Process for the preparation of cyclic polymers at high concentration and cyclic polymers obtained

Abstract

The application provides a preparation method of a cyclic polymer and the cyclic polymer prepared by the method. The preparation method comprises the following steps: obtaining a linear polymer precursor, wherein the linear polymer precursor has a group A, a group B and a side group F; combining a compound D with at least part of the side groups F of the linear polymer precursor, so that at least part of the side groups F of the linear polymer precursor are converted into charged groups; chemically reacting the group A and the group B to form a charged cyclic polymer; and optionally removing the charged groups to obtain the cyclic polymer. The preparation method of the cyclic polymer has strong universality, and various monomers commonly used in the market can be used to form various cyclic polymers. Moreover, the reaction process is simple, the solid content of the linear polymer precursor used in the reaction system is high, the by-products are few, and the cost of the treatment and separation process of the product is low.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing a cyclic polymer at a high concentration and the cyclic polymer prepared thereby, and belongs to the field of high polymer materials. BACKGROUND

[0002] Cyclic polymers have attracted much attention due to their unique properties, such as viscosity, thermal properties, self-assembly and surface tension. However, the synthesis of cyclic polymers is difficult, and the research on cyclic polymers is less reported compared with other structural polymers. Moreover, the large-scale preparation of cyclic polymers has been one of the important problems in the field of high polymers.

[0003] The methods developed so far mainly include ring expansion and ring closure. The ring expansion method is to design an activated cyclic small molecule first, and then gradually form a macromolecular cyclic polymer by inserting monomers into the cyclic molecule. This method can ensure the formation of a cyclic topological structure, but has the following limitations: not only the activated cyclic molecule needs to be designed separately, but also the corresponding catalyst needs to be screened. The most critical problem is that this method relies on ring-opening polymerization, so the types of monomers that can be selected are very limited, which limits the design and synthesis of cyclic polymers.

[0004] The ring closure method for preparing cyclic polymers is to design corresponding functional groups at the end of the polymer chain to couple and form a cyclic polymer. This preparation method avoids the problems of specific design and monomer selectivity in the ring expansion method. However, in the preparation process of the ring closure method, the end groups of different molecular chains may be connected to form linear polymer chains with larger molecular weight. This side reaction not only makes the product contain a large amount of non-cyclic polymers, but also makes the separation difficult and the cost high. In order to avoid the side reaction, it is necessary to reduce the collision probability between molecular chains as much as possible, that is, to control the reaction in an extremely dilute solution. However, in industrial production, an extremely dilute solution also means extremely high separation and purification cost.

[0005] Reference Document 1 discloses a method for preparing a cyclic polymer. The preparation method includes the following steps: 1) dissolving a polymer monomer, a chain transfer agent and an initiator in a reaction solvent, and then reacting under argon protection after oxygen removal to obtain a reaction mixture; 2) the reaction mixture undergoes a reversible addition-fragmentation chain transfer radical polymerization under oxygen-free conditions; and 3) the product is purified by dialysis, and then freeze-dried to obtain a cyclic polymer. However, this method produces a large amount of by-products, so the product contains a large amount of non-cyclic polymers, and the separation is difficult and the cost is high.

[0006] Reference document 2 discloses a cyclic polymer and a preparation method thereof. First, a monomer EPNA is obtained, and the monomer EPNA is subjected to a "click" reaction step-by-step polymerization by a thermal catalytic solid phase reaction to obtain a linear-PEPNA with an α-azido group and an ω-ethynyl group. A cyclic-PEPNA, i.e., the cyclic polymer, is obtained by a ring-closing reaction of the linear-PEPNA by an azido / ethynyl CuAAC method in an extremely dilute solution, where the mass concentration of the linear polymer is not more than 1.0 x 10 -4 g / mL. In order to avoid side reactions and as much as possible reduce the collision probability between molecular chains, the reaction is controlled to be carried out in an extremely dilute solution, which requires extremely high separation and purification costs.

[0007] Therefore, it has become an urgent problem to be solved to prepare a cyclic polymer with less by-products and low cost in the process of treating and separating the product under the condition of high solid content.

[0008] Reference document:

[0009] Reference document 1: CN114395060A

[0010] Reference document 2: CN102617855A SUMMARY

[0011] Problems to be solved by the invention

[0012] In view of the technical problems existing in the prior art, the present application first provides a preparation method of a cyclic polymer. The preparation method of the cyclic polymer of the present application has strong universality, can form various cyclic polymers using various monomers commonly available on the market, and has a simple reaction process, high solid content of the linear polymer precursor used in the reaction system, less by-products, and low cost in the process of treating and separating the product.

[0013] Solution to the problem

[0014] [1] A preparation method of a cyclic polymer, comprising the following steps:

[0015] obtaining a linear polymer precursor, the linear polymer precursor having a group A, a group B, and a side group F;

[0016] combining a compound D with at least part of the side groups F of the linear polymer precursor, so as to convert at least part of the side groups F of the linear polymer precursor into a charged group;

[0017] causing the group A and the group B to chemically react, to form a charged cyclic polymer;

[0018] optionally removing the charged group, to obtain a cyclic polymer.

[0019] [2] The preparation method according to the above [1], wherein the group A is selected from one or a combination of two of azido group, halogen; and / or,

[0020] the group B is selected from one or a combination of two or more of substituted or unsubstituted alkynyl group, ester group, halogen, hydroxyl group, substituted or unsubstituted amino group, substituted or unsubstituted amide group; and / or

[0021] the side group F is selected from one or a combination of two or more of carboxyl group, amino group, halogen, tertiary amine group, pyridine group, imidazole group.

[0022] [3] The preparation method according to the above [1] or [2], wherein the number average molecular weight of the linear polymer precursor is 5000 g / mol-200000 g / mol, preferably 10000 g / mol-100000 g / mol.

[0023] [4] The preparation method according to any one of the above [1]-[3], wherein the compound D comprises one or a combination of two or more of carboxylic acid compound, amino compound, halogenated compound, tertiary amine compound, pyridine compound, imidazole compound.

[0024] [5] The preparation method according to any one of the above [1]-[4], wherein the compound D and the linear polymer precursor convert at least part of the side group F of the linear polymer precursor into a charged group through quaternization reaction or salt formation reaction.

[0025] [6] The preparation method according to any one of the above [1]-[5], wherein the chemical reaction comprises one or a combination of two or more of click reaction, Staudinger reaction, coupling reaction.

[0026] [7] The preparation method according to any one of the above [1]-[6], wherein the concentration of the linear polymer precursor in the preparation system is 1-300 mg / mL, preferably 10-100 mg / mL.

[0027] [8] The preparation method according to any one of the above [1]-[7], wherein the temperature of the chemical reaction is 0-100℃, preferably 25-80℃; the time of the chemical reaction is 1-48 hours, preferably 3-36 hours.

[0028] [9] The preparation method according to any one of the above [1]-[8], wherein the chemical reaction is carried out in a solvent; preferably, the dielectric constant of the solvent is 2.2-49, preferably 2.6-37.

[0029]

[10] A cyclic polymer prepared by the method for preparing a cyclic polymer according to any one of the above [1] to [9], preferably, the cyclic polymer has a diameter of 3 to 100 nm.

[0030] Effects of the Invention

[0031] The method for preparing a cyclic polymer of the present application has strong universality, and can form various cyclic polymers using various monomers commonly available on the market; moreover, the reaction process is simple, the solid content of the linear polymer precursor used in the reaction system is high, by-products are few, and the cost of the process and separation of the product is low. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A gel permeation chromatography (GPC) curve comparison diagram of the linear polymer precursor and the cyclic polymer of Example 2 of the present application is shown.

[0033] Figure 2 A dynamic light scattering (DLS) data comparison diagram of the linear polymer precursor and the cyclic polymer of Example 2 of the present application is shown.

[0034] Figure 3 A sample picture of the cyclic polymer observed under a transmission electron microscope of Example 2 of the present application is shown, wherein the cyclic polymer is visualized by grafting PEO-CHO with Mn = 1000. DETAILED DESCRIPTION

[0035] Various exemplary embodiments, features, and aspects of the present application will be described in detail below. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0036] In addition, in order to better illustrate the present application, numerous specific details are given in the following detailed description. Those skilled in the art will understand that the present application can be practiced without certain specific details. In some instances, well-known methods, means, instruments and steps have not been described in detail in order to highlight the principles of the present application.

[0037] Unless otherwise specified, the units used in the present specification are international standard units, and the numerical values and numerical ranges appearing in the present application should be understood to include systematic errors that are unavoidable in industrial production.

[0038] In the present specification, the numerical range represented by "numerical value A to numerical value B" means a range including the end point values A and B.

[0039] In the present specification, a numerical range indicated using "above" or "below" means a numerical range including the number.

[0040] In the present specification, the meaning indicated using "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0041] In the present specification, "optionally" indicates the use or non-use of certain substances, components, execution of steps, application of conditions, and the like.

[0042] In the present specification, the unit names used are international standard unit names, and if not specifically stated, "%" used means a percentage by weight or mass.

[0043] In the present specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid. In addition, "(meth)" in the present specification indicates the same meaning throughout.

[0044] In the present specification, "halogen" means "chlorine atom" or "bromine atom" or "iodine atom".

[0045] In the present specification, "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", and the like mean that the specific elements (for example, features, structures, properties, and / or characteristics) described in relation to the embodiments are included in at least one of the embodiments described herein, and can be present in other embodiments or can not be present in other embodiments. In addition, it should be understood that the elements can be combined in various embodiments in any suitable manner.

[0046] The present application provides a method for producing a cyclic polymer, which is produced using a linear polymer precursor as a starting material. The method for producing a cyclic polymer of the present application is versatile, and can produce a wide variety of cyclic polymers using various monomers commonly found on the market. In addition, the reaction process is simple, the linear polymer precursor used in the reaction system has a high solid content, there are few by-products, and the cost of the process and separation of the product is low.

[0047] <Linear polymer precursor>

[0048] The linear polymer precursor of the present application is formed by polymerization of a polymer monomer. The type of polymer monomer is not particularly limited in the present application, as long as the linear polymer precursor formed after copolymerization has group A, group B, and side group F.

[0049] Specifically, in the present application, the polymer monomer can be one or a combination of two or more of a (meth)acrylic monomer, a (meth)acrylamide monomer, a styrene monomer, and an ethylene monomer.

[0050] For the (meth)acrylic monomer, it can include (meth)acrylic acid or (meth)acrylic alkyl ester. For the (meth)acrylic alkyl ester, straight-chain or branched-chain and alkyl having 1 to 10 carbon atoms can be exemplified. For example, as the above alkyl, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, and the like can be exemplified.

[0051] For the (meth)acrylamide monomer, it can include (meth)acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-hydroxyethyl acrylamide, N-hydroxymethyl acrylamide, or the like, or a combination of two or more thereof.

[0052] For the styrene monomer, it can include styrene, substituted styrene, or the like. For the substituted styrene, the substituent group can include alkyl, alkenyl, alkoxy, amino, or the like, the carbon atom number of the alkyl, alkenyl, alkoxy is preferably 1 to 5, and the alkyl, alkenyl, alkoxy can further include a substituent group.

[0053] For the ethylene monomer, it can include ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, isopentylene, butadiene, or the like.

[0054] In some specific embodiments, the linear polymer precursor of the present application can be obtained by polymerization of a monomer having a side group F, a monomer having a group A, and a monomer having a group B, wherein the group A and the group B are the same or different, the group A is different from the side group F, and the group B is different from the side group F.

[0055] In some specific embodiments, the linear polymer precursor of the present application can be obtained by polymerization of a monomer, and then introducing a group A, a group B, or a side group F into the linear polymer by some other chemical reaction, such as substitution reaction, or the like, as needed, to obtain the linear polymer precursor. Wherein the group A and the group B are the same or different, the group A is different from the side group F, and the group B is different from the side group F.

[0056] pendant group F

[0057] For the side group F, it can be selected from one or a combination of two or more of carboxyl, amino, halogen, tertiary amine group, pyridyl group, imidazolyl group.

[0058] For the type of the monomer having the side group F, the present application is not particularly limited as long as it can be copolymerized and has the above side group F. For the position of the side group F in the monomer, the present application is also not particularly limited, which can be any available hydrogen in the monomer.

[0059] Specifically, in the present application, the monomer containing a side group F can be one or a combination of two or more of a (meth)acrylic monomer containing a side group F, a (meth)acrylamide monomer containing a side group F, a styrene monomer containing a side group F, and an ethylene monomer containing a side group F.

[0060] In some specific embodiments, the (meth)acrylic monomer in which the side group F is a carboxyl group can be (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, or the like.

[0061] In some specific embodiments, the styrene monomer in which the side group F is a halogen can be a C 1-5 alkyl-substituted styrene, a halogen-substituted C 1-5 alkenyl-substituted styrene, and the like, for example: 4-chloromethylstyrene (VBC), 4-chloroethylstyrene, 4-bromomethylstyrene, 4-bromoethylstyrene, and the like. The styrene monomer in which the side group F is an amino group can be an amino-substituted styrene monomer, preferably the amino group can be protected by a protecting group, specifically can be protected by a tert-butyloxycarbonyl group, for example tert-butyl 4-vinylphenylcarbamate (AStBoc).

[0062] In some specific embodiments, the ethylene monomer in which the side group F is a pyridyl group can be 2-vinylpyridine or the like.

[0063] In some specific embodiments, the ethylene monomer in which the side group F is an imidazolyl group can be 2-vinylimidazole or the like.

[0064] In some specific embodiments, the (meth)acrylic monomer in which the side group F is a tertiary amine group can be 2-aminoethyl methacrylate or a salt thereof, for example 2-aminoethyl methacrylate hydrochloride (AMA) or the like.

[0065] group A

[0066] The group A of the present application can refer to the end group A of the linear polymer precursor. For the group A, it can be one or a combination of two or more selected from an azido group, a halogen. The group A of the present application can be introduced by directly using a monomer containing the group A, for example the group A can be introduced by a monomer containing a halogen; the group A of the present application can also be introduced by a substitution reaction after obtaining the linear polymer, for example introducing an azido group or the like after obtaining the linear polymer; of course, the present application can also be that the group A is introduced to a monomer by a substitution reaction, and then a polymerization reaction is performed.

[0067] In the present application, the monomer containing group A can be one or a combination of two or more of a (meth)acrylic monomer containing group A, a (meth)acrylamide monomer containing group A, a styrene monomer containing group A, and an ethylene monomer containing group A. The monomer containing group A of the present application can be the same as the monomer containing side group F, but the monomer containing group A of the present application can be different from the monomer containing side group F. For example, when group A is halogen, side group F can not be halogen.

[0068] In some specific embodiments, when group A is azido, it can be obtained by first substituting a linear polymer with an azido salt, thereby first providing a linear polymer having azido. Preferably, the linear polymer can have halogen, which is substituted with azido by using an azido salt.

[0069] In some specific embodiments, when group A is azido, it can be obtained by first providing a linear polymer, and then substituting the linear polymer with an azido salt, thereby providing a linear polymer precursor having azido.

[0070] In some specific embodiments, the styrene monomer having halogen as group A can be a C 1-5 alkyl-substituted styrene, a halogen-substituted C 1-5 alkenyl-substituted styrene, and the like, for example, 4-chloromethylstyrene (VBC), 4-chloroethylstyrene, 4-bromomethylstyrene, 4-bromoethylstyrene, and the like.

[0071] group B

[0072] Group B of the present application can refer to an end group B of the linear polymer precursor. In the present application, group A and group B can be the same or different. For group B, it can be selected from one or a combination of two or more of substituted or unsubstituted alkynyl, ester, halogen, hydroxyl, substituted or unsubstituted amino, and substituted or unsubstituted amide. The number of carbon atoms of the alkynyl group can be 1 to 5. For the substituent, the substituent can include alkyl, alkenyl, alkoxy, and the like, the number of carbon atoms of the alkyl, alkenyl, and alkoxy is preferably 1 to 5, and the alkyl, alkenyl, and alkoxy can further include a substituent.

[0073] In some specific embodiments, the styrene monomer having halogen as group B can be a C 1-5 alkyl-substituted styrene, a halogen-substituted C 1-5 alkenyl-substituted styrene, and the like, for example, 4-chloromethylstyrene (VBC), 4-chloroethylstyrene, 4-bromomethylstyrene, 4-bromoethylstyrene, and the like.

[0074] In some embodiments, the monomer having the group B can be an alkyl (meth)acrylate monomer, since the (meth)acrylate monomer contains an ester group. As the alkyl (meth)acrylate, a straight-chain or branched alkyl (meth)acrylate having 1 to 10 carbon atoms in the alkyl group can be exemplified. For example, as the alkyl group, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, a 2-ethylhexyl group, and the like can be exemplified.

[0075] In some embodiments, the monomer having the group B can be an alkyl (meth)acrylate monomer in which at least one H in the above-described alkyl (meth)acrylate monomer is replaced with an alkyne group. In addition, the alkyne group of the present application can be protected with a protecting group, and specifically, can be protected with a trimethylsilyl group, for example, 3-trimethylsilylpropargyl methacrylate.

[0076] In some embodiments, the monomer having the group B can be an alkyl (meth)acrylate monomer in which at least one H in the above-described alkyl (meth)acrylate monomer is replaced with an amino group, for example, 2-aminoethyl methacrylate.

[0077] In some embodiments, the monomer having the group B can be an alkyl (meth)acrylate monomer in which at least one H in the above-described alkyl (meth)acrylate monomer is replaced with a hydroxyl group, for example, hydroxyethyl methacrylate.

[0078] In some embodiments, the monomer having the group B can be a (meth)acrylamide monomer, since the (meth)acrylamide monomer contains an amide group. Specifically, it can include one or a combination of two or more of (meth)acrylamide, N-methyl acrylamide, N,N-dimethyl acrylamide, N-hydroxyethyl acrylamide, N-hydroxymethyl acrylamide, and the like.

[0079] polymerization

[0080] The polymerization reaction of the present application can be obtained by solution polymerization. The polymerization method includes random copolymerization, alternating copolymerization, block copolymerization, and the like.

[0081] In some specific embodiments, the polymerization reaction comprises polymerizing the polymer monomer in the presence of the RAFT agent and the initiator in a solvent to obtain the linear polymer precursor. The polymerization reaction of the present application can be obtained by simultaneously polymerizing the monomer having the side group F, the monomer having the group A, and the monomer having the group B; or by polymerizing the monomer having the side group F and the monomer having the group A first, and then polymerizing the monomer having the group B; or by polymerizing the monomer having the side group F and the monomer having the group B first, and then polymerizing the monomer having the group A. Of course, the polymerization reaction of the present application can also be obtained by polymerizing the polymer monomer first to obtain the linear polymer, and then introducing the group A, the group B, and the side group F.

[0082] As for the RAFT agent, the present application is not particularly limited, and can be a RAFT agent commonly used in the art. As a preference, the RAFT agent can be CPADB or D-CPADB, and the specific compounds are as follows, respectively:

[0083]

[0084] As for the initiator, it can be one or a combination of two or more selected from the group consisting of organic peroxides and azo compounds, the organic peroxides are preferably dibenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, benzoyl tert-butyl peroxide, methyl ethyl ketone peroxide, dodecanoyl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxydicarbonate, and the like; and the azo compounds are preferably azobis isobutyronitrile, azobis isohexyl nitrile, azobis isoamyl nitrile, azobis cyclohexyl methyl nitrile, dimethyl azobis isobutyrate, and the like.

[0085] As for the solvent, the present application is not particularly limited, and can be an organic solvent or water commonly used in the art, and is preferably an organic solvent. For example, ketones such as acetone, methyl ethyl ketone, dimethyl ketone, methyl isobutyl ketone, phenyl ethyl ketone, N-methyl-2-pyrrolidone, ethers such as tetrahydrofuran, dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and the like can be exemplified.

[0086] As for the conditions of the polymerization reaction, the present application is not particularly limited, and can be selected as needed, as long as the desired linear polymer precursor can be obtained. Generally, the polymerization reaction can be performed at a temperature of 50-100°C for 1-24 hours to obtain the polymerization product. As needed, the group A, the group B, or the side group F can be introduced into the polymerization product. After the final separation treatment, the linear polymer precursor is obtained.

[0087] For the method of separation treatment, the present application is not particularly limited, and can be a separation method commonly used in the art, such as using n-hexane to precipitate linear polymer precursors, etc. As preferred, the polymerization reaction is carried out in an oxygen-free environment, and deoxygenation treatment can be generally carried out by 1 to 5 times of freeze-pumping-thaw cycles.

[0088] In some specific embodiments, the number average molecular weight of the linear polymer precursor is 5000-200000 g / mol, preferably 10000-100000 g / mol.

[0089] <Method for preparing a cyclic polymer>

[0090] The method for preparing a cyclic polymer of the present application is carried out using a linear polymer precursor having side groups F, groups A and groups B as a starting material. It can comprise the following steps:

[0091] (1) combining compound D with at least part of the side groups F of the linear polymer precursor to convert at least part of the side groups F of the linear polymer precursor into charged groups;

[0092] (2) chemically reacting the groups A and the groups B to form a charged cyclic polymer;

[0093] (3) optionally removing the charged groups to obtain a cyclic polymer.

[0094] step (1)

[0095] The compound D is combined with at least part of the side groups F of the linear polymer precursor to convert at least part of the side groups F of the linear polymer precursor into charged groups. Step (1) of the present application introduces charged groups into the side groups of the linear polymer precursor, thereby charging the linear polymer precursor. In this process, the linear polymer precursor is charged by treatment, so that repulsion occurs between the polymer chains of the linear polymer precursor, and the magnitude of the inter-chain repulsion force generated by different amounts of charge is different. This repulsion effectively reduces the side reactions that occur between the molecular chains during cyclization, creating conditions for the subsequent intramolecular reaction of groups A and groups B, thereby realizing the preparation of products at high concentrations.

[0096] In some specific embodiments, the compound D and the linear polymer precursor convert at least part of the side groups F of the linear polymer precursor into charged groups through a quaternization reaction or a salt formation reaction. Taking the salt formation reaction (acid-base reaction) as an example, the side groups F of the linear polymer precursor are acidic or basic groups, and the compound D is a base or an acid (i.e. the reactive groups of the compound D that can react with the side groups F are basic or acidic groups) accordingly.

[0097] In some specific embodiments, the side group F is selected from one or more combinations of carboxyl group, amino group, halogen, tertiary amine group, pyridine group, imidazole group.

[0098] The compound D is any compound having a group capable of reacting with the side group F to convert it into a charged group. Exemplarily, the compound D includes one or more combinations of carboxylic acid compound, amino compound, halogen compound, tertiary amine compound, pyridine compound, imidazole compound. Specifically, the compound D can be trifluoroacetic acid, iodoethane, methyl imidazole, pyridine, etc.

[0099] Preferably, the combination of the side group F of the linear polymer precursor / the reactive group of the compound D can be a combination selected from the group consisting of carboxyl group / amino group, amino group / carboxyl group, halogen / tertiary amine group, halogen / pyridine group, halogen / imidazole group, tertiary amine group / halogen, pyridine group / halogen, imidazole group / halogen, etc.

[0100] Here, of the two groups separated by the symbol " / ", the group before the symbol " / " is the side group F of the linear polymer precursor, and the group after the symbol " / " is the reactive group of the compound D.

[0101] In step (1), a part of the side groups F of the linear polymer precursor can be converted into charged groups, and the other part can remain as the side group F; or all of the side groups F can be converted into charged groups. In some specific embodiments, after the reaction of step (1) is completed, the proportion of the side groups F converted into charged groups can be 10% to 100 mole%, preferably 60% to 100 mole% in terms of mole.

[0102] In some specific embodiments, step (1) is performed in a solvent. Specifically, the linear polymer precursor is dissolved in a solvent, and then the compound D is added, and the reaction is optionally performed with stirring. The time for stirring is not particularly limited in the present application, and can generally be 10 to 60 min.

[0103] The solvent is not particularly limited in the present application, and can be an organic solvent or water commonly used in the art. Further, the dielectric constant of the solvent is 2.2 to 49, preferably 2.6 to 37. Preferably, the solvent is an organic solvent. Exemplary organic solvents include ketones such as acetone, methyl ethyl ketone, dimethyl propyl ketone, methyl isobutyl ketone, phenyl ethyl ketone, N-methyl-2-pyrrolidone, etc., ethers such as tetrahydrofuran, dioxane, etc., aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, etc., amides such as N,N-dimethylformamide, N,N-dimethylacetamide, etc.

[0104] Further, the reaction temperature of step (1) is not particularly limited, and can be performed at 10 to 50°C.

[0105] Further, it should be noted that, in the preparation of the linear polymer precursor, when the linear polymer precursor needs to be introduced with an azido group, it can be introduced simultaneously with step (1), or the azido group can be introduced first and then step (1) is performed. Further, in order to accelerate the reaction efficiency, it is preferred that the azido group is introduced simultaneously with step (1).

[0106] step (2)

[0107] The group A and the group B are chemically reacted to form the charged cyclic polymer. The group A and the group B are a combination of groups that can be reacted with each other to form a covalent bond, and can be the same or different.

[0108] Preferably, the group A / group B is selected from the following combinations: azido / alkynyl, azido / ester, halogen / halogen, halogen / hydroxyl, halogen / amino, halogen / amido, and the like.

[0109] In the group combination described herein, one of the two groups separated by the symbol " / " is the group A, and the other is the group B, without being limited by the order of appearance.

[0110] Step (3) is performed under conditions that enable the chemical reaction of the group A and the group B, such as in the presence of a catalyst.

[0111] In some specific embodiments, the chemical reaction can include one or a combination of two or more of a click reaction, a Staudinger reaction, and a coupling reaction.

[0112] In one specific embodiment, the group A / group B is halogen / halogen, and in this case, step (3) can be performed in the presence of a catalyst, which can produce the charged cyclic polymer through a coupling reaction.

[0113] In one specific embodiment, the group A / group B is azido / alkynyl, and in this case, step (3) can be performed in the presence of a catalyst, which can produce the charged cyclic polymer through a click reaction.

[0114] In one specific embodiment, the group A / group B is azido / ester, and in this case, step (3) can be performed in the presence of a catalyst, which can produce the charged cyclic polymer through a Staudinger reaction.

[0115] In one specific embodiment, the group A / group B is halogen / hydroxyl, which can produce the charged cyclic polymer through a coupling reaction.

[0116] In one specific embodiment, group A / group B is halogen / amino, which can prepare charged cyclic polymers by coupling reaction.

[0117] In one specific embodiment, group A / group B is halogen / amido, which can prepare charged cyclic polymers by coupling reaction.

[0118] For the catalyst, the present application is not particularly limited, and the required catalyst can be selected according to the specific reaction. Among them, the catalyst for coupling reaction can be triphenylphosphine palladium and carbonate, such as triphenylphosphine palladium and cesium carbonate, etc.; the catalyst for Staudinger reaction can be triphenylphosphine; the catalyst for click reaction can be cuprous halide, such as cuprous bromide, etc.

[0119] In some specific embodiments, the concentration of reactants in the system of chemical reaction is 1 mg / mL-300 mg / mL, preferably 10-100 mg / mL.

[0120] In some specific embodiments, the temperature of the above chemical reaction can be 0-100℃, preferably 25-80℃, and the time of the chemical reaction can be 1-48 hours, preferably 3-36 hours.

[0121] step (3)

[0122] Finally, the charged group is optionally removed to obtain the cyclic polymer. According to the need, the charged group can be removed in the present application, and the cyclic polymer can be obtained by post-treatment method such as precipitation, washing, etc. Of course, the charged group can also not be removed in the present application. Only the post-treatment method such as precipitation, washing, etc. can be used to obtain the charged cyclic polymer.

[0123] For the method of removing the charged group, the present application is not particularly limited, and when an acidic compound D is used, a basic compound is used to remove it, and when a basic compound D is used, an acidic compound can be used to remove it.

[0124] For example, when trifluoroacetic acid is used as compound D, saturated NaHCO3 can be used for washing to remove compound D.

[0125] In addition, for the catalyst, it can be removed by water washing or in the process of precipitation. For example, triphenylphosphine palladium can be removed by using heated cyclohexane in the process of precipitating the cyclic polymer. When cuprous bromide is used as the catalyst, water dialysis can be used to remove copper ions.

[0126] <the cyclic polymer>

[0127] The present application also provides a cyclic polymer prepared by the method for preparing a cyclic polymer according to the present application, preferably, the cyclic polymer has a diameter of 3-100 nm. The diameter of the cyclic polymer of the present application can be determined by transmission electron microscopy (TEM) and assisted by dynamic light scattering (DLS).

[0128] Examples

[0129] The embodiments of the present application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. The specific conditions not indicated in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by purchase.

[0130] Example 1

[0131] In a 25 mL test tube, 10 mmol of methacrylic acid (MAA), 0.02 mmol of azobisisobutyronitrile (AIBN), 0.1 mmol of RAFT reagent D-CPADB, 0.2 mmol of 4-chloromethylstyrene (VBC) and 2 mL of dioxane were stirred uniformly, and then subjected to three cycles of freezing-pumping-thawing to remove oxygen. Polymerization was carried out at 80°C for 8 h. After the reaction was terminated by cooling, the reaction product was obtained. The reaction product was precipitated in n-hexane, washed three times and dried to obtain a pink linear polymer PVBC-b-PMAA-b-PVBC, i.e. a linear polymer precursor.

[0132] The above linear polymer was taken in a test tube, 1 mL of dimethylformamide (DMF) was added, and after dissolution, 2 mmol of methyl imidazole was added, and the linear polymer was stirred for 30 min to be charged. Then 1% of triphenylphosphine palladium and 1% of cesium carbonate (based on the total mass of the reactants) were added as catalysts, and the linear polymer was subjected to coupling reaction at a temperature of 80°C for 12 h to realize cyclization. After the coupling reaction was completed, the cyclic polymer was precipitated using n-hexane at 60°C, and the charged groups were removed at the same time, and then washed with water to remove cesium carbonate, and dried to obtain the cyclic polymer.

[0133] The RAFT reagent D-CPADB used therein has the following structural formula:

[0134]

[0135] Example 2

[0136] In a 50 mL test tube, 1 mmol of methyl methacrylate (MMA), 0.02 mmol of azobisisobutyronitrile (AIBN), 0.1 mmol of RAFT agent CPADB, 10 mmol of 4-vinylphenylcarbamic acid tert-butyl ester (AStBoc), and 2 mL of dioxane were stirred uniformly and then subjected to three cycles of freezing-pumping-thawing to remove oxygen. Block copolymerization was performed at 80°C for 8 h. After the reaction was terminated by cooling, the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times, and dried to obtain a pink linear polymer PMMA-b-PAStBoc.

[0137] The above linear polymer PMMA-b-PAStBoc was taken in a test tube, 0.02 mmol of azobisisobutyronitrile (AIBN), 0.2 mmol of 4-chloromethylstyrene (VBC), and 2 mL of dioxane were stirred uniformly and then subjected to three cycles of freezing-pumping-thawing to remove oxygen. Block copolymerization was performed at 80°C for 8 h. After the reaction was terminated by cooling, the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times, and dried to obtain a pink linear polymer PMMA-b-PAStBoc-b-PVBC.

[0138] The above linear polymer PMMA-b-PAStBoc-b-PVBC was taken in a test tube, 0.2 mmol of NaN3, 5 mmol of trifluoroacetic acid, and 1 mL of dimethylformamide were added, and the mixture was reacted for 24 h to obtain a third reaction product. The third reaction product was precipitated in n-hexane, washed three times, and dried to obtain a linear polymer PMMA-b-PStNH2-b-PVBC having an azido group and a charge at the end group, i.e., a linear polymer precursor.

[0139] The above linear polymer PMMA-b-PStNH2-b-PVBC having an azido group and a charge at the end group was taken in a test tube, dissolved in 1 mL of dimethylformamide (DMF), 0.2 mmol of a catalyst triphenylphosphine was added, the mixture was stirred for 30 min, 0.6 mmol of a catalyst triphenylphosphine was further added, and the mixture was heated to 40°C to perform Staudinger reaction, and the mixture was reacted for 8 h to achieve cyclization. After the reaction was terminated, the charged group was removed by washing with saturated NaHCO3, and the mixture was precipitated and dried in n-hexane at 60°C to remove triphenylphosphine, thereby obtaining a cyclic polymer.

[0140] The RAFT agent CPADB used in the above reaction has the following structure:

[0141]

[0142] Example 3

[0143] In a 50 mL test tube, 0.2 mmol of 3-trimethylsilylpropynyl methacrylate (NMA), 0.02 mmol of azobisisobutyronitrile, 0.1 mmol of RAFT agent CPADB, 10 mmol of tert-butyl 4-vinylphenylcarbamate (AStBoc), and 2 mL of dioxane were stirred uniformly, and then deoxygenated by freeze-pumping-thaw cycles three times. Block copolymerization was performed by heating at 80 °C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times, and then dried to obtain a pink linear polymer PNMA-b-PAStBoc.

[0144] The above polymer was taken in a test tube, 0.02 mmol of azobisisobutyronitrile, 0.2 mmol of 4-chloromethylstyrene, and 2 mL of dioxane were stirred uniformly, and then deoxygenated by freeze-pumping-thaw cycles three times. Block copolymerization was performed by heating at 80 °C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times, and then dried to obtain a pink linear polymer PNMA-b-PAStBoc-b-PVBC, i.e., a linear polymer precursor.

[0145] The above linear polymer PNMA-b-PAStBoc-b-PVBC was taken in a test tube, 0.2 mmol of NaN3, 5 mmol of trifluoroacetic acid were added, and the reaction was performed for 24 h to obtain a third reaction product. The third reaction product was precipitated in n-hexane, washed three times, and then dried to obtain a linear polymer PNMA-b-PStNH2-b-PVBC with an azide group at the end and with a charge.

[0146] The above linear polymer PNMA-b-PStNH2-b-PVBC with an azide group at the end and with a charge was taken in a test tube, dissolved in 1 mL of dimethylformamide (DMF), 0.2 mmol of a catalyst cuprous bromide was added, and a click reaction was performed at room temperature for 24 h to achieve cyclization. After the reaction was completed, the charged group was removed by washing with saturated NaHCO3, and the copper ion was removed by dialysis using deionized water, and a cyclic polymer was obtained.

[0147] Example 4

[0148] In a 50 mL test tube, 0.2 mmol of 3-trimethylsilylpropynyl methacrylate (NMA), 0.02 mmol of azobisisobutyronitrile, 0.1 mmol of RAFT agent CPADB, 10 mmol of tert-butyl 4-vinylphenylcarbamate (AStBoc), and 2 mL of dioxane were stirred uniformly, and then deoxygenated by freeze-pumping-thaw cycles three times. Block copolymerization was performed by heating at 80 °C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times, and then dried to obtain a pink linear polymer PNMA-b-PAStBoc.

[0149] The above polymer was taken in a test tube, 0.02 mmol of azobisisobutyronitrile, 0.1 mmol of 4-chloromethylstyrene and 2 mL of dioxane were added and stirred uniformly, and then oxygen was removed by freezing-pumping-thawing for three times. Block copolymerization was carried out at 80°C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times and dried, to obtain the pink linear polymer PHEMA-b-PAA-b-PVBC, i.e. the linear polymer precursor.

[0150] The above linear polymer PHEMA-b-PAA-b-PVBC was taken in a test tube, dissolved in 1 mL of dimethylformamide, and then 5 mmol of methyl imidazole was added and stirred for 30 min to charge the linear polymer, and then 1% of triphenylphosphine palladium and 1% of cesium carbonate (based on the total mass of the reactants) were added, so that the linear polymer was subjected to coupling reaction at a temperature of 80°C, and the coupling reaction was carried out for 24 h to realize cyclization. After the coupling reaction was completed, the cyclic polymer was precipitated by using n-hexane at 60°C, and the charged groups were removed at the same time, and then the cesium carbonate was removed by water washing, and after drying, the cyclic polymer was obtained.

[0151] Example 5

[0152] In a 50 mL test tube, 0.2 mmol of 2-aminoethyl methacrylate hydrochloride (AMA), 0.02 mmol of azobisisobutyronitrile (AIBN), 0.1 mmol of RAFT reagent CPADB, 10 mmol of methacrylic acid (AA), and 2 mL of dioxane were added and stirred uniformly, and then oxygen was removed by freezing-pumping-thawing for three times. Block copolymerization was carried out at 80°C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times and dried, to obtain the pink linear polymer PAMA-b-PAA.

[0153] The above linear polymer was taken in a test tube, 0.02 mmol of azobisisobutyronitrile (AIBN), 0.2 mmol of 4-chloromethylstyrene (VBC) and 2 mL of dioxane were added and stirred uniformly, and then oxygen was removed by freezing-pumping-thawing for three times. Block copolymerization was carried out at 80°C for 8 h. After the reaction was completed, the reaction was terminated by cooling, and the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times and dried, to obtain the pink linear polymer PAMA-b-PAA-b-PVBC, i.e. the linear polymer precursor.

[0154] The above linear polymer PAMA-b-PAA-b-PVBC was taken in a test tube, 1 mL of dimethylformamide (DMF) was added to dissolve the linear polymer, 5 mmol of methyl imidazole was added first, and the linear polymer was charged after stirring for 30 min. 1% of triphenylphosphine palladium and 1% of cesium carbonate (based on the total mass of the reactants) were added as catalysts, and the linear polymer was subjected to coupling reaction at a temperature of 80°C. The coupling reaction was carried out for 24 h to achieve cyclization. After the coupling reaction was completed, 60°C n-hexane was used to precipitate the cyclic polymer, and the charged groups were removed at the same time. After water washing to remove cesium carbonate, the cyclic polymer was dried to obtain the cyclic polymer.

[0155] Example 6

[0156] In a 50 mL test tube, 0.2 mmol of methyl acrylamide (MAAN), 0.02 mmol of azobisisobutyronitrile (AIBN), 0.1 mmol of RAFT reagent CPADB, 10 mmol of methacrylic acid (AA), and 2 mL of dioxane were stirred uniformly, and then oxygen was removed by three cycles of freezing-pumping-thawing. Block copolymerization was carried out at 80°C for 8 h. After the reaction was terminated by cooling, the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times, and dried to obtain the pink linear polymer PMAAN-b-PAA.

[0157] The above pink linear polymer PMAAN-b-PAA was taken in a test tube, 0.02 mmol of azobisisobutyronitrile (AIBN), 0.2 mmol of 4-chloromethylstyrene (VBC), and 2 mL of dioxane were stirred uniformly, and then oxygen was removed by three cycles of freezing-pumping-thawing. Block copolymerization was carried out at 80°C for 8 h. After the reaction was terminated by cooling, the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times, and dried to obtain the pink linear polymer PMAAN-b-PAA-b-PVBC, which was the linear polymer precursor.

[0158] The above pink linear polymer PMAAN-b-PAA-b-PVBC was taken in a test tube, 1 mL of dimethylformamide (DMF) was added to dissolve the linear polymer, 5 mmol of methyl imidazole was added first, and the linear polymer was charged after stirring for 30 min. 1% of triphenylphosphine palladium and 1% of cesium carbonate (based on the total mass of the reactants) were added as catalysts, and the linear polymer was subjected to coupling reaction at a temperature of 80°C. The coupling reaction was carried out for 24 h to achieve cyclization. After the coupling reaction was completed, 60°C n-hexane was used to precipitate the cyclic polymer, and the charged groups were removed at the same time. After water washing to remove cesium carbonate, the cyclic polymer was dried to obtain the cyclic polymer.

[0159] Example 7

[0160] In a 50 mL test tube, 1 mmol of methyl methacrylate (MMA), 0.02 mmol of azobisisobutyronitrile (AIBN), 0.1 mmol of RAFT reagent CPADB, 10 mmol of 2-vinylpyridine (2VP), and 2 mL of dioxane were stirred uniformly, and then oxygen was removed by three cycles of freezing-pumping-thawing. Block copolymerization was carried out at 80°C for 8 h. After the reaction was terminated by cooling, the first reaction product was obtained. The first reaction product was precipitated in n-hexane, washed three times, and dried to obtain a pink linear polymer PMMA-b-P2VP.

[0161] The above linear polymer PMMA-b-P2VP was taken in a test tube, 0.02 mmol of azobisisobutyronitrile (AIBN), 0.2 mmol of 4-chloromethylstyrene (VBC), and 2 mL of dioxane were stirred uniformly, and then oxygen was removed by three cycles of freezing-pumping-thawing. Block copolymerization was carried out at 80°C for 8 h. After the reaction was terminated by cooling, the second reaction product was obtained. The second reaction product was precipitated in n-hexane, washed three times, and dried to obtain a pink linear polymer PMMA-b-P2VP-b-PVBC, i.e., a linear polymer precursor.

[0162] The above linear polymer PMMA-b-P2VP-b-PVBC was taken in a test tube, 0.2 mmol of NaN3, 10 mmol of iodoethane, and 1 mL of dimethylformamide were added, and the mixture was reacted for 24 h to obtain a third reaction product. The third reaction product was precipitated in n-hexane, washed three times, and dried to obtain a linear polymer PMMA-b-P2VP-b-PVBC with an azido group and a charge at the end.

[0163] The above linear polymer PMMA-b-P2VP-b-PVBC with an azido group and a charge at the end was taken in a test tube, 1 mL of dimethylformamide (DMF) was added to dissolve the polymer, 0.2 mmol of catalyst triphenylphosphine was added, the mixture was stirred for 30 min, 0.6 mmol of catalyst triphenylphosphine was added, and the mixture was heated to 40°C to carry out Staudinger reaction, and the mixture was reacted for 8 h to achieve cyclization. After the reaction was completed, the charged group was removed by washing with saturated NaHCO3, and the mixture was precipitated and dried in n-hexane at 60°C to remove triphenylphosphine, thereby obtaining a cyclic polymer.

[0164] characterization

[0165] 1. GPC test

[0166] The gel permeation chromatography (GPC) test was carried out on Example 2, and the results are shown in Table 1. Figure 1 Figure 1 The gel permeation chromatography (GPC) curve comparison diagram of the linear polymer precursor and the cyclic polymer of Example 2 of the present application is shown in Figure 1. As shown in Figure 1, the linear polymer precursor and the cyclic polymer have different GPC curves.​Figure 1 It can be seen that the GPC curve is slightly right-shifted after the cyclization, which is consistent with the characteristics of the cyclic polymer.

[0167] 2. DLS test

[0168] The dynamic light scattering (DLS) test was performed on Example 2, and the results are shown in Figure 2 Figure 2 A comparison chart of the dynamic light scattering (DLS) data of the linear polymer precursor and the cyclic polymer of Example 2 of the present application is shown. From Figure 2 It can be seen that the average particle size of the cyclic polymer is smaller than that of the linear polymer precursor, further indicating that the cyclic polymer is prepared by the method of the present application.

[0169] 3. TEM test

[0170] A sample picture of the cyclic polymer of Example 2 was observed using a transmission electron microscope. Among them, the cyclic polymer was visualized by grafting PEO-CHO with Mn = 1000. Figure 3 A sample picture of the cyclic polymer of Example 2 of the present application was observed under a transmission electron microscope. From Figure 3 It can be seen that the cyclic polymer is prepared by the method of the present application.

[0171] industrial applicability

[0172] The cyclic polymer has no end group, and has smaller viscosity and hydrodynamic volume, thus having different physical and chemical properties from linear polymers. The cyclic polymer is not easy to entangle, can pass through some human organs well, has better permeability and retention effect, and thus realizes the targeted delivery of drugs. Due to the absence of end groups, the chemical properties are more stable, and thus have a longer circulation time in the blood circulation, and can be used to load slow-release drugs. Based on the end group-free characteristics, the cyclic polymer can overcome some common shortcomings of drugs, including low selectivity caused by fast metabolism, low cell permeability, insufficient conformational flexibility and stability, and thus realize the development of new drugs. In addition, by incorporating azobenzene repeating units in the main chain of the cyclic polymer, photoisomerization ability can be generated, which is expected to be used in potential optical data storage and liquid crystal displays, etc.

[0173] It should be noted that although the technical solutions of the present application are introduced with specific examples, those skilled in the art can understand that the present application should not be limited thereto.

[0174] ​Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments covered by the claims. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the spirit and scope of the described embodiments. It is intended that the scope of the application should only be limited by the appended claims.

Claims

1. A method for preparing a cyclic polymer, characterized by, The method comprises the following steps: obtaining a linear polymer precursor having groups A, groups B and side groups F; binding a compound D to at least part of the side groups F of the linear polymer precursor, and converting at least part of the side groups F of the linear polymer precursor into charged groups; chemically reacting the groups A and the groups B to form a charged cyclic polymer; optionally removing the charged groups to obtain a cyclic polymer; the groups A are selected from one or a combination of azido, halogen; the groups B are selected from one or a combination of substituted or unsubstituted alkynyl, ester, halogen, hydroxyl, substituted or unsubstituted amino, substituted or unsubstituted amide; the side groups F are selected from one or a combination of carboxyl, amino, halogen, tertiary amine, pyridyl, imidazolyl; the compound D comprises one or a combination of carboxylic compounds, amino compounds, halogenated compounds, tertiary amine compounds, pyridine compounds, imidazole compounds.

2. The production method according to claim 1, characterized by, The number average molecular weight of the linear polymer precursor is 5000-200000 g / mol.

3. The method of claim 2, wherein, The number average molecular weight of the linear polymer precursor is 10000-100000 g / mol.

4. The production method according to any one of claims 1 to 3, characterized by, The compound D and the linear polymer precursor convert at least part of the side groups F of the linear polymer precursor into charged groups through a quaternization reaction or a salt formation reaction.

5. The method of any one of claims 1-3, wherein, The chemical reaction comprises one or a combination of click reaction, Staudinger reaction, coupling reaction.

6. The method of any one of claims 1-3, wherein, In the preparation system, the concentration of the linear polymer precursor is 1-300 mg / mL.

7. The production method according to claim 6, wherein In the preparation system, the concentration of the linear polymer precursor is 10-100 mg / mL.

8. The method of any one of claims 1-3, wherein, The temperature of the chemical reaction is 0-100℃; and the time of the chemical reaction is 1-48 hours.

9. The production method according to claim 8, characterized by, The temperature of the chemical reaction is 25-80℃; and the time of the chemical reaction is 3-36 hours.

10. The method of any one of claims 1-3, wherein, The chemical reaction is carried out in a solvent.

11. The method of claim 10, wherein, The dielectric constant of the solvent is 2.2-49.

12. The method of claim 11, wherein, The dielectric constant of the solvent is 2.6-37.

13. A cyclic polymer, characterized by, Prepared by the method for preparing a cyclic polymer according to any one of claims 1-12.

14. The cyclic polymer of claim 13, wherein, The diameter of the cyclic polymer is 3-100 nm.

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