An impact-resistant hydrogel based on multi-scale synergistic toughening design and a preparation method thereof

Abstract

The application discloses an anti-impact hydrogel based on multi-scale synergistic reinforcing and toughening design and a preparation method thereof, and belongs to the technical field of polyurethane urea hydrogels.The application correlates the parameters of the microstructure of the polyurethane urea hydrogel with the macroscopic mechanical behavior by a molecular dynamics method.The application compares the change trend of the macroscopic mechanical behavior of the polyurethane urea hydrogel by regulating the parameters of the microstructure of the polyurethane urea hydrogel (such as the crosslinking density, the soft and hard phase distribution, the chain defect form and quantity of the polyurethane urea hydrogel).Then, the influence law of the parameters of the microstructure of the polyurethane urea hydrogel on the macroscopic mechanical behavior is mastered, the polyurethane urea hydrogel is designed from the microscale and the macroscale in the mode of genetic algorithm evolution, and the anti-impact hydrogel based on multi-scale synergistic reinforcing and toughening design is designed.The anti-impact hydrogel based on multi-scale synergistic reinforcing and toughening design has the advantages of being able to work coordinately in the microscale and the macroscale, excellent anti-impact performance, high strength and high toughness, simple preparation method and low raw material cost, and has great application prospect in the field of biological tissue engineering.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogel, and particularly relates to an impact-resistant hydrogel based on multi-scale synergistic reinforcement and toughening design and a preparation method thereof. BACKGROUND

[0002] Hydrogel is a high polymer material, has strong water absorption, and forms a stable gel state after water absorption. The basic structure is composed of cross-linked polymers, and the mechanical properties of polyurethane hydrogel are related to structure, cross-linking density, soft and hard phases, and chain defect form and quantity.

[0003] Hydrogel is often used as a tissue simulation material for cartilage, muscle and human organs (lungs, hearts, brains, etc.) due to its structural similarity to biological soft tissues. When hydrogel is used as a tissue and organ simulation material, the softness is similar to the characteristics of biological soft tissues, and after water absorption and swelling, it has the ability to permeate low molecular weight metabolic products. However, the current hydrogel still has some shortcomings. As a biomedical material, in addition to having certain biological tissue similarity and compatibility, it also needs to have sufficient strength and toughness. However, the strength of the current hydrogel is mainly affected by the chemical cross-linking points, but changing the density of the chemical cross-linking points will affect the water absorption rate.

[0004] In recent years, a new polymer material, polyurethane urea hydrogel, can be adjusted to meet specific functional requirements by changing the ratio of soft and hard phases in the molecular chain. When a hydrophilic polymer chain is selected as the soft segment of polyurethane urea, a hydrophilic polyurethane urea hydrogel material can be prepared, which has the common advantages of hydrogel and polyurethane urea. By adjusting the microstructure of the polyurethane urea hydrogel, the macroscopic mechanical properties of the material can be adjusted. Genetic algorithm model combined with molecular dynamics simulation method is used to design the polyurethane urea hydrogel according to the target performance. This provides a new idea for the multi-scale design of polyurethane urea hydrogel to enhance toughness. SUMMARY

[0005] The application provides a method for designing a polyurethane urea hydrogel with high strength, high toughness and high elongation by combining micro and macro scales. The genetic algorithm model combined with molecular dynamics simulation method is used to design the polyurethane urea hydrogel according to the target performance.

[0006] To achieve the above effects in the future, the application adopts the following technical solutions

[0007] An impact-resistant hydrogel based on multi-scale synergistic reinforcement and toughening design, characterized in that the polyurethane urea hydrogel is prepared by using a molecular dynamics model to adjust the cross-linking density, soft and hard phase distribution, chain defect form and quantity of the microstructure to study the changes in the macroscopic mechanical behavior of the polyurethane urea hydrogel.

[0008] The polyurethane urea hydrogel is designed from micro and macro multi-scale in an evolutionary mode of genetic algorithm.

[0009] The shock-resistant hydrogel based on multi-scale synergistic toughening design is characterized in that a model adopted by a molecular dynamics method is a coarse-grained molecular dynamics model of the polyurethane urea hydrogel.

[0010] The shock-resistant hydrogel based on multi-scale synergistic toughening design is characterized in that a form of intermolecular interaction of the coarse-grained polyurethane urea hydrogel is an OPLS force field.

[0011] The molecular dynamics simulation step of the polyurethane urea hydrogel micro-scale uniaxial impact is as follows:

[0012] (a) first, the coarse-grained molecular dynamics model of the polyurethane urea hydrogel is established by using LAMMPS software;

[0013] (b) the coarse-grained model of the polyurethane urea hydrogel is subjected to sufficient energy relaxation to obtain an optimal configuration;

[0014] (c) the initial configuration is generated by using Packmol software, the model is checked by using an NVE ensemble with a simulation step of 0.1 fs, the control temperature is 300.15-310.15 K, and the simulation time is 100-2500 ps;

[0015] (d) the shock wave is generated by using a non-equilibrium momentum mirror method to propagate through the simulation unit. The periodic boundary in the Z direction is removed, a velocity-VP is added to each particle in the hydrogel model, and a momentum mirror is set on the Z=0 plane; the particles hitting the momentum mirror are reflected back to generate and propagate the shock wave on the Z=0 plane;

[0016] (e) in the simulation process, the shock resistance, elongation and toughness of the polyurethane urea hydrogel system under specific microstructure parameters are collected by the coarse-grained molecular dynamics simulation software.

[0017] The shock-resistant hydrogel based on multi-scale synergistic toughening design is characterized in that the genetic algorithm is used to optimize the design with the key performance indicators of the polyurethane urea hydrogel as the target.

[0018] Further, the objective function is shown as formula 1;

[0019] (Formula 1);

[0020] The constraint condition of the multi-scale synergistic toughening design of the shock-resistant hydrogel is;

[0021] ;

[0022] ;

[0023] ;

[0024] constraint , , represents the comprehensive parameter of crosslinking density, soft and hard phase content, chain defect form and quantity in the molecular model of polyurethane urea hydrogel.

[0025] The genetic algorithm optimization design includes the following steps

[0026] (a) initializing population (n) by using genetic algorithm, randomly generating a set of values of design variables;

[0027] (b) the values of each set of design variables in the population are provided by the genetic algorithm program to the molecular dynamics simulation program for impact simulation of polyurethane urea hydrogel, to obtain its strength, toughness, elongation and other macroscopic performance indicators, and compared with the target performance indicators.

[0028] (c) calculating individual fitness, evaluating the fitness of design variables. The fitness function is as follows;

[0029] (Formula 2);

[0030] (d) encoding the initial design variables, using binary string to encode the design variables;

[0031] (e) copying, crossing and mutating the individuals to obtain the next generation population (n+1) of design variables, decoding the population (n+1), and repeating steps (a)-(e);

[0032] (f) termination condition: repeat the process of (a)-(e) until the optimal design that meets all the constraint conditions and has the maximum target function value is found. Otherwise, go to step (a) and continue iteration.

[0033] Further, the copying in step (e) is carried out by tournament selection

[0034] Further, the crossing in step (e) is carried out by uniform crossing BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a coarse-grained diagram of polyurethane urea hydrogel molecules

[0036] Figure 2 is a schematic diagram of momentum mirror method for generating shock wave

[0037] Figure 3 is a diagram of encoding crosslinking density using binary string

[0038] Figure 4 Flow chart of the combination of coarse-grained molecular dynamics and genetic algorithm DETAILED DESCRIPTION

[0039] The application will be further described in conjunction with specific embodiments, but the scope of protection of the application is not limited by the specific embodiments. In addition, any modification or change made by those skilled in the art to the application without departing from the technical scheme of the application will fall within the scope of the claims of the application.

[0040] In order to improve the impact strength, toughness and elongation of polyurethane urea hydrogel, the application uses the method of combining molecular dynamics simulation and genetic algorithm evolution mode to design polyurethane urea hydrogel from microscale and macroscale. The model used by the molecular dynamics method is a coarse-grained molecular dynamics model of polyurethane urea hydrogel. At the same time, the form of the intermolecular interaction of the coarse-grained polyurethane urea hydrogel is OPLS force field.

[0041] The coarse-grained potential energy function is defined using the OPLS force field as follows:

[0042] ;

[0043] ;

[0044] ;

[0045] wherein, , and are spring constants, , , are the corresponding equilibrium positions, and n is periodic.

[0046] The steps of the molecular dynamics simulation of the uniaxial impact of the polyurethane urea hydrogel at the microscale are as follows:

[0047] (a) First, a coarse-grained molecular dynamics model of polyurethane urea hydrogel with a length of 30 nm and a width of 10 nm is established by LAMMPS software;

[0048] (b) The coarse-grained model of the polyurethane urea hydrogel is subjected to sufficient energy relaxation to obtain the optimal configuration;

[0049] (c) The Packmol software is used to generate the initial configuration, and the model is checked using an NVE ensemble with a simulation step of 0.1 fs, a control temperature of 300.15-310.15 K, and a simulation time of 100-2500 fs.

[0050] (d) The shock wave is generated by the non-equilibrium momentum mirror method and propagates through the simulation unit. The periodic boundary in the Z direction is removed, a velocity VP is added to each particle in the hydrogel model, and a momentum mirror is set on the Z=0 plane; particles hitting the momentum mirror are reflected back, generating and propagating a shock wave on the Z=0 plane;

[0051] (e) During the simulation, the impact resistance, elongation, and toughness of the polyurethane urea hydrogel system under specific microstructure parameters are collected by the coarse-grained molecular dynamics simulation software.

[0052] With the key performance indicators of polyurethane urea hydrogel as the target, genetic algorithm optimization design is adopted, and the best material parameters, including the ratio of soft and hard phases, crosslinking density, and chain defects and number, are determined by the established molecular dynamics simulation method to achieve the optimal strength, toughness, and elongation at break.

[0053] Further, the objective function is shown as formula 4;

[0054] (Formula 4);

[0055] In formula 4, is a mathematical model of the comprehensive performance evaluation function of the polyurethane urea hydrogel impact resistance, wherein is the target strength, is the simulated strength, is the target toughness of the material, is the simulated toughness, is the target elongation, is the simulated elongation, is the actual cost of the material.

[0056] is the weight of the corresponding performance indicator, and the weight factor can be adjusted according to the importance of different performance indicators to ensure that the objective function can balance each performance indicator.

[0057] Further, the constraint condition of the multi-scale synergistic toughening design of the impact-resistant hydrogel is

[0058] ;

[0059] ;

[0060] ;

[0061] In the constraint condition, , , The cross-linking density, the soft and hard phase content, the chain defect form and the quantity comprehensive parameters in the molecular model of the polyurethane urea hydrogel.

[0062] The genetic algorithm optimization design includes the following steps.

[0063] (a) initializing the population (n) by using the genetic algorithm to randomly generate a set of values of the design variables;

[0064] (b) the values of each set of design variables in the population are provided by the genetic algorithm program to the molecular dynamics simulation program to perform the polyurethane urea hydrogel impact simulation, and the macroscopic performance indexes such as strength, toughness and elongation are obtained, and compared with the target performance indexes;

[0065] (c) calculating the individual fitness to evaluate the fitness of the design variables. The fitness function is as follows.

[0066] (Form 5);

[0067] In formula 5, is the target strength, is the simulated strength, is the target toughness of the material, is the simulated toughness, is the target elongation, is the simulated elongation, is the maximum elongation, is the elongation of each simulation. is the weight of the corresponding performance index.

[0068] (d) encoding the initial design variables, using a binary string to encode the design variables;

[0069] (e) copying, crossing and mutating the individual to obtain the next generation population (n+1) of design variables, decoding the population (n+1), and repeating steps (a)-(e);

[0070] (f) termination condition: repeat the process of (a)-(e) until the optimal design that meets all the constraint conditions and has the maximum target function value is found. Otherwise, go to step (a) and continue iteration.

[0071] The copying in step (e) is carried out by tournament selection.

[0072] The crossing in step (e) is carried out by uniform crossing.

[0073] Serial number Crosslinking density mol / cm 3 ]] Soft and hard phase Chain defect form and number Simulated impact strength MPa Simulated elongation % Target impact strength MPa Target elongation % 1 3920 70 14 7.18 548 7.5 500 2 2650 60 5 7.49 461 7.5 500 3 3880 60 9 6.75 461 7.5 500 4 3960 80 17 6.90 416 7.5 500 5 2990 50 14 7.16 403 7.5 500 6 3800 60 8 8.09 461 7.5 500 7 3970 60 9 7.36 431 7.5 500 8 2560 80 19 6.79 519 7.5 500 9 3750 40 15 8.25 585 7.5 500 10 2850 60 13 6.51 571 7.5 500 11 2760 60 3 8.03 521 7.5 500 12 3770 70 7 7.01 587 7.5 500 13 4350 50 12 6.55 555 7.5 500 14 3960 50 0 7.78 409 7.5 500 15 4060 60 13 6.53 475 7.5 500 16 2510 70 1 7.33 426 7.5 500 17 4440 80 8 7.92 522 7.5 500 18 2610 50 2 7.83 596 7.5 500 19 3240 60 13 7.35 475 7.5 500 20 4000 60 3 7.76 533 7.5 500 21 4230 60 8 9.92 438 10 400 22 3160 40 2 9.49 361 10 400 23 2990 60 15 9.87 389 10 400 24 3240 50 17 10.32 428 10 400 25 2780 70 7 10.60 382 10 400 26 2810 60 20 10.01 367 10 400 27 2750 70 6 10.02 441 10 400 28 4160 70 12 9.01 397 10 400 29 2530 40 5 9.68 364 10 400 30 3730 40 10 9.46 376 10 400 31 4490 80 5 10.86 417 10 400 32 4470 70 1 9.51 368 10 400 33 3290 60 15 10.47 369 10 400 34 2930 80 16 9.93 401 10 400 35 4340 80 1 10.75 373 10 400 36 4460 40 9 9.86 393 10 400 37 3170 60 7 10.46 430 10 400 38 3140 80 9 10.88 397 10 400 39 3580 70 14 9.85 427 10 400 40 4370 70 19 10.33 352 10 400

Claims

1. A method for preparing an impact-resistant hydrogel based on a multiscale synergistically reinforced toughening design, characterized by: The preparation method is: (1) first, mixing polyether diol PEG2000 and polyether triol 303, through a series of steps to obtain isocyanate prepolymer component; (2) 2,2-dimethylol propionic acid, diethylene glycol, dichloromethane, dibutyl ester and dibutyltin dilaurate and a certain amount of deionized water are put into the dispersion kettle to prepare the compound component; (3) the two components prepared in steps (1) and (2) are mixed in a certain proportion, and the obtained sol is sterilized and poured into a mold to form a polyurethane urea hydrogel at room temperature; The polyurethane urea hydrogel is used to study the change of the macroscopic mechanical behavior of the polyurethane urea hydrogel by adjusting the crosslinking density, soft and hard phase distribution, chain defect form and quantity of the microstructure using molecular dynamics model; The polyurethane urea hydrogel is designed from micro and macro multi-scale using genetic algorithm evolution mode; The key performance indicators of the polyurethane urea hydrogel are taken as the target, and the genetic algorithm is used for optimization design, and the best material parameters including the ratio of soft and hard phases, crosslinking density and chain defect and quantity are determined by the established molecular dynamics simulation method to achieve the optimal strength, toughness and elongation at break; The molecular dynamics simulation steps of the polyurethane urea hydrogel microscale uniaxial impact are as follows: (a) first, the coarse-grained molecular dynamics model of the polyurethane urea hydrogel is established by LAMMPS software; (b) the coarse-grained molecular dynamics model of the polyurethane urea hydrogel is fully energy relaxed to obtain the optimal configuration; (c) use Packmol software to generate the initial configuration; (d) use non-equilibrium momentum mirror method to generate shock wave propagation through simulation unit, remove the periodic boundary in Z direction, add velocity-VP to each particle in the coarse-grained molecular dynamics model of the hydrogel, and set the momentum mirror on the Z=0 plane; the particles hitting the momentum mirror are reflected back to generate and propagate the shock wave on the Z=0 plane; (e) in the simulation process, the impact strength, elongation and toughness of the polyurethane urea hydrogel system under the microstructure parameters are collected by the coarse-grained molecular dynamics simulation software; The constraint conditions of the multi-scale synergistic reinforcing and toughening design of the impact resistant hydrogel are ； ； ； In the constraints , , represents the comprehensive parameter of crosslinking density, soft and hard phase content, chain defect form and quantity in the molecular model of polyurethane urea hydrogel; The genetic algorithm optimization design includes the following steps (A) initialize the population (n) using genetic algorithm, and randomly generate a set of design variable values; (B) the numerical value of each set of design variables in the population is provided by the genetic algorithm program to the molecular dynamics simulation program for polyurethane urea hydrogel impact simulation to obtain its macroscopic performance index, which is compared with the target performance index; (C) calculate the individual fitness, evaluate the fitness of the design variables, and the fitness function is as follows (Formula 5) In formula 5 target strength, simulated strength, target toughness, simulated toughness, target elongation, simulated elongation, maximum elongation, simulated elongation, weight of the corresponding performance index; (D) encode the initial design variables using binary string to encode the design variables; (E) copy, cross and mutate the individuals to obtain the next generation population (n+1) of design variables, decode the population (n+1), and repeat steps (A)-(E); (F) Termination condition: repeat steps (A)-(E) until the optimal design is found that satisfies all the constraints and has the maximum objective function value, otherwise go to step (A) and continue iteration.

2. A method for preparing an impact resistant hydrogel based on multi-scale synergistic reinforcement and toughening design according to claim 1, characterized in that: The form of the coarse-grained intermolecular interactions of the polyurethane urea hydrogel is OPLS force field; The coarse-grained potential energy function is defined using OPLS force field as follows: ； ； ； wherein , and are spring constants, , , are the respective equilibrium positions, n is the periodicity, and represents the dihedral angle, also called the torsion angle.

3. A method of preparing an impact resistant hydrogel based on multi-scale synergistic reinforcement and toughening design according to claim 1, characterized in that: The step (a) uses the elastic network model to simulate the interaction between polymer chains.

4. A method of preparing an impact resistant hydrogel based on multi-scale synergistic reinforcement and toughening design according to claim 1, characterized in that: The objective function is shown as formula 4 (Formula 4) In formula 4 is a mathematical model of the impact resistance comprehensive performance evaluation function of the polyurethane urea hydrogel, wherein is the target strength, is the simulated strength, is the target toughness of the material, is the simulated toughness, is the target elongation rate, is the simulated elongation rate, is the actual cost of the material, are weights of the corresponding performance indicators, and the weight factors are adjusted according to the importance of different performance indicators to ensure that the objective function can balance various performance indicators.

5. The method for preparing an impact-resistant hydrogel based on multi-scale synergistic reinforcement and toughening design according to claim 1, characterized in that: The replication used in the step (E) is tournament selection replication. The crossover used in the step (E) is uniform crossover.

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