A dual side chain extender, its preparation method and application in synthesis of ion conductive polyurethane

Abstract

This invention discloses a double-sided chain extender, its preparation method, and its application in the synthesis of ion-conducting polyurethane. The structure of the double-sided chain extender is shown in Formula I. The double-sided chain extender is prepared by a Michael addition reaction of an acceptor compound and 3-amino-1,2-propanediol. The acceptor compound is selected from one of the following: acrylic acid, 2-acryloylamino-2-methyl-1-propanesulfonic acid, acryloyloxyethyltrimethylammonium chloride, 1-vinyl-3-butylimidazolium chloride, 3-((2-(acryloyloxy)ethyl)dimethylammonium)propane-1-sulfonate, 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onthium-4-yl)ethane-1-sulfonate. This invention provides the application of the double-sided chain extender in the synthesis of ion-conducting polyurethane with excellent mechanical properties and ion transport capabilities. I.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to a double-side-chain chain extender, its preparation method, and its application in the synthesis of ion-conducting polyurethane. Background Technology

[0002] Due to the thermodynamic incompatibility between the soft and hard segments, polyurethane elastomers are prone to microphase separation, forming a microstructure in which the hard segments are dispersed in the soft segment matrix or the two interpenetrate. This unique microphase separation structure endows polyurethane with both the high strength of plastics and the high elasticity of rubber, making it widely used in seals, tires, rollers, flexible electronics and smart wearables (such as shoe sole sensors).

[0003] In recent years, with the rise of flexible electronics and smart materials, endowing polyurethane with conductivity, antibacterial properties, or self-healing properties has become a research hotspot. The mainstream strategy is to introduce ionic groups (such as sulfonates, carboxylates, and quaternary ammonium salts) or to physically composite them with ionic liquids to prepare ion-conductive polyurethane elastomers.

[0004] However, existing chain extension technologies face significant technical bottlenecks in constructing high-performance ion-conducting polyurethanes: 1. Structural limitations and low ionic density of traditional chain extenders: Currently commercially available ionic chain extenders (such as DMPA and DMBA) or simple monoquaternary ammonium salt diols have a single molecular structure, typically introducing only one ionic center (single charge) at each chain extension site. This low ionic density structure necessitates a significant increase in hard segment content to achieve sufficient conductivity, which often severely compromises the flexibility of soft segments, leading to excessively high material modulus and decreased elasticity. Furthermore, some traditional chain extenders (such as MOCA), while exhibiting excellent performance, pose carcinogenic risks and are subject to strict environmental regulations, necessitating green alternatives.

[0005] 2. Weak "lock-in" ability and poor compatibility of ionic liquids: In the preparation of polyurethane / ionic liquid composites, due to the lack of strong interaction between the polymer chains and the free ionic liquid, only physical doping is relied upon. Over time or with environmental changes (such as pressure or heat), the ionic liquid is prone to migration and precipitation from the matrix. This not only leads to stickiness on the material surface and degradation of mechanical properties, but also causes an exponential decrease in ionic conductivity over time, seriously affecting the long-term stability of the sensor.

[0006] 3. The contradiction between the degree of microphase separation and ion channel construction: Traditional small-molecule chain extenders are small in size and cannot form a sufficient volume fraction in the hard segment region to induce strong microphase separation. Incomplete phase separation results in ionic groups being randomly dispersed within the insulating polyurethane matrix, making it difficult to form continuous ion transport channels. This discontinuous channel increases the energy barrier for ion hopping, limiting carrier migration efficiency and thus reducing the sensitivity of the material in sensing applications.

[0007] Therefore, the present invention aims to provide a double-chain chain extender prepared based on Michael addition reaction and its application in polyurethane elastomers, in order to solve the problems of low ion density, easy precipitation of ionic liquids and imperfect ion channel construction in the prior art. Summary of the Invention

[0008] The purpose of this invention is to provide a dual-side-chain chain extender, its preparation method, and its application in the synthesis of ion-conductive polyurethane. The dual-side-chain chain extender provided by this invention, as an ionic polyurethane chain extender, can yield high-performance polyurethane elastomers with excellent mechanical properties and ion transport capabilities.

[0009] The present invention achieves the above-mentioned objectives through the following technical solutions: In a first aspect, the present invention provides a dual-side-chain chain extender, the structure of which is shown below:

[0010] Formula I

[0011] Where -R=

[0012]

[0013]

[0014]

[0015] or in This indicates that the end group is connected to a nitrogen atom.

[0016] As a preferred option, -R is

[0017] In a second aspect, the present invention provides a method for preparing the double-sided chain extender described in the first aspect, wherein the preparation method comprises: subjecting an acceptor compound and a donor compound to a Michael addition reaction to generate a double-sided chain extender; The donor compound is selected from 3-amino-1,2-propanediol of formula II:

[0018] Formula II

[0019] The acceptor compound is selected from one of the following: acrylic acid, 2-acryloylamino-2-methyl-1-propanesulfonic acid as shown in Formula III, acryloyloxyethyltrimethylammonium chloride as shown in Formula IV, 1-vinyl-3-butylimidazolium chloride as shown in Formula V, 3-((2-(acryloyloxy)ethyl)dimethylammonium)propane-1-sulfonate as shown in Formula VI, and 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onthiol-4-yl)ethane-1-sulfonate as shown in Formula VII (preparation method refers to the following literature: G. Wang, H. Ni, Y. Li, H. Torun, S. Chen, MW Shahzad, X. Zhang, SY Zheng, BB Xu, J. Yang, Supramolecular Zwitterionic Hydrogels for Information Encryption, Soft Electronics and Energy Storage at IcyTemperature, Adv. Funct. Mater. 2025, 35, 2505048.),

[0020] Formula III

[0021] Formula IV

[0022] Formula V

[0023] Style VI

[0024] Formula VII.

[0025] Preferably, the Michael addition reaction is carried out in a reaction solvent selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, acetonitrile, and water.

[0026] Preferably, the Michael addition reaction is carried out at a temperature of 50-70°C for 6-12 hours.

[0027] Preferably, the molar ratio of the acceptor compound to the donor compound is (2.0-4.2):1.

[0028] When the acceptor compound is 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onthiol-4-yl)ethane-1-sulfonate, the preparation steps of the Michael addition reaction are shown in reaction formula I below:

[0029] Reaction I

[0030] When the acceptor compound is 1-vinyl-3-butylimidazolium chloride, the preparation steps of the Michael addition reaction are shown in reaction formula II below:

[0031] Reaction formula II

[0032] When the acceptor compound is acryloyloxyethyltrimethylammonium chloride, the preparation steps of the Michael addition reaction are shown in reaction formula III below:

[0033] Reaction Formula III

[0034] When the acceptor compound is 2-acrylamido-2-methyl-1-propanesulfonic acid, the preparation steps of the Michael addition reaction are shown in reaction formula IV below:

[0035] Reaction IV

[0036] After the Michael addition reaction, the present invention provides a double-sided chain extender that can be obtained through simple post-processing. This simple post-processing, depending on the product properties, may involve adding a precipitant (preferably acetone), followed by separation and drying to obtain the double-sided chain extender; or it may involve direct rotary evaporation to obtain the product.

[0037] Thirdly, the present invention provides the application of the dual-side-chain chain extender described in the first aspect in the synthesis of ion-conductive polyurethane, wherein the application is specifically as follows: (1) Polyurethane prepolymer is obtained by reacting polyol and isocyanate under the action of a catalyst; (2) The polyurethane prepolymer is reacted sequentially with two chain extenders to obtain an ionic polyurethane elastomer; the two chain extenders are a hydrogen-bonding chain extender and an ionic chain extender, the ionic chain extender being the double-side-chain chain extender described in the first aspect; the molar ratio of the polyurethane prepolymer to the ionic chain extender is 1:0.2~0.6, wherein the number of moles of the polyurethane prepolymer is based on the number of moles of -NCO contained therein; the molar ratio of the hydrogen-bonding chain extender to the ionic chain extender is 3:1~1:3; (3) The obtained ionic polyurethane elastomer is compounded with an ionic liquid to obtain ionic conductive polyurethane.

[0038] Preferably, the polyol is selected from one or more of polytetrahydrofuran (PTMEG) (Mn=500-2000), polycaprolactone (PCL) (Mn=400-2000), and polypropylene glycol (PPG) (Mn=200-800).

[0039] The structural formula of polytetrahydrofuran (PTMEG) is shown in Formula VIII:

[0040] Formula VIII

[0041] The structural formula of polycaprolactone (PCL) is shown in Formula IX:

[0042] Formula IX

[0043] The structural formula of polypropylene glycol (PPG) is shown in Formula X:

[0044] Formula X

[0045] Preferably, the isocyanate is selected from one or more of 4,4-diisocyanate dicyclohexylmethane (HMDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI).

[0046] The structural formula of 4,4-diisocyanate dicyclohexylmethane (HMDI) is shown in Formula XI:

[0047] Formula XI

[0048] The structural formula of isophorone diisocyanate (IPDI) is shown in Formula XII:

[0049] Formula XII

[0050] Preferably, the catalyst is dibutyltin dilaurate (DBTDL). The molar amount of the catalyst added is preferably 0.1%-0.5% of the molar amount of the polyol.

[0051] Preferably, before prepolymerization, the polyol should be placed in a vacuum oven to remove water before use.

[0052] Preferably, the molar ratio of polyol to isocyanate is 1:3.

[0053] Preferably, the reaction temperature of the polyol and isocyanate is 70-80℃, and the reaction time is 2-4h.

[0054] When the polyol (R1) is PTMEG or PCL and the isocyanate is HMDI, the preparation steps of the prepolymer are shown in reaction formula V below:

[0055] Reaction formula V.

[0056] Preferably, the hydrogen bond extender is selected from one or more of azidodiacid hydrazide (ADH), ureo-4-pyridone (UPy), or 1,4-butanediol (BDO).

[0057] The two chain extenders described in this invention are used separately in the preparation of ionic polyurethane elastomers, and there are no particular requirements regarding the order of their use. Preferably, during the chain extension stage, the reaction temperature after adding either the hydrogen-bonding chain extender or the ionic chain extender is 40-60°C, and the reaction time is 16-24 hours.

[0058] Preferably, the ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4), 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF6), and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine ([EMIM]TFSI). The structure of the ionic liquid is shown below:

[0059] Preferably, the mass ratio of the ionic polyurethane elastomer to the ionic liquid is 1:0.1-1:1.

[0060] This invention successfully prepared a double-sided chain extender by incorporating a double-chain ionic long chain onto a diol chain via a Michael addition reaction. When this double-sided chain extender is applied to the chain extension process of polyurethane prepolymers, its high hydrogen bond density and interionic interactions effectively improve the regularity of the hard segment region and suppress the microphase separation and coarsening problem caused by the rapid crystallization of small-molecule chain extenders. This significantly improves the toughness and dynamic mechanical properties of the polyurethane elastomer while maintaining its high strength and high modulus. Furthermore, the ion-rich environment provided by the double-sided chain extender effectively regulates the charge distribution of the system and promotes ion transport.

[0061] Compared with the prior art, the present invention has the following beneficial effects: 1. The double-side-chain chain extender designed in this invention has a flexible long chain in the middle of its molecule, which is equivalent to introducing a soft segment into a traditional hard segment structure. This "rigid-flexible" structure can effectively disrupt the regular arrangement of hard segments, inhibit excessive crystallization, and achieve finer and more uniform microphase separation, thereby giving the polyurethane elastomer excellent mechanical properties. At the same time, the introduction of ionic segments constructs ion channels, improving the conductivity and electromechanical sensing sensitivity of the ion-conductive polyurethane. Moreover, the ion-conductive polyurethane prepared by this invention has excellent stability, exhibiting long-term stability in terms of mechanical properties, conductivity, and electromechanical sensing response performance. In addition, the ion-conductive polyurethane of this invention also exhibits good antibacterial properties.

[0062] 2. Environmentally friendly: This invention avoids the use of harmful chain extenders such as MOCA, and the raw materials used are low in toxicity, making it more environmentally friendly and safe.

[0063] 3. Simple preparation process: The synthesis of chain extenders and the preparation process of polyurethane are mature, the conditions are mild, and it is easy to realize industrial production. Attached Figure Description

[0064] Figure 1 This is the ¹H NMR spectrum of the double-side chain extender obtained in step (1) of Example 1.

[0065] Figure 2 These are the infrared spectral results of the ion-type polyurethane elastomers obtained in Examples 1, 4, and 5.

[0066] Figure 3 These are the stress-strain curves of the ionic polyurethane elastomers obtained in Examples 1, 4, and 5.

[0067] Figure 4 These are the stress-strain curves of the ionic polyurethane elastomer prepared in Example 1 under different strain stretching-unloading conditions.

[0068] Figure 5This is the long-cycle tensile-unloading curve of the ionic polyurethane elastomer prepared in Example 1 at 50% strain.

[0069] Figure 6 This is a bar chart showing the changes in the ionic conductivity of ion-conductive polyurethane over different number of days.

[0070] Figure 7 The response speed of the ion-conductive polyurethane of Example 1 to changes in resistance under tensile strain is shown.

[0071] Figure 8 The change in the sensitivity coefficient of the ion-conductive polyurethane of Example 1 to changes in resistance under tensile strain.

[0072] Figure 9 These are anti-pollution fluorescent photographs of the ion-conductive polyurethanes of Examples 1 and 4. Detailed Implementation

[0073] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various modifications or alterations to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0074] In this invention, the preparation method of 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onthiol-4-yl)ethane-1-sulfonate is referenced in [Adv. Funct. Mater. 2025 35 2505048.].

[0075] Example 1: (1) Synthesis of the double-sided chain extender (using 3-amino-1,2-propanediol and 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onth-4-yl)ethane-1-sulfonate as raw materials): Nitrogen gas was introduced into a 500 mL four-necked flask equipped with a stirrer, thermometer and constant pressure dropping funnel. 40 mol of 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onth-4-yl)ethane-1-sulfonate was dissolved in 150 mL of DMF. 20 mol of 3-amino-1,2-propanediol was dissolved in 100 mL of DMF and slowly added dropwise to the system. After the addition was complete, the temperature was raised to 50 °C and the reaction was carried out for 12 h. After the reaction was complete, the mother liquor was poured into ice-cold acetone to precipitate, and centrifuged to obtain a yellow oily product, which is the target chain extender.

[0076] (2) In a dry reactor, 4 mol of polytetrahydrofuran (PTMEG-2000) with a number average molecular weight of 2000 was added, and the mixture was dehydrated under vacuum at 110 °C and 0.095 MPa for 2 hours. Then the temperature was lowered to 80 °C, and 10 mol of 4,4-diisocyanate dicyclohexylmethane (HMDI) and 0.5% mol (relative to polytetrahydrofuran) of catalyst DBTDL were added. The mixture was reacted at 80 °C for 4 hours under nitrogen protection to obtain the prepolymer.

[0077] (3) Preparation of ionic polyurethane elastomer: After cooling the prepolymer obtained in step (2) of Example 1 to 60°C, 2 mol of ADH was added and stirred for 12 h. Then, 4 mol of the double-side chain extender obtained in step (1) was quickly added and the reaction was continued at 60°C for 12 h. The mother liquor was then poured into deionized water to precipitate, and the precipitate was dried to obtain the ionic polyurethane elastomer.

[0078] (4) Preparation of ion-conductive polyurethane: Take 2g of the ion-type polyurethane elastomer and 2g of [EMIM]TFSI obtained in step (3) of Example 1 and dissolve them in 10ml of LDM. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0079] Example 2: (1) Synthesis of a double-sided chain extender (using 3-amino-1,2-propanediol and 2-acrylamido-2-methyl-1-propanesulfonic acid as raw materials): Nitrogen gas was introduced into a 500 mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel for protection. 40 mol of 2-acrylamido-2-methyl-1-propanesulfonic acid was dissolved in 150 mL of NMP. 20 mol of 3-amino-1,2-propanediol was dissolved in 100 mL of NMP and slowly added dropwise to the system. After the addition was complete, the temperature was raised to 60 °C and the reaction was carried out for 8 h. After the reaction was completed, the mother liquor was poured into ice-cold acetone to precipitate the product. After centrifugation, a yellow oily product was obtained, which was the target chain extender.

[0080] (2) Same as step (2) in Example 1.

[0081] (3) Preparation of ionic polyurethane elastomer: After cooling the prepolymer obtained in step (2) of Example 2 to 60°C, 2 mol of ADH was added and stirred for 12 h. Then, 4 mol of the double-side chain extender obtained in step (1) was quickly added and the reaction was continued at 60°C for 12 h. The mother liquor was then poured into deionized water to precipitate, and the precipitate was dried to obtain the ionic polyurethane elastomer.

[0082] (4) Preparation of ion-conductive polyurethane: Take 2g of the ion-type polyurethane elastomer and 2g of [EMIM]TFSI obtained in step (3) of Example 2 and dissolve them in 10ml of LDM. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0083] Example 3: (1) Synthesis of a double-sided chain extender (using 3-amino-1,2-propanediol and 1-vinyl-3-butylimidazolium chloride as raw materials): Nitrogen gas was introduced into a 500 mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel for protection. 40 mol of 1-vinyl-3-butylimidazolium chloride was dissolved in 150 mL of THF. 20 mol of 3-amino-1,2-propanediol was dissolved in 100 mL of THF and slowly added dropwise to the system. After the addition was complete, the temperature was raised to 60 °C and the reaction was carried out for 8 h. After the reaction was completed, the mother liquor was rotary evaporated at 40 °C to obtain a yellow oily product, which was the target chain extender.

[0084] (2) Same as step (2) in Example 1.

[0085] (3) Preparation of ionic polyurethane elastomer: After cooling the prepolymer obtained in step (2) of Example 3 to 60°C, 2 mol of ADH was added and stirred for 12 h. Then, 4 mol of the double-side chain extender obtained in step (1) was quickly added and the reaction was continued at 60°C for 12 h. The mother liquor was then poured into deionized water to precipitate, and the precipitate was dried to obtain the ionic polyurethane elastomer material.

[0086] (4) Preparation of ion-conductive polyurethane: Take 2g of the ion-type polyurethane elastomer and 2g of [EMIM]TFSI obtained in step (3) of Example 3 and dissolve them in 10ml of LDMF. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0087] Example 4: (1) Same as step (1) in Example 1.

[0088] (2) Same as step (2) in Example 1.

[0089] (3) Preparation of ionic polyurethane elastomer: After cooling the prepolymer obtained in step (2) of Example 4 to 60°C, 3 mol of ADH was added and stirred for 12 h. Then, 3 mol of the double-side chain extender obtained in step (1) of Example 4 was quickly added, and the reaction was continued at 60°C for 12 h. The mother liquor was then poured into deionized water to precipitate, and the precipitate was dried to obtain the ionic polyurethane elastomer.

[0090] (4) Preparation of ion-conductive polyurethane: Take 2g of the ion-type polyurethane elastomer and 2g of [EMIM]TFSI obtained in step (3) of Example 4 and dissolve them in 10ml of LDM. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0091] Example 5: (1) Same as step (1) in Example 1.

[0092] (2) Same as step (2) in Example 1.

[0093] (3) Preparation of ionic polyurethane elastomer: After cooling the prepolymer obtained in step (2) of Example 5 to 60°C, 4 mol of ADH was added and stirred for 12 h. Then, 2 mol of the double-side chain extender obtained in step (1) of Example 5 was quickly added, and the reaction was continued at 60°C for 12 h. The mother liquor was then poured into deionized water to precipitate, and the precipitate was dried to obtain the ionic polyurethane elastomer.

[0094] (4) Preparation of ion-conductive polyurethane: Take 2g of the ion-type polyurethane elastomer and 2g of [EMIM]TFSI obtained in step (3) of Example 5 and dissolve them in 10ml of LDMF. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0095] Comparative Example 1: (1) Same as step (2) in Example 1.

[0096] (2) Preparation of polyurethane elastomer: After cooling the prepolymer obtained in step (1) to 60°C, 2 mol of ADH was added and stirred for 12 h. Then, 4 mol of BDO was quickly added and the reaction was continued at 75°C for 12 h. The mother liquor was then poured into deionized water to precipitate the polyurethane elastomer after drying.

[0097] (3) Preparation of ion-conductive polyurethane: Take 2g of polyurethane masterbatch and 2g of [EMIM]TFSI obtained in step (2) of Comparative Example 3 and dissolve them in 10ml of LDMF. Then transfer the solution to a polytetrafluoroethylene plate and dry it in an oven at 100℃ for 24h to form a film, thus obtaining ion-conductive polyurethane.

[0098] The structure of the double-sided chain extender obtained in step (1) of Example 1 was characterized and confirmed by 1H NMR spectroscopy. A Bruker Avance III 400 MHz NMR spectrometer was used, and measurements were performed at 25°C. Deuterated water (D₂O) was used as the test solvent, and tetramethylsilane (TMS) was used as an internal standard to calibrate the chemical shift. The results are as follows: Figure 1As shown, the chemical shifts of each characteristic peak are in good agreement with the simulation predictions, confirming the successful synthesis of the target compound.

[0099] The functional groups and surface structure of the ionic polyurethane elastomer described in this invention were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). A Thermo Scientific Nicolet iS50 Fourier transform infrared spectrometer was used, equipped with a single-reflectance diamond ATR accessory. During testing, the sample was directly covered and pressed firmly onto the surface of the ATR crystal detection window, and the reflectance signal was directly acquired at 25°C. The spectral acquisition parameters were set as follows: spectral scanning range of 4000 cm⁻¹. - ¹ Up to 650 cm - ¹, The instrument resolution is set to 4 cm. - ¹, the signal accumulation scan for each spectrum was performed 32 times. Air background data was collected before testing to subtract interference from carbon dioxide and water vapor in the environment. The infrared spectral results of the ionomer polyurethane elastomers in Examples 1, 4, and 5 are as follows: Figure 2 As shown. 3550cm -1 The -OH / -NH- peak appears and at 1040 cm⁻¹ -1 The appearance of the -SO3 peak proves that the ionic chain extender was successfully introduced and the polyurethane was successfully synthesized.

[0100] The mechanical properties of the ionomer polyurethane elastomers obtained in Examples 1, 4, and 5 were all tested using a universal testing machine. The mechanical properties of the samples were tested using a BZ2.5 / pN1S material mechanics testing system (ZWICK GmbH, Germany). The samples were cut into dumbbell-shaped strips, with the middle strip measuring 14.0 mm × 2.0 mm. Both ends were fixed to clamps with an initial clamping distance of 14 mm, and the tensile speed was set to 50 mm / min. The relevant results (stress-strain curves) are shown below. Figure 3 As shown. Compared with Examples 4-5, the ionic polyurethane elastomer of Example 1 exhibits superior overall mechanical properties: a fracture stress of 31.2 MPa, an elongation at break of 2257.8%, and a fracture toughness as high as 262.4 MJ / m³. This is attributed to the introduction of more ionic chain extenders, which optimizes the microphase separation structure, thereby improving the mechanical properties of the system.

[0101] The mechanical stability of the ionomer polyurethane elastomer in Example 1 was further analyzed. After cyclic tensile testing at strains ranging from 100% to 600%, the stress-strain curves showed a small hysteresis loop, indicating good mechanical stability. Figure 4 It also demonstrated its long-cycle stability at 50% strain and exhibited good mechanical retention. Figure 5 This proves that it has good mechanical properties.

[0102] Comparing Examples 1-5, the conductivity differences of ion-conductive polyurethanes with different types and ratios of ion-type chain extenders were compared. Electrochemical impedance spectroscopy (EIS) of the ion-conductive polyurethanes was measured using an electrochemical workstation (CHI760E). First, the sample to be tested was cut into pieces with a diameter of 16 mm and an area of ​​64 mm². 2 A circular sample was prepared and its thickness was recorded. The sample was placed between two stainless steel electrodes and connected to an electrochemical workstation (CHI760E) to begin measurement. The specific results are shown in Table 1.

[0103] Table 1. Conductivity results of the examples and comparative examples

[0104] Comparing the conductivity of Examples 1-3, it is evident that the zwitterionic chain extender is more effective than the anionic or cationic chain extender in improving the system's conductivity. This is due to its higher ion density, which helps to construct more efficient ion transport channels. Comparing the conductivity of Example 1 with Examples 4-5, it is clear that reducing the amount of zwitterionic chain extender significantly reduces the conductivity of the polyurethane. The conductivity of Comparative Example 1 is significantly lower than that of the other examples, demonstrating that the presence of the ionic chain extender greatly contributes to improving the ionic conductivity of ion-conductive polyurethane.

[0105] To demonstrate the superior stability of ionic polyurethane elastomers to ionic liquids, this invention characterized the changes in ionic conductivity of the ionic conductive polyurethanes of Example 1 and Comparative Example 1 over different number of days. Figure 6 As shown, it is evident that the ionic conductivity of this component remained almost unchanged after seven days due to the introduction of an ionic chain extender in Example 1, demonstrating that the introduction of the zwitterionic chain extender greatly improved the long-term stability of the polyurethane elastomer and the ionic liquid.

[0106] The electromechanical sensing response performance of the ion-conductive polyurethane described in this invention was simultaneously tested using a universal testing machine and an electrochemical workstation CHI760E. The prepared elastomer film was cut to standard dimensions (length × width × thickness: 15 mm × 2 mm × 0.5 mm), with copper foil tape leading to the ends and connected to the CHI760E electrochemical workstation for real-time resistance signal recording. During testing, the sample was clamped at both ends on the universal testing machine. Uniaxial tension was applied to the sample at a constant rate of 50 mm / min at room temperature. The relative rate of change of resistance (ΔR / R0) was calculated using the formula ΔR / R0 = (R - R0) / R0, where R0 is the initial resistance of the sample and R is the real-time resistance under tensile strain. The sensor sensitivity, i.e., the strain factor (GF), was calculated from the slope within the linear fitting interval: GF = (ΔR / R0) / ε, where ε is the applied tensile strain.

[0107] The present invention further investigated the response speed and sensitivity of the ion-conductive polyurethane of Example 1 to changes in resistance under tensile strain. Figure 7 The figure shows the response speed of the ion-conductive polyurethane of Example 1 to changes in resistance under tensile strain. As can be seen from the figure, its response time is 249 ms under tension and 109 ms under unloading, exhibiting an extremely fast response speed. Figure 8 The figure shows the sensitivity coefficient of the ion-conductive polyurethane of Example 1 to changes in resistance under tensile strain. As can be seen from the figure, the rate of resistance change exhibits extremely high linear correlation when stretched to 800%, demonstrating its good stability.

[0108] The ion-conductive polyurethane samples from Examples 1 and 4 were immersed in liquid bacterial strains (Escherichia coli and Staphylococcus aureus). The selected strains were cultured overnight on agar plates to obtain single colonies, which were then inoculated into the corresponding liquid media (Louis-Bertney medium for Escherichia coli, and tryptone-soy medium for Staphylococcus aureus) and incubated at 37°C for 12 hours (Escherichia coli) / 6 hours (Staphylococcus aureus). Subsequently, the resulting high-density bacterial solution was immediately diluted to the original co-culture bacterial solution, with OD values ​​of 0.1 (Escherichia coli) or 0.05 (Staphylococcus aureus), respectively. Pre-sterilized ion-conductive polyurethane samples (irradiated with UV light for 1 hour) were placed in 6-well plates, and a certain amount of the diluted bacterial solution was added. After co-culturing for 24 hours (E. coli) or 12 hours (Staphylococcus aureus) under shaking conditions (37°C, 120 rpm), the co-cultured samples were removed, and the unadhered bacteria on the sample surface were rinsed three times with PBS buffer. Then, the samples were treated with diluted LIVE / DEAD Backlight Active Reactivity Kit solution (Thermo Fisher Scientific Inc., New York) for 20 minutes. The specific viability and antifouling properties of the zwitterionic hydrogels were observed under a fluorescence microscope (Echo Revolve R4) using a 20x lens. All samples were randomly selected for imaging examination, and statistical analysis was performed using ImageJ software. The surface antibacterial properties were investigated by statistically analyzing the bacterial density; the specific results are shown below. Figure 9 And Table 2.

[0109] Table 2. Antibacterial performance results of Examples 1 and 4

[0110] like Figure 9 As shown in Table 2, the ion-conductive polyurethane in Example 1 has a higher density of zwitterionic groups, and its bacterial density is significantly lower than that of the ion-conductive polyurethane in Example 4. This result fully demonstrates that, because high-density zwitterionic groups can form a dense hydration layer on the material surface, this hydration layer can effectively prevent the non-specific adsorption and adhesion of biomolecules such as proteins, bacteria, and algae, thus endowing the material with durable and broad-spectrum antifouling capabilities.

[0111] In summary, the technical solution of this invention can not only improve mechanical properties by introducing double-chain ionic groups into the chain extender through Michael addition reaction to induce microphase separation, but also construct ion transport channels with high ion density, endowing polyurethane with good electrical conductivity, as well as good electromechanical sensing response and antibacterial properties, providing a reliable technical path for the development of high-performance ion-conductive polyurethane materials.

[0112] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0113] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0114] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A double-side-chain chain extender, characterized in that: The structure of the dual-side-chain chain extender is shown below: Ⅰ Where -R= or in This indicates that the end group is connected to a nitrogen atom.

2. A method for preparing the double-side-chain chain extender as described in claim 1, characterized in that: The preparation method is as follows: the acceptor compound and the donor compound undergo a Michael addition reaction to generate a bi-side chain extender. The donor compound is selected from 3-amino-1,2-propanediol of formula II: II The acceptor compound is selected from one of the following: acrylic acid, 2-acryloylamino-2-methyl-1-propanesulfonic acid as shown in Formula III, acryloyloxyethyltrimethylammonium chloride as shown in Formula IV, 1-vinyl-3-butylimidazolium chloride as shown in Formula V, 3-((2-(acryloyloxy)ethyl)dimethylammonium)propane-1-sulfonate as shown in Formula VI, and 2-(1-(6-(((2-(acryloyloxy)ethyl)carbamoyl)oxo)hexyl)pyridin-1-onthium-4-yl)ethane-1-sulfonate as shown in Formula VII. III IV V VI VII.

3. The preparation method according to claim 2, characterized in that: The Michael addition reaction is carried out in a reaction solvent selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, acetonitrile, and water; the reaction temperature of the Michael addition reaction is 50~70℃, and the reaction time is 6~12h.

4. The preparation method according to claim 2, characterized in that: The molar ratio of the acceptor compound to the donor compound is (2.0-4.2):

1.

5. The application of the double-side-chain chain extender as described in claim 1 in the synthesis of ion-conductive polyurethane, wherein the application specifically comprises: (1) Polyurethane prepolymer is obtained by reacting polyol and isocyanate under the action of a catalyst; (2) The polyurethane prepolymer is reacted sequentially with two chain extenders to obtain an ionic polyurethane elastomer; the two chain extenders are a hydrogen-bonding chain extender and an ionic chain extender, the ionic chain extender being the double-side chain extender; the molar ratio of the polyurethane prepolymer to the ionic chain extender is 1:0.2~0.6, wherein the number of moles of the polyurethane prepolymer is based on the number of moles of -NCO contained therein, and the molar ratio of the hydrogen-bonding chain extender to the ionic chain extender is 3:1~1:3; (3) The obtained ionic polyurethane elastomer is compounded with an ionic liquid to obtain ionic conductive polyurethane.

6. The application as described in claim 5, characterized in that: The polyol is selected from one or more of polytetrahydrofuran, polycaprolactone, and polypropylene glycol; the isocyanate is selected from one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, and hexamethylene diisocyanate; and the catalyst is dibutyltin dilaurate.

7. The application as described in claim 5, characterized in that: The hydrogen bond chain extender is selected from one or more of diacid hydrazide, ureo-4-pyridone, or 1,4-butanediol.

8. The application as described in claim 5, characterized in that: In step (2), the reaction temperature after adding hydrogen bonding chain extender or ionic chain extender is 40-60℃ and the reaction time is 16-24h.

9. The application as described in claim 5, characterized in that: The ionic liquid is selected from one or more of 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl)imine.

10. The application as described in claim 5, characterized in that: The mass ratio of the ionic polyurethane elastomer to the ionic liquid is 1:0.1-1:1.

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