CN113990402A - Method for describing structure-effect evolution of polyurethane material through molecular simulation technology - Google Patents
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Abstract
The invention relates to a method for describing structure-activity relationship evolution of a polyurethane high polymer material by a molecular dynamics simulation technology. A set of random bonding model method for polyurethane high polymer materials is established by constructing a relatively reasonable initial mixing model and taking the truncation radius and the marked atoms as reflecting criteria. On one hand, the method provides technical support for researching the structural evolution and the performance evolution in the reaction process of the polyurethane material, and simultaneously provides ideas for constructing relatively complex random models. The invention proves the linear correlation between the glass transition temperature and Young modulus of the polyurethane material and the reactivity by calculating the evolution of the glass transition temperature of the polyurethane material with different reactivities and uniaxial tensile simulation. Meanwhile, the feasibility of the modeling method of the polyurethane random crosslinking model is also verified.
Description
Technical Field
The invention relates to the field of chemical computer simulation and calculation and polyurethane high polymer materials, in particular to a method for establishing a polyurethane random cross-linked network model and structure-effect evolution thereof by using a molecular simulation technology.
Background
Polyurethane polymer is a material with wide application, and is commonly used in a plurality of fields such as automobile, rocket missile propulsion, transportation, foundation building and the like. The traditional high polymer material often needs to be added with specific components to form a high polymer composite material to meet the requirements of production and life, and polyurethane high polymer is no exception. However, due to the strong association of the components, the interface effect and the multi-scale effect of the multi-interface composite material, the forming process is slow, and various effects are mutually staggered. The structure-effect evolution relationship of the materials is not possible to describe from the macroscopic scale, and the traditional experimental means has the problems of long experimental period and large experimental consumption. A random cross-linking model is constructed through a molecular simulation technology, the evolution of the structure and the performance in the whole cross-linking process is described, and prediction guidance is provided for the design of an experiment. Effectively overcomes the defects of long experimental period and large consumption.
Disclosure of Invention
One of the purposes of the invention is to adopt a script program to identify the atoms of the reaction, and then realize the establishment of a full-atom random cross-linking model; effectively constructing models with different crosslinking degrees in the crosslinking process;
the second purpose of the invention is to predict the experiment result by molecular dynamics simulation, thus reducing the experiment period and cost;
the third purpose of the invention is to provide an idea for establishing various complex polymer bonding models;
the fourth purpose of the invention is to find out the corresponding relation of structure and effect by analyzing the structural change in the bonding process, discuss the micro-action mechanism of different results and optimize the manufacturing process of the polyurethane high polymer material.
The technical scheme of the invention is as follows:
1. a method for describing the structure-effect evolution of a polyurethane material by a molecular simulation technology is characterized by comprising the following steps:
(1) construction of polyurethane polymer full-atom component model
Firstly, establishing an open-loop model of monomers 3, 3-bis (azidomethyl) oxetane (BAMO) and Tetrahydrofuran (THF), and establishing a 10-42 polymerization degree diblock copolymer containing BAMO and THF as an adhesive material by a Build Polymers tool of Materials students; performing Forcite-Geometry Optimization on the macromolecular chain to obtain a more reasonable molecular structure; then, Materials Studios are used for establishing micromolecule additives such as a chain extender (diethylene glycol), a cross-linking agent (trimethylolethane) and a curing agent (2, 4-toluene diisocyanate), and the structure of the micromolecule is optimized by using Forcite- > Geometry Optimization to obtain a reasonable molecular configuration; through the steps, the full-atom model of the four components can be obtained; in the whole crosslinking process, hydroxyl and isocyanate groups react to form carbamate groups, so atoms participating in the reaction need to be marked in advance, and a Perl script program can identify key atoms of the reaction; the hydroxyl oxygen atom and the isocyanate carbon atom in the molecule are respectively marked as "R1" and "R2", which can ensure that no deviation of the reaction sites occurs;
(2) construction of polyurethane high-molecular all-atom mixed crystal cell
Establishing a four-component mixed model according to the ratio of the hydroxyl number to the isocyanate number of 1: 1-2; in order to obtain a more reasonable initial mixed configuration, firstly establishing 5-10 Amorphous unit cells through an Amorphous Cell module of Materials students, then respectively carrying out Geometry Optimization on the 5-10 unit cells, carrying out structural Optimization on the system after carrying out structural Optimization on the 5-10 unit cells, and selecting the system with the lowest energy as the initial configuration; the lower the energy, the easier it is to form this configuration in practical macroscopic experiments;
(3) relaxation of polyurethane polymer full-atom initial model
Performing kinetic relaxation on the initial structure obtained in the previous step, performing kinetic simulation for 2-4ns by using NVT (noise, vibration and harshness) ensemble at the temperature of 300K to obtain a relatively reasonable system conformation, and performing simulation for 2-4ns by using NPT ensemble to ensure that the density of a unit cell is 1.2g/cm3The vicinity of the structure rises and falls along with the fluctuation of the simulation temperature, and the initial structure can be considered to be balanced without large change;
(4) construction of polyurethane macromolecule all-atom random cross-linking model
Reading the balance configuration obtained in the last step into a Perl script calculation cycle of Materials students; by identifying the pre-labeled reactive atoms, it is possible for different reactive atoms set within the truncation radius to bond, i.e., a reaction between R1 and R2; the truncation radius is increased along with the progress of the simulation calculation process, so that the action range of the active atoms is increased, and the model can reach the preset reactivity; the initial cutoff distance set in the work is 0.35nm, the calculation is increased by 0.05-0.2nm each time, when the cutoff distance reaches 1.35-1.8nm, the program is interrupted no matter whether the preset reactivity is reached, and the system rushing and distortion caused by excessive bonding are prevented; within each truncation distance, there are five relaxations, so that the configuration after each bond is completed is optimized;
(5) calculation of all-atom structure-activity relationship of polyurethane polymer
Outputting polyurethane random cross-linking models with different cross-linking degrees, and firstly carrying out 5-cycle high-temperature annealing on the models, wherein the low temperature is 300K, and the high temperature is 600K; a low-energy relaxation configuration is obtained; then analyzing the glass transition temperature of each model; in this work, a method of thermal expansion coefficient was employed; cooling for 30-50K and 12-20 times from 650K; at each temperature, firstly carrying out NVT system balance of 1-2ns, carrying out NPT ensemble balance of 1-2ns, and taking the last 0.5-1ns data of the NPT process to obtain the density of the system at the corresponding temperature; establishing a temperature-density relation graph, and obtaining an intersection point of two straight lines by fitting the two straight lines with different slopes, so as to obtain the glass transition temperature; for the demonstration analysis of the mechanical property of the material, the model with different crosslinking degrees is subjected to uniaxial stretching in the work, the slope of an elastic area, namely the Young modulus, is respectively counted, and the maximum tensile strength is analyzed to obtain an evolution curve of the material property in the whole crosslinking process.
2. In a preferred embodiment of the present invention, the established all-atom stochastic cross-linking model is characterized in that the simulated force field selects compossii in Materials students in establishing the stochastic bonding model, and the subsequent kinetic simulation uses OPLS-AA force field; and judging the equilibrium state of the model through the density of the system.
3. In a preferred embodiment of the present invention, the created full-atom random cross-linking model is characterized in that the four-component full-atom model is bonded by labeled atom recognition to prevent the occurrence of the reaction between the same atoms.
4. In a preferred embodiment of the present invention, the established full-atom random crosslinking model is characterized in that the polymer chain is a block copolymer having a degree of polymerization of 10 to 42.
5. In a preferred embodiment of the present invention, the established all-atom random cross-linking model is characterized in that the initial configuration is constructed randomly, and has relatively low energy and more predictive and guiding effects on the actual process.
6. In a preferred embodiment of the present invention, the established full-atom random cross-linking model is characterized in that the dynamic simulation is the performance evolution in the whole cross-linking process, and has a certain regularity.
7. In a preferred embodiment of the present invention, the established full-atom random cross-linking model is characterized in that the cross-linking process is judged by the distance of active atoms, and the closer the distance is, the preferential reaction is performed, and the collision probability is simulated to be higher.
8. In a preferred embodiment of the present invention, the created full-atom random cross-linking model is characterized in that the Perl script can be extended to the reaction types of other groups to create a corresponding random linking model.
Advantageous results of the invention
(1) The invention adopts script program to identify the atom of reaction, and then realizes the establishment of full atom random cross-linking model; effectively constructing models with different crosslinking degrees in the crosslinking process;
(2) the invention adopts molecular simulation to predict the experiment result, thus reducing the experiment period and cost;
(3) the invention provides ideas for establishing various complex polymer bonding models;
(4) the invention finds the corresponding relation of structure effect by analyzing the structural change in the bonding process, discusses the micro-action mechanism of different results and optimizes the manufacturing process of the polyurethane high polymer material.
Detailed description of the preferred embodiments
(1) Construction of polyurethane polymer full-atom component model
Firstly, establishing an open-loop model of monomers 3, 3-bis (azidomethyl) oxetane (BAMO) and Tetrahydrofuran (THF), and establishing a 10-polymerization degree diblock copolymer containing BAMO and THF as a binder material by using a Build Polymers tool of Materials students; performing Forcite-Geometry Optimization on the macromolecular chain, and selecting a COMPASSII force field to obtain a more reasonable molecular structure; then, Materials Studios are used for establishing micromolecular additives such as a chain extender (diethylene glycol), a cross-linking agent (trimethylolethane) and a curing agent (2, 4-toluene diisocyanate), and the like, and the structure is optimized to obtain a more reasonable molecular configuration; through the steps, the full-atom model of the four components can be obtained; and respectively marking the hydroxyl oxygen atom as "R1" and the isocyanate carbon atom as "R2" in each component;
(2) construction of polyurethane high-molecular all-atom mixed crystal cell
Establishing a four-component mixed model according to the ratio of the hydroxyl number to the isocyanate number of 1: 2; in order to obtain a more reasonable initial mixed configuration, 5 Amorphous unit cells are established through an Amorphous Cell module of Materials students, then, the 5 unit cells are subjected to structural Optimization of Geometry Optimization respectively, a COMPASSII force field is selected, the total energy of the system after the structural Optimization is carried out on the 5 unit cells is compared, and the lowest total energy is selected as the initial configuration;
(3) relaxation of polyurethane polymer full-atom initial model
Performing kinetic relaxation on the initial structure obtained in the previous step, performing kinetic simulation for 2ns by using NVT (noise, vibration and harshness) ensemble at the temperature of 300K to obtain a relatively reasonable system conformation, and performing simulation for 2ns by using NPT ensemble to keep the density of a unit cell at 1.2g/cm3On the left and right sides, and the initial structure can be considered to reach balance without large change;
(4) construction of polyurethane macromolecule all-atom random cross-linking model
Reading the balance configuration obtained in the last step into a Perl script calculation cycle of Materials students; by identifying pre-labeled reactive atoms, different reactive atoms set within the cutoff radius may be bonded; the initial truncation radius is set to be 0.35nm, each calculation is increased by 0.1nm, and the maximum truncation radius is 1.35 nm; in each calculation of the truncation radius, there are five relaxations, so that the configuration after each bond is completed is optimized; then outputting structural models with different crosslinking degrees for dynamic analysis;
(5) calculation of all-atom structure-activity relationship of polyurethane polymer
Outputting polyurethane random cross-linking models with different cross-linking degrees, and firstly carrying out 5 cycles of high-temperature annealing on the models, wherein the low temperature is 300K, and the high temperature is 600K, so that a low-energy relaxation configuration is obtained; then, analyzing the glass transition temperature by adopting a thermal expansion coefficient method; cooling for 30-50K and 12-20 times from 650K; at each temperature, firstly carrying out NVT system balance of 1ns, carrying out NPT ensemble balance of 1ns, and taking the last 0.5ns data of the NPT process to obtain the density of the system at the corresponding temperature; establishing a temperature-density relation graph, and fitting two straight lines with different slopes to obtain an intersection point of the two straight lines so as to obtain the glass transition temperature; adopting uniaxial tension, calculating the modulus and tensile strength of an elastic zone, and establishing a corresponding relation between mechanical properties and structural evolution;
compared with the experimental result, the model established in the process can better reflect the linear relation of the glass transition temperature with the crosslinking degree in the random crosslinking process of the polyurethane polymer, can predict the corresponding linear relation of the Young modulus and the crosslinking degree, and can be used for predicting the experimental result.
Claims (8)
1. A method for describing the structure-effect evolution of a polyurethane material by a molecular simulation technology comprises the following steps:
(1) construction of polyurethane polymer full-atom component model
Firstly, establishing an open-loop model of a monomer 3, 3-bis (azidomethyl) oxetane (BAMO) and Tetrahydrofuran (THF), establishing a diblock copolymer with a polymerization degree of 10-42, which comprises the BAMO and the THF, as an adhesive material through Build Polymers tools of Materials students, performing Forcite- > Geometry Optimization on a high molecular chain to obtain a reasonable molecular structure, then establishing small molecular additives such as a chain extender (diethylene glycol), a cross-linking agent (trimethylolethane) and a curing agent (2, 4-toluene diisocyanate) through Materials students, performing structure Optimization on the small molecular structure by using Forcite- > Geometry Optimization to obtain a reasonable molecular configuration, and obtaining a full-atom model of four components through the steps, wherein the whole cross-linking process is that hydroxyl reacts with an isocyanate group to form a carbamate group, therefore, atoms participating in the reaction need to be labeled in advance, so that the Perl script program can identify key atoms of the reaction, and hydroxyl oxygen atoms and isocyanate carbon atoms in the molecules are respectively labeled as "R1" and "R2", which can ensure that no deviation occurs in the reaction sites;
(2) construction of polyurethane high-molecular all-atom mixed crystal cell
Establishing a four-component mixing model according to the proportion of hydroxyl number to isocyanate number being 1:1-2, in order to obtain a more reasonable initial mixing configuration, establishing 5-10 Amorphous unit cells through an Amorphous Cell module of Materials students, then respectively performing Geometryoptimization on the 5-10 unit cells, performing structural Optimization on the system after performing structural Optimization on the 5-10 unit cells, selecting the system with the lowest energy as the initial configuration, wherein the lower the energy is, the easier the configuration is to be formed in an actual macroscopic experiment;
(3) relaxation of polyurethane polymer full-atom initial model
Performing kinetic relaxation on the initial structure obtained in the previous step, performing kinetic simulation for 2-4ns by using NVT (noise, vibration and harshness) ensemble at the temperature of 300K to obtain a relatively reasonable system conformation, and performing simulation for 2-4ns by using NPT ensemble to ensure that the density of a unit cell is 1.2g/cm3The vicinity of the structure rises and falls along with the fluctuation of the simulation temperature, and the initial structure can be considered to be balanced without large change;
(4) construction of polyurethane macromolecule all-atom random cross-linking model
Reading the balance configuration obtained in the previous step into a Perl script calculation cycle of Materials students, wherein different active atoms set within a truncation radius are likely to be bonded by identifying pre-marked active atoms, namely, a reaction between R1 and R2 is carried out, the truncation radius is increased along with the progress of a simulation calculation process, so that the action range of the active atoms is increased, the model can reach the preset reactivity, the initial truncation distance set in the work is 0.35nm, the increase of the truncation radius is 0.05-0.2nm in each calculation, when the truncation distance reaches 1.35-1.8nm, the program is interrupted no matter whether the preset reactivity is reached, the phenomenon that the system is rushed and distorted due to excessive bonding is prevented, five relaxations exist in each truncation distance, and the configuration after each bonding is completed is optimized;
(5) calculation of all-atom structure-activity relationship of polyurethane polymer
Outputting polyurethane random cross-linking models with different cross-linking degrees, firstly carrying out 5-cycle high-temperature annealing on the models, wherein the low temperature is 300K, the high temperature is 600K, obtaining low-energy relaxation configuration, then carrying out analysis of glass transition temperature on each model, in the work, adopting a thermal expansion coefficient method, cooling 30-50K and 12-20 times each time from 650K, carrying out NVT system balance of 1-2ns and NPT ensemble balance of 1-2ns at each temperature, taking the last 0.5-1ns data of the NPT process, taking density average, obtaining the density of the system at the corresponding temperature, establishing a temperature-density relation diagram, obtaining the intersection point of two straight lines by fitting the two straight lines with different slopes, obtaining the glass transition temperature, and carrying out modeling analysis on the mechanical properties of the material, in the work, the models with different crosslinking degrees are subjected to uniaxial stretching, the slope of an elastic area, namely the Young modulus, is respectively counted, and the maximum tensile strength is analyzed to obtain an evolution curve of the material performance in the whole crosslinking process.
2. The established all-atom stochastic cross-linking model of claim 1, wherein the simulated force field selects COMPASSII in Materials students for establishing the stochastic bonding model, and the subsequent dynamics simulation adopts OPLS-AA force field to judge the equilibrium state of the model through the density of the system.
3. The full-atom stochastic cross-linking model created according to claim 1, wherein the four-component full-atom model prevents the occurrence of reactions between atoms by tagging atom recognition bonds.
4. The full-atom random crosslinking model established in claim 1, wherein the polymer chain is a block copolymer with a degree of polymerization of 10 to 42.
5. The full-atom stochastic cross-linking model created according to claim 1, wherein the initial configuration is constructed randomly, with relatively low energy, and is more predictive and instructive of the actual process.
6. The full-atom stochastic cross-linking model of claim 1, wherein the kinetic simulation is a performance evolution of the entire cross-linking process with a certain regularity.
7. The full-atom stochastic cross-linking model created according to claim 1, wherein the cross-linking process is determined by reactive atom distance, and wherein the closer the distance, the more preferential reaction, the greater the probability of collision is simulated.
8. The full-atomic random cross-linking model established according to claim 1, wherein the Perl script can be extended to the reaction types of other groups to establish a corresponding random linking model.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114664390A (en) * | 2022-05-23 | 2022-06-24 | 苏州创腾软件有限公司 | Method and system for generating cross-linked polymer space network structure in simulation mode |
| CN115831259A (en) * | 2022-12-12 | 2023-03-21 | 华东理工大学 | Performance prediction method of polycyanate ester and application thereof |
| CN116206695A (en) * | 2023-05-09 | 2023-06-02 | 苏州创腾软件有限公司 | Cross-linking system molecular model construction method and device based on simulated annealing method |
| CN117229471A (en) * | 2023-11-15 | 2023-12-15 | 长春设备工艺研究所 | Modification method of polyurethane elastomer and 3D printing temperature parameter optimization method thereof |
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- 2021-12-17 CN CN202111549389.1A patent/CN113990402A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114664390A (en) * | 2022-05-23 | 2022-06-24 | 苏州创腾软件有限公司 | Method and system for generating cross-linked polymer space network structure in simulation mode |
| CN115831259A (en) * | 2022-12-12 | 2023-03-21 | 华东理工大学 | Performance prediction method of polycyanate ester and application thereof |
| CN115831259B (en) * | 2022-12-12 | 2023-09-05 | 华东理工大学 | Performance prediction method of polycyanate and application thereof |
| CN116206695A (en) * | 2023-05-09 | 2023-06-02 | 苏州创腾软件有限公司 | Cross-linking system molecular model construction method and device based on simulated annealing method |
| CN117229471A (en) * | 2023-11-15 | 2023-12-15 | 长春设备工艺研究所 | Modification method of polyurethane elastomer and 3D printing temperature parameter optimization method thereof |
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