alternating structure is mainly obtained (as shown in Figure A below); when the amount of o-phthalaldehyde is less than that of the epoxy compound, the growth of the ring-opening-closing alternating sequence of o-phthalaldehyde and the epoxy compound is mainly carried out first, and then the epoxy compound is ring-opened and homopolymerized in situ at the end of the copolymer chain, and finally a block copolymer is obtained (as shown in Figure B below).

[0042]

[0043] (4) The catalytic / initiating system composed of the active hydrogen group-containing compound, organic base and alkyl borane in the present invention has universality for the copolymerization of aromatic dialdehyde compounds and epoxides, thus enriching the structure and properties of the main-chain acetal-functionalized copolymers.

[0044] (5) The thermal decomposition temperature of the main-chain acetal-functionalized copolymer prepared in the present invention can reach 200 °C, while the highest thermal decomposition temperature of the corresponding homopolymer of phthalaldehyde is 120 °C. In contrast, the thermal stability of the copolymer has been greatly improved.

[0045] (6) The main-chain acetal-functionalized copolymer prepared in the present invention is stable under alkaline conditions, while it has a degradation behavior under acidic conditions. Among them, for the copolymer synthesized from aromatic dialdehyde compounds and epoxides in equal proportions, it can be completely degraded in dilute acid; while for the copolymer prepared with epoxides in excess of aromatic dialdehyde compounds, it is partially degraded in dilute acid, and finally a polyether with a smaller molecular weight is obtained. This property makes the main-chain acetal-functionalized copolymer promising to be applied in degradable materials. Description of the Drawings

[0046] Figure 1 SEC curve (left) and 1 H NMR spectrum (right) of the main-chain acetal-functionalized copolymer (OPAPO) prepared by ring-opening and ring-closing copolymerization of phthalaldehyde and propylene oxide in Example 1 of the present invention.

[0047] Figure 2 MALDI-ToF MS spectrum of the main-chain acetal-functionalized copolymer (OPAPO) prepared by ring-opening and ring-closing copolymerization of phthalaldehyde and propylene oxide in Example 1 of the present invention.

[0048] Figure 3 SEC curve (left) and 1 H NMR spectrum (right) of the main-chain acetal-functionalized polyether (PO-co-OPA) prepared by ring-opening and ring-closing copolymerization of phthalaldehyde and propylene oxide in Example 4 of the present invention.

[0049] Figure 4 MALDI-ToF MS spectrum of the main-chain acetal-functionalized polyether (PO-co-OPA) prepared by ring-opening and ring-closing copolymerization of phthalaldehyde and propylene oxide in Example 4 of the present invention.

[0050] Figure 5 SEC curve (left) and 1 H NMR spectrum (right) of the main-chain acetal-functionalized copolymer (EO-co-OPA) prepared by ring-opening and ring-closing copolymerization of phthalaldehyde and ethylene oxide in Example 7 of the present invention.

[0051] Figure 6 This is the MALDI-ToF MS spectrum of the main-chain acetal-functionalized copolymer (EO-co-OPA) prepared by the ring-opening and ring-closing copolymerization of phthalaldehyde and ethylene oxide in Example 7 of the present invention. Detailed implementation manners

[0052] The present invention will be further described in detail below with reference to the examples and the drawings, but the implementation manners of the present invention are not limited thereto.

[0053] In the examples of the present invention, those not specified in specific conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. The raw materials, reagents, etc. not specified in the manufacturer are all conventional products that can be obtained by purchasing in the market.

[0054] In the following examples:

[0055] The conversion rate of monomers, the structural characteristics of polymers, etc. are obtained through nuclear magnetic resonance hydrogen spectrum ( 1 1H NMR). The test instrument is a Bruker AV400 liquid nuclear magnetic resonance spectrometer, and the solvent is deuterated chloroform or deuterated dimethyl sulfoxide.

[0056] The relative molecular weight and molecular weight distribution of polymers are obtained through size exclusion chromatography / gel permeation chromatography (SEC / GPC). The test instrument is an Agilent 1260 Infinity gel permeation chromatograph, and the mobile phase is tetrahydrofuran (for polyethylene oxide samples, tetrahydrofuran added with 5% v / v triethylamine is used instead). Two chromatographic columns of the same specification are connected in series, the column temperature is 35 °C, and the flow rate is 1 mL min -1 , and a series of polystyrene or polyethylene oxide standard samples are used to calibrate the calibration curve.

[0057] The complete mass spectrum information of polymers is obtained through matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS). The test instrument is a Bruker Autoflex III Smartbeam MALDI-ToF mass spectrometer, and a poly(methyl methacrylate) standard sample is used for calibration.

[0058] In the following examples, the parts described in the formula are all in mole parts.

[0059] Example 1

[0060] In this example, the ring-opening and ring-closing copolymerization of phthalaldehyde and propylene oxide is carried out with p-xylene glycol and a metal-free Lewis acid-base pair as the catalytic / initiating system to prepare a main-chain acetal-functionalized copolymer.

[0061] In an inert atmosphere, a p - xylyl alcohol / tetrahydrofuran solution (1 part of p - xylyl alcohol, with a concentration of 0.5 mol / L in the solution), 0.2 part of phosphazene base t BuP2 and a triethylborane / tetrahydrofuran solution (0.6 part of triethylborane, with a concentration of 1 mol / L in the solution) were added to a reaction vessel and stirred to mix evenly. Subsequently, an o - phthalaldehyde / tetrahydrofuran solution (40 parts of o - phthalaldehyde, with a concentration of 2 mol / L in the solution) and 40 parts of propylene oxide (the molar concentrations of o - phthalaldehyde and propylene oxide in the system were both 1.6 mol / L) were added successively. The reaction vessel was sealed and stirred at room temperature (20 - 25 °C) for 24 h. The reaction was terminated with acetic acid, the crude product was collected, precipitated in methanol, and dried under vacuum to obtain the product. Samples were taken during the polymerization process for monitoring, 1 The conversion rates of o - phthalaldehyde and propylene oxide were both 100% as measured by 1H NMR. The theoretical number - average molecular weight M n,th was calculated to be 7.7 kg / mol based on the feed ratio and conversion rates of p - xylyl alcohol, o - phthalaldehyde, and propylene oxide. The molecular weight of the crude product was 5.5 kg / mol and the dispersity was 1.16 as measured by SEC.

[0062] SEC and 1 the 1H NMR test results are as Figure 1 shown. In addition, the product was characterized by MALDI - ToF MS, and an alternating structure of o - phthalaldehyde ring - closure and propylene oxide ring - opening in the copolymer was confirmed, and the results are as Figure 2 shown.

[0063] In the existing catalytic system, the ceiling temperature for the polymerization of o - phthalaldehyde is - 43 °C, so the homo - or copolymerization of o - phthalaldehyde can only be carried out at low temperatures. So far, there has never been a literature report on the living polymerization reaction of o - phthalaldehyde at room temperature. In this example, the use of a three - component catalytic / initiating system activates both o - phthalaldehyde and propylene oxide, so the copolymerization reaction can proceed. Thus, based on a three - component metal - free catalytic / initiating system composed of a neutral organic base, triethylborane, and a hydroxy - containing compound, this example provides a method for the efficient and controllable ring - opening - ring - closing copolymerization of o - phthalaldehyde and propylene oxide at room temperature, realizing the preparation of a main - chain acetal - functionalized copolymer.

[0064] Comparative Example 1

[0065] In this comparative example, the amount of alkyl borane was changed to 0.15 part, and the others were the same as in Example 1. After stirring at room temperature for 48 h, no change in the color of the reaction solution was observed. Samples of the mixed solution were taken for analysis, 1 1H NMR showed that the conversion rates of o - phthalaldehyde and propylene oxide were 0, and no polymer peaks appeared in the SEC curve. It indicates that no copolymer was formed at this feed ratio.

[0066] Example 2

[0067] In this example, the neutral organic base was replaced with the amidine organic base DBU, and the others were the same as in Example 1. The reaction was carried out at room temperature (20 - 25 °C) for 72 h. Samples were taken and monitored during the polymerization process. 1 The conversions of phthalaldehyde and propylene oxide were both 100% measured by 1H NMR. The theoretical number-average molecular weight Mn was calculated from the feeding ratios and conversions of terephthalyl alcohol, phthalaldehyde and propylene oxide. n,th It was 7.7 kg / mol. The molecular weight Mw of the crude product measured by SEC n,SEC was 5.0 kg / mol, and the dispersity was 1.18.

[0068] Example 3

[0069] In this example, a main-chain acetal-functionalized copolymer with a large molecular weight was synthesized by adjusting the ratio of the initiator to the monomer. Under an inert atmosphere, an aqueous / tetrahydrofuran solution (1 part of water, with a concentration of 0.5 mol / L in this solution), 2 parts of the guanidine organic base PMG and a triethylborane / tetrahydrofuran solution (6 parts of triethylborane, with a concentration of 1 mol / L in this solution) were added to the reaction vessel and stirred and mixed evenly. Subsequently, a phthalaldehyde / tetrahydrofuran solution (400 parts of phthalaldehyde, with a concentration of 2 mol / L in this solution) and 400 parts of propylene oxide (the molar concentrations of phthalaldehyde and propylene oxide in the system were both 1.6 mol / L) were added in sequence. The reaction vessel was sealed and reacted at room temperature (20 - 25 °C) for 24 h. The reaction was terminated with acetic acid, the crude product was collected, precipitated in methanol, and dried in vacuo to obtain the product. Samples were taken and monitored during the polymerization process. 1 The conversions of phthalaldehyde and propylene oxide were both 100% measured by 1H NMR. The theoretical number-average molecular weight Mn was calculated from the feeding ratios and conversions of water, phthalaldehyde and propylene oxide. n,th It was 76.8 kg / mol. The molecular weight Mw of the crude product measured by SEC n,SEC was 52.4 kg / mol, and the dispersity was 1.22.

[0070] Example 4

[0071] In this example, terephthalyl alcohol and a metal-free Lewis acid-base pair were used as the catalytic / initiating system to carry out the ring-opening / ring-closing copolymerization of phthalaldehyde and propylene oxide to prepare a main-chain acetal-functionalized polypropylene oxide.

[0072] In an inert atmosphere, add a p-xylene glycol / tetrahydrofuran solution (1 part of p-xylene glycol, with a concentration of 0.5 mol / L in this solution), 0.05 part of the guanidine-based organic base MTBD, and a triethylborane / tetrahydrofuran solution (0.15 part of triethylborane, with a concentration of 1 mol / L in this solution) into a reaction vessel, and stir and mix evenly. Subsequently, add an o-phthalaldehyde / 2-methyltetrahydrofuran solution (400 parts of o-phthalaldehyde, with a concentration of 2 mol / L in this solution) and 100 parts of propylene oxide (the molar concentrations of o-phthalaldehyde and propylene oxide in the system are 0.49 mol / L and 8.2 mol / L respectively). Seal the reaction vessel and react at room temperature (20 - 25 °C) for 12 h. Open the reactor, terminate the reaction with acetic acid, collect the crude product, remove the catalyst in the crude product through a neutral alumina adsorption column, remove the solvent, and perform vacuum drying to obtain the product. Sample and monitor the polymerization process, 1 The conversion rates of o-phthalaldehyde and propylene oxide were both 100% measured by 1H NMR. Calculate the theoretical number-average molecular weight Mn n,th to be 6.6 kg / mol based on the feeding ratios and conversion rates of p-xylene glycol, o-phthalaldehyde, and propylene oxide. The molecular weight Mw n,SEC of the crude product measured by SEC was 8.9 kg / mol, and the dispersity was 1.09.

[0073] The SEC and 1 1H NMR test results are as Figure 3 shown. The product was characterized by MALDI-ToF MS, and the results are as Figure 4 shown.

[0074] Example 5

[0075] In this example, the amount of alkyl borane Et3B was changed to 0.5 part, and the others were the same as in Example 4. React at room temperature (20 - 25 °C) for 2 h to obtain the product. Sample and monitor the polymerization process, 1 The conversion rates of o-phthalaldehyde and propylene oxide were both 100% measured by 1H NMR. Calculate the theoretical number-average molecular weight Mn n,th to be 6.6 kg / mol based on the feeding ratios and conversion rates of p-xylene glycol, o-phthalaldehyde, and propylene oxide. The molecular weight Mw n,SEC of the crude product measured by SEC was 9.8 kg / mol, and the dispersity was 1.08.

[0076] Example 6

[0077] In this example, the reaction temperature was adjusted to 80 °C, and the others were the same as in Example 3. After reacting for 72 h, the product was obtained. Sample and monitor the polymerization process, 1The conversions of phthalaldehyde and propylene oxide measured by \(^1H\) NMR were 100% and 59% respectively. The theoretical number-average molecular weight \(M\) was calculated from the feed ratios and conversions of terephthalyl alcohol, phthalaldehyde and propylene oxide. n,th was 4.4 kg / mol. The molecular weight \(M\) measured by SEC n,SEC was 5.1 kg / mol and the dispersity was 1.18.

[0078] Example 7

[0079] In this example, terephthalyl alcohol and a metal-free Lewis acid-base pair were used as the catalytic / initiating system to carry out the ring-opening / ring-closing copolymerization of phthalaldehyde and ethylene oxide to prepare a main-chain acetal-functionalized polyethylene oxide.

[0080] In an inert atmosphere, a solution of terephthalyl alcohol / tetrahydrofuran (1 part of terephthalyl alcohol, with a concentration of 0.5 mol / L in this solution), a solution of triethylamine DABCO / tetrahydrofuran (0.25 part of DABCO, with a concentration of 0.5 mol / L in this solution) and a solution of triethylborane / tetrahydrofuran (0.75 part of triethylborane, with a concentration of 1 mol / L in this solution) were pre-mixed evenly. A solution of phthalaldehyde / 2-methyltetrahydrofuran (6 parts of phthalaldehyde, with a concentration of 2 mol / L in this solution) and an appropriate amount of 2-methyltetrahydrofuran were added to the reaction vessel. Then the reaction vessel was connected to a vacuum line to remove the gas in the bottle, cooled in an ice bath, and 100 parts of dry ethylene oxide were added at -30 to -20 °C. Finally, the pre-mixed catalytic / initiating system reagent was added under an inert gas atmosphere, and then the reaction vessel was sealed and reacted at room temperature for 48 h. In this example, the molar concentrations of phthalaldehyde and ethylene oxide were 0.48 mol / L and 8 mol / L respectively. The reactor was opened, the reaction was terminated with acetic acid, an appropriate amount of solvent was added to dissolve, precipitated in ether, and dried in vacuo to obtain the product. Samples were taken for monitoring during the polymerization process. 1 The conversions of phthalaldehyde and ethylene oxide measured by \(^1H\) NMR were both 100%. The theoretical number-average molecular weight \(M\) was calculated from the feed ratios and conversions of terephthalyl alcohol, phthalaldehyde and ethylene oxide. n,th was 5.2 kg / mol. The molecular weight measured by SEC was \(M\) n,SEC was 6.5 kg / mol and the dispersity was 1.06.

[0081] SEC and 1 the \(^1H\) NMR test results were as Figure 5 shown. The product was characterized by MALDI-ToF MS, and the results were as Figure 6 shown.

[0082] Example 8

[0083] In this example, benzoic acid and metal-free Lewis acid-base pairs were used as the catalytic / initiating system to carry out the ring-opening and ring-closing copolymerization of 4,5-dichlorophthalaldehyde and n-butyl glycidyl ether to prepare a main-chain acetal-functionalized poly(n-butyl glycidyl ether).

[0084] Under an inert atmosphere, 1 part of benzoic acid, 0.75 part of triaminophosphine HMTP, and a triethylborane / tetrahydrofuran solution (3 parts of triethylborane, with a concentration of 1 mol / L in this solution) were added to a reaction vessel and stirred and mixed evenly. Subsequently, a 4,5-dichlorophthalaldehyde / 1,4-dioxane solution (50 parts of 4,5-dichlorophthalaldehyde, with a concentration of 2 mol / L in this solution) and 300 parts of n-butyl glycidyl ether (the molar concentrations of 4,5-dichlorophthalaldehyde and n-butyl glycidyl ether in the system were 0.7 mol / L and 4.2 mol / L, respectively) were added successively. The reaction vessel was sealed and reacted at room temperature (20 - 25 °C) for 48 h. The reaction vessel was opened, the crude product was collected, and the catalyst in the crude product was removed by passing through a neutral alumina adsorption column. After removing the solvent and drying under vacuum, the product was obtained. Samples were taken and monitored during the polymerization process. 1 The conversions of 4,5-dichlorophthalaldehyde and n-butyl glycidyl ether were both 100% as measured by \(^1H\) NMR. The theoretical number-average molecular weight \(M_n\) was calculated based on the feeding ratios and conversions of benzoic acid, 4,5-dichlorophthalaldehyde, and n-butyl glycidyl ether. n,th was 49.2 kg / mol. The molecular weight \(M_n\) measured by SEC n,SEC was 38.4 kg / mol, and the dispersity was 1.21.

[0085] Example 9

[0086] In this example, N-ethylpropanamide and metal-free Lewis acid-base pairs were used as the catalytic / initiating system to carry out the ring-opening and ring-closing copolymerization of 2-hexyl-5,6-dialdehyde-isatin-1,3-dione and 2-biphenyl glycidyl ether to prepare a main-chain acetal-functionalized copolymer.

[0087] In an inert atmosphere, 1 part of N-ethylpropanamide, 0.5 part of amidine-based organic base DBN, and 2 parts of triisopropylborane were added to a reaction vessel and stirred to mix evenly. Subsequently, a solution of 2-hexyl-5,6-diformylisoindoline-1,3-dione / 1,3-dimethylpropyleneurea (50 parts of 2-hexyl-5,6-diformylisoindoline-1,3-dione, with a concentration of 5 mol / L in this solution) and 150 parts of 2-biphenyl glycidyl ether (the molar concentrations of 2-hexyl-5,6-diformylisoindoline-1,3-dione and 2-biphenyl glycidyl ether were 1.9 mol / L and 2.8 mol / L respectively) were added successively. The reaction vessel was sealed and reacted at 50 °C for 48 h. The reaction was terminated with acetic acid, the crude product was collected, precipitated in methanol, and dried under vacuum to obtain the product. Samples were taken for monitoring during the polymerization process, 1 The conversion rates of 2-hexyl-5,6-diformylisoindoline-1,3-dione and 2-biphenyl glycidyl ether measured by 1H NMR were 100% and 84% respectively. The theoretical number-average molecular weight Mn was calculated based on the feeding ratios and conversion rates of N-ethylpropanamide, 2-hexyl-5,6-diformylisoindoline-1,3-dione, and 2-biphenyl glycidyl ether n,th to be 57.2 kg / mol. The molecular weight Mn measured by SEC n,SEC was 51.8 kg / mol, and the dispersity was 1.17.

[0088] Example 10

[0089] In this example, pentaerythritol and a metal-free Lewis acid-base pair were used as the catalytic / initiating system to carry out ring-opening and ring-closing copolymerization of thiophene-2,3-dicarboxaldehyde and epoxybutane to prepare tetra-armed main-chain acetal-functionalized poly(epoxybutane).

[0090] In an inert atmosphere, 1 part of pentaerythritol, 0.5 part of TMAP, and a solution of tributylborane / tetrahydrofuran (1.5 parts of tributylborane, with a concentration of 1 mol / L in this solution) were added to a reaction vessel and stirred to mix evenly. Subsequently, a solution of thiophene-2,3-dicarboxaldehyde / ethyl acetate (20 parts of thiophene-2,3-dicarboxaldehyde, with a concentration of 5 mol / L in this solution) and 1000 parts of epoxybutane (the molar concentrations of thiophene-2,3-dicarboxaldehyde and epoxybutane in the system were 0.2 mol / L and 10.8 mol / L respectively) were added successively. The reaction vessel was sealed and reacted at room temperature (20 - 25 °C) for 36 h. The reactor was opened, the reaction was terminated with acetic acid, the crude product was collected, and the catalyst in the crude product was removed by passing through a neutral alumina adsorption column. The solvent was removed and dried under vacuum to obtain the product. Samples were taken for monitoring during the polymerization process, 1 The conversion rates of thiophene-2,3-dicarboxaldehyde and epoxybutane measured by 1H NMR were both 100%. The theoretical number-average molecular weight Mn was calculated based on the feeding ratios and conversion rates of pentaerythritol, thiophene-2,3-dicarboxaldehyde, and epoxybutanen,th is 74.9 kg / mol. The molecular weight M measured by SEC n,SEC is 70.3 kg / mol, and the dispersity is 1.14.

[0091] The above embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a main-chain acetal-functionalized copolymer, characterized in that, It includes the following steps: Under a nitrogen or inert atmosphere, an aromatic dialdehyde compound and an epoxide are added to a three-component metal-free catalytic / initiating system, and a polymerization reaction is carried out at -20 to 80 °C for 0.1 to 120 h to obtain a main-chain acetal-functionalized copolymer; The three-component metal-free catalytic / initiating system consists of a hydrogen-containing active compound, an organic base, and an alkyl borane; The molar ratio of the aromatic dialdehyde compound, the epoxide, the hydrogen-containing active compound, and the organic base is (1 to 1000):(20 to 5000):1:(0.01 to 10), and the molar ratio of the organic base to the alkyl borane is 1:(1 to 30); The aromatic dialdehyde compound is at least one of the following structural formulas: Among them, X in (2) 1 ~X 4 are the same or different and are the following groups, provided that X 1 ~X 4 cannot be H at the same time: The hydrogen-containing active compound is at least one of water, p-xylene glycol, benzoic acid, N-ethylpropanamide, and pentaerythritol; The organic base is at least one of tert-butylimino-tris(dimethylamino)phosphorane, 1-tert-butyl-2,2,4,4,4-penta(dimethylamino)-2λ 5 ,4λ 5 -bis(phosphazene), 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylideneamino]-2λ 5 ,4λ 5 -bis(phosphazene), 1,8-diazabicycloundec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, triethylenediamine, tris(dimethylamino)phosphine, and 2,8,9-trimethyl-2,5,8,9-tetraaza-1-phosphabicyclo[3,3,3]undecane; The alkyl borane is at least one of triethyl borane, tributyl borane, and triisopropyl borane; 2. The method for preparing a main-chain acetal-functionalized copolymer according to claim 1, characterized in that, The aromatic dialdehyde compound is at least one of phthalaldehyde, 4,5-dichlorophthalaldehyde, 2-hexyl-5,6-dialdehyde-isoindoline-1,3-dione, and thiophene-2,3-dicarboxaldehyde; 3. The method for preparing a main-chain acetal-functionalized copolymer according to claim 1, characterized in that, The epoxide is at least one of ethylene oxide, a straight-chain alkyl ethylene oxide with 1 to 20 carbon atoms in the alkyl group, a straight-chain alkyl glycidyl ether with 1 to 16 carbon atoms in the alkyl group, isopropyl glycidyl ether, tert-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, 2-biphenyl glycidyl ether, allyl glycidyl ether, propargyl glycidyl ether, a straight-chain alkyl carboxylic acid glycidyl ester with 1 to 16 carbon atoms in the alkyl group, and glycidyl methacrylate; 4. The method for preparing a main-chain acetal-functionalized copolymer according to claim 3, characterized in that, The epoxide is at least one of ethylene oxide, propylene oxide, butylene oxide, n-butyl glycidyl ether, and 2-biphenyl glycidyl ether; 5. The method for preparing a main-chain acetal-functionalized copolymer according to claim 1, characterized in that, The molar ratio of the aromatic dialdehyde compound, the epoxide, the hydrogen-containing active compound, and the organic base is (6 to 400):(40 to 1000):1:(0.05 to 2), and the molar ratio of the organic base to the alkyl borane is 1:(3 to 10); 6. The method for preparing a main-chain acetal-functionalized copolymer according to claim 1, characterized in that, The concentration of the epoxide at the start of the polymerization reaction is 1 to 18 mol / L; The temperature of the polymerization reaction is 20 to 80 °C, and the reaction time is 2 to 72 h; 7. The method for preparing a main-chain acetal-functionalized copolymer according to claim 1, characterized in that, The polymerization reaction is carried out in the epoxide monomer or in at least one solvent of tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, ethyl acetate, cyclopentyl methyl ether, benzene, toluene, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, 1,3-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinone.

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