Methods and materials of printing three-dimensional objects

Abstract

Embodiments of the present disclosure provide a polymerizable material configured to produce three-dimensional objects by additive manufacturing methods. The polymerizable material comprises a first reactive component, a second reactive component, and a photoinitiator. A cured product of the first reactive component has a first glass transition temperature of less than 50˚C, a cured product of the second reactive component has a second glass transition temperature of greater than 100˚C, and a difference between the second glass transition temperature and the first glass transition temperature is greater than 80˚C.

Description

Attorney Docket No: 20744-D045WO00METHODS AND MATERIALS OF PRINTING THREE-DIMENSIONAL OBJECTS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Provisional Patent Application No. 63 / 735,303, filed on December 17, 2024, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of additive manufacturing, and particularly relates to a polymerizable material configured to produce three- dimensional objects by additive manufacturing methods, a method of forming a three- dimensional object, and a clear dental aligner.BACKGROUND

[0003] The clear dental aligner (such as a direct-printed clear dental aligner) is an important product in digital orthodontic treatment. 3D direct printing technology for the clear dental aligner without brackets has received widespread attention due to its high degree of customization. This technology not only eliminates the step of manufacturing traditional physical tooth models but also enables fully digital design and rapid prototyping of dental aligners. However, the performance of the printing materials directly determines the final effect of the dental aligners. The photopolymerizable 3D printing resins currently available on the market often struggle to balance hardness and toughness - they are either hard and brittle, or tough and soft, unable to meet the comprehensive mechanical performance requirements of dental aligners. Although shape memory polymer (SMP) materials can restore their initial shape when heated, the phase transition of such materials from a glassy state (rigid) to a rubbery state (soft) will significantly reduce material stiffness and cause stress relaxation, affecting mechanical properties and resulting in orthodontic force decay.

[0004] Therefore, there is a desire to provide a long-term stable polymerizable material that balances active shape memory function and mechanical performance for producing three-dimensional objects by additive manufacturing methods.SUMMARY

[0005] One or more embodiments of the present disclosure provide a polymerizable material configured to produce three-dimensional objects by additive manufacturing methods. The polymerizable material comprises a first reactive component, a second reactive component, and a photoinitiator. A cured product of the first reactive component has a first glass transition temperature of less than 50°C, a cured product of the second reactive component has a second glass transition temperature of greaterAttorney Docket No: 20744-D045WO00 than 100°C, and a difference between the second glass transition temperature and the first glass transition temperature is greater than 80°C.

[0006] In some embodiments, a cured product of the polymerizable material comprises a glass phase and a rubber phase, the glass phase and the rubber phase are phase-separated, and a weight percentage of the glass phase to the rubber phase is greater than 50%.

[0007] In some embodiments, the glass phase maintains a structural rigidity of the cured product of the polymerizable material, and the rubber phase enables the cured product of the polymerizable material to undergo deformation under stress, the deformation being reversible via external thermal excitation.

[0008] In some embodiments, a peak glass transition temperature of the cured product of the polymerizable material is greater than 100°C.

[0009] In some embodiments, an initial glass transition temperature of the cured product of the polymerizable material is greater than 20°C.

[0010] In some embodiments, the initial glass transition temperature of the cured product of the polymerizable material is less than 40°C

[0011] In some embodiments, a Full Width at Half Maximum (FWHM) of a Dynamic Mechanical Analysis (DMA) curve of the cured product of the polymerizable material is greater than 40°C.

[0012] In some embodiments, the first reactive component is a blocked polyurethane prepolymer prepared by a reaction of a diisocyanate and a diol compound.

[0013] In some embodiments, the diol compound comprises a polyester diol or a polyether diol.

[0014] In some embodiments, a molecular weight of the diol compound is in a range of 1000-3500.

[0015] In some embodiments, a molar ratio of the diisocyanate to the diol compound is in a range of 1 .3-2.2.

[0016] In some embodiments, the diol compound comprises a first diol compound and a second diol compound, and the first diol compound and the second diol compound are different diols.

[0017] In some embodiments, the glass transition temperature of the first diol compound is lower than the glass transition temperature of the second diol compound, and a melting point of the first diol compound is lower than the melting point of the second diol compound.

[0018] In some embodiments, when preparing the first reactive component, a molarAttorney Docket No: 20744-D045WG00 ratio of the first diol compound to the second diol compound is 0.1 -1.

[0019] In some embodiments, the second reactive component comprises a (meth)acrylate functional group connected to a cyclic compound.

[0020] In some embodiments, the cyclic compound is as a side chain into a polymer backbone during polymerization of the polymerizable material, and the cyclic compound does not include heterocycles containing only oxygen.

[0021] In some embodiments, the polymerizable material further comprises a third reactive component, a cured product of the third reactive component has a third glass transition temperature of greater than 120°C, and a difference between the third glass transition temperature and the first glass transition temperature is greater than 100°C.

[0022] In some embodiments, the third reactive component comprises a urethane dimethacrylate (IIDMA) prepolymer, and the LIDMA prepolymer includes isocyanate groups.

[0023] One or more embodiments of the present disclosure provide a method of forming a three-dimensional object. The method comprises providing a printing region; filling the printing region with the polymerizable material according to the embodiments of the present disclosure; irradiating the printing region with light to form a three- dimensional intermediate object; and heating or microwave irradiating the three- dimensional intermediate object to form the three-dimensional object.

[0024] One or more embodiments of the present disclosure provide a clear dental aligner printed by the method according to the embodiments of the present disclosure.

[0025] In some embodiments, a difference in elastic modulus tested via DMA of the clear dental aligner between 37°C and 25°C is less than 10%, and the clear dental aligner restores at least 80% of its orthodontic force at a temperature above 60°C.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure is further described in terms of exemplary embodiments. These exemplary embodiments are described in detail with reference to the drawings. The drawings are not to scale. These embodiments are nonlimiting exemplary embodiments, in which like reference numerals represent similar structures throughout the several views of the drawings, and wherein:

[0027] FIG. 1 is a schematic diagram showing a working principle of thermal excitation reversal of a cured product of a polymerizable material according to some embodiments of the present disclosure;

[0028] FIG. 2 is a schematic diagram showing Dynamic Mechanical Analysis (DMA) of a cured product of a polymerizable material according to some embodiments of theAttorney Docket No: 20744-D045WG00 present disclosure;

[0029] FIG. 3 is a flowchart of a method of forming a three-dimensional object according to some embodiments of the present disclosure;

[0030] FIG. 4 is a schematic diagram showing thermal excitation recovery of a clear dental aligner according to some embodiments of the present disclosure; and

[0031] FIG. 5 is a schematic diagram of printing parameters according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0032] In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well-known methods, procedures, systems, components, and / or circuitry have been described at a relatively high level, without detail, in order to avoid unnecessarily obscuring aspects of the present disclosure. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present disclosure is not limited to the embodiments shown, but to be accorded the widest scope consistent with the claims.

[0033] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise,” “comprises,” and / or “comprising,” “include,” “includes,” and / or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] These and other features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, may become more apparent upon consideration of the following description with reference to the accompanying drawings, all of which form a part of this disclosure. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended to limit the scope of the present disclosure. It is understood that theAttorney Docket No: 20744-D045WO00 drawings are not to scale.

[0035] Clear dental aligners are representative products in the field of orthodontics. With the increasing aesthetic demands of people, the application of the clear dental aligners is becoming increasingly widespread. Unlike traditional fixed orthodontic appliances, which focus on bracket positioning and archwire mechanical design, the clear dental aligners, as complete force units, have material properties that directly determine the feasibility and effectiveness of the treatment plan. The initial mechanical properties of the materials used are closely related to achieved orthodontic outcomes. The thermoforming film materials, which are currently widely used in clear dental aligner applications, exhibit varying degrees of performance instability and are easily affected by temperature, humidity, and saliva, leading to orthodontic force decay.

[0036] On this basis, 3D direct printing technology for clear dental aligners without brackets, as an emerging technology, has received widespread attention. Compared to traditionally thermoformed dental aligners, this technology does not require making physical tooth models; and clear dental aligners can be directly digitally designed and printed, offering a higher degree of customization. However, a polymer network formed by the photopolymerization of a resin material used for direct printing is likely to be affected by a wearing environment, leading to issues of stress relaxation. In other words, the material can provide a large amount of stress at the start of wear, which is used to provide the orthodontic force required for orthodontics. But over time, the stress of the material will quickly decay to a relatively small value, thus affecting the orthodontic effect. The photopolymerizable 3D printing resins currently available on the market often struggle to balance hardness and toughness - they are either hard and brittle, or soft and tough, unable to meet the comprehensive mechanical performance requirements of aligners. Therefore, how to meet multiple performance requirements of directly printed aligners under the conditions of single-material 3D printing has always been a significant technical challenge in the industry.

[0037] Shape memory polymers (SMPs) were once considered one of the potential directions to address these issues. Such materials can "remember" their original shape and recover to it after deformation when activated by stimuli such as heat. A common hypothesis posits that SMPs activated at intraoral temperatures (37°C) could generate the "recovery force" required for tooth movement. However, this hypothesis is fundamentally flawed due to the inherent phase transition behavior of the material. When SMPs are designed to activate shape memory around body temperature, the transition from a glassy state (rigid) to a rubbery state (flexible) leads to excessiveAttorney Docket No: 20744-D045WO00 softening of the material, significantly reducing material stiffness (with a modulus reduction of over 70%) and causing substantial internal stress relaxation. This premature relaxation impairs mechanical properties, resulting in rapid orthodontic force decay and further raising significant concerns about clinical efficacy. Furthermore, some SMPs demonstrate a more limited "shape-only" memory effect: while they can achieve geometric restoration upon thermal activation, they fail to sustainably recover their original mechanical properties. Even if the aligner regains its original shape, the concomitant loss of stiffness and orthodontic force output renders it ineffective for achieving controlled and sustained tooth movement. These limitations of traditional aligner materials and shape memory polymers highlight the urgent need for developing a novel direct-printed aligner material. One or more embodiments of the present disclosure provide a polymerizable material configured to produce three-dimensional objects by additive manufacturing methods.

[0038] The additive manufacturing refers to a process of constructing three- dimensional objects by adding materials layer by layer, often also called 3D printing. The three-dimensional objects refer to products with specific three-dimensional geometric shapes and functions made by additive manufacturing technologies. Merely by way of example, the three-dimensional objects include clear dental aligners. The polymerizable material refers to a substance composed of small molecule units, which can form polymers through a polymerization reaction under external conditions (such as light, heat, radiation, the addition of chemical initiators, etc.). The polymerizable material described in the embodiments of the present disclosure can be used to produce three-dimensional objects via additive manufacturing methods.

[0039] In some embodiments, the polymerizable material includes a first reactive component, a second reactive component, and a photoinitiator.

[0040] The first reactive component refers to one of the raw materials for preparing the polymerizable material. In some embodiments, the first reactive component is a reactive monomer or a reactive prepolymer.

[0041] In some embodiments, a cured product of the first reactive component has a first glass transition temperature (Tg1 ) of less than 50°C. The cured product refers to a polymer material formed after the first reactive component undergoes a curing reaction, possessing a three-dimensional network cross-linked structure or insoluble and infusible properties. In some embodiments, the cured product of the first reactive component has a first glass transition temperature of less than 30°C. In some embodiments, the cured product of the first reactive component has a first glassAttorney Docket No: 20744-D045WQ00 transition temperature of less than 15°C. In some embodiments, the cured product of the first reactive component has a first glass transition temperature of less than 0°C. It is understandable that the glass transition temperature is a critical temperature at which a polymer transitions from a rigid glassy state to a soft and highly elastic state (rubbery state). That the cured product of the first reactive component has the first glass transition temperature of less than 50°C means that under normal service conditions (e.g., an oral environment, etc.), the cured product of the first reactive component is in the highly elastic state. A material region constituted by the cured product of the first reactive component (called a rubber phase) can undergo large and reversible elastic deformations, while providing the necessary flexibility and wearing comfort for the subsequently produced clear dental aligner.

[0042] In some embodiments, the first reactive component may be a polyurethane prepolymer. A molecular structure of the polyurethane prepolymer may include soft segments and hard segments. It is understandable that in the cured product of the polymerizable material, the soft segments tend to form the rubber phase, providing elasticity to the cured product of the polymerizable material; the hard segments tend to form a glass phase, providing rigidity and strength to the cured product of the polymerizable material. Through the combined action of the microphase-separated structure of the soft segments and the hard segments, the cured product of the polymerizable material ultimately achieves a balance of toughness and rigidity.

[0043] In some embodiments, the first reactive component is a blocked polyurethane prepolymer prepared by a reaction of a diisocyanate and a diol compound.

[0044] The diisocyanate is one of the raw materials for synthesizing the polyurethane prepolymer. Its molecule contains two isocyanate groups (-NCO), which are highly chemically reactive. In the synthesis of the polyurethane prepolymer, the diisocyanate participates in forming the hard segments to provide rigidity.

[0045] In some embodiments, the diisocyanate includes at least one of isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), toluene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI), p-phenylene diisocyanate (PPDI), or cyclohexane diisocyanate (CHDI).

[0046] Preferably, the diisocyanate is isophorone diisocyanate (IPDI). It is understandable that the molecular structure of IPDI contains a cyclohexane ring and an isophorone ring. The cyclic structures provide good rigidity, help form sturdy hard segments, and provide high moduli and strength for the cured product of theAttorney Docket No: 20744-D045WG00 polymerizable material.

[0047] Preferably, the diisocyanate is at least one of 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), p-phenylene diisocyanate (PPDI), cyclohexane diisocyanate (CHDI), or hexamethylene diisocyanate (HDI). It is understandable that these diisocyanates have more complex structures, which helps optimize a network structure of the cured product of the polymerizable material, thereby improving the mechanical properties.

[0048] The molecule of the diol compound contains two hydroxyl groups. In the synthesis of the polyurethane prepolymer, the diol compound participates in forming the soft segments to provide elasticity.

[0049] In some embodiments, the diol compound includes polyester diol or polyether diol.

[0050] The polyester diol has an ester group (-COO-) on its molecular chains. The ester group is a polar group, enabling stronger hydrogen bonding and dipole-dipole interactions between chains in the molecular structure. While providing elasticity, the polyester diol also imparts higher mechanical strength, wear resistance, and anti-creep (anti-stress relaxation) performance to the material, making it more suitable for the performance requirements of aligners and thus a preferred diol compound. In some embodiments, the polyester diol is at least one of polycaprolactone diol (PCL) or polycarbonate diol (PCDL). It is understandable that compared to the polyether diol, the polyester diol has a smaller molecular weight, which is more helpful in improving the mechanical properties of the final cured product of the polymerizable material.

[0051] The polyether diol has an ether bond (-O-) on its molecular chains. The large bond angle around the oxygen atom of the ether bond and extremely low rotational barrier make the molecular chains very flexible, providing excellent dynamic elasticity and flexural fatigue resistance, but the mechanical strength is relatively weak. In some embodiments, the polyether diol is at least one of polyethylene glycol diol (PEG), a polypropylene glycol diol (PPG), polytetramethylene ether glycol (PTMG / PTMEG), or tris(3-methyl ether) glycol (PO3G).

[0052] In some embodiments, a molecular weight of the diol compound is in a range of 1000-3500. It is understandable that the molecular weight of the diol compound directly determines a length of the soft segments in the polyurethane prepolymer, thereby affecting the corresponding material properties. It is understandable that when the molecular weight of the diol compound is less than 1000, a diol chain is too short, and the soft segments in the synthesized polyurethane prepolymer are also very short.Attorney Docket No: 20744-D045WO00 This makes the proportion of the hard segments in the generated polyurethane prepolymer relatively too high, resulting in overly rigid materials that lack elasticity, flexibility, and impact resistance. When the molecular weight of the diol compound is greater than 3500, overly long soft segments are formed, which physically hinder and separate the aggregation of the hard segments during polymerization. This may prevent the hard segments from effectively connecting into a continuous network structure (i.e., the glass phase is fragmented). By controlling the molecular weight of the diol compound within the range of 1000-3500, the length of the diol chain is sufficient to form effective flexible soft segments, providing excellent elasticity and toughness. At the same time, its length is not enough to excessively interfere with a rigid network formed by the hard segments, allowing the glass phase to become a continuous phase of a polymerized part.

[0053] In some embodiments, the molecular weight of the diol compound is in a range of 1300-3200. In some embodiments, the molecular weight of the diol compound is in a range of 1600-2900. In some embodiments, the molecular weight of the diol compound is in a range of 1900-2600. In some embodiments, the molecular weight of the diol compound is in a range of 2100-2300.

[0054] In some embodiments, a molar ratio of the diisocyanate to the diol compound is in a range of 1.3-2.2. In some embodiments, preferably, the molar ratio of the diisocyanate to the diol compound is in a range of 1 .5-2.0.

[0055] Controlling the molar ratio to be greater than 1 is the key to synthesizing the polyurethane prepolymer. This molar ratio condition ensures an excess of di isocyanate monomers, thereby guaranteeing that ends of a molecular chain of the polyurethane prepolymer are terminated with isocyanate groups (-NCO) rather than hydroxyl groups (-OH) after the reaction. Having terminal -NCO groups is a necessary prerequisite for the subsequent blocking reaction with hydroxyl-containing (meth)acrylate monomers, such as hydroxyethyl acrylate (HEA) or hydroxyethyl methacrylate (HEMA), to successfully introduce (meth)acrylate double bonds capable of participating in photocuring cross-linking. If the molar ratio is less than or equal to 1 , the ends of the molecular chain of the polyurethane prepolymer will be hydroxyl groups, preventing effective blocking.

[0056] Meanwhile, the molar ratio should not be excessively high. If the molar ratio significantly exceeds 2.2, there will be an excessive amount of free diisocyanate monomers in the reaction system. This not only increases the toxicity of the system, adversely affecting product biocompatibility, but may also introduce excessive hardAttorney Docket No: 20744-D045WC00 segment structures during the subsequent blocking reaction, thereby impairing the performance balance of the final cured material.

[0057] Therefore, controlling the molar ratio within the range of 1.3 to 2.2 offers comprehensive advantages: it can not only ensure that the ends of the molecular chain of the polyurethane prepolymer are reactive isocyanate groups (thereby creating necessary conditions for introducing double bonds), but also effectively control the molecular weight and viscosity of the polyurethane prepolymer. Generally, within the range of 1.3 to 2.2, the closer the molar ratio is to the lower limit, the longer the molecular chain and the higher the viscosity of the polyurethane prepolymer; whereas the closer the molar ratio is to the upper limit, the shorter the molecular chain of the polyurethane prepolymer and the lower the viscosity of the polyurethane prepolymer. By precisely adjusting this ratio, a suitable viscosity for processes such as 3D printing may be obtained. In addition, the hard segment structures of the polyurethane prepolymer synthesized with this molar ratio help to synergistically form a continuous, interpenetrating glass phase structure with the second reactive component in the final cured material, thereby enhancing the overall mechanical properties of the material.

[0058] In some embodiments, the molar ratio of the diisocyanate to the diol compound is in a range of 1.1 -1.8. In some embodiments, the molar ratio of the diisocyanate to the diol compound is in a range of 1.2-1 .6. In some embodiments, the molar ratio of the diisocyanate to the diol compound is in a range of 1.3-1.4. In some embodiments, the molar ratio of the diisocyanate to the diol compound is 1 .33.

[0059] It is understandable that the synthesis of the blocked polyurethane prepolymer may include two stages. The first stage is synthesizing an NCO-terminated prepolymer, where the reaction of the diisocyanate and the diol compound generates a polyurethane prepolymer with reactive isocyanate groups at both ends of the molecular chains (i.e., an NCO-terminated polyurethane prepolymer). The second stage is a blocking reaction stage, where the NCO-terminated prepolymer is reacted with a blocking agent (i.e., a capping agent) to generate the blocked polyurethane prepolymer. After the blocking reaction, the originally highly active NCO terminal groups are replaced by inert blocking agent molecules or groups, making the generated blocked polyurethane prepolymer stable in nature and only reactivatable under specific conditions (such as heating, light irradiation, etc.).

[0060] In some embodiments, the molecular structure of the blocked polyurethaneAttorney Docket No: 20744-D045WO00 prepolymer may be represented aswhere R is a polymer chain(a main structure, a polyurethane chain segment pre-formed by the reaction of the diisocyanate and the diol compound), and X and Z are blocking groups connected to both ends of the polymer chain R (provided by the blocking agent, they may be the same or different, optionally bearing reactive terminal groups). In some embodiments, the blocking agent includes at least one of hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), methyl hydroxypropyl acrylate (HPO-MA / HPMA), hydroxybutyl acrylate (HBA), methyl hydroxyethyl acrylate (HEMA), N-(hydroxymethyl)acrylamide (NMA), N-(2-Hydroxyethyl)acrylamide (HEAA), N-[tris(hydroxymethyl)methyl]acrylamide (THMA), or N-(2-Hydroxypropyl)methacrylamide (HPMA). X and Z correspond to structural moieties introduced by these blocking agent molecules after substituting for the NCO terminal groups.

[0061] An exemplary synthesis process of the first reactive component includes the following steps S1-S5.

[0062] Step S1 , the diol compound is added to a reaction kettle based on a metered molar ratio, and the diol compound is stirred and heated until an internal temperature of the reaction kettle rises to a mixing temperature. In some embodiments, the mixing temperature is 50°C-75°C. Preferably, the mixing temperature is 60°C-65°C.

[0063] Step S2, the diisocyanate is added to the reaction kettle based on a metered molar ratio, and the mixture is mixed at the mixing temperature for a first mixing time. In some embodiments, the first mixing time is 5-15 min. Preferably, the first mixing time is 10 min. The molar ratio of the diisocyanate to the diol compound is as described previously.

[0064] Step S3, a catalyst at a specified concentration is added, the internal temperature of the reaction kettle is raised and controlled not to exceed an upper temperature limit. In some embodiments, the upper temperature limit is 80°C. In some embodiments, the catalyst is a Gaussmit organic bismuth catalyst TMG720. In some embodiments, a concentration of the catalyst is 450ppm-550ppm. Preferably, the concentration of the catalyst is 500ppm.

[0065] Step S4, after a reaction temperature rise stops, an isothermal reaction is performed at the reaction temperature based on a reaction time, and an isocyanate value (an NCO value) is tested by titration to ensure the NCO value reaches aAttorney Docket No: 20744-D045WC00 theoretical value. The NCO value refers to a molar ratio of the isocyanate groups (NCO) to the hydroxyl groups (OH). The NCO may come from the diisocyanate, and the OH may come from the diol compound and an optional chain extender (a short-chain diol or a short-chain diamine, e.g., 1 ,4-butanediol, etc.) depending on the researcher’s needs. In some embodiments, the reaction temperature is 60°C-90°C. Preferably, the reaction temperature is 70°C-80°C. In some embodiments, the reaction time is 2 hours- 5 hours. Preferably, the reaction time is 3 hours-4 hours. In some embodiments, the theoretical value of the NCO value is 1.2-1.5. Preferably, the theoretical value of the NCO value is 1 .33.

[0066] Step S5, the temperature is lowered to the lower limit of the reaction temperature; a polymerization inhibitor at a specified concentration is added; the blocking agent is added based on a metered molar ratio; an isothermal reaction is then performed at the reaction temperature for the reaction time; and the NCO value is tested by titration to ensure complete reaction of the NCO. It is understandable that the polymerization inhibitor can inhibit a thermal polymerization side reaction of the blocking agent itself during a high-temperature blocking reaction, ensuring that each blocking agent molecule can effectively and individually react with the NCO groups at the end of the prepolymer, thereby generating a blocked prepolymer with a regular structure and a controllable molecular weight. In some embodiments, the polymerization inhibitor is a Monomethyl Ether of Hydroquinone (MEHQ). In some embodiments, a concentration of the polymerization inhibitor is 450ppm-550ppm. Preferably, the concentration of the polymerization inhibitor is 500ppm. A metered molar ratio of the blocking agent may be set according to the molar ratio of the diisocyanate to the diol compound to ensure the blocking agent effectively blocks the remaining NCO groups.

[0067] It is understandable that in the synthesized blocked polyurethane prepolymer, the soft segments come from a long and flexible polymer chain (e.g., polyether diol or polyester diol), and the hard segments come from the diisocyanate. In addition, the blocking agent may also provide the hard segments.

[0068] In some embodiments, the diisocyanate IPDI is reacted with the diol compound to generate the NCO-terminated polyurethane prepolymer, then the blocking agent HEA is added to generate the first reactive component (i.e., the aforementioned blocked polyurethane prepolymer). The specific chemical process route is:Attorney Docket No: 20744-D045WQ00wherein DBTDL is the catalyst.

[0069] In some embodiments, the diisocyanate HMDI is reacted with the diol compound to generate the NCO-terminated polyurethane prepolymer, then the blocking agent HEMA is added to generate the first reactive component (i.e., the aforementioned blocked polyurethane prepolymer). The specific chemical process route is:

[0070] In some embodiments, the chain extender is added during the synthesis process of the first reactive component. It reacts with the diisocyanate to jointly provide the hard segments in the synthesized blocked polyurethane prepolymer. Whether the chain extender is added may be determined according to the researchers’ needs. Merely by way of example, the chain extender may include any one of 1 ,4-Butanediol (BDO), 1 ,4-Cyclohexanedimethanol (CHDM), 1 ,6-Hexanediol (HDO), or 1 ,12- Dodecanediol (DDO).

[0071] In some embodiments, the diol compound includes a first diol compound and a second diol compound. In some embodiments, the first diol compound and the second diol compound are different diols.

[0072] The first diol compound refers to a diol compound that has stronger elasticity in the oral environment. The second diol compound refers to a diol compound that hasAttorney Docket No: 20744-D045WQ00 higher crystallinity in the oral environment. The oral environment may include a physiological oral environment and an artificially simulated oral environment. The artificially simulated oral environment refers to an oral-like test system constructed by artificially controlling variables such as temperature, humidity, pH, mechanical load, chemical media, which is used to evaluate material properties under biomimetic conditions.

[0073] In some embodiments, the glass transition temperature of the first diol compound is lower than the glass transition temperature of the second diol compound.

[0074] In some embodiments, the glass transition temperature of the first diol compound is -60°C ~ -50°C. In some embodiments, the glass transition temperature of the first diol compound is -58°C ~ -52°C. In some embodiments, the glass transition temperature of the first diol compound is -56°C ~ -54°C.

[0075] In some embodiments, the glass transition temperature of the second diol compound is -30°C ~ -20°C. In some embodiments, the glass transition temperature of the second diol compound is -28°C — 22°C. In some embodiments, the glass transition temperature of the second diol compound is -26°C ~ -24°C.

[0076] In some embodiments, a melting point of the first diol compound is lower than the melting point of the second diol compound.

[0077] In some embodiments, the melting point of the first diol compound is 30°C ~ 35°C. In some embodiments, the melting point of the first diol compound is 31 °C ~ 34°C. In some embodiments, the melting point of the first diol compound is 32°C ~ 33°C.

[0078] In some embodiments, the melting point of the second diol compound is 40°C ~ 55°C. In some embodiments, the melting point of the second diol compound is 43°C ~ 52°C. In some embodiments, the melting point of the second diol compound is 46°C ~ 49°C.

[0079] In some embodiments, at an application temperature (e.g., an oral temperature, or the like), the second diol compound in the polyurethane prepolymer may exhibit a higher crystallization tendency or crystallinity than the first diol compound. Compared with using a single diol compound to form soft segments in the polyurethane prepolymer to provide elasticity, the embodiments of the present disclosure adopt two diol compounds with different crystallization tendencies. This design introduces more hierarchical phase-separated structures into the final polymer network, thereby facilitating more precise regulation of the comprehensive properties (e.g., modulus, toughness, shape memory recovery force, and stress relaxation resistance) of the finalAttorney Docket No: 20744-D045WO00 polymer. It should be noted that the embodiments of the present disclosure have no specific requirement on the sequential arrangement of the soft segment structure formed by the two diol compounds. It is understandable that by introducing a first diol compound with a lower glass transition temperature and a lower melting point, and a second diol compound with a higher glass transition temperature and a higher melting point, the soft segments of the generated polyurethane prepolymer can balance both elasticity and low stress relaxation. Based on the previous use of a single diol compound to generate a first reactive component with a two-phase structure, this approach further balances elasticity and stress relaxation performance.

[0080] In some embodiments, the first diol compound and the second diol compound are at least one of PTMG2000, PCL2000, PCL3000, etc.

[0081] In some embodiments, when preparing the first reactive component, a molar ratio of the first diol compound to the second diol compound is in a range of 0.1 -1.

[0082] In some embodiments, when preparing the first reactive component, the molar ratio of the first diol compound to the second diol compound is in a range of 0.2-0.9. In some embodiments, the molar ratio of the first diol compound to the second diol compound is in a range of 0.3-0.8. In some embodiments, the molar ratio of the first diol compound to the second diol compound is in a range of 0.4-0.7. In some embodiments, the molar ratio of the first diol compound to the second diol compound is in a range of 0.5-0.6.

[0083] It is understandable that when using only the first diol compound with better elasticity or only the second diol compound with higher crystallinity, it may result in poor properties in either elasticity or stress relaxation of the obtained first reactive component and the final cured product. When using two diol compounds, if a proportion of the first diol compound is higher and a proportion of the second diol compound is lower, the prepared aligner has stronger elasticity, performs better in a plugging and unplugging bending test (as can be understood, the aligner needs to undergo repeated bending deformation when being worn and taken off; the plugging and unplugging bending test can evaluate properties such as bending fatigue), but the stress relaxation properties are poorer. When the proportion of the first diol compound is lower and the proportion of the second diol compound is higher, the prepared aligner has weaker elasticity, performs poorly in the plugging and unplugging bending test, but the stress relaxation properties are better.

[0084] When using the first diol compound and the second diol compound as the diol compound, the exemplary synthesis process of the first reactive component includesAttorney Docket No: 20744-D045WC00 the following steps S6-S10.

[0085] Step S6, the first diol compound, the second diol compound, and a small molecule diol chain extender are added to a reaction kettle based on a metered molar ratio, and the mixture is mixed at a mixing temperature for a second mixing time. Whether the small molecule diol chain extender is added may be determined according to the researchers’ needs. In some embodiments, the mixing temperature is 50°C- 75°C. Preferably, the mixing temperature is 60°C-65°C. In some embodiments, the second mixing time is 20-50 min. Preferably, the second mixing time is 30 min. In some embodiments, a molar ratio of the chain extender to the diol compound (including the first diol compound and the second diol compound) is in the range of 0.1 -1. Preferably, the molar ratio of the chain extender to a total amount of the diol compound is 0.5.

[0086] Step S7, the diisocyanate is added to the reaction kettle based on a metered molar ratio, and the mixture is mixed at the mixing temperature for the first mixing time. The molar ratio of the diisocyanate to the diol compound (including the first diol compound and the second diol compound) is as described previously.

[0087] Step S8, a catalyst at the specified concentration is added, and the internal temperature of the reaction kettle is raised and controlled not to exceed an upper temperature limit. In some embodiments, the upper temperature limit is 80°C. In some embodiments, the catalyst is Gaussmit organic bismuth catalyst TMG720. In some embodiments, the concentration of the catalyst is 500ppm.

[0088] Step S9, after the reaction temperature rise stops, an isothermal reaction is performed at a reaction temperature based on a reaction time, and the NCO value is tested by titration to ensure the NCO value reaches the theoretical value. In some embodiments, the reaction temperature is 60°C-90°C. Preferably, the reaction temperature is 70°C-80°C. In some embodiments, the reaction time is 2 hours-5 hours. Preferably, the reaction time is 3 hours-4 hours. In some embodiments, the theoretical value of the NCO value is 1.2-1.5. Preferably, the theoretical value of the NCO value is 1.33.

[0089] Step S10, the temperature is lowered to the lower limit of the reaction temperature; the blocking agent is added based on a metered molar ratio; an isothermal reaction is then performed at the reaction temperature for the reaction time; and the NCO value is tested by titration to ensure complete reaction of the NCO. The metered molar ratio of the blocking agent may be set according to the molar ratio of the diisocyanate to the diol compound (including the first diol compound and the second diol compound) to ensure the blocking agent effectively blocks the remainingAttorney Docket No: 20744-D045WG00NCO groups.

[0090] In some embodiments, the first reactive component is at least one of PTMG2000 / IPDI / HEA prepolymer, PTMG2000 / IPDI / HEMA prepolymer, PTMG650 / IPDI / HEMA prepolymer, PCL2000 / IPDI / HEA prepolymer, PCL2000 / IPDI / HEMA prepolymer, PCDL2000 / IPDI / HEA prepolymer, or PCDL2000 / IPDI / HEMA prepolymer.

[0091] The second reactive component refers to one of the raw materials for preparing the polymerizable material. In some embodiments, the second reactive component is the reactive monomer or the reactive prepolymer.

[0092] In some embodiments, a cured product of the second reactive component has a second glass transition temperature (Tg2) of greater than 100°C. In some embodiments, the cured product of the second reactive component has a second glass transition temperature of greater than 120°C. In some embodiments, the cured product of the second reactive component has a second glass transition temperature of greater than 140°C. In some embodiments, the cured product of the second reactive component has a second glass transition temperature of greater than 160°C. It is understandable that setting the cured product of the second reactive component to have the second glass transition temperature greater than 100°C means that under the normal service conditions, the second reactive component is in a glassy state. A material region constituted by the second reactive component (called the glass phase) can provide high modulus (rigidity), strength, and shape stability, enabling the subsequently produced clear dental aligner to resist deformation and continuously apply orthodontic force to the teeth.

[0093] In some embodiments, a difference between the second glass transition temperature and the first glass transition temperature is greater than 80°C. In some embodiments, the difference between the second glass transition temperature and the first glass transition temperature is greater than 100°C. In some embodiments, the difference between the second glass transition temperature and the first glass transition temperature is greater than 120°C. In some embodiments, the difference between the second glass transition temperature and the first glass transition temperature is greater than 140°C. In some embodiments, the difference between the second glass transition temperature and the first glass transition temperature is greater than 160°C. It is understandable that by setting the difference between the second glass transition temperature and the first glass transition temperature to be greater than 80°C, it can drive and stabilize the microphase-separated structure, achievingAttorney Docket No: 20744-D045WO00 performance synergy. The greater the difference in the glass transition temperature between the two polymers (i.e., the cured products of the aforementioned two components), the greater the difference in polarity and segment flexibility, leading to incompatibility during polymerization, and spontaneously separating into two independent phases, and ultimately forming a stable structure with the glass phase as the continuous phase and the rubber phase as the dispersed phase. The phase- separated structure perfectly combines the advantages of the two materials: the glass phase is responsible for bearing the load, providing strength and stiffness; the rubber phase is responsible for dispersing stress, providing elasticity and toughness. The synergistic effect of the two achieves a "1 +1 >2" effect, enabling the material to simultaneously possess both high strength and high toughness, which are seemingly contradictory properties. Furthermore, a rigid glass phase network can restrict the slippage and rearrangement of flexible molecular chains under a sustained stress, giving the material extremely low stress relaxation and ensuring long-term stability of the orthodontic force.

[0094] In some embodiments, the second reactive component includes a (meth)acrylate functional group connected to a cyclic compound. In some embodiments, the second reactive component is a mono-functional monomer or a difunctional compound. The mono-functional monomer refers to a compound containing only one (meth)acrylate group that can participate in the polymerization reaction in its molecule. The di-functional compound refers to a compound containing two (meth)acrylate groups that can participate in the polymerization reaction in its molecule.

[0095] In some embodiments, the second reactive component includes a (meth)acrylate functional group connected to a cyclic compound. In some embodiments, the cyclic compound is a carbocyclic compound or a nitrogen-containing heterocyclic compound.

[0096] It is understandable that the cyclic structures, suspended on side chains, can help improve the anti-stress relaxation performance of the resulting polymer compound, which is important to the orthodontic material. The molecular chains of the polymer are stretched under deformation. Particularly at an oral temperature (e.g., at approximately 37°C), over time, the chains undergo rearrangement to relieve the internal stress. This causes the applied force to gradually diminish even while the aligner remains in its original position. These cyclic structures can increase the rigidity of the polymer network by introducing rigid segments, therefore restricting segmental motion, making it harder for the polymer chain to rearrange under stress.Attorney Docket No: 20744-D045WO00

[0097] In some embodiments, the cyclic compound acts as a side chain of the polymer backbone during polymerization of the polymerizable material, and the cyclic compound does not include heterocycles containing only oxygen. It is understandable that the cyclic structure of the cyclic compound (e.g., the ring of a nitrogen-containing heterocyclic compound) may contain oxygen atoms in the ring. However, heterocycles containing only oxygen should be avoided, as the purpose of the second reactive component is to introduce high glass transition temperature (Tg) segments into the polymer network. Heterocycles containing only oxygen are generally more flexible and tend to lower the overall Tg, as they increase the mobility of the synthesized polymer chains.

[0098] In some embodiments, the second reactive component is at least one of Acryloyl morpholine (ACMO), Cyclic Trimethylolpropane Formal Acrylate (CTFA), Isobornyl acrylate (IBOA), Isobornyl methacrylate (IBOMA), Trimethylcyclohexyl acrylate (TMCHA), or Dicyclopentenyl acrylate (DCPA).

[0099] The photoinitiator is used to initiate a photopolymerization reaction. It is understandable that the photoinitiator may be any suitable photoinitiator that can initiate the photopolymerization reaction under a light source for initiating the photopolymerization reaction. In some embodiments, a wavelength of light used to initiate the photopolymerization reaction is in the range of 350nm-450nm. In some embodiments, the wavelength of light used to initiate the photopolymerization reaction is in the range of 360nm-440nm. In some embodiments, the wavelength of light used to initiate the photopolymerization reaction is in the range of 370nm-430nm. In some embodiments, the wavelength of light used to initiate the photopolymerization reaction is in the range of 380nm-410nm. In some embodiments, the wavelength of light used to initiate the photopolymerization reaction is 405nm. In some embodiments, the wavelength of light used to initiate the photopolymerization reaction is 385nm.

[0100] In some embodiments, the photoinitiator includes benzoin ether derivativesAttorney Docket No: 20744-D045WO00alkbis(q5-cyclopentadien-1 -y l)-bis[2 ,6-dif luoro-3-( 1 H-pyrrol-1 -yl)-phenyl]titaniumwherein R1-R16 are independently selected fromH or alkyl groups.

[0101] In some preferred embodiments, the photoinitiator used is benzoyl phosphine oxides, including 2,4,6-Trimethylbenzoyl diphenyl phosphine oxide (TPO)-Trimethylbenzoyl phenyl methyl phosphineAttorney Docket No: 20744-D045WO00 oxide (TMO)trimethylbenzoyl)phenyl phosphine oxide (819)2,4,6-T rimethylbenzoyl ethoxyphenyl phosphine oxide (TEPO)

[0102] In some embodiments, the polymerizable material further includes a third reactive component. The third reactive component refers to one of the raw materials for preparing the polymerizable material. In some embodiments, the third reactive component is the reactive monomer or the reactive prepolymer.

[0103] In some embodiments, a cured product of the third reactive component has a third glass transition temperature (Tg3) of greater than 120°C. In some embodiments, the cured product of the third reactive component has a third glass transitionAttorney Docket No: 20744-D045WO00 temperature of greater than 130°C. In some embodiments, the cured product of the third reactive component has a third glass transition temperature of greater than 140°C. In some embodiments, the cured product of the third reactive component has a third glass transition temperature of greater than 150°C. It is understandable that the cured product of the third reactive component, compared with the cured product of the first reactive component and the cured product of the second reactive component, possesses a higher glass transition temperature, thereby providing a more optimized glass phase for the final photopolymerized polymer network and enhancing the rigidity and toughness required for the final cured product of polymerizable material.

[0104] In some embodiments, a difference between the third glass transition temperature and the first glass transition temperature is greater than 100°C. In some embodiments, the difference between the third glass transition temperature and the first glass transition temperature is greater than 110°C. In some embodiments, the difference between the third glass transition temperature and the first glass transition temperature is greater than 120°C. In some embodiments, the difference between the third glass transition temperature and the first glass transition temperature is greater than 130°C. In some embodiments, the difference between the third glass transition temperature and the first glass transition temperature is greater than 140°C. In some embodiments, the difference between the third glass transition temperature and the first glass transition temperature is greater than 150°C. It is understandable that the substantial temperature difference between the third glass transition temperature and the first glass transition temperature can help promote phase separation between the glass phase and the rubber phase in the polymer, thereby further optimizing the performance of the material.

[0105] In some embodiments, the third reactive component includes a polyurethane dimethacrylate prepolymer. In some embodiments, the LIDMA prepolymer includes isocyanate groups. It is understandable that during polymerization, the isocyanate groups can introduce the cyclic structures (such as carbocyclic rings, nitrogencontaining heterocycles, etc.) as side chains into the polymer backbone, increasing the rigidity of the polymer network.

[0106] In some embodiments, the third reactive component is at least one of an IPDI / HEMA prepolymer, a TMDI / HEMA prepolymer, a HMDI / HEMA prepolymer, a CHMDI / HEMA prepolymer, or a UDMA. CHMDI is 1 ,4- Bis(isocyanatomethyl)cyclohexane, and UDMA is urethane di-methacrylate.

[0107] In some embodiments, the polymerizable material includes an antioxidant. TheAttorney Docket No: 20744-D045WO00 antioxidant may be used to inhibit or delay an oxidative degradation process of the polymer material, thereby extending the service life of the cured product of the polymerizable material. In some embodiments, the antioxidant is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010), octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076), 2-Ethylhexyl 3-(3,5-di- tert-butyl-4-hydroxyphenyl)propanoate (Irganox 1135).

[0108] In some embodiments, the first reactive component is the PTMG2000 / IPDI / HEA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCDL2000 / IPDI / HEA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCDL2000 / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the TMDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is CTFA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is TMCHA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is IBOA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is IBOMA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the HMDI / HEMA prepolymer.Attorney Docket No: 20744-D045WQ00 In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the CHMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCL2000 / IPDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the IPDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCDL2000 / IPDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the IPDI / HEMA prepolymer. In some embodiments, the first reactive component is the TMDI / HEMA prepolymer, the second reactive component is DCPA, and the third reactive component is the IPDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCDL2000 / IPDI / HEA prepolymer, the second reactive component is DCPA, and the third reactive component is the IPDI / HEMA prepolymer. In some embodiments, the first reactive component is the PCDL2000 / IPDI / HEA prepolymer, the second reactive component is DCPA, and the third reactive component is the IPDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG2000 / IPDI / HEMA prepolymer, the second reactive component is CTFA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG650 / IPDI / HEMA prepolymer, the second reactive component is CTFA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG2000 / IPDI / HEMA prepolymer, the second reactive component is IBOA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG2000 / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG2000 / IPDI / HEMA prepolymer, the second reactive component is IBOMA, and the third reactive component is the TMDI / HEMA prepolymer. In some embodiments, the first reactive component is the PTMG2000 / PCL2000 / CHDM / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is LIDMA. In some embodiments, the first reactive component is the PTMG2000 / PCL3000 / BDO / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is LIDMA. In some embodiments, the first reactive component is the PTMG2000 / PCL3000 / CHDM / IPDI / HEMA prepolymer, the second reactive component is ACMO, and the third reactive component is LIDMA.

[0109] In some embodiments, the cured product of the polymerizable materialAttorney Docket No: 20744-D045WO00 includes the glass phase and the rubber phase, and the glass phase and the rubber phase are phase-separated. It is understandable that the glass phase may be provided by at least one of the hard segments in the first reactive component (i.e., formed by the diisocyanate and the chain extender (if any)), the blocking agent, the second reactive component, and the third reactive component; the rubber phase may be provided by the soft segments in the first reactive component (i.e., the diol compound).

[0110] In some embodiments, the glass phase is the continuous phase, and the rubber phase is a dispersed phase. In some embodiments, a weight percentage of the glass phase relative to the total weight of the glass phase and the rubber phase is greater than 50%. In some embodiments, the weight percentage of the glass phase relative to the total weight of the glass phase and the rubber phase is greater than 55%. In some embodiments, the weight percentage of the glass phase relative to the total weight of the glass phase and the rubber phase is greater than 60%. In some embodiments, the weight percentage of the glass phase relative to the total weight of the glass phase and the rubber phase is greater than 65%. In some embodiments, the weight percentage of the glass phase relative to the total weight of the glass phase and the rubber phase is greater than 70%. It is understandable that a high proportion of the continuous glass phase, on one hand, can enable the material to have sufficiently high stiffness and strength to generate and maintain effective orthodontic force. On the other hand, it restricts the motion of the molecular chains through the rigid glass phase network, thereby maximizing the inhibition of stress relaxation.

[0111] It is understandable that the polymer network formed by the photopolymerization of the resin material used for direct printing generally has good elasticity. Therefore, compared to the traditional thermoformed aligner, a directly printed aligner is more comfortable to wear. However, because the directly printed aligner is the photopolymerized polymer network, the orthodontic force of the direct printed aligners is more easily affected by temperature, humidity, and saliva. As the wearing time increases, the stress of the aligner material will quickly decay to a relatively small value. By selecting and blending various components of the polymerizable material formulation, the embodiments of the present disclosure precisely control the microstructure of the cured product of the polymerizable material, and construct a polymer system with controllable phase separation characteristics. The polymer system uses the glass phase as the continuous phase to provide the strength and stiffness required by the material, and the rubber phase as the dispersed phase to contribute toughness and elasticity. The synergistic effect of the two phasesAttorney Docket No: 20744-D045WG00 significantly improves the macroscopic performance of the material, enabling it to simultaneously possess high strength, high hardness, and excellent toughness.

[0112] In some embodiments, the glass phase maintains structural rigidity of the cured product of the polymerizable material, the rubber phase enables the cured product of the polymerizable material to undergo deformation under stress, and the deformation is reversible via external thermal excitation. It is understandable that the glass phase maintaining the structural rigidity means that at a daily use temperature (e.g., oral temperature 37°C or room temperature 25°C), the glass phase is in a rigid glassy state. Applied to aligners, this manifests as the aligners being able to remain rigid, providing continuous, stable orthodontic force to correct teeth. The rubber phase enabling the cured product to undergo deformation under pressure means that when a sufficiently large external force is applied, although the glass phase is very hard, the soft rubber phase allows the material to undergo temporary, reversible elastic deformation. Applied to aligners, this manifests as the aligners having a certain toughness, enabling it to be inserted and fitted to the teeth, providing necessary wearing comfort and safety. Deformation being reversible via external thermal excitation means that after the material is deformed, the molecular chains of the rubber phase are in a stretched state or a compressed state and store elastic potential energy, while the glass phase acts to "lock" the deformation at low temperatures. Once subjected to thermal excitation (e.g., heating to a specified temperature), the mobility of the glass phase segments increases, its rigidity temporarily decreases, and the elastic potential energy stored in the rubber phase is released, driving the material to recover to its initially set shape, exhibiting a thermally triggered shape memory function. Applied to aligners, this manifests as the ability to restore both the geometric shape and the orthodontic force of the aligner simultaneously through thermal treatment methods (such as immersion in hot water), effectively overcoming the problems of stress relaxation and force decay during long-term wear.

[0113] FIG. 1 is a schematic diagram showing a working principle of thermal excitation reversal of a cured product of a polymerizable material according to some embodiments of the present disclosure. As shown in FIG. 1 , an exemplary cured product of the polymerizable material (ActiveMemory™ Polymer) may include the hard segments and the soft segments. Initially, the cured product is in its original state; at oral temperature, the soft segments remain rigid. When the aligner made from the cured product is worn on the teeth and subjected to external force, the cured product is in a deformed state; at oral temperature, the soft segments deform and temporarilyAttorney Docket No: 20744-D045WO00 fix the current shape. When thermal excitation is applied (e.g., heating to 60°C), the cured product enters a transition state where the soft segments completely lose rigidity and the hard segments begin to dominate the macroscopic behavior of the material. Driven by the recovery force of the hard segments, the material undergoes dynamic recovery; the cured product is in a recovery state, the soft flexible molecular chains are rearranged, the deformation is reversed, and the cured product completely recovers its permanent shape. After cooling, the soft segments regain rigidity (i.e. , return to their original state).

[0114] In some embodiments, a peak glass transition temperature (Tgp) of the cured product of the polymerizable material is greater than 100°C. The peak glass transition temperature refers to a temperature corresponding to the peak of a test curve (e.g., a tan 5 peak in DMA) of the cured product of the polymerizable material, used to characterize the point of most active molecular motion during the glass transition. It is understandable that if the peak glass transition temperature is too small, it will weaken the material's stress relaxation resistance and the fatigue resistance. Moreover, when the thermal excitation temperature exceeds the peak glass transition temperature of the material (e.g., when a user uses boiling water for thermal excitation of the aligner), the aligner will not only fail to achieve the expected shape recovery, but its polymer network structure will also suffer irreversible damage due to overheating, leading to permanent failure of the device. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 100°C- 110°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 110°C-120°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 120°C-130°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 130°C-140°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 140°C-150°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 150°C-160°C. In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is in a range of 160°C-170°C.

[0115] FIG. 2 is a schematic diagram showing Dynamic Mechanical Analysis (DMA) of a cured product of a polymerizable material according to some embodiments of the present disclosure, where (a) is a loss factor curve, and (b) is a storage modulus curve.Attorney Docket No: 20744-D045WG00 As shown in FIG. 2(a), the peak glass transition temperature of the cured product of the polymerizable material (corresponding to the "DCA" curve in FIG. 2(a)) is 130°C, the peak glass transition temperature of the market product, Graphy’s TC-85 resin (a shape memory resin, corresponding to the "a certain 3D printing resin" curve in FIG. 2(a)) is 92°C, and the peak glass transition temperature of the market product duplex thermoformed film (corresponding to the "a certain composite film" curve in FIG. 2(a)) is 64°C.

[0116] In some embodiments, the peak glass transition temperature of the cured product of the polymerizable material is less than 180°C. By limiting the upper limit of the peak glass transition temperature, secondary thermal polymerization during the post-printing processing (see the steps using LuxCreo's LuxOven or LuxOven Pro described later) can be avoided.

[0117] In some embodiments, an initial glass transition temperature (Tgi) of the cured product of the polymerizable material is greater than 20°C. The initial glass transition temperature refers to a temperature at which the test curve (e.g., the tan 5 curve in DMA or a loss modulus curve) of the cured product of the polymerizable material begins to deviate from a baseline, determined by an intersection of the baseline and a tangent to the initial rising slope of the transition. In some embodiments, the initial glass transition temperature (Tgi) of the cured product of the polymerizable material is greater than 30°C. It is understandable that if the initial glass transition temperature is too small, it may result in insufficient orthodontic force of the prepared aligner, extremely fast decay, poor shape stability, and short fatigue life. As shown in FIG. 2(a), the initial glass transition temperature of the cured product of the polymerizable material (corresponding to the "DCA" curve in FIG. 2a) is about 30°C-50°C, the initial glass transition temperature of the market product, Graphy’s TC-85 resin (the shape memory resin, corresponding to the "a certain 3D printing resin" curve in FIG. 2(a) is about 22°C, and the initial glass transition temperature of the market product duplex thermoformed film (corresponding to the "a certain composite film" curve in FIG. 2a) is about 55°C-60°C.

[0118] In some embodiments, the initial glass transition temperature of the cured product of the polymerizable material may be less than 40°C. It is understandable that if the initial glass transition temperature is too high, it may cause the material to remain in the glassy state at oral temperature, making the prepared aligner very rigid, resulting in a poor wearing experience. Furthermore, thermal excitation would require a higher temperature environment, which is inconvenient for implementing the shape recoveryAttorney Docket No: 20744-D045WO00 function.

[0119] It is understandable that the directly printed aligner of the embodiments of the present disclosure has an active memory function. When thermally excited, local phase transition of the material promotes the release of internal stress and results in material creep. After creep occurs, reversible deformation can take place at temperatures above a specified point. The higher the temperature, the faster the recovery, and it can completely and accurately return to its initial shape within a few minutes. A design of currently available 3D printing resins on the market that claim to have shape memory function (or referred to as traditional shape memory polymers, e.g., SMPs, the market product, Graphy’s TC-85 resin, or the like) is based on a recent hypothesis: if resins can be activated at the intraoral temperature (may be referred to as "intraorally activated SMPs"), they can generate the "recovery force" required for tooth movement. This mechanism overlooks the key behavior of such materials: at an activation temperature, they undergo a phase transition from the glassy state (rigid) to the rubbery state (soft). The process that inherently degrades their mechanical properties and relaxes the borne orthodontic force. Specifically: 1 . Intraoral Softening: When SMP resins are designed to be activated around body temperature (typically, the initial glass transition temperature (Tgi) of their cured product is < 40°C), the phase transition significantly softens the material, leading to a substantial reduction in modulus and strength (e.g., over 70%), resulting in premature decay of the orthodontic force and affecting clinical efficacy. 2. Shape-Only Memory: Some of these resins can only achieve geometric shape recovery but fail to sustainably restore their mechanical properties. Even if an appearance of the aligner is restored, the loss of stiffness and orthodontic force still makes it difficult to achieve controlled and sustained tooth movement.

[0120] The cured product of the polymerizable material in the embodiments of the present disclosure, through precise selection and mixture of each component, increases the initial glass transition temperature of the material to at least 20°C, effectively reducing the stress relaxation of the material under intraoral use conditions. At the same time, the peak glass transition temperature is raised to above 100°C — this not only means that even if boiling water is used as a heat source for thermal excitation, it will not damage the prepared aligners, but also endows the material with excellent thermomechanical stability. Moreover, a modulus of the material of the embodiment of the present disclosure is not sensitive to high temperatures, and it can still maintain a certain level of rigidity even at high temperatures around 100°C,Attorney Docket No: 20744-D045WG00 ensuring the precision of shape memory.

[0121] In some embodiments, a Full Width at Half Maximum (FWHM) of the Dynamic Mechanical Analysis (DMA) curve of the cured product of the polymerizable material is greater than 40°C. As shown in FIG. 2(a), the FWHM of the cured product of the polymerizable material (corresponding to the "DCA" curve in FIG. 2(a)) is about 65°C, the FWHM of the market product, Graphy’s TC-85 resin (the shape memory resin, corresponding to the "a certain 3D printing resin" curve in FIG. 2(a)) is about 25°C, and the FWHM of the market product duplex thermoformed film (corresponding to the "a certain composite film" curve in FIG. 2(a)) is about 10°C.

[0122] It is understandable that the breadth of the FWHM is directly governed by the designed glass transition temperature differences (e.g., Tg2-Tg1 , Tg3-Tg1 ) mentioned previously, a broader FWHM, achieved through the control exerted by such design, means the material undergoes a wide range of a molecular relaxation processes over a broad temperature range. When thermally excited, a polymer material with a very narrow FWHM p will experience a sharp stress relaxation process when the temperature reaches its peak glass transition temperature. This increases the difficulty and complexity when applying the thermal excitation to aligners. An ideal process would be the aligners experience a long-tail or multi-phase stress relaxation process, as different molecular segments relax at different rates, so the aligners will not undergo rapid and sudden softening.

[0123] One or more embodiments of the present disclosure provide a method of forming a three-dimensional object.

[0124] FIG. 3 is a flowchart of a method of forming a three-dimensional object according to some embodiments of the present disclosure. In some embodiments, the process 300 may be executed by a processor of a device for making the three- dimensional object. As shown in FIG. 3, the process 300 may include the following steps 310 to 340.

[0125] Step 310, a printing region is provided. The printing region refers to a physical space for printing the three-dimensional object. For example, the printing region includes a building platform, a resin tank, etc., of a device for making the three- dimensional object (such as a vat photopolymerization (VAT-PP) 3D printer). The printing region may be provided directly by the device for making the three-dimensional object. In some embodiments, the device for making the three-dimensional object may be an iLux Pro Dental (ILPD) printer.

[0126] Step 320, the printing region is filled with the polymerizable material accordingAttorney Docket No: 20744-D045WG00 to the embodiments of the present disclosure. The polymerizable material according to the embodiments of the present disclosure may be directly injected into the printing region.

[0127] Step 330, the printing region is irradiated with light and a three-dimensional intermediate object is formed. The three-dimensional intermediate object is an intermediate awaiting processing to form the three-dimensional object. It is understandable that the three-dimensional intermediate object just after 3D printing has mostly completed only part of its chemical reaction, is not fully cured, has low strength, unstable performance, and contains unreacted resin and impurities. Subsequent processes (such as step 340) are needed to allow the material to reach its designed optimal final performance. By presetting printing parameters, the light source of the device for making the three-dimensional object can be controlled to irradiate the printing region, curing the polymerizable material layer by layer to form a cured three-dimensional structure, which is the three-dimensional intermediate object.

[0128] Step 340, the three-dimensional intermediate object is heated or microwave irradiated to form the three-dimensional object. The three-dimensional intermediate object may be removed from the device for making the three-dimensional object and placed into a heating device or a microwave device for post-processing (i.e., heating or microwave irradiation) to form the three-dimensional object. In some embodiments, the heating device may be LuxCreo's LuxOven (a thermal curing oven specifically designed for 3D printing post-processing), etc. More details about heating may be found in the description related to subsequent embodiments.

[0129] One or more embodiments of the present disclosure provide a clear dental aligner. In some embodiments, the clear dental aligner may be printed by the aforementioned method of forming the three-dimensional object.

[0130] FIG. 4 is a schematic diagram showing thermal excitation recovery of a clear dental aligner according to some embodiments of the present disclosure, where (a) is geometric restoration, and (b) is force recovery. In FIG. 4(a), region A represents an area with minimal deformation, while region B represents an area with relatively large deformation. In some embodiments, a difference in elastic modulus (tested via DMA) (also referred to as DMA modulus) of the clear dental aligner between 25°C and 37°C is less than 10%, and the clear dental aligner restores at least 80% of its orthodontic force at a temperature above 60°C. It is understandable that when used to make orthodontic appliances such as the aligners, the cured product of the polymerizable material described in the embodiments of the present disclosure (hereinafter referredAttorney Docket No: 20744-D045WG00 to as "the cured product") exhibits working principles and performance advantages fundamentally different from the aforementioned intraoral SMP resins. Its core lies in an innovative dual-mechanism synergistic strategy: 1 . Primary Mechanism - Inherent Mechanical Force: Unlike SMP resins that rely on intraoral temperature activation to generate therapeutic force, the cured product primarily relies on its inherent, temperature-insensitive elastic deformation to provide and maintain orthodontic force during normal wear. Its elastic modulus exhibits minimal variation (difference < 10%) between oral temperature (37°C) and room temperature (25°C), thereby enabling continuous, stable, and predictable delivery of orthodontic force within an optimal range throughout the entire treatment period 2. Secondary Mechanism — Thermal Restoration Recovery: After creep deformation occurs, the aligner can be "reset" via external thermal excitation (e.g., immersion in hot water above 60°C). This process can precisely restore the aligner to its original geometry (with a tolerance of less than 0.1 mm) and initial force level (restoring over 80% of initial force as shown in FIG. 4(a)). This recovery is complete, consistent, and repeatable over a plurality of cycles (as shown in FIG. 4(b)), allowing the aligner to regain a like-new performance state through daily care. Additionally, the material exhibits excellent thermomechanical elasticity. Its glass transition temperature exceeds 100°C, far higher than intraoral environment temperature. This ensures that even under thermal excitation, the aligner maintains structural integrity and geometric accuracy — preventing excessive softening that could compromise performance. Notably, the aforementioned performance advantages observed in practical applications — including stable orthodontic force delivery, precise thermal-induced recovery, and reliable structural integrity under thermal excitation — collectively result from several key technical features in a formulation design of the polymerizable material. These features include: adjusting the ratio of soft to hard segments, tuning the glass transition temperatures (Tg) of individual components, and precisely controlling the Tg differences between different components. The polymerizable material of the present application will be further elaborated below in conjunction with specific embodiments. It should be noted that the reaction conditions, reaction materials, and amounts of the reaction materials in the embodiments are only for illustrating the polymerizable material and do not limit the protection scope of the present application.

[0131] The following are the equipment and post-processing methods involved in the Examples and the embodiments.

[0132] FIG. 5 is a schematic diagram of printing parameters according to someAttorney Docket No: 20744-D045WC00 embodiments of the present disclosure. The Examples and the embodiments are printed using an iLux Pro Dental (ILPD) printer, with the printing parameters shown in FIG. 5. After printing based on the method of forming the three-dimensional object described in the embodiments of the present disclosure, obtained printed parts (e.g., the clear dental aligners) are subjected to post-processing, as shown in steps S11 - S14.

[0133] S11 , the printed parts corresponding to the embodiments and comparative examples are washed twice using an iLuxWash Dental wash box with IPA as a washing reagent, 4 minutes each time.

[0134] S12, washed printed parts are dried at ambient conditions.

[0135] S13, thermal curing is performed using Lux Creo's LuxOven (a thermal curing oven specifically designed for 3D printing post-processing) for the DCA (resin type) curing; DCA is the second-generation dental 3D printing photopolymerizable resin developed by LuxCreo.

[0136] S14, UV curing is performed using an iLuxCure Pro or an iLuxCure Dental curing box (a UV curing device custom-tailored by LuxCreo for DCA resin) for the DCA (resin type) curing.Comparative Examples 1-4 and Embodiments 1-4

[0137] (1 ) Preparation of Cured Product of the Polymerizable material

[0138] According to the mass ratios shown in Table 1 (on 100-part by mass basis), the first reactive component (a blocked polyurethane prepolymer prepared using the single diol compound), the second reactive component, and the third reactive component are mixed, and then polymerized using a photopolymerization initiator. The resulting polymer is printed using the method of forming the three-dimensional object described in the embodiments of the present disclosure to obtain the printed parts. The printed parts are then processed using the aforementioned post-processing method to obtain Comparative Examples 1 -4 and Embodiments 1 -4.

[0139] (2) Performance Testing

[0140] Yield strength, yield elongation, elastic modulus, tensile strength, elongation at break, tear strength, viscosity, percentage of residual tensile force (refers to the residual tensile force after decay; a higher value indicates less force decay and better stress relaxation resistance), and bending fatigue of Comparative Examples 1 -4 and Embodiments 1 -4 obtained in (1 ) are evaluated. Specific data are shown in Table 3.

[0141] Table 1 shows the components used in Comparative Examples 1 -4 and Embodiments 1 -4 and the corresponding glass transition temperature data.Attorney Docket No: 20744-D045WQ00Table 1 : Various Embodiments of the Present Application

[0142] Table 2 shows the specific components of the first reactive component, theAttorney Docket No: 20744-D045WC00 second reactive component, and the third reactive component used in Comparative Examples 1-4 and Embodiments 1-4.Table 2: Various embodiments of the first reactive components, the second reactive components, and the third reactive components

[0143] Table 3 shows test results for Comparative Examples 1-4 and Embodiments1-4.Table 3: Test Results of Various EmbodimentsAttorney Docket No: 20744-D045WC00

[0144] From Tables 1-3, it may be seen that Comparative Example 1 has too low Tg1 , resulting in correspondingly low Tgi and Tgp. This imparts higher elasticity to the material, but its tear strength (8.4 N / mm) and percentage of residual tensile force (9.8%) are too low, indicating poor anti-stress relaxation performance and too fast decay of orthodontic force.

[0145] Comparative Example 2 exhibited excessively low Tg2, resulting in correspondingly low Tgi and Tgp. This led to the lowest overall elastic modulus of the material, making it extremely soft. While it demonstrated the best elongation at break, its residual tensile force decayed to an extremely low level, indicating severe stressAttorney Docket No: 20744-D045WC00 relaxation. The mechanical properties were too weak to effectively correct teeth.

[0146] Comparative Example 3 exhibited excessively high Tg1 and correspondingly high Tgi, resulting in excessively rigid material. Its elongation at break was only 21 .62%, significantly lower than that of other embodiments and comparative examples. With an extremely short fatigue life (33 bending cycles), it completely failed to meet the usage requirements for repeated insertion and removal of the aligner.

[0147] Comparative Example 4 exhibited excessively low Tg2 and correspondingly low Tgp, along with low tensile strength, showing inferior performance compared to Embodiment 1 .

[0148] Compared to Comparative Example 4, Embodiment 1 replaced the second component IBOA (with low Tg2) with ACMO (with high Tg2), resulting in comprehensive enhancement across all properties. It demonstrated higher tensile strength (42.3 MPa), higher modulus (1280 MPa), good residual tensile force (15.7%), outstanding elongation at break (68.6%) and tear strength (15.5 N / mm), as well as good bending fatigue resistance (365 cycles). While maintaining good elasticity, it significantly improved strength and modulus, representing an overall performance enhancement.

[0149] Embodiment 2 showed high residual tensile force (26.4%), the highest tensile strength (45.1 MPa), and very high tear strength (18.2 N / mm), demonstrating excellent resistance to stress relaxation and the ability to provide longer-lasting orthodontic force.

[0150] Embodiment 3 exhibited the highest tensile strength (48.3 MPa), extremely high tear strength (25.7 N / mm), and the highest residual tensile force (30.2%). This indicates optimal mechanical properties and force retention, combining exceptional durability with the most effective resistance to stress relaxation.

[0151] Embodiment 4 performed at the forefront in all key performance metrics: high elongation at break (78.4%), high tensile strength (39.5 MPa), high tear strength (14.5 N / mm), high residual tensile force (29.7%), and excellent bending fatigue resistance (397 cycles). It achieved high levels in nearly all critical performance indicators without significant weaknesses.

[0152] In summary, Embodiments 1 -4 obtained using the formulations of the embodiments of the present disclosure generally show comprehensive improvement in performance compared to Comparative Examples 1 -4, achieving a good balance between strength and toughness.Embodiment 5-10

[0153] (1 ) Preparation of Cured Product of the Polymerizable materialAttorney Docket No: 20744-D045WC00

[0154] According to the metered molar ratios shown in Table 4, the first diol compound, the second diol compound, the diisocyanate, and the chain extender are mixed and reacted, then the blocking agent is added for reaction to generate the first reactive component (a blocked polyurethane prepolymer prepared using two diol compounds). Next, according to the mass ratios shown in Table 5 (on 100-part by mass basis), the first reactive component, second reactive component, and third reactive component are mixed and polymerized using a photopolymerization initiator. The resulting polymer is printed using the method of forming a three-dimensional object described in the embodiments of the present disclosure to obtain printed parts. The printed parts are then processed using the aforementioned post-processing methods to obtain Embodiments 5-10.

[0155] (2) Performance Testing

[0156] Yield strength, yield elongation, elastic modulus, tensile strength, elongation at break, tear strength, viscosity, percentage of residual tensile force, and bending fatigue of Embodiments 5-10 obtained in (1 ) are evaluated. Specific data are shown in Table 6.

[0157] Table 4 shows the components and corresponding metered molar ratio data used when preparing the first reactive components (i.e., prepolymers 5-10) for Embodiments 5-10.Table 4: Metered Molar Ratio of Components for the First Reactive Component ofVarious EmbodimentsAttorney Docket No: 20744-D045WO00

[0158] Table 5 shows the components and corresponding mass ratio data used in Embodiments 5-10, wherein Prepolymers 5-10refer to the first reactive components corresponding to Embodiments 5-10, prepared from the components in Table 4.Table 5: The Mass Ratio of Components for Various EmbodimentsTable 6: Test Results for Each EmbodimentAttorney Docket No: 20744-D045WO00

[0160] From Tables 4-5, it may be seen that the various performance indicators ofEmbodiments 5-10 are generally good. Embodiment 8 shows the best performance in terms of the percentage of residual tensile force and the bending fatigue, making it a preferred formulation. Furthermore, compared to Embodiments 5-10 (which use blocked polyurethane prepolymers prepared with two diol compounds), Embodiments 1-4 (which use blocked polyurethane prepolymers prepared with the single diol compound) perform relatively poorly in terms of the stress relaxation resistance and the bending fatigue. Using two diol compounds to prepare the blocked polyurethane prepolymer results in a more significant improvement in material properties.

[0161] Table 7 shows the components used in Embodiments 11-27 and the corresponding glass transition temperature data.Table 7 : Various embodiments of the present applicationAttorney Docket No: 20744-D045WQ00Attorney Docket No: 20744-D045WO00

[0162] Table 8 shows the specific components of the first reactive component, the second reactive component, and the third reactive component used in Embodiments 12-27.Table 8: Various embodiments of the first reactive components, the second reactive components, and the third reactive componentsAttorney Docket No: 20744-D045WO00

[0163] Having thus described the basic concepts, it may be rather apparent to those skilled in the art after reading this detailed disclosure that the foregoing detailed disclosure is intended to be presented by way of example only and is not limiting. Various alterations, improvements, and modifications may occur and are intended for those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested by this disclosure, and are within the spirit and scope of the exemplary embodiments of this disclosure.

[0164] Moreover, certain terminology has been used to describe embodiments of the present disclosure. For example, the terms “one embodiment,” “an embodiment,” and / or “some embodiments” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this disclosure are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined as suitable in one or more embodiments of the present disclosure.

[0165] Furthermore, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claimed processes and methods to any order except as may be specified in the claims. Although the above disclosure discusses through various examples what is currently considered to be a variety of useful embodiments of the disclosure, it is to be understood that such detail is solely for that purpose, and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover modifications and equivalent arrangements that are within the spirit and scope of the disclosed embodiments. For example, although the implementation of various components described above may be embodied in a hardware device, it may also be implemented as a software only solution, e.g., an installation on an existing server or mobile device.

[0166] Similarly, it should be appreciated that in the foregoing description ofAttorney Docket No: 20744-D045WQ00 embodiments of the present disclosure, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the various inventive embodiments. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, inventive embodiments lie in less than all features of a single foregoing disclosed embodiment.

[0167] In some embodiments, the numbers expressing quantities or properties used to describe and claim certain embodiments of the application are to be understood as being modified in some instances by the term “about,” “approximate,” or “substantially.” For example, “about,” “approximate,” or “substantially” may indicate ±20% variation of the value it describes, unless otherwise stated. Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the application are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[0168] In closing, it is to be understood that the embodiments of the application disclosed herein are illustrative of the principles of the embodiments of the application. Other modifications that may be employed may be within the scope of the application. Thus, by way of example, but not of limitation, alternative configurations of the embodiments of the application may be utilized in accordance with the teachings herein. Accordingly, embodiments of the present application are not limited to that precisely as shown and described.

Claims

Attorney Docket No: 20744-D045WO00WHAT IS CLAIMED IS :1 . A polymerizable material configured to produce three-dimensional objects by additive manufacturing methods, wherein the polymerizable material comprises: a first reactive component, wherein a cured product of the first reactive component has a first glass transition temperature of less than 50°C; a second reactive component wherein a cured product of the second reactive component has a second glass transition temperature of greater than 100°C, and a difference between the second glass transition temperature and the first glass transition temperature is greater than 80°C; and a photoinitiator.

2. The polymerizable material of claim 1 , wherein a cured product of the polymerizable material comprises a glass phase and a rubber phase, the glass phase and the rubber phase are phase-separated, and a weight percentage of the glass phase relative to a total weight of the glass phase and the rubber phase is greater than 50%.

3. The polymerizable material of claim 2, wherein the glass phase maintains a structural rigidity of the cured product of the polymerizable material, and the rubber phase enables the cured product of the polymerizable material to undergo deformation under stress, the deformation being reversible via external thermal excitation.

4. The polymerizable material of any one of claims 1 -3, wherein a peak glass transition temperature of the cured product of the polymerizable material is greater than 100°C.

5. The polymerizable material of any one of claims 1 -4, wherein an initial glass transition temperature of the cured product of the polymerizable material is greater than 20°C.

6. The polymerizable material of claim 5, wherein the initial glass transition temperature of the cured product of the polymerizable material is less than 40°C.

7. The polymerizable material of any one of claims 1 -6, wherein a Full Width atAttorney Docket No: 20744-D045WO00 Half Maximum (FWHM) of a Dynamic Mechanical Analysis (DMA) curve of the cured product of the polymerizable material is greater than 40°C.

8. The polymerizable material of any one of claims 1-7, wherein the first reactive component is a blocked polyurethane prepolymer prepared by a reaction of a diisocyanate and a diol compound.

9. The polymerizable material of claim 8, wherein the diol compound comprises a polyester diol or a polyether diol.

10. The polymerizable material of claim 8 or 9, wherein a molecular weight of the diol compound is in a range of 1000-3500.11 . The polymerizable material of any one of claims 8-10, wherein a molar ratio of the diisocyanate to the diol compound is in a range of 1.3-2.2.

12. The polymerizable material of any one of claims 8-11 , wherein the diol compound comprises a first diol compound and a second diol compound, and the first diol compound and the second diol compound are different diols.

13. The polymerizable material of claim 12, wherein the glass transition temperature of the first diol compound is lower than the glass transition temperature of the second diol compound, and a melting point of the first diol compound is lower than the melting point of the second diol compound.

14. The polymerizable material of claim 12 or 13, wherein when preparing the first reactive component, a molar ratio of the first diol compound to the second diol compound is 0.1-1 .

15. The polymerizable material of any one of claims 1-14, wherein the second reactive component comprises a (meth)acrylate functional group connected to a cyclic compound.

16. The polymerizable material of claim 15, wherein the cyclic compound is as a side chain into a polymer backbone during polymerization of the polymerizableAttorney Docket No: 20744-D045WQ00 material, and the cyclic compound does not include heterocycles containing only oxygen.

17. The polymerizable material of any one of claims 1-16, further comprising a third reactive component, wherein a cured product of the third reactive component has a third glass transition temperature of greater than 120°C, and a difference between the third glass transition temperature and the first glass transition temperature is greater than 100°C.

18. The polymerizable material of claim 17, wherein the third reactive component comprises a urethane di-methacrylate (LIDMA) prepolymer, and the LIDMA prepolymer includes isocyanate groups.

19. A method of forming a three-dimensional object, comprising: providing a printing region; filling the printing region with the polymerizable material of any one of claims 1 - 18; irradiating the printing region with light to form a three-dimensional intermediate object; and heating or microwave irradiating the three-dimensional intermediate object to form the three-dimensional object.

20. A clear dental aligner printed by the method of claim 19.21 . The clear dental aligner of claim 20, wherein a difference in elastic modulus tested via DMA of the clear dental aligner between 25°C and 37°C is less than 10%, and the clear dental aligner restores at least 80% of its orthodontic force at a temperature above 60°C.

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