method

Abstract

A method for increasing or decreasing the authetic response strain threshold of an oriented nematic liquid crystal elastomer, comprising the step of chemically modifying the oriented nematic liquid crystal elastomer.

Description

[Technical Field]

[0001] The present invention relates to a method for increasing or decreasing the authentic response strain threshold in an authentic liquid crystal elastomer, and more particularly to a method for increasing or decreasing the authentic response strain threshold in an authentic liquid crystal elastomer, comprising the step of increasing or decreasing the crosslinking density and / or glass transition temperature (Tg) of the liquid crystal elastomer. [Background technology]

[0002] Auxetic materials have a negative Poisson's ratio, which is described as the negative ratio of the proportional decrease in transverse measurements to the proportional increase in length in a sample of material that is elastically stretched or compressed. When stretched, auxetic materials become thicker in one or both directions perpendicular to the applied deformation.

[0003] Austhetic materials are of particular interest due to their desirable enhanced mechanical properties and potential meta-acoustic properties. Some authetic materials exist naturally, while others, including the first synthetic authetic materials, are carefully manipulated structures that exhibit their authetic behavior due to their bulk structure, such as re-entrant honeycomb-like structures or chiral-based structures. Such authetic materials are used in applications including sportswear due to their improved shock absorption and shear resistance.

[0004] As described in International Publication No. WO 2019 / 077361 A1 pamphlet, an aligned nematic liquid crystal elastomer having cholesteric properties has recently been developed. Cholesteric liquid crystal elastomers have significant advantages over conventional synthetic cholesteric structures, including transparency, no effective lower limit on the size of the material / device, improved strength (without porosity), and the availability of a variety of manufacturing methods. Cholesteric liquid crystal elastomers can also be chemically adjusted, which also provides a significant advantage over existing technologies. Molecular liquid crystal elastomers are soft materials and are more likely to be compatible with living tissues, and thus are likely to provide improved performance in biomedical applications.

[0005] A factor limiting the potential use of molecular cholesteric liquid crystal elastomer materials is that a negative Poisson's ratio is only observed at a specific deformation threshold, hereinafter referred to as the cholesteric response strain threshold.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] Different uses of molecular cholesteric materials require the material to have specific physical properties. Therefore, it is desirable to be able to finely adjust the properties of molecular cholesteric materials.

MEANS FOR SOLVING THE PROBLEM

[0007] The applicant has surprisingly developed a method for increasing or decreasing the cholesteric response strain threshold in an aligned nematic liquid crystal elastomer. The ability to increase or decrease the cholesteric response strain threshold in such a way may expand the applicability of cholesteric liquid crystal elastomers. For example, it may be possible to finely adjust the properties of the liquid crystal elastomer according to the desired end use. In particular, it may be advantageous to lower the cholesteric response strain threshold of the liquid crystal elastomer. For example, it may be advantageous to lower the cholesteric response strain threshold so that the cholesteric regime is achieved at a lower strain value.

[0008] According to a first aspect of the present invention, there is provided a method for increasing (raising) or decreasing (lowering) the cholesteric response strain threshold of a nematic liquid crystal elastomer, the method comprising the step of chemically modifying the nematic liquid crystal elastomer.

[0009] According to a second aspect of the present invention, there is provided the use of a chemically modified nematic liquid crystal elastomer in a method for increasing or decreasing the cholesteric response strain threshold of a nematic liquid crystal elastomer.

[0010] Detailed description The method of the present invention comprises the step of chemically modifying a nematic liquid crystal elastomer.

[0011] The cholesteric response strain threshold may be decreased (using one or more of the methods described herein or other methods). The cholesteric response strain threshold may be increased (using one or more of the methods described herein or other methods).

[0012] Advantageously, it has been found by the inventors that decreasing the cholesteric response strain threshold means, for example, that the cholesteric response may be observed at a lower cholesteric response strain threshold, so that the nematic liquid crystal elastomer may be used in different applications. Applying strain / stress to the nematic liquid crystal elastomer to reach the cholesteric response strain threshold can be very time consuming. Decreasing the cholesteric response strain threshold may mean that less strain / stress has to be applied to the material to observe the response and / or that the stress / strain only has to be applied for a shorter period of time. In the latter case, this may significantly shorten the time required for the nematic liquid crystal elastomer to enter the cholesteric state.

[0013] Advantageously, the ability to "fine-tune" the authetic response strain threshold of an oriented nematic liquid crystal elastomer, that is, to increase or decrease it, means that the properties of the material may be adapted to its desired application (in which case a lower or higher authetic response strain threshold may be desirable). For example, in an application where a damaged joint is supported by the material, it may be advantageous to allow some movement of the joint before the authetic response resists deformation.

[0014] Chemical modification may be intended to alter specific physical properties of the oriented liquid crystal elastomer. For example, chemical modification may be intended to increase (raise) or decrease (lower) the glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer, and / or to change the crosslinking density of the oriented nematic liquid crystal elastomer. Surprisingly, the inventors have found that altering the glass transition temperature (Tg) and / or crosslinking density of the oriented nematic liquid crystal elastomer affects the authetic response strain threshold of the oriented nematic liquid crystal elastomer. While we do not wish to be bound by theory, it is thought that increasing the conformational degrees of freedom of the components of the oriented liquid crystal elastomer lowers the authetic response strain threshold, and vice versa, that is, decreasing the conformational degrees of freedom of the components of the oriented liquid crystal elastomer increases the authetic response strain threshold.

[0015] Preferably, the method may include a step of modifying the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer.

[0016] To avoid misunderstanding, any reference herein to the modification of oriented nematic liquid crystal elastomers (by the methods described herein or otherwise) refers to unmodified or "starting" oriented nematic liquid crystal elastomers, which may be chemically modified in any way that affects the authetic response strain threshold. It will be understood that the modification may include one or more chemical modifications.

[0017] The oriented nematic liquid crystal elastomer may be modified by any preferred method. In one embodiment, the oriented nematic liquid crystal elastomer may be modified by increasing or decreasing the crosslinking density of the oriented nematic liquid crystal elastomer. For example, the oriented nematic liquid crystal elastomer may be modified by increasing the crosslinking density of the oriented nematic liquid crystal elastomer. For example, the oriented nematic liquid crystal elastomer may be modified by decreasing the crosslinking density of the oriented nematic liquid crystal elastomer.

[0018] Oriented nematic liquid crystal elastomers may be modified by increasing or decreasing their Tg. For example, an oriented nematic liquid crystal elastomer may be modified by increasing its Tg. For example, an oriented nematic liquid crystal elastomer may be modified by decreasing its Tg.

[0019] The inventors have also found that reducing the crosslinking density and / or glass transition temperature (Tg) of the liquid crystal elastomer lowers the authetic response strain threshold of the oriented nematic liquid crystal elastomer. Conversely, they have found that increasing the crosslinking density and / or glass transition temperature (Tg) of the liquid crystal elastomer increases the authetic response strain threshold of the oriented nematic liquid crystal elastomer. Therefore, it has been advantageously found that the properties of the oriented nematic elastomer, particularly the authetic response strain threshold, can be fine-tuned according to the desired end application.

[0020] The method may include a step of increasing the authetic response strain threshold of the oriented nematic liquid crystal elastomer. In such embodiments, the method may include increasing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer. Therefore, the method may include increasing the authetic response strain threshold of the oriented nematic liquid crystal elastomer by increasing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer.

[0021] The method may include a step of reducing the authetic response strain threshold of the oriented nematic liquid crystal elastomer. In such embodiments, the method may include reducing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer. Therefore, the method may include reducing the authetic response strain threshold of the oriented nematic liquid crystal elastomer by reducing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer.

[0022] The oriented nematic liquid crystal elastomer may contain any preferred material. Examples of preferred materials are described in International Publication No. 2019077361A1, the entire contents of which are incorporated herein by reference.

[0023] Oriented nematic liquid crystal elastomers preferably exhibit a mechanical Fredericks transition (MFT). The mechanical Fredericks transition is defined as a deformation mode of an aligned elastomer, where the orientation vector in the plane of the elastomer film appears to rotate sharply at critical strain and reorient in a direction parallel to the stress axis at critical elongation. Materials exhibiting this property have been described by Mitchell et al. (Mitchell, GR, Davis, FJ, and Guo, W., Phys. Rev. Lett., 1993, 71(18), 2947) and Roberts et al. (Roberts, PMS, Mitchell, GR, and Davis, FJ, J. Phys. II). The MFT was first described by France, 1997, 7, 1337 and by Roberts, PMS, Mitchell, GR, Davis, FJ, and Pople, JA, Mol.Cryst.Liq.Cryst., 1997, 299, 181. The MFT is often described by analogy to the well-known electric field (or magnetic field) Fredericks transition (EFT) that occurs in low molar mass nematic display devices. In the EFT, the orientation vectors reorient abruptly beyond a clear critical field (or voltage) and gradually align with respect to the electric field as the field amplitude increases. The EFT threshold is theoretically discontinuous, but it is known to soften when an ideal LC monodomain with orientation precisely parallel or perpendicular to the substrate is not actually achieved. Nevertheless, the threshold is sharp and distinct. The apparent sharp rotation of the orientation vectors observed in the MFT is due to an alternative deformation mode called semi-soft elasticity. This differs from the orientation vector rotation response of oriented elastomers that deform via elasticity (SSE). In the case of semi-soft elasticity, the orientation vector rotates relatively gradually, rotating over a plateau-like region of the tensile load curve on the deformation plane.

[0024] The microfilm film (MFT) of a given liquid crystal elastomer can be observed / measured by preparing a film of the material in which the orientation vector lies in the plane of the film, applying stress in a direction perpendicular or nearly perpendicular to the orientation vector, and tracking the orientation of the orientation vector using, for example, polarized light microscopy.

[0025] The oriented nematic liquid crystal elastomer preferably contains a monodomain liquid crystal elastomer. More preferably, the oriented nematic elastomer is a monodomain liquid crystal elastomer.

[0026] In this specification, "monodomain" means that the orientation vectors of the elastomer are aligned macroscopically within the sample. Monodomain orientation across a sample can be determined, for example, by polarized light microscopy, in which monodomain orientation is characterized by uniform birefringence when the macroscopic sample is observed between orthogonal polarizers (orthogonal nicols).

[0027] Preferably, the oriented nematic elastomer comprises a monodomain liquid crystal elastomer containing a polymer component, a liquid crystal mesogenic component, and a crosslinking agent, wherein the liquid crystal mesogenic component is physically linked to the polymer component.

[0028] Preferably, the liquid crystal mesogen component is physically linked to the polymer component via a flexible spacer.

[0029] Preferably, the flexible spacer is C2~C 10 Alkylene group, preferably linear C2-C 10 The flexible spacer may contain an alkylene group, more preferably a linear C3-C7 alkylene group, and most preferably a linear C6 alkylene group. For example, the flexible spacer may contain an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, or a desilene group.

[0030] The liquid crystal mesogen component of the above-mentioned liquid crystal elastomer may contain any preferred nematic mesogen.

[0031] Preferably, the liquid crystal mesogenic component includes a liquid crystal core component selected from the group consisting of aromatic rings, aliphatic rings, polyaromatic rings, polyaliphatic rings, phenyl, biphenyl, benzene, and combinations thereof.

[0032] Preferably, the liquid crystal core component includes a plurality of aromatic rings and / or aliphatic rings.

[0033] Preferably, the liquid crystal core component is selected from one or more of the following systems. [ka]

[0034] In the above formula, R and R' are each independently selected from the group consisting of alkyl, alkoxy, halogen (halide), -NO2, or -CN, and these alkyl and alkoxy groups may be divalent when they form part of the linking groups that connect the liquid crystal core to the polymer component, and X and Y are each independently selected from the group consisting of -CH=CH-, -C≡C-, -CH=N-, -N=N-, or -C(O)O-, preferably R and R' are each independently selected from alkyl and -CN, and preferably X and / or Y are -C(O)O-.

[0035] In a preferred embodiment, the liquid crystal core component is selected from one or more of the following systems. [ka] In the above formula, R and R' are each independently selected from the group consisting of alkyl, alkoxy, halogen, -NO2, or -CN, and these alkyl and alkoxy groups may be divalent when they form part of the linking groups that connect the liquid crystal core to the polymer component, and X and Y are each independently selected from the group consisting of -CH=CH-, -C≡C-, -CH=N-, -N=N-, or -C(O)O-, preferably R and R' are each independently selected from alkyl and -CN, and preferably X and / or Y is -C(O)O-.

[0036] In certain embodiments, the liquid crystal mesogenic component exists as part of the side chain of the polymer component; that is, the liquid crystal mesogenic component is a pendant group extending from the backbone of the polymer component.

[0037] In certain embodiments, the liquid crystal mesogenic component exists as part of the polymer component's backbone.

[0038] The liquid crystal mesogenic component may form part of both the side chains and the backbone of the polymer component.

[0039] The crosslinking agent preferably includes a bifunctional monomer having the same functional properties as the polymer component.

[0040] Preferably, the crosslinking agent also contains a mesogenic component. Preferably, the mesogenic component contains a liquid crystal core component selected from one or more of the following systems. [ka]

[0041] In the above formula, R and R' are each independently selected from the group consisting of alkyl, alkoxy, halogen, -NO2, or -CN, and these alkyl and alkoxy groups may be divalent when they form part of the linking groups that connect the liquid crystal core to the polymer component, and X and Y are each independently selected from -CH=CH-, -C≡C-, -CH=N-, -N=N-, or -C(O)O-, preferably R and R' are each independently selected from alkyl and -CN, and preferably X and / or Y are -C(O)O-.

[0042] In a preferred embodiment, the liquid crystal core component is selected from one or more of the following systems. [ka] In the above formula, R and R' are each independently selected from the group consisting of alkyl, alkoxy, halogen, -NO2, or -CN, and these alkyl and alkoxy groups may be divalent when they form part of the linking groups that connect the liquid crystal core to the polymer component, and X and Y are each independently selected from the group consisting of -CH=CH-, -C≡C-, -CH=N-, -N=N-, or -C(O)O-, preferably R and R' are each independently selected from alkyl and -CN, and preferably X and / or Y is -C(O)O-.

[0043] The polymer component described above may be any preferred polymer component. Preferably, the polymer component includes (alk) acrylate polymers such as acrylate polymers or methacrylate polymers, vinyl polymers, siloxane polymers, thiol polymers, amine polymers, or epoxide polymers, or combinations thereof. The polymer component may also be an (alk) acrylate polymer (or poly(alk) acrylate). Preferably, the polymer component includes polyacrylate. Those skilled in the art will understand that poly(alk) acrylate is typically formed from one or more (alk) acrylate monomers (e.g., the (alk) acrylate monomers defined below). The terms “(alk) acrylate,” “(meth) acrylate,” and similar terms used herein are used as conventionally herein to refer to both alk acrylates and acrylates such as methacrylate and acrylate.

[0044] In certain embodiments, the polymer component is formed from both a mesogenic component and a non-mesogenic component.

[0045] Preferably, the mesogenic component is formed from a mesogenic monomer containing monomer units linked to the liquid crystal core component.

[0046] In preferred embodiments of the present invention, the polymer component comprises polyacrylate, the liquid crystal core component is a 4-cyano-biphenyl-4'yloxy component, and the crosslinking agent comprises a bis-oxybenzoyloxy-2-methylbenzene-containing component.

[0047] The elastomer is preferably formed by polymerizing a reaction mixture containing a mesogenic monomer, a crosslinking agent, and an initiator. In other words, the elastomer may be a reaction product of a reaction mixture containing a mesogenic monomer, a crosslinking agent, and an initiator. The reaction mixture may further contain an unreactive mesogenic component to broaden the nematic phase range before polymerization. In preferred embodiments, the crosslinking agent also contains a mesogenic component.

[0048] It will be understood that the amounts of each component present in the reaction mixture before polymerization may appropriately depend on the desired end use. For example, as described below, the amount of the crosslinking agent may be changed to increase or decrease the crosslinking density of the oriented nematic liquid crystal elastomer. For example, as described below, the amount of the non-mesogenic monomer having one or more crosslinkable functional groups may be changed to increase or decrease the crosslinking density of the oriented nematic liquid crystal elastomer.

[0049] Preferably, the mesogenic monomer constitutes 5-50% by moles, more preferably 10-30% by moles, and most preferably 15% by moles of the reaction mixture before polymerization. In the final elastomer, the proportion of material derived from the mesogenic monomer is preferably 20-70% by moles, and most preferably 30-60% by moles. To avoid misunderstanding, the terms "mol %" and "mol %" are used interchangeably herein.

[0050] Preferably, the crosslinking agent constitutes 1 to 20 mol%, for example, 3 to 20 mol%, for example, 3 to 10 mol%, for example, 3 to 8 mol%, of the reaction mixture before polymerization. Preferably, the crosslinking agent constitutes 1 to 20 mol%, of the reaction mixture before polymerization.

[0051] In embodiments in which the oriented nematic liquid crystal elastomer is modified to increase its crosslinking density, the crosslinking agent may constitute 5 to 20 mol%, for example 5 to 15 mol%, for example 5 to 10 mol%, for example 5 to 8 mol%, or even 8 mol%, of the reaction mixture before polymerization. In embodiments in which the oriented nematic liquid crystal elastomer is modified to decrease its crosslinking density, the crosslinking agent may constitute 1 to 5 mol%, for example 2 to 5 mol%, for example 3 to 5 mol%, for example 4 to 5 mol%, or even 4 to 4.5 mol%, of the reaction mixture before polymerization. In the final elastomer, the proportion of material derived from the crosslinking agent may be 2 to 20 mol%, for example 3 to 17 mol%, for example 3 to 15 mol%, for example 3 to 10 mol%. In embodiments in which an oriented nematic liquid crystal elastomer is modified to increase its crosslinking density, the proportion of material derived from the crosslinking agent may be 2 to 20 mol%, for example 2 to 15 mol%, for example 2 to 10 mol%, for example 2 to 8 mol%, for example 3 to 5 mol%, for example 3 to 4 mol%, or even 3.5 mol%. In embodiments in which an oriented nematic liquid crystal elastomer is modified to decrease its crosslinking density, the proportion of material derived from the crosslinking agent may be 0.5 to 5 mol%, for example 1 to 3 mol%, for example 1 to 2.5 mol%, for example 1.5 to 2 mol%, or even 1.8 mol%.

[0052] The selected initiator appropriately depends on the polymer used and may be any suitable initiator. However, when the polymer is a polyacrylate, the initiator is preferably a photoinitiator. Possible photoinitiators are well known to those skilled in the art and include benzoin ethers, benzyl ketals, α-dialkoxyacetophenones, α-hydroxyalkylphenones, acylphosphine oxides, benzophenones, and thioxanthones. Preferably, the photoinitiator is methyl benzoylmate. Preferably, the initiator is present in an amount of 1 to 2 mol%, for example 1.5 mol%, relative to the total moles of the reaction mixture.

[0053] If non-mesogenic monomers are present in the reaction mixture, this non-mesogenic mixture preferably constitutes 10 to 40 mol%, more preferably 15 to 30 mol%, and most preferably 15 to 20 mol% of the reaction mixture. In the final elastomer, if non-mesogenic monomers are present, the proportion of material derived from non-mesogenic monomers is preferably 20 to 60 mol%, and most preferably 35 to 50 mol%.

[0054] If an unreactive mesogen is present in the reaction mixture, it preferably constitutes 10 to 70 mol%, more preferably 20 to 60 mol%, or 30 to 60 mol%, and most preferably 55 mol%, of the reaction mixture. In a preferred embodiment, the unreactive mesogen is 4-cyano-4'-hexyloxybiphenyl.

[0055] In certain embodiments, the mesogenic monomer is 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate, 4-(6-acryloyloxy-hexyloxy)phenyl methoxybenzoate, or 4-(trans-4-propylcyclohexyl)benzoate 4-{6-(acryloyloxy)hexyloxy}phenyl, the crosslinking agent is 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene, the non-mesogenic monomer is 2-ethylhexyl acrylate, and the non-reactive mesogen, if present, is 4-cyano-4'-hexyloxybiphenyl.

[0056] The selection of mesogenic monomers may modify the Tg of the resulting oriented nematic liquid crystal elastomer.

[0057] In certain embodiments, the mesogenic monomer is 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate, the crosslinking agent is 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene, the non-mesogenic monomer is 2-ethylhexyl acrylate, and if present, the non-reactive mesogen is 4-cyano-4'-hexyloxybiphenyl, or the mesogenic monomer is 4-(6-acryloyloxy-hexyloxy)phenyl 4-methoxybenzoate and 4-{6-(acryloyloxy)hexyloxy}phenyl 4-(trans-4-propylcyclohexyl)benzoate, and the crosslinking agent is 1,4-bis-[4-(6-acryloyloxyhexyloxy) The monomer is benzoyloxy]-2-methylbenzene, the non-mesogenic monomer is 2-ethylhexyl acrylate, and if present, the non-reactive mesogen is 4-cyano-4'-hexyloxybiphenyl, or the mesogenic monomer is 4-(6-acryloyloxy-hexyloxy)phenyl 4-methoxybenzoate and 4-{6-(acryloyloxy)hexyloxy}phenyl 4-(trans-4-propylcyclohexyl)benzoate, the crosslinking agent is 4-bis-[4-(3-acryloyloxypropyloxy)benzoyloxy]-2-methylbenzene, the non-mesogenic monomer is 2-ethylhexyl acrylate, and if present, the non-reactive mesogen is 4-cyano-4'-hexyloxybiphenyl.

[0058] In certain embodiments, the mesogenic monomer is 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate, the crosslinking agent component is 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene, the non-mesogenic monomer is 2-ethylhexyl acrylate, and the non-reactive mesogen, if present, is 4-cyano-4'-hexyloxybiphenyl.

[0059] If the crosslinking agent contains a mesogenic component and may therefore be considered a mesogenic monomer, the ratio of mesogenic monomer to non-mesogenic monomer in the final elastomer is preferably 2:1 to 1:1.

[0060] The Tg of the oriented nematic liquid crystal elastomer may be any preferred Tg. It will be understood that the Tg of the oriented nematic liquid crystal elastomer may appropriately depend on the desired end use. For example, the Tg of the oriented nematic liquid crystal elastomer may be modified (by one or more of the methods described herein or otherwise) to increase or decrease the Tg, as described below.

[0061] The Tg of the oriented nematic liquid crystal elastomer may be -150 to 50°C, for example -100 to 50°C, for example -80 to 50°C, for example -60 to 50°C, for example -40 to 50°C, for example -20 to 50°C, for example -10 to 40°C, for example -5 to 30°C, for example 0 to 25°C, for example 1 to 23°C, or even 2 to 20°C.

[0062] Appropriate methods for measuring Tg are known to those skilled in the art. Where reported herein, Tg was measured according to ASTM E1356-08(2014) ("Standard Test Method for Assignment of the Glass Transition Temperatures by Differential Scanning Calorimetry," heat flux differential scanning calorimetry (DSC), sample pan: aluminum, reference: blank, calibration: indium and adamantane (solid-solid transition), heating rate: 10°C / min). Tg is reported as the midpoint of the transition. All Tg values ​​reported herein were measured in this manner unless otherwise specified.

[0063] As described herein, the method may include a step of modifying the crosslinking density of the oriented nematic liquid crystal elastomer.

[0064] The crosslinking density may be modified by any suitable method. Examples of suitable methods for modifying the crosslinking density of oriented nematic liquid crystal elastomers are known to those skilled in the art. For example, the crosslinking density may be modified by changing the amount of crosslinking agent, by changing the type of crosslinking agent used, and / or by changing the amount of monomers having one or more crosslinkable functional groups, such as acrylate monomers having one or more crosslinkable functional groups.

[0065] The crosslinking density may be modified by changing the amount of crosslinking agent (i.e., in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In certain embodiments, the crosslinking density may be decreased by reducing the amount of crosslinking agent used (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer), i.e., by reducing the mol% of crosslinking agent present in the reaction mixture before polymerization. In certain embodiments, the crosslinking density may be increased by increasing the amount of crosslinking agent used (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer), i.e., by increasing the mol% of crosslinking agent present in the reaction mixture before polymerization.

[0066] If reducing the amount of crosslinking agent used reduces the crosslinking density of the oriented nematic liquid crystal elastomer, the molar percentage of the crosslinking agent present in the reaction mixture before polymerization may be reduced by any preferred amount. For example, the molar percentage of the crosslinking agent present in the reaction mixture before polymerization may be at least 1 mol%, e.g., at least 1.5 mol%, e.g., at least 2 mol%, e.g., at least 2.5 mol%, e.g., at least 3 mol%, e.g., at least 3.5 mol%, e.g., at least 4 mol%, e.g., at least 4.5 mol%, e.g., at least 5 mol%, e.g., at least 5.5 mol%, e.g., at least 6 mol%, e.g., at least 7 mol%, e.g., at least 7.5 mol%, e.g., at least 8 mol%, e.g., at least 8.5 mol%, e.g., at least 9 mol%, e.g., at least 9.5 mol%, or even at least 10 mol% lower in the reaction mixture used to form the modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form the unmodified oriented nematic liquid crystal elastomer.

[0067] If reducing the amount of crosslinking agent used reduces the crosslinking density of the oriented nematic liquid crystal elastomer, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 10%, for example at least 15%, for example at least 20%, for example at least 25%, for example at least 30%, for example at least 35%, for example at least 40%, for example at least 45%, for example at least 50%, compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer, in the reaction mixture used to form the modified oriented nematic liquid crystal elastomer.

[0068] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 10% lower (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0069] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 20% lower (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0070] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 30% lower (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0071] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 40% lower (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0072] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 50% lower (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0073] If increasing the amount of crosslinking agent used increases the crosslinking density of the oriented nematic liquid crystal elastomer, the molar percentage of the crosslinking agent present in the reaction mixture before polymerization may be increased by any preferred amount. For example, the molar percentage of the crosslinking agent present in the reaction mixture before polymerization may be at least 1 mol%, e.g., at least 1.5 mol%, e.g., at least 2 mol%, e.g., at least 2.5 mol%, e.g., at least 3 mol%, e.g., at least 3.5 mol%, e.g., at least 4 mol%, e.g., at least 4.5 mol%, e.g., at least 5 mol%, e.g., at least 5.5 mol%, e.g., at least 6 mol%, e.g., at least 7 mol%, e.g., at least 7.5 mol%, e.g., at least 8 mol%, e.g., at least 8.5 mol%, e.g., at least 9 mol%, e.g., at least 9.5 mol%, or even at least 10 mol% higher in the reaction mixture used to form the modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form the unmodified oriented nematic liquid crystal elastomer.

[0074] If increasing the amount of crosslinking agent used increases the crosslinking density of the oriented nematic liquid crystal elastomer, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 10%, for example at least 15%, for example at least 20%, for example at least 25%, for example at least 30%, for example at least 35%, for example at least 40%, for example at least 45%, for example at least 50%, compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer, in the reaction mixture used to form the modified oriented nematic liquid crystal elastomer.

[0075] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 10% higher (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0076] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 20% higher (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0077] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 30% higher (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0078] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 40% higher (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0079] In certain embodiments, the amount of crosslinking agent present in the reaction mixture before polymerization may be at least 50% higher (based on the number of moles or mol% of crosslinking agent present in the reaction mixture before polymerization) in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

[0080] The crosslinking density may be modified by changing the amount of monomers having one or more crosslinkable functional groups (i.e., in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In certain embodiments, the crosslinking density may be decreased by reducing the amount of monomers having one or more crosslinkable functional groups present in the reaction mixture before polymerization (compared to the unmodified oriented nematic liquid crystal elastomer). In certain embodiments, the crosslinking density may be increased by increasing the amount of monomers having one or more crosslinkable functional groups present in the reaction mixture before polymerization (compared to the unmodified oriented nematic liquid crystal elastomer).

[0081] Monomers having one or more crosslinkable functional groups are known to those skilled in the art. Preferably, the monomer having one or more crosslinkable functional groups is mesogenic, and more preferably a mesogenic acrylate monomer. Suitable examples of monomers having one or more crosslinkable functional groups include, but are not limited to, those having one or more acids, hydroxyls, oxiranes, and / or unsaturated functional groups.

[0082] The crosslinking density may be modified by changing the type of crosslinking agent used. For example, different crosslinking agents or combinations of crosslinking agents may be used in the modified version compared to the unmodified oriented nematic liquid crystal elastomer. For example, in embodiments where the bis-(acryloyloxyalkyloxy)benzoyloxy-2-methylbenzene crosslinking agent is used, the crosslinking density may be modified by changing the length of the alkyl chain. In such embodiments, the crosslinking density of the oriented nematic liquid crystal elastomer may be decreased (in the unmodified version compared to the modified oriented nematic liquid crystal elastomer) by increasing the length of the alkyl chain in the bis-(acryloyloxyalkyloxy)benzoyloxy-2-methylbenzene crosslinking agent. In such embodiments, the crosslinking density of the oriented nematic liquid crystal elastomer may be increased (in the unmodified version compared to the modified oriented nematic liquid crystal elastomer) by decreasing the length of the alkyl chain in the bis-(acryloyloxyalkyloxy)benzoyloxy-2-methylbenzene crosslinking agent. For example, as a mere example, when a bis-(acryloyloxyalkyloxy)benzoyloxy-2-methylbenzene crosslinking agent is used, the crosslinking density of the oriented nematic liquid crystal elastomer may be reduced by using the bis-(acryloyloxynonyloxy)benzoyloxy-2-methylbenzene crosslinking agent in a modified oriented nematic liquid crystal elastomer compared to using the bis-(acryloyloxyhexyloxy)benzoyloxy-2-methylbenzene crosslinking agent in an unmodified oriented nematic liquid crystal elastomer.Those skilled in the art will understand that the reverse is true when attempting to increase the crosslinking density of an oriented nematic liquid crystal elastomer; that is, when a bis-(acryloyloxyalkyloxy)benzoyloxy-2methylbenzene crosslinking agent is used, the crosslinking density of the oriented nematic liquid crystal elastomer may be increased, for example, by using a bis-(acryloyloxyhexyloxy)benzoyloxy-2methylbenzene crosslinking agent in a modified oriented nematic liquid crystal elastomer compared to using a bis-(acryloyloxynonyloxy)benzoyloxy-2methylbenzene crosslinking agent in an unmodified oriented nematic liquid crystal elastomer.

[0083] Preferably, the crosslinking density may be reduced. More preferably, the crosslinking density may be reduced by reducing the amount of crosslinking agent used, i.e., by reducing the molar percentage of the crosslinking agent present in the reaction mixture before polymerization (compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the authentic response strain threshold is appropriately reduced (compared to the unmodified oriented nematic liquid crystal elastomer).

[0084] As described herein, the method may include a step of modifying the Tg of the oriented nematic liquid crystal elastomer.

[0085] Tg may be modified by any preferred method. Examples of suitable methods for modifying the Tg of an oriented nematic liquid crystal elastomer are known to those skilled in the art. For example, the Tg of an oriented nematic liquid crystal elastomer may be modified by including, excluding, and / or changing the amount of one or more Tg-modifying components present in the oriented nematic liquid crystal elastomer, for example, by increasing or decreasing them, and / or by controlling the polymerization process.

[0086] Suitable Tg-modifying components include, but are not limited to, plasticizers, non-mesogenic monomers, mesogenic monomers, flexible spacers, solvents, and / or combinations thereof.

[0087] The Tg-modifying component may contain a plasticizer. Suitable plasticizers are known to those skilled in the art. Typically, a plasticizer is a substance added to a material to make it softer and more flexible. Therefore, although we do not wish to be bound by theory, it is thought that the inclusion of one or more plasticizers at higher levels will make the oriented nematic liquid crystal elastomer more flexible, for example, by increasing the conformational degrees of freedom of the material, and thus lower the Tg and authentic response strain threshold. Examples of suitable plasticizers include, but are not limited to, poly(ethylhexyl acrylate), for example, poly(2-ethylhexyl acrylate), for example, poly(ethylhexyl acrylate) and / or poly(2-ethylhexyl acrylate) containing at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 (2-)ethylhexyl acrylate units; esters, for example, adipic acid esters, azelaic acid esters, citrate esters, benzoic acid esters, phthalate esters (including orthophthalate esters and terephthalate esters), sebacate esters and trimellitic acid esters; and combinations thereof.

[0088] In certain embodiments, the Tg of the oriented nematic liquid crystal elastomer may be reduced by including or increasing the amount of one or more plasticizers present in the oriented nematic liquid crystal elastomer (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the unmodified oriented nematic liquid crystal elastomer may contain less of one or more plasticizers compared to the modified oriented nematic liquid crystal elastomer. Preferably, when one or more plasticizers are used to reduce the Tg of the oriented nematic liquid crystal elastomer, the unmodified oriented nematic liquid crystal elastomer may be substantially free of plasticizers, while the modified oriented nematic liquid crystal elastomer may contain at least one plasticizer.

[0089] In certain embodiments, the Tg of the oriented nematic liquid crystal elastomer may be increased by eliminating or reducing the amount of one or more plasticizers present in the oriented nematic liquid crystal elastomer (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the unmodified oriented nematic liquid crystal elastomer may contain a larger amount of one or more plasticizers compared to the modified oriented nematic liquid crystal elastomer. Preferably, when one or more plasticizers are used to increase the Tg of the oriented nematic liquid crystal elastomer, the unmodified oriented nematic liquid crystal elastomer may contain at least one plasticizer, while the modified oriented nematic liquid crystal elastomer may contain substantially no plasticizers.

[0090] When the Tg of the oriented nematic liquid crystal elastomer is reduced, the Tg may be reduced by any preferred amount. For example, the Tg of the modified oriented nematic liquid crystal elastomer may be at least 1°C, for example at least 2°C, for example at least 3°C, for example at least 4°C, for example at least 5°C, for example at least 6°C, for example at least 7°C, for example at least 8°C, for example at least 9°C, for example at least 10°C, for example at least 11°C, for example at least 12°C, for example at least 13°C, for example at least 14°C, for example at least 15°C, for example at least 16°C, for example at least 17°C, for example at least 18°C, for example at least 19°C, or even at least 20°C lower than the Tg of the unmodified oriented nematic liquid crystal elastomer.

[0091] When the Tg of the oriented nematic liquid crystal elastomer is increased, the Tg may be increased by any preferred amount. For example, the Tg of the modified oriented nematic liquid crystal elastomer may be at least 1°C, for example at least 2°C, for example at least 3°C, for example at least 4°C, for example at least 5°C, for example at least 6°C, for example at least 7°C, for example at least 8°C, for example at least 9°C, for example at least 10°C, for example at least 11°C, for example at least 12°C, for example at least 13°C, for example at least 14°C, for example at least 15°C, for example at least 16°C, for example at least 17°C, for example at least 18°C, for example at least 19°C, or even at least 20°C higher than the Tg of the unmodified oriented nematic liquid crystal elastomer.

[0092] The oriented nematic liquid crystal elastomer may contain any preferred amount of plasticizer. For example, in the final elastomer, the proportion of material derived from the plasticizer may be 1 to 50% by mass, for example 1 to 40% by mass, for example 1 to 30% by mass, for example 1 to 20% by mass, for example 1 to 10% by mass. Those skilled in the art will understand that the amount of plasticizer present appropriately depends on the desired Tg. For example, if it is desirable to lower the Tg of the oriented nematic liquid crystal elastomer, the amount of plasticizer present in the modified oriented nematic liquid crystal elastomer will typically be greater than the amount of plasticizer present in the unmodified oriented nematic liquid crystal elastomer (and vice versa if it is desirable to increase the Tg of the oriented nematic liquid crystal elastomer).

[0093] One or more plasticizers may be added to the oriented nematic liquid crystal elastomer by any suitable method at any suitable time. For example, the plasticizer may be added before, during, and / or after the formation of the oriented liquid crystal elastomer. For example, the plasticizer may be added to the reaction mixture used to form the oriented nematic liquid crystal elastomer, or it may be used to modify the oriented nematic liquid crystal elastomer once it has been formed.

[0094] One or more plasticizers may be added to the oriented nematic liquid crystal elastomer before, during, or after polymerization of the reaction mixture used to form the oriented nematic liquid crystal elastomer. In certain embodiments, one or more plasticizers may be added to the reaction mixture before polymerization of the reaction mixture used to form the oriented nematic liquid crystal elastomer. In certain embodiments, one or more plasticizers may be added to the reaction mixture during polymerization of the reaction mixture used to form the oriented nematic liquid crystal elastomer. When one or more plasticizers are added to the reaction mixture used to form the oriented nematic liquid crystal elastomer before or during polymerization, the plasticizers may be copolymerized into the polymer chain. Those skilled in the art will understand that only certain plasticizers, for example, those having unsaturated bonds that can participate in free radical polymerization reactions, may be copolymerized into the polymer chain.

[0095] In certain embodiments, one or more plasticizers may be added to the oriented nematic liquid crystal elastomer after polymerization, i.e., to the oriented nematic liquid crystal elastomer which is the reaction product of the reaction mixture. When one or more plasticizers are added to the oriented nematic liquid crystal elastomer after polymerization, the one or more plasticizers may be added thereto by any preferred method. For example, one or more plasticizers may be added directly to the oriented nematic liquid crystal elastomer, either alone or dissolved, dispersed, or suspended in a suitable solvent or mixture of solvents. When used, preferred solvents include, but are not limited to, cyclohexane, dichloromethane (DCM), hexane, pentane, heptane, xylene, benzene, petroleum ether, toluene, toluene / methanol, DCM / methanol, and / or combinations thereof.

[0096] The Tg-modified component may include a non-mesogenic monomer. The Tg may be modified by changing the conformational degree of freedom within the non-mesogenic monomer. Suitable non-mesogenic monomers are known to those skilled in the art. Examples of suitable non-mesogenic monomers include, but are not limited to, monomers having a pendant C2-C12 alkyl, alkenyl, or alkynyl group, such as acrylate monomers having a pendant C2-C12 alkyl, alkenyl, or alkynyl group. To avoid misunderstanding, a monomer having a pendant C2-C12 alkyl, alkenyl, or alkynyl group may have one or more pendant C2-C12 alkyl, alkenyl, or alkynyl groups. The pendant C2-C12 alkyl, alkenyl, or alkynyl group may be linear or branched. The pendant C2-C12 alkyl, alkenyl, or alkynyl group may or may not be substituted. Typically, non-mesogenic monomers having pendant C2-C12 alkyl, alkenyl, or alkynyl groups may be included, or their amounts may be increased, to lower the Tg of the oriented nematic liquid crystal elastomer. While we do not wish to be bound by theory, it is thought that including or increasing the amount of monomers in a modified oriented nematic liquid crystal elastomer, and having the poly(monomer) of that monomer have a lower Tg than the polymer component in the unmodified oriented nematic liquid crystal elastomer, can lower the Tg of the material.

[0097] In certain embodiments, the Tg of the oriented nematic liquid crystal elastomer may be reduced by including or increasing the amount of non-mesogenic monomers having pendant C2-C12 alkyl, alkenyl, or alkynyl groups present in the oriented nematic liquid crystal elastomer (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the unmodified oriented nematic liquid crystal elastomer may contain a smaller amount of non-mesogenic monomers having pendant C2-C12 alkyl, alkenyl, or alkynyl groups compared to the modified oriented nematic liquid crystal elastomer.

[0098] The oriented nematic liquid crystal elastomer may contain any preferred amount of a non-mesogenic monomer having a pendant C2-C12 alkyl, alkenyl, or alkynyl group. For example, the reaction mixture may contain 0.5-60 mol%, for example 1-50 mol%, of a non-mesogenic monomer having a pendant C2-C12 alkyl, alkenyl, or alkynyl group before polymerization. Those skilled in the art will understand that the amount of non-mesogenic monomer having a pendant C2-C12 alkyl, alkenyl, or alkynyl group present depends appropriately on the desired Tg. For example, if it is desirable to lower the Tg of an oriented nematic liquid crystal elastomer, the amount of non-mesogenic monomers having pendant C2-C12 alkyl, alkenyl, or alkynyl groups present in the modified oriented nematic liquid crystal elastomer will typically be greater than the amount of non-mesogenic monomers having pendant C2-C12 alkyl, alkenyl, or alkynyl groups present in the unmodified oriented nematic liquid crystal elastomer (and vice versa if it is desired to increase the Tg of the oriented nematic liquid crystal elastomer).

[0099] Non-mesogenic monomers may be appropriately added to the reaction mixture used to form an oriented nematic liquid crystal elastomer.

[0100] The Tg-modifying component may include a mesogenic monomer. Preferred mesogenic monomers are as specified herein. Tg may be modified by changing the conformational degrees of freedom within the mesogenic monomer. Although we do not wish to be bound by theory, Tg may be decreased by increasing the conformational degrees of freedom within the mesogenic monomer. For example, the mesogenic monomer may include an alkyl chain, and Tg may be modified by changing the length of the alkyl chain. For example, in embodiments in which the mesogenic monomer 6-(4-cyano-biphenyl-4'-yloxy)alkyl acrylate is used, Tg may be modified by changing the length of the alkyl chain. In such embodiments, the Tg of the oriented nematic liquid crystal elastomer may be decreased by increasing the length of the alkyl chain in the 6-(4-cyano-biphenyl-4'-yloxy)alkyl acrylate monomer (in the unmodified form compared to the modified oriented nematic liquid crystal elastomer). In such embodiments, the Tg of the oriented nematic liquid crystal elastomer may be increased by reducing the length of the alkyl chain in the 6-(4-cyano-biphenyl-4'-yloxy)alkyl acrylate monomer (in the unmodified version compared to the modified oriented nematic liquid crystal elastomer). For example, as a mere example, when the 6-(4-cyano-biphenyl-4'-yloxy)alkyl acrylate monomer is used, the Tg of the oriented nematic liquid crystal elastomer may be decreased by using 6-(4-cyano-biphenyl-4'-yloxy)nonyl acrylate in the modified oriented nematic liquid crystal elastomer compared to using 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate in the unmodified oriented nematic liquid crystal elastomer.Those skilled in the art will understand that the reverse is true when attempting to increase the Tg of an oriented nematic liquid crystal elastomer; that is, when a 6-(4-cyano-biphenyl-4'-yloxy)alkyl monomer is used, the Tg of the oriented nematic liquid crystal elastomer may be increased, for example, by using 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate in a modified oriented nematic liquid crystal elastomer compared to using 6-(4-cyano-biphenyl-4'-yloxy)nonyl acrylate in an unmodified oriented nematic liquid crystal elastomer. The Tg may be modified by utilizing an alternative mesogenic monomer or by replacing a portion of the mesogenic monomer with an alternative mesogenic monomer. Suitable alternative mesogenic monomers are as specified herein.

[0101] The Tg-modifying component may include flexible spacers. Suitable flexible spacers are as specified herein. In certain embodiments, the Tg of the oriented nematic liquid crystal elastomer may be reduced by including or increasing the amount of flexible spacers present in the oriented nematic liquid crystal elastomer (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the unmodified oriented nematic liquid crystal elastomer may contain a smaller amount of one or more flexible spacers compared to the modified oriented nematic liquid crystal elastomer. In certain embodiments, the Tg of the oriented nematic liquid crystal elastomer may be increased by eliminating or reducing the amount of one or more flexible spacers present in the oriented nematic liquid crystal elastomer (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer). In such embodiments, the unmodified oriented nematic liquid crystal elastomer may contain a larger amount of one or more flexible spacers compared to the modified oriented nematic liquid crystal elastomer.

[0102] The Tg of the oriented nematic liquid crystal elastomer may be modified by changing the properties of the flexible spacer. For example, the Tg of the oriented nematic liquid crystal elastomer may be modified by changing the length of the flexible spacer, such as by changing the length of the alkyl chain present in the flexible spacer. In such embodiments, the Tg may be appropriately decreased by increasing the length of the alkyl chain present in the flexible spacer. In such embodiments, the Tg may be appropriately increased by decreasing the length of the alkyl chain present in the flexible spacer.

[0103] The Tg of oriented nematic liquid crystal elastomers may be modified by controlling the polymerization process. Suitable methods for controlling the polymerization process are known to those skilled in the art. Examples of preferred methods for controlling the polymerization process include, but are not limited to, the use of techniques such as photo-induced electron / energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. PET-RAFT is a form of free radical polymerization that provides spatial and temporal control of the polymerization reaction, meaning that the polymer size, composition, and structure can be precisely controlled. Although not bound by theory, it is thought that spatiotemporal control of polymerization may be improved using PET-RAFT polymerization, and thus a desired glass transition temperature, i.e., an increase or decrease in Tg, can be achieved. While not bound by theory, it is also conceivable that the desired glass transition temperature may be achieved using PET-RAFT by stopping / starting polymerization to change the degree of curing, by changing the amounts of photocatalyst and RAFT agent to adjust the molecular weight / molecular weight distribution, by specifically controlling the number distribution of monomers between crosslinking groups, by specific control over the monomer sequence, and / or by controlling the degree of branching.

[0104] Those skilled in the art will understand that the Tg of an oriented nematic liquid crystal elastomer can be affected by altering its crosslinking density. However, they will also understand that there is not necessarily a linear relationship between crosslinking density and Tg. For example, reducing the crosslinking density of an oriented nematic liquid crystal elastomer does not necessarily reduce the material's Tg. Furthermore, the relationship with the concentration of crosslinking groups may be nonlinear.

[0105] Preferably, Tg may be reduced. More preferably, Tg may be reduced by including or increasing the amount of plasticizer present (in the unmodified version compared to the modified oriented nematic liquid crystal elastomer). In such embodiments, the authentic response strain threshold is appropriately reduced (in the modified version compared to the unmodified oriented nematic liquid crystal elastomer).

[0106] The oriented nematic liquid crystal elastomer may be manufactured by any suitable method. Preferably, the oriented nematic liquid crystal elastomer is a) A step of applying an orientation means to a substrate, b) A step of applying liquid crystal elastomer components to a substrate and enabling (allowing) them to form an oriented nematic phase, c) A step of curing the liquid crystal elastomer component to form an oriented nematic liquid crystal elastomer. It may be manufactured by a method that includes [a certain component].

[0107] Various techniques exist for oriented mesogenic compositions. For example, there are techniques for generating monodomains during synthesis, including applying a magnetic field, mechanical brushing, mechanical shear orientation, flow, applying an electric field, applying a thermal gradient, or providing one or more oriented layers. Monomer solutions may also be heated, cooled, or exposed to other environmental factors to influence the synthesis of the monomer mixture into an oriented state.

[0108] Preferably, the aligning means is preferably an alignment (orientation) force applied by the substrate to apply a static force to the substrate, and / or a mechanical shear alignment.

[0109] In a second aspect, the invention extends to the use of a chemically modified aligned nematic liquid crystal elastomer in a method of increasing or decreasing the cholesteric response strain threshold of an aligned nematic liquid crystal elastomer.

[0110] Preferred features of the second aspect of the invention are as defined in relation to the first aspect of the invention.

[0111] The term "alk" or "alkyl", as used herein, unless otherwise defined, is a straight-chain, branched, cyclic or polycyclic moiety or combination thereof and is a saturated hydrocarbon radical containing from 1 to 20 carbon atoms, such as from 1 to 10 carbon atoms, such as from 1 to 8 carbon atoms, such as from 1 to 6 carbon atoms, or further from 1 to 4 carbon atoms. These radicals are chloro, bromo, iodo, cyano, nitro, OR 19 、OC(O)R 20 、C(O)R 21 、C(O)OR 22 、NR 23 R 24 、C(O)NR 25 R 26 、SR 27 、C(O)SR 27 、C(S)NR 25 R 26 、optionally substituted with aryl or Het, wherein R 19 ~R 27Each of these independently represents hydrogen, aryl, or alkyl, and / or may be interrupted by an oxygen atom, a sulfur atom, or a cyrano group or a dialkylsiloxane group. Examples of such radicals may be independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, pentyl, isoamyl, hexyl, cyclohexyl, 3-methylpentyl, octyl, etc. The term "alkylene," as used herein, refers to the alkyl group of a divalent radical as defined above. For example, an alkyl group such as methyl, represented as -CH3, becomes methylene, -CH2- when represented as alkylene. Other alkylene groups should be understood accordingly.

[0112] The term "alkenyl," as used herein, refers to hydrocarbon radicals having, for example, up to four double bonds, being linear, branched, cyclic, or polycyclic moieties or combinations thereof, and containing 2 to 18 carbon atoms, e.g., 2 to 10 carbon atoms, e.g., 2 to 8 carbon atoms, e.g., 2 to 6 carbon atoms, or a further 2 to 4 carbon atoms. These radicals include hydroxyl, chloro, bromo, iodo, cyano, nitro, OR 19 ,OC(O)R 20 , C(O)R 21 , C(O)OR 22 , NR 23 R 24 , C(O)NR 25 R 26 , SR 27 , C(O)SR 27 , C(S)NR 25 R 26 , or may be optionally replaced with an aryl, in the formula, R 19 ~R 27Each of these independently represents hydrogen, aryl, or alkyl, and / or may be interrupted by an oxygen atom, a sulfur atom, or a silano group or a dialkylsiloxane group. Examples of such radicals may be independently selected from alkenyl groups, including vinyl, allyl, isopropenyl, pentenyl, hexenyl, heptenyl, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, 1-propenyl, 2-butenyl, 2-methyl-2-butenyl, isoprenyl, farnesyl, geranyl, geranylgeranyl, etc. The term “alkenylene,” as used herein, refers to the alkenyl group of a divalent radical as defined above. For example, an alkenyl group such as ethenyl, represented as -CH=CH2, becomes ethenylene-CH=CH- when represented as alkenylene. Other alkenylene groups should be understood accordingly.

[0113] The term "alkynyl," as used herein, refers to hydrocarbon radicals having, for example, up to four triple bonds, being linear, branched, cyclic, or polycyclic moieties or combinations thereof, and having 2 to 18 carbon atoms, for example 2 to 10 carbon atoms, for example 2 to 8 carbon atoms, for example 2 to 6 carbon atoms, or even 2 to 4 carbon atoms. These radicals include hydroxyl, chloro, bromo, iodo, cyano, nitro, OR 19 ,OC(O)R 20 , C(O)R 21 , C(O)OR 22 , NR 23 R 24 , C(O)NR 25 R 26 , SR 27 , C(O)SR 27 , C(S)NR 25 R 26 , or may be optionally replaced with an aryl, in the formula, R 19 ~R 27Each of these independently represents hydrogen, an aryl, or a lower alkyl group, and / or may be interrupted by an oxygen atom, a sulfur atom, or a cyrano group or a dialkylsiloxane group. Examples of such radicals may be independently selected from alkynyl radicals, including ethynyl, propynyl, propargyl, butynyl, pentynyl, hexynyl, etc. The term "alkynylene," as used herein, refers to the alkynyl group of a divalent radical as defined above. For example, an alkynyl group such as ethynyl, represented as -C≡CH, becomes ethynylene-C≡C- when represented as alkynylene. Other alkynylene groups should be understood accordingly.

[0114] The term "aryl," as used herein, refers to organic radicals derived from aromatic hydrocarbons by the removal of one hydrogen atom, comprising a monocyclic, bicyclic, or polycyclic carbocyclic ring with up to seven members in each ring, where at least one ring is aromatic. These radicals include hydroxy, chloro, bromo, iodo, cyano, nitro, OR 19 ,OC(O)R 20 , C(O)R 21 , C(O)OR 22 , NR 23 R 24 , C(O)NR 25 R 26 , SR 27 , C(O)SR 27 , C(S)NR 25 R 26 , or may be optionally replaced with an aryl, in the formula, R 19 ~R 27Each of these independently represents hydrogen, an aryl or lower alkyl group, and / or may be interrupted by an oxygen atom or a sulfur atom, or a cyrano group or a dialkylsilicon group. Examples of such radicals may be independently selected from phenyl, p-tolyl, 4-methoxyphenyl, 4-(tert-butoxy)phenyl, 3-methyl-4-methoxyphenyl, 4-fluorophenyl, 4-chlorophenyl, 3-nitrophenyl, 3-aminophenyl, 3-acetamidophenyl, 4-acetamidophenyl, 2-methyl-3-acetamidophenyl, 2-methyl-3-aminophenyl, 3-methyl-4-aminophenyl, 2-amino-3-methylphenyl, 2,4-dimethyl-3-aminophenyl, 4-hydroxyphenyl, 3-methyl-4-hydroxyphenyl, 1-naphthyl, 2-naphthyl, 3-amino-1-naphthyl, 2-methyl-3-amino-1-naphthyl, 6-amino-2-naphthyl, 4,6-dimethoxy-2-naphthyl, tetrahydronaphthyl, indanyl, biphenyl, phenanthryl, anthril, or acenaphthyl. The term "arylene," as used herein, refers to the aryl group of a divalent radical as defined above. For example, an aryl group such as phenyl, represented as -Ph, becomes phenylene, -Ph- when represented as arylene. Other arylene groups should be understood accordingly.

[0115] To avoid misunderstanding, references to alkyl, alkenyl, alkynyl, aryl, or aralkyl groups in this specification should be interpreted accordingly. For example, references to alkyl in aminoalkyl groups or alk in alkoxyl groups should be interpreted as the aforementioned alk or alkyl, etc.

[0116] Where used herein, unless otherwise explicitly stated, all numerical values, such as those representing values, ranges, quantities, or percentages, may be interpreted as if preceded by the word "approximately," even if the word "approximately" does not explicitly appear. Furthermore, numerical ranges indicated by endpoints include all integers and, where appropriate, fractions (fractions) contained within that range (for example, 1-5 may include 1, 2, 3, and 4 when referring to several elements, and may also include 1.5, 2, 2.75, and 3.80 when referring to measured values). Endpoint indications also include the endpoint values ​​themselves (for example, 1.0-5.0 includes both 1.0 and 5.0). Any numerical ranges listed herein are intended to include all subranges contained within them.

[0117] The singular form encompasses the plural form, and vice versa. For example, this specification refers to "a" crosslinker, "an" acrylate polymer, "an" elastomer, etc., but one or more of each of these and any other components may be used. As used herein, the term "polymer" refers to both oligomers and homopolymers and copolymers, and the prefix "poly" refers to two or more.

[0118] As used herein, the terms “comprising,” “comprises,” and “comprised of” are synonymous with “including,” “includes,” or “containing,” and are inclusive or open-ended forms and do not exclude any further unlisted components, elements, or methods or processes. In addition, although the present invention is described using the term “comprising,” the coating compositions detailed herein may also be described as “consisting essentially of” or “consisting of.”

[0119] As used herein, the term "and / or" means, when used in a list of two or more items, that any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a list is described as containing groups A, B, and / or C, the list may include A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0120] All features included herein may be combined with any of the embodiments described above in any combination. [Brief explanation of the drawing]

[0121] Embodiments of the present invention will now be described with reference to the following examples and drawings.

[0122] [Figure 1A] Figure 1A shows graphs of z-strain versus x-strain (10 minutes between 5% strain steps at 23°C) for Examples 1A and 1B, respectively.

[0123] [Figure 1B] Figure 1B shows the instantaneous Poisson ratio versus x-strain graphs calculated from the polynomial fit of the data in Figure 1A, for each of Examples 1A and 1B.

[0124] [Figure 2A] Figure 2A shows graphs of z-strain versus x-strain (10 minutes between 5% strain steps at 23°C) for Examples 2A and 2B, respectively.

[0125] [Figure 2B] Figure 2B shows the graphs of the instantaneous Poisson ratio versus x-strain calculated from the polynomial fit of the data in Figure 1A for each of Examples 2A and 2B.

[0126] [Figure 3A] Figure 3A shows graphs of z-strain versus x-strain (10 minutes between 5% strain steps at 23°C) for Examples 3B and 3C, respectively.

[0127] [Figure 3B] Figure 3B shows the graphs of the instantaneous Poisson ratio versus x-strain calculated from the polynomial fit of the data in Figure 1A for each of Examples 3B and 3C.

[0128] [Figure 4A] Figure 4A is a graph of z-strain versus x-strain (10 minutes between 5% strain steps at 23°C) for Example 4A.

[0129] [Figure 4B] Figure 4B is a graph of the instantaneous Poisson ratio versus x-strain calculated from the polynomial fit of the data in Figure 1A for Example 4A. [Examples]

[0130] An oriented nematic liquid crystal elastomer film was synthesized using the following materials according to the following method. 2-ethylhexyl acrylate (EHA), 6-(4-cyano-biphenyl-4'-yloxy)hexyl acrylate (A6OCB), 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (RM82), 4-Cyano-4'-hexyloxybiphenyl (6OCB), and Methyl benzoylformate (MBF)

[0131] Example 1 - Effect of Crosslinking Density In this example, oriented nematic liquid crystal elastomer films with different crosslinking densities (Examples 1A and 1B) were prepared using the following starting monomer mixtures. [Table 1]

[0132] A liquid crystal elastomer film was prepared by polymerizing a monomer mixture inside a thin film mold with a thickness of approximately 100 μm, a width of approximately 25 mm, and a length of approximately 70 mm. The film was cured at room temperature in a planar orientation with a nematic phase. The surface of the mold was coated with a thin layer of PVA orientation, and the rubbing direction was antiparallel. The film was polymerized for 2 hours. After polymerization, the film was removed from the mold and held overnight in a methanol / DCM solvent mixture to wash away 6OCB.

[0133] The resulting liquid crystal elastomer films (i.e., after the removal of 6OCB) contained 8.0 mol% and 4.2 mol% of the crosslinking agent for Examples 1A and 1B, respectively.

[0134] These liquid crystal elastomer films were tested according to the following method.

[0135] Test method The film was distorted in 0.05 (5%) steps, and the film was allowed to be equilibrated for 10 minutes between each distortion step. Local strain ε in the x and y directions x and ε y Each of these was tracked, and the strain in the z direction (authentic response) was calculated based on the measured strains in the x and y directions using Equation 1, assuming that the volume of the liquid crystal elastomer remained constant.

number

[0136] Below the authentic response distortion threshold, the distortion in the z-direction decreases as the applied distortion in the x-direction increases. Above the authentic response distortion threshold, the distortion in the z-direction increases as the applied distortion in the x-direction increases. Therefore, the authentic response distortion threshold can be determined based on the calculated distortion in the z-direction.

[0137] All measurements were obtained using a liquid crystal elastomer film at room temperature (23°C).

[0138] The results are shown in Figures 1A and 1B. Figure 1A shows graphs of the z-direction strain as the applied strain in the x-direction increases for each of Examples 1A and 1B. Figure 1B shows graphs of Poisson's ratio for each of Examples 1A and 1B. Poisson's ratio ν xz The first factor is determined using Equation 2, and the true strain is determined based on the engineering strain using Equation 3. ν xz =-dε z,真 / dε x,真 (Formula 2) ε 真 =ln(ε 工学 +1) (Formula 3)

[0139] As shown in Figures 1A and 1B, the authentic response strain threshold of Example 1A (where the strain in the z-direction begins to increase in Figure 1A and the Poisson's ratio becomes negative in Figure 1B) is higher than that of Example 1B (79±5% and 32±5%, respectively). Figures 1A and 1B also show that the authentic behavior of the materials in Examples 1A and 1B is modified under these experimental conditions, as indicated by the overall shape of the strain response and Poisson's ratio.

[0140] Therefore, this embodiment demonstrates that reducing the crosslinking density of the liquid crystal elastomer leads to a decrease in the authentic response strain threshold of the liquid crystal elastomer. Conversely, this embodiment demonstrates that the authentic response strain threshold of the liquid crystal elastomer can be increased by increasing the crosslinking density of the liquid crystal elastomer.

[0141] Example 2 - Effects of Tg An oriented nematic liquid crystal elastomer film was prepared according to Example 1A above. After polymerization, one film was tested without further modification (Example 2A). To another film, 50% by mass of poly(2-ethylhexyl acrylate), a plasticizer having about 10 monomer units, was directly added to the film at 60°C (Example 2B).

[0142] Where reported herein, Tg was measured using a standard "heat-cool-heat" method according to ASTM E1356-08(2014) ("Standard Test Method for Assignment of the Glass Transition Temperatures by Differential Scanning Calorimetry," heat flux differential scanning calorimetry (DSC), sample pan: aluminum, reference: blank, calibration: indium and adamantane (solid-solid transition), heating rate: 10°C / min). The sample was equilibrated at -60°C and then heated to 80°C at a heating rate of 10°C / min. The sample was then cooled to -60°C and heated to 80°C at a heating rate of 10°C / min. This cooling / heating cycle, i.e., -60°C to 80°C, was then repeated one more time (so that three cooling / heating cycles were performed). The glass transition was measured as the inflection point of the transition in the second cooling cycle. The Tg values ​​for Examples 2A and 2B are provided below. [Table 2]

[0143] These films were tested according to the test method described above.

[0144] Figure 2A shows graphs of the z-direction strain as the applied strain in the x-direction increases for each of Examples 2A and 2B. Figure 2B shows graphs of Poisson's ratio for each of Examples 2A and 2B.

[0145] As shown in Figures 2A and 2B, the authentic response strain threshold of Example 2A (where the strain in the z-direction begins to increase in Figure 2A and the Poisson's ratio becomes negative in Figure 2B) is higher than that of Example 1B (79±5% and 37±5%, respectively). Figures 2A and 2B also show that the authentic behavior of the materials in Examples 2A and 2B is modified under these experimental conditions, as indicated by the overall shape of the strain response and Poisson's ratio.

[0146] Therefore, this embodiment demonstrates that reducing the Tg of a liquid crystal elastomer leads to a decrease in the authentic response strain threshold of the liquid crystal elastomer. Conversely, this embodiment demonstrates that the authentic response strain threshold of a liquid crystal elastomer can be increased by increasing the Tg of the liquid crystal elastomer.

[0147] Example 3 - Effect of Chain Length Oriented nematic liquid crystal elastomer films were prepared according to Example 1A above, but in Examples 3B and 3C, the monofunctional mesogenic monomer 4'-(6-hydroxyhexyloxy)-[1,1'-biphenyl]-4-carbonitrile (A6OCB) was replaced with the following monomers. 3B: 4-(4-cyano-biphenyl-4'-yloxy)butyl acrylate (A4OCB) 3C: 5-(4-cyano-biphenyl-4′-yloxy)pentyl acrylate (A5OCB)

[0148] All other components of the LCE were identical to those of the original unmodified authentic LCE, and the molar percentages of each component were also identical.

[0149] The change in monomer resulted in a change in the glass transition temperature (Tg) of the LCE (recorded as the starting value when the sample was heated at 10°C / min). Tg was measured as described above in Example 2. [Table 3]

[0150] The film was tested according to the test method described above. Reducing the chain length of the monofunctional mesogenic monomer results in an increase in Tg.

[0151] Figure 3A shows graphs of the z-direction strain as the applied strain in the x-direction increases for each of Examples 1A, 3B, and 3C. Figure 3B shows graphs of Poisson's ratio for each of Examples 1A, 3B, and 3C.

[0152] As shown in Figures 3A and 3B, the authentic response strain threshold of Example 3B (where the strain in the z-direction begins to increase in Figure 3A and the Poisson's ratio becomes negative in Figure 3B) is higher than that of Example 3C, and the authentic response strain threshold of Example 3C is higher than that of Example 1A (81±5%, 65±5%, and 57±5%, respectively). Figures 3A and 3B also show that the authentic behavior of the materials in Examples 3B and 3C is modified under these experimental conditions, as indicated by the overall shape of the strain response and Poisson's ratio.

[0153] Therefore, this embodiment demonstrates that the chain length of the monomer can be used to change the Tg, and further demonstrates that decreasing the Tg of the liquid crystal elastomer results in a decrease in the authentic response strain threshold of the liquid crystal elastomer. Conversely, this embodiment further demonstrates that the authentic response strain threshold of the liquid crystal elastomer can be increased by increasing the Tg of the liquid crystal elastomer.

[0154] Example 4 - Alternative Functionality in Mesogenic Monomers An oriented nematic liquid crystal elastomer film was prepared according to Example 1A above, but in Example 4B, the monofunctional mesogenic monomer 4'-(6-hydroxyhexyloxy)-[1,1'-biphenyl]-4-carbonitrile (A6OCB) was replaced with the following monomer. 4B: 4-Methoxybenzoic acid 4-(6-acryloyloxyhexyloxy)phenyl ester

[0155] All other components of the LCE were identical to those of the original unmodified authentic LCE, and the molar percentages of each component were also identical.

[0156] The change in monomer resulted in a change in the glass transition temperature (Tg) of the LCE (recorded as the starting value when the sample was heated at 10°C / min). Tg was measured as described above in Example 2. [Table 4]

[0157] The film was tested according to the test method described above.

[0158] Figure 4A shows graphs of the z-direction strain as the applied strain in the x-direction increases for each of Examples 1A and 4B. Figure 4B shows graphs of Poisson's ratio for Examples 1A and 4B.

[0159] As shown in Figures 4A and 4B, the authentic response strain threshold of Example 4B (where the strain in the z-direction begins to increase in Figure 4A and the Poisson's ratio becomes negative in Figure 4B) is lower than that of Example 1A (35±5% and 57±5%, respectively). Figures 4A and 4B also show that the authentic behavior of the material in Example 4B is modified under these experimental conditions compared to the material in Example 1A, as indicated by the overall shape of the strain response and Poisson's ratio.

[0160] Therefore, this embodiment demonstrates that modifying the functionality of monomers can be used to adjust the Tg, and further demonstrates that decreasing the Tg of a liquid crystal elastomer results in a decrease in the authentic response strain threshold of the liquid crystal elastomer. Conversely, this embodiment further demonstrates that the authentic response strain threshold of a liquid crystal elastomer can be increased by increasing the Tg of the liquid crystal elastomer.

[0161] In Example 4C, LCE was prepared using the following starting monomer mixture. [Table 5] In the table, SRB-CHEM-023 is 2,5-di(4'-butyloxybenzoyloxy)benzoic acid (4"-acryloyloxybutyl).

[0162] The change in monomer resulted in a change in the glass transition temperature (Tg) of the LCE (recorded as the starting value when the sample was heated at 10°C / min). Tg was measured as described above in Example 2. [Table 6]

[0163] The film was tested according to the test method described above.

[0164] The authentic response distortion threshold of Example 4C is higher than that of Example 1A (76±5% and 57±5%, respectively).

[0165] Therefore, this embodiment again demonstrates that modifying the functionality of monomers can be used to adjust the Tg.

[0166] Attention is drawn to all papers and documents filed concurrently with or prior to this specification and made available to the public together with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0167] All of the features disclosed herein (including the appended claims, abstract and drawings), and / or all of the steps of any method or process so so disclosed, may be combined in any combination except in which at least some of such features and / or steps are mutually exclusive.

[0168] Each feature disclosed herein (including the attached claims, abstract, and drawings) may be replaced by an alternative feature serving the same, equivalent, or similar purpose unless expressly stated otherwise. Accordingly, unless expressly stated otherwise, each disclosed feature is merely an example of a general set of equivalent or similar features.

[0169] The present invention is not limited to the details of the embodiments described above. The present invention extends to any novel feature or any novel combination of any feature disclosed herein (including the appended claims, abstract and drawings), or to any novel step or any novel combination of any method or process as so disclosed herein.

Claims

1. A method for increasing or decreasing the authetic response strain threshold of an oriented nematic liquid crystal elastomer, comprising the step of chemically modifying the oriented nematic liquid crystal elastomer.

2. The method according to claim 1, comprising the step of modifying the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer.

3. The method includes a step of reducing the authentic response strain threshold of the oriented nematic liquid crystal elastomer by reducing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer, Alternatively, the method includes a step of increasing the authentic response strain threshold of the oriented nematic liquid crystal elastomer by increasing the crosslinking density and / or glass transition temperature (Tg) of the oriented nematic liquid crystal elastomer. The method according to claim 2.

4. The method according to any one of claims 1 to 3, wherein the oriented nematic liquid crystal elastomer is a reaction product of a reaction mixture comprising a mesogenic monomer, a crosslinking agent, an initiator, and optionally a non-mesogenic monomer.

5. The method according to claim 4, wherein the crosslinking density is modified by changing the amount of crosslinking agent, by changing the type of crosslinking agent used, and / or by changing the amount of monomers having one or more crosslinkable functional groups present in the reaction mixture.

6. The method according to claim 4 or 5, wherein the crosslinking density is reduced by reducing the amount of crosslinking agent present in the reaction mixture.

7. The method according to claim 6, wherein the amount of crosslinking agent present in the reaction mixture is at least 10%, for example at least 20%, for example at least 30%, for example at least 50%, for example at least 50%, in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer, compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

8. The method according to claim 4 or 5, wherein the crosslinking density is increased by increasing the amount of crosslinking agent present in the reaction mixture.

9. The method according to claim 8, wherein the amount of crosslinking agent present in the reaction mixture is at least 10%, for example at least 20%, for example at least 30%, for example at least 50%, for example at least 50%, in the reaction mixture used to form a modified oriented nematic liquid crystal elastomer, compared to the reaction mixture used to form an unmodified oriented nematic liquid crystal elastomer.

10. The method according to any one of claims 2 to 9, wherein the glass transition temperature (Tg) is modified by including, excluding, and / or changing the amount of one or more Tg-modifying components present in the oriented nematic liquid crystal elastomer, and / or by controlling the polymerization process used to form the oriented nematic liquid crystal elastomer.

11. The method according to claim 10, wherein the Tg modifying component is selected from the group consisting of plasticizers, non-mesogenic monomers, mesogenic monomers, flexible spacers, solvents, and / or combinations thereof.

12. The method according to claim 11, wherein the glass transition temperature (Tg) is reduced by including or increasing the amount of one or more plasticizers present in the oriented nematic liquid crystal elastomer.

13. The method according to claim 12, wherein the unmodified oriented nematic liquid crystal elastomer is substantially free of plasticizers, and the modified oriented nematic liquid crystal elastomer contains at least one plasticizer, for example, in an amount of 1 to 50% by mass.

14. The method according to claim 11, wherein the glass transition temperature (Tg) is increased by eliminating or reducing the amount of one or more plasticizers present in the oriented nematic liquid crystal elastomer.

15. The method according to claim 14, wherein the unmodified oriented nematic liquid crystal elastomer contains at least one plasticizer in an amount of, for example, 1 to 50% by mass, and the modified oriented nematic liquid crystal elastomer is substantially free of plasticizers.

16. The method according to claim 11, wherein the glass transition temperature (Tg) is increased by reducing the conformational degrees of freedom in the mesogenic monomer and / or non-mesogenic monomer, or the glass transition temperature (Tg) is decreased by increasing the conformational degrees of freedom in the mesogenic monomer and / or non-mesogenic monomer.

17. Use of chemically modified oriented nematic liquid crystal elastomers in a method for increasing or decreasing the authentic response strain threshold of oriented nematic liquid crystal elastomers.

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