Method for manufacturing liquid crystal oligomer, liquid crystal oligomer manufactured therefrom, liquid crystal elastomer formed from liquid crystal oligomer, and material including same, and applications thereof

Abstract

The present disclosure provides a method for manufacturing a liquid crystal oligomer, comprising a step of preparing a liquid crystal mixture by mixing a liquid crystal monomer represented by chemical formula 1 and a chain extender represented by chemical formula 2. Chemical formulas 1 and 2 are explained in the present disclosure.

Description

A method for manufacturing a liquid crystal oligomer, a liquid crystal oligomer manufactured therefrom, a liquid crystal elastomer formed from said liquid crystal oligomer, a material comprising the same, and an application thereof.

[0001] The embodiments of the present disclosure relate to a method for manufacturing a liquid crystal oligomer, and more specifically, to a method for manufacturing a liquid crystal oligomer that has a controlled molecular weight and can have a powder-like form having crystalline properties without substantially occurring entanglement.

[0002] Liquid Crystal Oligomers (LCOs) are oligomers formed by the combination of liquid crystal monomers and chain extenders. Liquid Crystal Elastomers (LCEs), formed by the cross-linking of liquid crystal oligomers, are polymers that simultaneously possess high elasticity and high strain due to the polymer chains, as well as orientation, optical anisotropy, and self-assembly characteristics due to the liquid crystal monomers. Liquid crystal monomers can be bonded to the main chain or side chains of the polymer chain. When liquid crystal monomers are uniformly oriented within the liquid crystal elastomer, the degree of order of the liquid crystal molecules changes due to heat, light, or chemical stimuli, thereby transforming the polymer chain structure. Furthermore, upon removal of such stimuli, the polymer may possess reversibility, allowing it to return to its pre-transformation state depending on the polymer cross-linking structure.

[0003] The performance reliability of applications such as artificial muscles, soft robots, flexible devices, actuators, or sensors can be improved by using liquid crystal elastomers that possess specific thermal and / or mechanical properties. However, there is a problem in that it is difficult to achieve specific properties because linear chain structures grow as liquid crystal monomers and chain extenders polymerize until they are completely consumed, and entanglement between linear chain structures may occur after a certain period of time. Furthermore, since this specific period is a relatively short duration of seconds to minutes, which is difficult to manage, it is practically difficult to control the occurrence of entanglement. Meanwhile, entangled liquid crystal elastomers generally take on a paste-like form, resulting in poor long-term storage stability and potentially degrading processability for subsequent processes, such as solution processes like coating.

[0004] Conventionally, as molecular weight growth proceeds rapidly between a liquid crystal monomer and a chain extender having a single composition and a single molar ratio, entanglement occurs and a non-crystalline paste-like liquid crystal oligomer is formed, and as a liquid crystal elastomer is manufactured from such a liquid crystal oligomer, there was a problem in that it was difficult to control the thermal and mechanical properties of the liquid crystal elastomer.

[0005] The embodiments of the present disclosure are intended to solve various problems, including those mentioned above, by providing a method for manufacturing a liquid crystal oligomer having a specific molecular weight, in which entanglement does not substantially occur or is prevented, and which possesses crystallinity. Furthermore, by optimizing the structure of the liquid crystal elastomer using such a liquid crystal oligomer, the present disclosure aims to provide a liquid crystal elastomer having specific characteristics. However, these problems are exemplary and the scope of the present disclosure is not limited by them.

[0006] According to one aspect of the present disclosure, a method for preparing a liquid crystal oligomer is provided, comprising the step of preparing a liquid crystal mixture by mixing a liquid crystal monomer represented by the following chemical formula 1 and a chain extender represented by the following chemical formula 2:

[0007] <Chemical Formula 1>

[0008]

[0009] Among the above chemical formula 1,

[0010] CY 11 , CY 12 and Ar 13 are independent of each other, at least one R 10 C3-C substituted or unsubstituted 30 It is a cabocyclic group, and

[0011] L1 is *-C(=O)O-*' and * is (Ar 13 ) a2 It is a combined site with, and *' is CY 12 It is a combination site with,

[0012] a1 and a2 are independently 0 or 1, and

[0013] m and n are independently selected from integers 1 to 20, and

[0014] R 10 -F, -Cl, -Br, -I, C1-C 10 Alkyl groups and C6-C 20 Selected from among the Arilgi,

[0015] <Chemical Formula 2>

[0016]

[0017] Among the above chemical formula 2,

[0018] L 21 and L 22 are independently *-O-*' or *-C(=O)O-*', and

[0019] a21 and a22 are independently 0 or 1, and

[0020] q, r, and s are independently selected from integers 1 to 20.

[0021] According to the present embodiment, the method for manufacturing the liquid crystal oligomer may further include the step of adding a base catalyst to the liquid crystal mixture.

[0022] According to the present embodiment, the method for manufacturing the liquid crystal oligomer may further include the step of performing a polymerization reaction with respect to the liquid crystal mixture at 15°C to 100°C.

[0023] According to the present embodiment, the liquid crystal mixture may not contain a crosslinking agent.

[0024] According to the present embodiment, the crosslinking agent may include three or more thiol groups.

[0025] According to the present embodiment, the chain extender can be represented by the following chemical formula 2-1:

[0026] <Chemical Formula 2-1>

[0027]

[0028] In the above chemical formula 2-1, t is selected from integers from 1 to 30.

[0029] According to the present embodiment, the method for manufacturing the liquid crystal oligomer may further include the step of adding an alcohol-based solvent to the liquid crystal mixture to terminate the reaction.

[0030] According to the present embodiment, the number of moles of the liquid crystal monomer may be greater than the number of moles of the chain extender.

[0031] According to one aspect of the present disclosure, a liquid crystal oligomer is provided by the method for manufacturing a liquid crystal oligomer described above.

[0032] According to the present embodiment, the liquid crystal oligomer may include acrylate groups at both ends.

[0033] According to the present embodiment, the polydispersity of the liquid crystal oligomer may be 1 to 5.

[0034] According to the present embodiment, the viscosity of the liquid crystal oligomer may be 10 cP to 10,000 cP.

[0035] According to one aspect of the present disclosure, a liquid crystal elastomer formed by crosslinking the liquid crystal oligomer described above is provided.

[0036] According to one aspect of the present disclosure, an artificial muscle made of the liquid crystal elastomer described above is provided.

[0037] According to one aspect of the present disclosure, an actuator made of the liquid crystal elastomer described above is provided.

[0038] Other perspectives, aspects, features, and advantages other than those described above will become clear from the specific details, claims, and drawings for implementing the invention below.

[0039] According to an exemplary embodiment of the present disclosure as described above, a liquid crystal oligomer having a specific molecular weight and in a crystalline powder form can be manufactured in which entanglement does not substantially occur or is prevented. This improves the processability of subsequent processes using the liquid crystal oligomer and enables the manufacture of a liquid crystal elastomer having consistent (predictable) characteristics. Of course, the scope of the present disclosure is not limited by these effects.

[0040] FIG. 1 is a flowchart of a method for manufacturing a liquid crystal oligomer according to one embodiment of the present disclosure.

[0041] Figures 2 and 3 are drawings showing non-limiting examples of liquid crystal monomers.

[0042] Figure 4 is a diagram showing a non-limiting example of a chain extender.

[0043] Figure 5 is a diagram showing a non-limiting example of a base catalyst.

[0044] Figure 6 is a diagram showing an example of synthesizing a liquid crystal oligomer.

[0045] Figure 7 is a diagram showing another example of synthesizing a liquid crystal oligomer.

[0046] Figure 8 is a diagram showing the results of visual observation of liquid crystal oligomers prepared according to Example 1 and Comparative Example 1, respectively.

[0047] Figure 9 is a diagram showing the results of measuring the viscosity of each liquid crystal oligomer prepared in the examples.

[0048] FIG. 10 is a figure showing the spectral results obtained through FT-IR analysis for each liquid crystal oligomer prepared in the examples and each of the reactants used in their synthesis.

[0049] Figure 11 is a diagram showing the results of size exclusion column chromatography analysis of liquid crystal oligomers according to the examples.

[0050] FIGS. 12 and 13 are according to embodiments 1 These are diagrams showing H-NMR spectra.

[0051] The present disclosure is capable of various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various forms.

[0052] In the following embodiments, terms such as first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0053] In the following examples, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0054] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0055] In the following embodiments, when a part such as a layer, region, or component is described as being on or above another part, it includes not only cases where it is directly on top of another part, but also cases where another region, component, etc. is interposed in between.

[0056] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, and therefore the present disclosure is not necessarily limited to what is depicted.

[0057] Where an embodiment can be implemented differently, a specific sequence of operations may be performed differently from the order described. For example, two steps described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0058] In this specification, “A and / or B” indicates the case where it is A, B, or A and B. And, “at least one of A and B indicates the case where it is A, B, or A and B.”

[0059] In the following embodiments, when layers, regions, components, etc. are described as being connected, this includes cases where the layers, regions, components are directly connected, or / or cases where other layers, regions, components are interposed between the layers, regions, components to be indirectly connected. For example, when layers, regions, components, etc. are described as being electrically connected in this specification, it indicates cases where the layers, regions, components, etc. are directly electrically connected, and / or cases where other layers, regions, components, etc. are interposed between them to be indirectly electrically connected.

[0060] The x-axis, y-axis, and z-axis are not limited to the three axes of an orthogonal coordinate system but can be interpreted in a broader sense that includes them. For example, the x-axis, y-axis, and z-axis may be orthogonal to each other, but they may also refer to different directions that are not orthogonal to each other.

[0061] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure is complete and to fully inform those skilled in the art of the scope of the present disclosure, and the present disclosure is defined only by the scope of the claims.

[0062] The terms used in this disclosure are for describing the embodiments and are not intended to limit this disclosure. In this disclosure, the singular form may include the plural form unless specifically stated otherwise in the text. As used in this disclosure, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned. Throughout the disclosure, "and / or" may include each of the components mentioned and all combinations of one or more.

[0063] The word "exemplary" is used in this disclosure to mean "used as an example or illustration." Any embodiment described as "exemplary" in this disclosure should not be interpreted as being preferred or having an advantage over other embodiments.

[0064] Unless otherwise defined, all terms used in this disclosure (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which this disclosure pertains. Additionally, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0065] In the present disclosure, the word “oligomer” may refer to a low-molecular-weight compound in chain form that has a molecular weight of hundreds of g / mol to tens of thousands of g / mol (e.g., number average molecular weight) and does not have a cross-linked structure. The word “elastomer” may refer to a high-molecular-weight compound in network form that has a molecular weight of tens of thousands of g / mol to hundreds of thousands of g / mol (e.g., number average molecular weight) and has some cross-linked structure. An elastomer may be formed from an oligomer, and the oligomer and the elastomer may be distinguished based on whether they have a cross-linked structure (e.g., three or more cross-linking sites) and / or a molecular weight of tens of thousands of g / mol (e.g., a number average molecular weight of 40,000 g / mol, 30,000 g / mol, 20,000 g / mol, or 10,000 g / mol).

[0066] C1-C in the present disclosure 10An alkyl group refers to a linear or branched aliphatic hydrocarbon monovalent group having 1 to 10 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, a neopentyl group, an isopentyl group, a sec-pentyl group, a 3-pentyl group, a sec-isoopentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, and an n-decyl group. It includes isodecyl groups, sec-decyl groups, tert-decyl groups, etc.

[0067] C3-C in the present disclosure 30 A carbocyclic group refers to a cyclic group having 3 to 30 carbon atoms composed only of carbon as ring-forming atoms, and specific examples thereof include a cyclopropane group, a cyclobutane group, a cyclopentane group, a cyclohexane group, a cycloheptane group, a cyclooctane group, a cyclobutene group, a cyclopentene group, a cyclohexene group, a cycloheptene group, a benzene group, a naphthalene group, a pentylene group, an azulene group, an acenaphtylene group, a phenalene group, a phenanthrene group, anthracene group, a fluoranthene group, a triphenylene group, a pyrene group, and the like.

[0068] C3-C in the present disclosure 30 A heterocyclic group refers to a cyclic group having 3 to 30 carbon atoms that includes, in addition to carbon, a heteroatom as a ring-forming atom. Specific examples thereof include pyridine groups, pyrimidine groups, triazine groups, pyrrolidine groups, dihydropyrrole groups, azephane groups, azepine groups, tetrahydroazepine groups, etc. Examples of heteroatoms include nitrogen, sulfur, oxygen, phosphorus, silicon, boron, etc.

[0069] C6-C in the present disclosure 20An aryl group refers to a monovalent group having a carbocyclic aromatic system having 6 to 20 carbon atoms, and specific examples thereof include a phenyl group, a pentalenyl group, a naphthyl group, an azulenyl group, an indacenyl group, an acenaphthyl group, a phenalenyl group, a phenanthrenyl group, anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, etc.

[0070] FIG. 1 is a flowchart of a method for manufacturing a liquid crystal oligomer according to one embodiment of the present disclosure.

[0071] Referring to FIG. 1, a manufacturing method according to one embodiment of the present disclosure may include the steps of: preparing a liquid crystal mixture by mixing a liquid crystal monomer represented by Formula 1 described below and a chain extender represented by Formula 2 described below (S10); adding a base catalyst to the liquid crystal mixture (S20); performing a polymerization reaction with respect to the liquid crystal mixture at 15°C to 100°C (S30); and adding an alcohol-based solvent to the liquid crystal mixture to terminate the reaction (S40).

[0072] According to one embodiment, the liquid crystal mixture may not contain a crosslinking agent. For example, the crosslinking agent may contain three or more thiol groups. That is, a chain extender having two thiol groups represented by Formula 2 described below is clearly different from a crosslinking agent, and a crosslinking agent having three or four thiol groups is not added to form the liquid crystal oligomer according to the present disclosure. Accordingly, the liquid crystal oligomer can grow in a chain form with suitable crosslinking points, and entanglement between chains may not substantially occur.

[0073] According to one embodiment, the moles of the liquid crystal monomer may be greater than the moles of the chain extender. For example, the ratio of the moles of the liquid crystal monomer to the moles of the chain extender may be 1.01:1 to 1.5:1, 1.05:1 to 1.5:1, 1.05:1 to 1.3:1, or 1.1:1 to 1.2:1. Specifically, the ratio of the moles of the liquid crystal monomer to the moles of the chain extender may be 1.1:1.

[0074] According to one embodiment, in step S30, the polymerization reaction may be carried out at 15°C to 60°C, 15°C to 40°C, 15°C to 30°C, 15°C to 25°C, 20°C to 60°C, 20°C to 40°C, 20°C to 30°C, or 20°C to 25°C. For example, the polymerization reaction may be carried out at room temperature (about 20°C to about 25°C). By carrying out the polymerization reaction within the above-described temperature range, it may be easy to obtain the liquid crystal oligomer at a desired molecular weight within a manageable time.

[0075] According to one embodiment, examples of the alcohol-based solvent include methanol, ethanol, propanol, etc. The alcohol-based solvent may be used in combination with a non-alcohol-based solvent.

[0076] According to another aspect of the present disclosure, a liquid crystal oligomer is provided by the method for manufacturing a liquid crystal oligomer described above.

[0077] In the above method for manufacturing a liquid crystal oligomer, since the molar amount of the liquid crystal monomer is greater than the molar amount of the chain extender, the liquid crystal oligomer may include acrylate groups at both ends. The acrylate groups at both ends can serve as crosslinking points for forming a liquid crystal elastomer.

[0078] According to one embodiment, the polydispersity index (PDI) of the liquid crystal oligomer may be 1 to 5. For example, the polydispersity index of the liquid crystal oligomer may be 1 to 4.5, 1 to 4.3, 1 to 3.5, or 1 to 3.0. That is, the liquid crystal oligomer prepared according to the present disclosure may substantially have a specific molecular weight. The method for preparing a liquid crystal oligomer according to the present disclosure can control the molecular weight of the prepared liquid crystal oligomer by controlling the reaction time within a manageable time.

[0079] According to one embodiment, the viscosity of the liquid crystal oligomer may be 10 cP to 10,000 cP. For example, the viscosity of the liquid crystal oligomer may be approximately 50 cP to approximately 3,000 cP. That is, the liquid crystal oligomer may substantially prevent entanglement or prevent excessive entanglement.

[0080] According to another aspect of the present disclosure, a liquid crystal elastomer formed by crosslinking the liquid crystal oligomer described above is provided. Such a liquid crystal elastomer can be applied in various applications such as actuators, artificial muscles, robots (soft robots), flexible devices, sensors, adhesives, shock absorbers, noise absorbers, electronic device substrates, and encapsulation materials.

[0081] According to another aspect of the present disclosure, an actuator made of the liquid crystal oligomer described above is provided. Additionally, an artificial muscle comprising said actuator and acting upon the application of voltage or light stimulation is provided.

[0082] Liquid crystal monomer

[0083] Liquid crystal monomers can be represented by the following chemical formula 1:

[0084] <Chemical Formula 1>

[0085]

[0086] Among the above chemical formula 1,

[0087] CY 11 , CY 12 and Ar 13 are independent of each other, at least one R 10 C3-C substituted or unsubstituted 30 It is a cabocyclic group, and

[0088] L1 is *-C(=O)O-*' and * is (Ar 13 ) a2 It is a combined site with, and *' is CY 12 It is a combination site with,

[0089] a1 and a2 are independently 0 or 1, and

[0090] m and n are independently selected from integers 1 to 20, and

[0091] R 10 -F, -Cl, -Br, -I, C1-C 10 Alkyl groups and C6-C 20 It can be selected from among the Arilgi.

[0092] According to one embodiment, m and n may be independently selected from integers 1 to 15. Each of m and n may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11. In one example, m and n may be the same. In another example, m and n may be different.

[0093] According to one embodiment, CY 11 , CY 12 and Ar 13 The groups can independently be six-membered rings. The said six-membered rings can be benzene groups or cyclohexane groups. For example, CY 11 , CY 12 and Ar 13 ☐ may be a group represented independently of any one of the following chemical formulas CY-1 to CY-6:

[0094]

[0095] Among the above chemical formulas CY-1 to CY-6,

[0096] R 10 is the same as described in Chemical Formula 1 above, and

[0097] b4 is selected from integers from 0 to 4, and

[0098] b8 is selected from integers from 0 to 8, and

[0099] * and *' are each bonding sites with neighboring atoms.

[0100] In the above Chemical Formula 1, when a1 is 0, (L1) a1 can mean a single combination.

[0101] In the above Chemical Formula 1, when a2 is 0, (Ar 13 ) a2 can mean a single combination.

[0102] For example, when a1 and a2 are each 0, the liquid crystal monomer can be represented by the following chemical formula 1-1:

[0103] <Chemical Formula 1-1>

[0104]

[0105] In the above chemical formula 1-1, CY 11 , CY 12 , m and n are each the same as described in Chemical Formula 1 above.

[0106] As another example, when a1 is 1, the liquid crystal monomer can be represented by the following chemical formula 1-2:

[0107] <Chemical Formula 1-2>

[0108]

[0109] In the above chemical formula 1-2, CY 11 , CY 12 , Ar 13 , a2, m and n are each the same as described in Chemical Formula 1 above.

[0110] As another example, if a2 is 1, Ar 13 Since this exists, the liquid crystal monomer can be represented by the following chemical formula 1-3:

[0111] <Chemical Formula 1-3>

[0112]

[0113] Among the above chemical formulas 1-3,

[0114] CY 13 Ar in the above Chemical Formula 1 13 It is identical to the explanation for,

[0115] CY 11 , CY 12 , L1, a1, m, and n are each the same as described in Chemical Formula 1 above.

[0116] According to one embodiment, the liquid crystal monomer may be represented by any one of the following chemical formulas 1-11 to 1-26:

[0117] <Chemical Formula 1-11>

[0118]

[0119] <Chemical Formula 1-12>

[0120]

[0121] <Chemical Formula 1-13>

[0122]

[0123] <Chemical Formula 1-14>

[0124]

[0125] <Chemical Formula 1-15>

[0126]

[0127] <Chemical Formula 1-16>

[0128]

[0129] <Chemical Formula 1-17>

[0130]

[0131] <Chemical Formula 1-18>

[0132]

[0133] <Chemical Formula 1-19>

[0134]

[0135] <Chemical Formula 1-20>

[0136]

[0137] <Chemical Formula 1-21>

[0138]

[0139] <Chemical Formula 1-22>

[0140]

[0141] <Chemical Formula 1-23>

[0142]

[0143] <Chemical Formula 1-24>

[0144]

[0145] <Chemical Formula 1-25>

[0146]

[0147] <Chemical Formula 1-26>

[0148]

[0149] Among the above chemical formulas 1-11 to 1-26,

[0150] R 11, R 12a , R 12b and R 13 Each is R in the above Chemical Formula 1 10 It is identical to the explanation for,

[0151] Ar 13 , L1, a1, a2, m, and n are each the same as described in Chemical Formula 1 above, and

[0152] b4 is selected from integers 0 to 4.

[0153] Figures 2 and 3 are drawings showing non-limiting examples of liquid crystal monomers.

[0154] Referring to FIGS. 2 and 3, the liquid crystal monomer may be any one of compounds A1 to A16, but is not limited thereto.

[0155] The liquid crystal monomer is a diacrylate compound containing acrylate groups at both ends, and monoacrylate compounds, triacrylate compounds, tetraacrylate compounds, etc., are clearly different from the liquid crystal monomer described above. Since the liquid crystal monomer is a diacrylate compound, the liquid crystal oligomer formed therefrom has properties such as elasticity and orientation, and has appropriate crosslinking points, so it can be polymerized at a manageable speed and manufactured in an unentangled form.

[0156] Chain extender

[0157] The chain extender can be represented by the following chemical formula 2:

[0158] <Chemical Formula 2>

[0159]

[0160] Among the above chemical formula 2,

[0161] L 21 and L 22 are independently *-O-*' or *-C(=O)O-*', and

[0162] a21 and a22 are independently 0 or 1, and

[0163] q, r, and s are independently selected from integers 1 to 20.

[0164] That is, the chain extender may include two thiol groups.

[0165] According to one embodiment, q, r, and s may be independently selected from integers 1 to 15. Each of q, r, and s may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11. q, r, and s may be identical to each other. q and r may be identical to each other and q and s may be different from each other. q and s may be identical to each other and q and r may be different from each other. r and s may be identical to each other and r and q may be different from each other. q, r, and s may be different from each other.

[0166] According to one embodiment, the chain extender may be represented by any one of the following chemical formulas 2-1 to 2-3:

[0167] <Chemical Formula 2-1>

[0168]

[0169] <Chemical Formula 2-2>

[0170]

[0171] <Chemical Formula 2-3>

[0172]

[0173] Among the above chemical formulas 2-1 to 2-3,

[0174] q, r, and s are each the same as described in Chemical Formula 2 above, and

[0175] t is selected from integers 1 to 30.

[0176] In the above chemical formula 2-1, t can be selected from integers from 1 to 20. For example, t can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15.

[0177] If a chain extender outside the range of the chemical formulas 2-1 to 2-3 described above is applied, the prepared liquid crystal oligomer may not have crystallinity and may have a paste-like form. Consequently, the storage stability of the prepared liquid crystal oligomer may be reduced.

[0178] Figure 4 shows non-limiting examples of chain extenders.

[0179] Referring to FIG. 4, the chain extender may be any one of compounds B1 to B5, but is not limited thereto.

[0180] The above chain extender is a dithiol compound containing thiol groups at both ends, and monothiol compounds, trithiol compounds, tetrathiol compounds, etc. are clearly different from the chain extender described above. Since the above chain extender is a dithiol compound, it can form a liquid crystal oligomer, and the liquid crystal oligomer formed therefrom has properties such as elasticity and orientation, and has appropriate crosslinking points so that it can be polymerized at a controllable rate and manufactured in an unentangled form.

[0181] base catalyst

[0182] The base catalyst may contain a nitrogen atom. The base catalyst may be represented by the following chemical formula 3-1 or 3-2:

[0183]

[0184] Among the above chemical formulas 3-1 and 3-2,

[0185] CY3 is C3-C 30 It is a heterocyclic group, and

[0186] R 31 to R 35 are independently hydrogen, -F, -Cl, -Br, -I, C1-C 10 Alkyl groups and C6-C 20 Selected from among the Arilgi,

[0187] b6 is selected from integers from 0 to 6, and

[0188] c3 is selected from integers from 0 to 20.

[0189] According to one embodiment, CY3 may be a five-membered ring, a six-membered ring, or a seven-membered ring. CY3 may contain only one heteroatom (nitrogen atom) as shown in Chemical Formula 3-2, and the remaining ring-forming atoms may be carbon atoms. For example, the base catalyst represented by Chemical Formula 3-2 may contain two nitrogen atoms.

[0190] According to one embodiment, in the above chemical formula 3-1, R 31 to R 33 At least one of them is C1-C 10 It can be an alkyl group.

[0191] Figure 5 is a diagram showing a non-limiting example of a base catalyst.

[0192] Referring to FIG. 5, the base catalyst may be any one of compounds C1 to C5, but is not limited thereto.

[0193] Synthesis Example 1

[0194] Figure 6 is a diagram showing an example of synthesizing a liquid crystal oligomer at room temperature by mixing the liquid crystal monomer and chain extender described above and adding a base catalyst.

[0195] Referring to Fig. 6, the acrylate group of the liquid crystal monomer and the thiol group of the chain extender react to polymerize, and since the number of moles of the liquid crystal monomer is greater than the number of moles of the chain extender, a liquid crystal oligomer having acrylate groups at both ends can be synthesized.

[0196] Synthesis Example 2

[0197] Figure 7 is a diagram showing another example of synthesizing a liquid crystal oligomer at room temperature by mixing the liquid crystal monomer and chain extender described above and adding a base catalyst.

[0198] Referring to Figures 6 and 7, it can be seen that the shape of the repeating unit differs depending on the type of chain extender (non-oxide-based compounds and oxide-based compounds). x in Figures 6 and 7 may represent any natural number.

[0199] The synthesis method of liquid crystal oligomers other than the liquid crystal oligomers synthesized in Synthesis Examples 1 and 2 above can be easily recognized by those skilled in the art by referring to the synthesis route and raw materials.

[0200] Example 1 (Preparation of Liquid Crystal Oligomer)

[0201] 100 parts by weight of chloroform were mixed with 2 parts by weight of n-butylamine (see Compound C3 in Fig. 5) as a base catalyst, RM82 (see Compound A6 in Fig. 2) as a liquid crystal monomer, and 1,6-hexanedithiol (HDT) (see Compound B2 in Fig. 4) as a chain extender in a molar ratio of 1.1:1 at room temperature (about 25°C).

[0202] A liquid crystal oligomer was prepared by adding an excess amount of methanol after 5 minutes to terminate the reaction.

[0203] Examples 2 to 4 (change in reaction time)

[0204] A liquid crystal oligomer was prepared in the same manner as in Example 1 above, except that instead of performing the reaction for 5 minutes, the reaction was terminated after performing the reaction time shown in Table 1 below.

[0205] Comparative Example 1

[0206] A liquid crystal oligomer was prepared in the same manner as in Example 1, except that pentaerythritol tetrakis(3-mercaptopropionate; PETMP) was added as a crosslinking agent and the reaction was carried out at 150°C instead of room temperature.

[0207] Evaluation Example 1 (Visual evaluation of entanglement)

[0208] Figure 8 is a diagram showing the results of visual observation of liquid crystal oligomers prepared according to Example 1 and Comparative Example 1, respectively.

[0209] Referring to FIG. 8, it can be seen that the liquid crystal oligomer according to Comparative Example 1 is entangled and does not dissolve in an organic solvent, making further processing impossible. However, the liquid crystal oligomer according to Example 1 does not substantially exhibit entanglement and can be dissolved or precipitated in an organic solvent; thus, it can be seen that upon separation, it can be obtained in a powder form (e.g., in the form of a crystalline powder rather than a paste). As a result, it can be seen that the liquid crystal oligomers according to the embodiments of the present disclosure are suitable for further processing and easy to store.

[0210] Evaluation Example 2 (Viscosity Evaluation)

[0211] FIG. 9 is a figure showing the results of measuring the viscosity of liquid crystal oligomers prepared according to each of Examples 1 to 4. Specifically, the viscosity of each liquid crystal oligomer was measured at 5-day intervals for 30 days under constant temperature and humidity using a rotational viscometer equipped with Brookfield RVD-III ULTRA equipment.

[0212] Referring to FIG. 9, it can be seen that as the reaction time increases, the viscosity of the prepared liquid crystal oligomer increases, but has a viscosity of about 10 cP to 10,000 cP. As a result, it can be seen that the liquid crystal oligomer prepared according to the example does not substantially cause entanglement or prevents excessive entanglement, and subsequently has good processability.

[0213] Evaluation Example 3 (Fourier transform infrared spectroscopy (FT-IR) analysis)

[0214] In the FT-IR spectrum, the thiol functional group is at approximately 2560 cm⁻¹. -1 To about 2565cm -1 A peak may appear in the vicinity, and the acrylate functional group is at approximately 800 cm⁻¹ -1 To about 810cm -1 A peak may appear in the vicinity.

[0215] FIG. 10 is a figure showing the spectral results obtained through FT-IR analysis for each liquid crystal oligomer prepared in Examples 1 to 4 and each of RM82 and HDT used in their synthesis.

[0216] Referring to Fig. 10, RM82 without thiol functional groups is approximately 2560 cm -1 To about 2565cm -1 It does not have a peak in the vicinity, and the HDT containing the thiol functional group is approximately 2560 cm⁻¹. -1 To about 2565cm -1 It can be confirmed that it has a peak in the vicinity. Additionally, RM82 containing an acrylate functional group is at approximately 800 cm⁻¹. -1 To about 810cm -1 It has a peak in the vicinity, and the HDT without acrylate functional groups is approximately 800 cm⁻¹. -1 To about 810cm -1 It can be confirmed that there is no peak in the vicinity.

[0217] The liquid crystal oligomers according to each of Examples 1 to 4 are approximately 2560 cm⁻¹ -1 To about 2565cm -1 Since it does not have a peak in the vicinity, it can be seen that it does not contain a thiol functional group, and at approximately 800 cm⁻¹ -1 To about 810cm -1 It can be seen that it contains an acrylate functional group as it has a peak in the vicinity. Since RM82 is used in excess of HDT as a reactant, this result implies that acrylate is present at both ends of the liquid crystal oligomer prepared, as can be confirmed in Figure 6 or 7.

[0218] Evaluation Example 4 (Size-Exclusion Chromatography (SEC) Analysis)

[0219] Each liquid crystal oligomer prepared in Examples 1 to 4 was passed through a porous material having pores, and the amount reached during the retention time to reach the detector was measured.

[0220] FIG. 11 is a diagram showing the SEC analysis results of liquid crystal oligomers according to Examples 1 to 4.

[0221] Referring to Fig. 11, it can be seen that as the reaction time increases during synthesis, polymerization proceeds further, and the retention time of the liquid crystal oligomer with a large molecular weight increases. Additionally, by referring to the distribution according to retention time, it can be seen that the liquid crystal oligomers according to Examples 1 to 4 contain polymer chains having a relatively specific range of molecular weight distribution rather than polymer chains having various molecular weights.

[0222] Evaluation Example 5 (Gel Permeation Chromatography (GPC) Analysis)

[0223] Each liquid crystal oligomer prepared in Examples 1 to 4 was dissolved in tetrahydrofuran (THF) and its number-average molecular weight (M) was determined using GPC. n ) and weight-average molecular weight (M w ) was calculated, and the Poly Dispersity Index (PDI) was calculated from it, and the results are shown together in Table 1 below.

[0224] Evaluation Example 6 (Nuclear Magnetic Resonance (NMR) Analysis)

[0225] For each liquid crystal oligomer prepared in Examples 1 to 4 1 The degree of polymerization (DP) was calculated by analyzing the protons of specific functional groups using H-NMR, and the results are shown together in Table 1 below.

[0226] FIG. 12 is for Examples 1, 3 and 4 1 Figure 13 is a diagram showing the H-NMR spectrum and specifically shows the proton analysis results for Example 2.

[0227] Referring to FIGS. 12 and 13, it can be seen that each liquid crystal oligomer prepared according to the examples has spectral results of similar trends. Referring to FIG. 13, peaks i (2.62 ppm), m (2.55 ppm), and k (2.75 ppm) can be identified, indicating that polymerization between the acrylate functional group and the thiol functional group has occurred. For example, peaks f, g, and h appearing at 5.85 ppm to 6.45 ppm correspond to six protons present in the diacrylate at both ends, and their peak integral values ​​can be used to correct other peaks. Peak a appearing at 8.13 ppm corresponds to an aromatic proton, and the degree of polymerization (DP) can be calculated through its peak integral value.

[0228] No. Reaction time M n M w PDIDP Example 15 min 25 25 69 812.76 1.59 Example 2 30 min 37 5 31 15 713.08 2.87 Example 3 4 hours 64 21 21 65 63.37 3.64 Example 4 24 hours 70 9 23 00 214.23 5.06

[0229] From Table 1, it can be seen that the liquid crystal oligomers according to Examples 1 to 4 have a relatively low polydispersity density (PDI) over time, which reduces the likelihood of excessive entanglement of polymer chains and makes it easier to obtain liquid crystal oligomers with a specific molecular weight. Furthermore, by controlling the polymerization rate and terminating the reaction within a sufficiently manageable time, liquid crystal oligomers with desired physical properties can be selectively produced. Therefore, compared to conventional methods in which liquid crystal oligomers are produced within a difficult-to-manage time of seconds to minutes, resulting in entanglement and high polydispersity, liquid crystal oligomers with desired physical properties can be obtained more easily according to the examples. Although the methods for manufacturing liquid crystal oligomers have been described so far, the present disclosure is not limited thereto. For example, liquid crystal oligomers produced by such manufacturing methods are also considered to fall within the scope of the present disclosure.

[0230] Although the present disclosure has been described with reference to embodiments, these are merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true scope of technical protection of the present disclosure should be determined by the technical spirit of the appended claims.

Claims

1. A step (S10) of preparing a liquid crystal mixture by mixing a liquid crystal monomer represented by the following chemical formula 1 and a chain extender represented by the following chemical formula 2; A step (S30) of performing a polymerization reaction on the liquid crystal mixture at 15°C to 40°C; and A method for manufacturing a liquid crystal oligomer, comprising the step (S40) of adding an alcohol-based solvent to the liquid crystal mixture to terminate the reaction: <Chemical Formula 1> Among the above chemical formula 1, CY 11 , CY 12 and Ar 13 are independent of each other, at least one R 10 C3-C substituted or unsubstituted 30 It is a cabocyclic group, and L1 is *-C(=O)O-*' and * is (Ar 13 ) a2 It is a combined site with, and *' is CY 12 It is a combination site with, a1 and a2 are independently 0 or 1, and m and n are independently selected from integers 1 to 20, and R 10 -F, -Cl, -Br, -I, C1-C 10 Alkyl groups and C6-C 20 Selected from among the Arilgi, <Chemical Formula 2> Among the above chemical formula 2, L 21 and L 22 are independently *-O-*' or *-C(=O)O-*', and a21 and a22 are independently 0 or 1, and q, r, and s are independently selected from integers 1 to 20, and The above liquid crystal mixture does not contain a crosslinking agent, and The above liquid crystal oligomer is in the form of a crystalline powder.

2. In Paragraph 1, A method for manufacturing a liquid crystal oligomer, further comprising the step (S20) of adding a base catalyst to the liquid crystal mixture.

3. In Paragraph 1, A method for preparing a liquid crystal oligomer in which the above-mentioned crosslinking agent contains three or more thiol groups.

4. In Paragraph 1, A method for preparing a liquid crystal oligomer, wherein the above chain extender is represented by the following chemical formula 2-1: <Chemical Formula 2-1> In the above chemical formula 2-1, t is selected from integers from 1 to 30.

5. In Paragraph 1, A method for manufacturing a liquid crystal oligomer in which the number of moles of the liquid crystal monomer is greater than the number of moles of the chain extender.

6. Liquid crystal oligomer manufactured by the manufacturing method according to paragraph 1.

7. In Paragraph 6, The above liquid crystal oligomer is a liquid crystal oligomer containing acrylate groups at both ends.

8. In Paragraph 6, A liquid crystal oligomer having a polydispersity of 1 to 5.

9. In Paragraph 6, A liquid crystal oligomer having a viscosity of 10 cP to 10,000 cP.

10. A liquid crystal elastomer formed by cross-linking a liquid crystal oligomer according to claim 6.

11. An artificial muscle comprising a liquid crystal elastomer according to paragraph 10.

12. An actuator comprising a liquid crystal elastomer according to paragraph 10.

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