Methods for analyzing interactions between polymer materials

Abstract

To provide a method capable of accurately calculating interaction energy between a polymer and an organic molecule.SOLUTION: A method is for analyzing the interaction between a polymer and an organic molecule. In the method, a computer executes: a step S6 for calculating structural relaxation on the basis of molecular dynamics calculation for a mixed model including a polymer model and an organic molecule model; a step S7 for extracting a local model including one organic molecule model and a plurality of polymer models arranged around the organic molecule model from the mixed model after structural relaxation; and a step S8 for calculating interaction energy between the polymer model and the organic molecule model on the basis of a fragment molecular orbital method for the local model.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for analyzing interactions in polymeric materials. [Background technology]

[0002] The following Patent Document 1 describes a method for determining the interaction potential of a polymeric material, in which the interaction energy at the interface between a filler and a molecular chain is calculated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-042434 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the physical properties of polymeric materials such as rubber, additives made of organic molecules are mixed into the materials. The physical properties of such mixed materials are considered to be influenced by the interaction energy between the polymer and the organic molecules. Therefore, the development of mixed polymeric materials requires accurate calculation of the interaction energy.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a method capable of calculating the interaction energy between a polymer and an organic molecule with high accuracy. [Means for solving the problem]

[0006] The present invention is a method for analyzing an interaction between a polymer and an organic molecule, comprising the steps of: inputting a plurality of polymer models obtained by modeling the polymer into a computer; and inputting at least one organic molecular model obtained by modeling the organic molecule into the computer, wherein the computer executes the steps of: calculating structural relaxation based on a molecular dynamics calculation for a mixed system model including the polymer models and the organic molecular model; extracting a local model including one organic molecular model and a plurality of polymer models arranged around the organic molecular model from the mixed system model after the structural relaxation; and calculating an interaction energy between the polymer model and the organic molecular model based on a fragment molecular orbital method for the local model.

[0007] In the method for analyzing interactions of polymer materials according to the present invention, the step of extracting the local model may include a step of defining a region separated by a predetermined distance from the organic molecular model, and a step of extracting the local model so that the polymer model located outside the region is excluded.

[0008] In the method for analyzing interactions in polymer materials according to the present invention, the distance may be a distance at which a magnitude of interaction between the polymer model and the organic molecule model becomes zero.

[0009] In the method for analyzing interactions of polymer materials according to the present invention, the process of extracting the local model may include a process of including in the local model a cut model obtained by cutting a portion of the polymer model spanning a boundary of the region that is located inside the region.

[0010] In the method for analyzing interactions of polymer materials according to the present invention, the polymer model may be an all-atom model, and the process of extracting the local model may include a process of combining a hydrogen atom model, which models hydrogen atoms, with the cut model to obtain a stable structure of the cut model.

[0011] In the method for analyzing interactions of polymer materials according to the present invention, the polymer model is an all-atom model defined by connecting multiple monomer models that model monomers of the polymer, and the process of extracting the local model may include a process of including the monomer model in the cut model when the monomer model straddles the boundary. Effect of the Invention

[0012] The method for analyzing interactions in polymer materials of the present invention employs the above steps, making it possible to accurately calculate the interaction energy between a polymer and an organic molecule. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an example of a computer for executing a method for analyzing interactions of polymeric materials. [Diagram 2] 1 is a structural formula showing an example of a polymer. [Diagram 3] 1 is a flowchart showing an example of a processing procedure of a method for analyzing interactions of polymer materials. [Figure 4] FIG. 1 is a conceptual diagram showing an example of a polymer model. [Diagram 5] FIG. 1 is a conceptual diagram showing an example of an organic molecular model. [Figure 6] FIG. 1 is a conceptual diagram showing an example of a cell in which a polymer model and an organic molecule model are arranged. [Figure 7] FIG. 2 is a conceptual diagram illustrating an example of a force field. [Figure 8] FIG. 1 is a conceptual diagram showing an example of a mixed system model after structural relaxation. [Figure 9] 13 is a flowchart showing an example of a processing procedure of an extraction step. [Figure 10] FIG. 1 is a conceptual diagram showing an example of a region defined in a mixed system model. [Figure 11] FIG. 1 is a conceptual diagram illustrating an example of a local model. [Figure 12] 13A and 13B are conceptual diagrams illustrating an example of a cut model. [Figure 13] 13 is a flowchart showing an example of a processing procedure of an extraction step in the second embodiment. [Figure 14] FIG. 2A is a conceptual diagram showing an example of a cut model before it is stabilized, and FIG. 2B is a conceptual diagram showing an example of a stable structure of the cut model. [Figure 15] 13 is a flowchart showing an example of a processing procedure of an extraction step in the third embodiment. [Figure 16] FIG. 1(a) is a conceptual diagram showing an example of a polymer model before cleavage, and FIG. 1(b) is a conceptual diagram showing an example of a cleavage model including a monomer model. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the drawings are intended to enhance understanding of the contents of the invention, and therefore some of the drawings may be exaggerated, and the scales of the drawings may not be strictly consistent.

[0015] The polymer material interaction analysis method of the present embodiment (hereinafter, simply referred to as the "analysis method") is a method for analyzing interactions between polymers and organic molecules. A computer is used in the analysis method of the present embodiment.

[0016] [computer] 1 is a perspective view showing an example of a computer 1 for executing a method for analyzing interactions of polymeric materials. The computer 1 includes a main body 1a, a keyboard 1b, a mouse 1c, and a display device 1d. The main body 1a is provided with, for example, a central processing unit (CPU), a ROM, a working memory, a storage device such as a magnetic disk, and disk drive devices 1a1 and 1a2. The storage device stores software for executing the analysis method and the like in advance.

[0017] [Polymer materials] The polymer material includes, for example, rubber, resin, elastomer, etc. The polymer and organic molecules constituting the polymer material are not particularly limited as long as they are the objects of analysis of the interaction.

[0018] [Polymer] 2 is a structural formula showing an example of the polymer 2. In this embodiment, the polymer 2 is exemplified as styrene-butadiene rubber, but may be other polymers (e.g., isoprene rubber, etc.). In this embodiment, the polymer (molecular chain) 2 is formed by linking monomers (in this example, monomers of styrene-butadiene rubber) 3 with a degree of polymerization n.

[0019] [Organic molecules] The organic molecule of this embodiment is configured as an additive for improving the physical properties of the polymer material. Examples of additives (organic molecules) include phenol resin and terpene resin. Such organic molecules can form a new network structure in addition to the network structure of the polymer 2 (shown in FIG. 2) in the polymer material, and therefore can improve the physical properties of the polymer material. As the organic molecule of this embodiment, a phenol resin is adopted.

[0020] [Method of analyzing interactions between polymer materials] Next, an example of a processing procedure of a method for analyzing interactions of polymer materials will be described with reference to a flowchart shown in FIG.

[0021] [Polymer model input process] In the analysis method of this embodiment, first, a plurality of polymer models obtained by modeling a polymer 2 are input to a computer 1 (step S1). FIG.

[0022] The polymer model 5 of this embodiment is configured as an all-atom model. The polymer model 5 may be configured as, for example, a united atom model (not shown). In this embodiment, the polymer model 5 is defined by linking (linking via bonds 8) a plurality of monomer models 6 modeled on monomers 3 (shown in FIG. 2) of the polymer 2.

[0023] The monomer model 6 of this embodiment includes an atomic model 7 modeled after the atoms constituting the polymer 2 shown in FIG. 2, and a bond (bonding chain model) 8 connecting the atomic models 7, 7 together.

[0024] The atomic model 7 is treated as a mass point in an equation of motion in a simulation based on molecular dynamics calculation described below. For example, parameters such as mass, diameter, charge, and initial coordinates are defined for the atomic model 7. The atomic model 7 of this embodiment includes a carbon atom model 7C that models a carbon atom of the polymer 2 (shown in FIG. 2 ) and a hydrogen atom model 7H that models a hydrogen atom of the polymer 2.

[0025] The bond 8 is for binding adjacent atomic models 7, 7. The bond 8 in this embodiment includes a main chain 8A connecting the carbon atom models 7C, 7C, and a side chain 8B connecting the carbon atom model 7C and the hydrogen atom model 7H.

[0026] In the monomer model 6, the bond length between each of the atomic models 7, 7 and the bond angle between three adjacent atomic models 7 connected via a bond 8 are defined. Furthermore, in the monomer model 6, the dihedral angle between three adjacent atomic models 7 in four atomic models 7 connected via a bond 8 is defined. This defines the three-dimensional structure of the polymer model 5. In such a monomer model 6, the bond length, bond angle, and dihedral angle change when the monomer model 6 is subjected to an external or internal force according to convention. This changes the three-dimensional structure of the monomer model 6.

[0027] The bond length, bond angle, and dihedral angle can be appropriately defined. The potential constants for defining the bond length, bond angle, and dihedral angle in this embodiment are defined based on the COMPASS II force field described in the paper (Huai Sun et al., "COMPASS II: extended coverage for polymer and drug-like molecule databases", J. Mol. Model. vol. 22, no. 2, article 47, 2016, pp. 1-10).

[0028] In step S1 of the present embodiment, a plurality of the above-mentioned monomer models 6 are linked together to define one polymer model 5. The number of the monomer models 6 included in one polymer model 5 can be appropriately set based on, for example, the degree of polymerization n of the polymer 2 shown in FIG.

[0029] In step S1, a plurality of polymer models 5 are defined. The number of monomer models 6 in each polymer model 5 may be the same or different. For example, simulation software (Materials Studio ("Materials Studio" is a registered trademark)) manufactured by Dassault Systemes may be used to create the polymer models 5. The plurality of polymer models 5 are stored in the computer 1.

[0030] [Organic molecular model input process] Next, in the analysis method of this embodiment, at least one organic molecule model obtained by modeling an organic molecule is input to the computer 1 (step S2). In this embodiment, one organic molecule model 10 is input, but multiple organic molecule models 10 may be input. Fig. 5 is a conceptual diagram showing an example of the organic molecule model 10.

[0031] The organic molecular model 10 of this embodiment is configured as an all-atom model. The organic molecular model 10 may be configured as, for example, a united atom model (not shown). The organic molecular model 10 of this embodiment includes an atomic model 11 that models atoms constituting an organic molecule (not shown), and a bond (bonding chain model) 12 that bonds the atomic models 11, 11 together.

[0032] The atomic model 11 and the bond 12 are defined in the same manner as the atomic model 7 and the bond 8 of the polymer model 5 (monomer model 6) shown in Fig. 4. The atomic model 11 includes a carbon atom model 11C and a hydrogen atom model 11H. The bond 8 in this embodiment includes a main chain 12A connecting the carbon atom models 11C, 11C, and a side chain 12B connecting the carbon atom model 11C and the hydrogen atom model 11H.

[0033] The bond lengths, bond angles, and dihedral angles of the organic molecule model 10 are defined based on the above-mentioned paper. The above-mentioned simulation software can be used to create the organic molecule model 10. The organic molecule model 10 is stored in the computer 1.

[0034] [Cell input process] Next, in the analysis method of this embodiment, a cell, which is a virtual space corresponding to a part of a polymer material (not shown), is input to the computer 1 (step S3). Fig. 6 is a conceptual diagram showing an example of a cell 15 in which a polymer model 5 and an organic molecule model 10 are arranged. In Fig. 6, only a part of the polymer model 5 is shown.

[0035] The cell 15 of this embodiment has at least a pair of faces 16, 16 facing each other (in this embodiment, three pairs of faces 16, 16 facing each other). The cell 15 of this embodiment is defined as a rectangular parallelepiped or a cube (in this embodiment, a cube). A periodic boundary condition is defined for each face 16, 16. The length L1 of each side of the cell 15 can be appropriately set based on, for example, the description of a patent document (JP Patent Publication No. 2019-032278). The cell 15 is stored in the computer 1.

[0036] [Placement process] Next, in the analysis method of this embodiment, a plurality of polymer models 5 and at least one organic molecule model 10 are placed inside the cell 15 (step S4). The number of polymer models 5 can be appropriately set based on, for example, the computational power of the computer 1, the size of the cell 15, and the size (degree of polymerization) of the polymer model 5. On the other hand, the number of organic molecule models 10 in this embodiment is one.

[0037] In step S4 of this embodiment, a plurality of polymer models 5 and at least one (one in this example) organic molecule model 10 are randomly arranged by the computer 1. The procedure for randomly arranging these is not particularly limited. In this embodiment, for example, the polymer models 5 and the organic molecule model 10 are randomly arranged based on the modified Markov method. For example, the above-mentioned simulation software or the like can be used for these arrangements (initial arrangements).

[0038] In step S4, the polymer model 5 and the organic molecule model 10 are placed inside the cell 15 to define a mixed system model 18 including the polymer model 5 and the organic molecule model 10. The mixed system model 18 is stored in the computer 1.

[0039] [Force field definition process] Next, in the simulation method of this embodiment, a force field (interaction) F is defined for the polymer model 5 and the organic molecule model 10 included in the mixed system model 18 (step S5). The force field F of this embodiment is defined by the computer 1. Fig. 7 is a conceptual diagram for explaining an example of the force field F. In Fig. 7, only a part of the force field F is representatively shown.

[0040] The force field F of this embodiment includes a first force field Fa, a second force field Fb, and a third force field Fc (not shown). The first force field Fa is defined between the atomic models 7, 7 of the adjacent polymer models 5, 5 (a combination of all the atomic models 7, 7). The second force field Fb is defined between the atomic model 7 of the polymer model 5 and the atomic model 11 of the organic molecular model 10 (a combination of all the atomic models 7 and all the atomic models 11). The third force field Fc is defined between the atomic models 11, 11 of the adjacent organic molecular models 10, 10 (a combination of all the atomic models 11, 11).

[0041] These force fields F (first force field Fa to third force field Fc) can be defined as appropriate. In this embodiment, the first force field Fa to third force field Fc are defined based on the above-mentioned COMPASS II force field. For example, the above-mentioned simulation software or the like can be used to define the force field F. The force field F (first force field Fa to third force field Fc) is stored in the computer 1.

[0042] [Structural relaxation calculation process] Next, in the analysis method of this embodiment, the computer 1 calculates structural relaxation based on molecular dynamics (MD) calculations for the mixed system model 18 (shown in FIG. 6) including the polymer model 5 and the organic molecular model 10 (step S6). In step S6, for example, Newton's equation of motion is applied to the cell 15 (mixed system model 18) shown in FIG. 6 for a predetermined time, assuming that the polymer model 5 and the organic molecular model 10 follow classical mechanics. Then, in step S6, the motion of the polymer model 5 and the organic molecular model 10 progresses at a predetermined time interval (simulation unit time (micro time)) Δt.

[0043] In the calculation of the structural relaxation of this embodiment, the pressure and temperature are kept constant, or the volume and temperature are kept constant, in the cell 15 (mixed system model 18). As a result, in step S6, the initial positions of the polymer model 5 and the organic molecule model 10 can be accurately relaxed by approximating the molecular motion of an actual polymer material.

[0044] In step S6, structural relaxation is calculated until the initial configurations of the polymer model 5 and the organic molecule model 10 are sufficiently relaxed. As a result, in step S6, a mixed system model 18 in which the polymer model 5 and the organic molecule model 10 are in an equilibrium state (artificial effects are removed) can be created. Fig. 8 is a conceptual diagram showing an example of the mixed system model 18 after structural relaxation.

[0045] The relaxation calculation can be performed using, for example, the above-mentioned simulation software. The mixed system model 18 after the structural relaxation is stored in the computer 1.

[0046] Incidentally, the interaction energy between the polymer model 5 and the organic molecule model 10 can be calculated based on the fragment molecular orbital method (FMO method) described later. It is difficult to apply the fragment molecular orbital method to a large-scale calculation targeting the entire mixed system model 18 shown in Fig. 8. For this reason, in the analysis method of this embodiment, the interaction energy between the polymer model 5 and the organic molecule model 10 is calculated for the local model 20 (shown in Fig. 11) extracted from the mixed system model 18.

[0047] [Extraction process (first embodiment)] Next, in the analysis method of this embodiment, the computer 1 extracts a local model 20 from the mixed system model 18 after the structural relaxation (extraction step S7). In the extraction step S7 of this embodiment, a local model 20 (shown in FIG. 11) including one organic molecular model 10 and a plurality of polymer models 5 arranged around the organic molecular model 10 is extracted from the mixed system model 18 after the structural relaxation (shown in FIG. 8). This makes it possible to extract the organic molecular model 10 and a plurality of polymer models 5 interacting with the organic molecular model 10. FIG. 9 is a flowchart showing an example of the processing procedure of the extraction step S7.

[0048] [Extraction process (area definition process)] In the extraction step S7 of this embodiment, first, a region 21 for extracting a local model 20 is defined (step S71). Fig. 10 is a conceptual diagram showing an example of the region 21 defined in the mixed model 18. In Fig. 10, the mixed model 18 after the structural relaxation shown in Fig. 8 is shown in a simplified form.

[0049] In step S71 of this embodiment, a region 21 is defined that is separated from the organic molecular model 10 by a predetermined distance L2. When a plurality of organic molecular models 10 are included in the mixed system model 18, first, an organic molecular model 10 to be analyzed is selected from them. Then, the region 21 is defined based on the selected organic molecular model 10.

[0050] The region 21 in this embodiment is for virtually dividing a part of the cell 15 (mixed system model 18). The region 21 in this embodiment is specified by the coordinate values ​​of the cell 15, etc. Moreover, in the region 21, conditions (e.g., force field, etc.) that affect the polymer model 5 and the organic molecule model 10 are not defined. Therefore, the relaxed structure of the mixed system model 18 is maintained.

[0051] The region 21 in this embodiment is defined as a cube, but is not particularly limited to this. The region 21 may be, for example, a rectangular parallelepiped, a sphere, or an ellipsoid (prolate spheroid). In the region 21 in this embodiment, faces 22 are defined that separate the inside and outside of the region 21. Such faces 22 define a boundary 23 of the region 21. Since the region 21 in this embodiment is defined as a cube, three pairs of faces 22, 22 that face each other are defined.

[0052] In this embodiment, each face 22 of the region 21 is defined at a position separated from the central part 25 of the organic molecular model 10 by the above-mentioned distance L2. The central part 25 is not particularly limited as long as the organic molecular model 10 can be defined on the center side of the region 21. The central part 25 in this embodiment is set at the center of gravity of the organic molecular model 10.

[0053] The distance L2 in this embodiment is defined as the shortest distance from the center 25 of the organic molecular model 10 to each face 22 of the region 21. The distance (shortest distance) L2 can be set appropriately. The distance L2 in this embodiment is set to a distance at which the magnitude of the interaction (in this example, the second force field Fb (shown in FIG. 7)) between the polymer model 5 and the organic molecular model 10 becomes zero. As a result, only a plurality of polymer models 5 that interact with the organic molecular model 10 are arranged inside the region 21.

[0054] The distance at which the magnitude of the interaction becomes zero can be set appropriately. In this embodiment, it is specified as the distance at which the interaction with the atomic model 11 arranged closest to the center 25 among the atomic models 11 constituting the organic molecular model 10 becomes zero. The region 21 is stored in the computer 1.

[0055] [Extraction process (exclusion process)] Next, in the extraction step S7 of this embodiment, the local model 20 is extracted so as to exclude the polymer models 5 arranged outside the region 21 (step S72). In step S72 of this embodiment, the polymer models 5 arranged outside the region 21 without straddling the boundary 23 (face 22) of the region 21 are excluded from the polymer models 5 constituting the local model 20. Furthermore, in step S72 of this embodiment, the polymer models 5 straddling the boundary 23 (face 22) of the region 21 are also excluded.

[0056] As described above, the distance L1 in this embodiment (i.e., the distance from the organic molecular model 10 to the boundary 23 (face 22)) is set to a distance at which the magnitude of the interaction (in this example, the second force field Fb) between the polymer model 5 and the organic molecular model 10 becomes zero. As a result, in step S72, a local model 20 is defined in which polymer models 5 that do not interact with the organic molecular model 10 (i.e., polymer models disposed outside the region 21) are excluded. FIG. 11 is a conceptual diagram showing an example of the local model 20.

[0057] Incidentally, among the polymer model 5 spanning the boundary 23 (face 22) of the region 21, the portion (atomic model 7) disposed inside the region 21 interacts with the organic molecule model 10. For this reason, it is desirable to include such a portion in the local model 20 and calculate the interaction energy between the polymer model 5 and the organic molecule model 10.

[0058] [Extraction process (cutting process)] In the extraction step S7 of the present embodiment, a cut model 26 obtained by cutting a portion of the polymer model 5 that straddles the boundary 23 (face 22) of the region 21 and that is disposed inside the region 21 is included in the local model 20 (step S73). Figures 12(a) and (b) are conceptual diagrams illustrating an example of the cut model 26.

[0059] In step S73 of this embodiment, first, as shown in Fig. 12(a), in the polymer model 5, bonds 8 (indicated by two-dot chain lines) that straddle the boundary 23 (face 22) of the region 21 are deleted. Note that, in the case where an atomic model 7 of the polymer model 5 straddles the boundary 23 (not shown), the bond 8 closest to the boundary 23 is deleted. Then, in step S73, the portion disposed inside the region 21 is defined as a cut model 26, as shown in Fig. 12(b).

[0060] In step S73, when a plurality of bonds 8 straddle the boundary 23 of the region 21 in one polymer model 5, these bonds 8 may be deleted. This allows a plurality of cut models (not shown) to be defined from one polymer model 5.

[0061] Thus, in the extraction step S7 of this embodiment, a local model 20 (shown in FIG. 11 ) including one organic molecule model 10 (not shown) and a polymer model 5 (including a cut model 26 in this example) disposed inside the region 21 is extracted from the mixed system model 18 after structural relaxation. The local model 20 is stored in the computer 1.

[0062] [Interaction energy calculation process] Next, in the analysis method of this embodiment, the computer 1 calculates the interaction energy between the polymer model 5 and the organic molecule model 10 (shown in FIG. 10) based on the fragment molecular orbital method for the local model 20 (step S8).

[0063] The fragment molecular orbital method (FMO method) is a quantum chemical method that can calculate interaction energy by dividing a molecular system into small fragments. Details of the fragment molecular orbital method are described in, for example, the literature (Tatsuya Nakano et al., "Introduction to the Fragment Molecular Orbital Method - Ab Initio Quantum Chemical Calculation of Proteins Using ABNIT-MP", Advance Soft Co., Ltd., July 10, 2004).

[0064] In step S8 of this embodiment, first, the polymer model 5 and the organic molecule model 10 included in the local model 20 are divided into fragments. Next, the interaction energy (e.g., electrostatic, polarization, exchange, and charge transfer energy) between adjacent fragments is calculated (FMO calculation). Then, the sum of the interaction energies acting from the fragments of the polymer model 5 to the fragments of the organic molecule model 10 is calculated. This allows the interaction energy between the polymer and the organic molecule contained in the polymer material to be calculated.

[0065] The local model 20 (shown in FIG. 11) of this embodiment is obtained by extracting the organic molecular model 10 and a plurality of polymer models 5 (including the cut model 26 shown in FIG. 12(b)) that interact with the organic molecular model 10 from the mixed system model 18 shown in FIG. 8. By calculating the interaction energy E based on the fragment molecular orbital method for such a local model 20, the interaction energy between the polymer and the organic molecule contained in the polymer material can be calculated with high accuracy.

[0066] For the calculation of the interaction based on the fragment molecular orbital method, for example, quantum chemical calculation software (for example, GAMESS or ABINIT-MP, etc.), molecular modeling software (for example, Facio, etc.) are used. The interaction energy is stored in the computer 1.

[0067] The interaction energy calculated by the analysis method of this embodiment is useful for designing and manufacturing polymeric materials having desired physical properties.

[0068] [Extraction process (second embodiment)] Incidentally, as shown in Fig. 12(b), when the polymer model 5 is cut inside the monomer model 6 (shown in Fig. 4) in the extraction step S7 (cutting step S73) of the previous embodiment, the cut model 26 may include an atomic model 7 having an unpaired electron. Such a cut model 26 is chemically unstable. Therefore, when the interaction energy between the polymer model 5 and the organic molecule model 10 is calculated based on such a cut model 26, the interaction energy may not be calculated with sufficient accuracy.

[0069] In the extraction step S7 of this embodiment, a stable structure of the cut model 26 is obtained. Fig. 13 is a flowchart showing an example of a processing procedure of the extraction step S7 of the second embodiment. In this embodiment, the same components as those in the previous embodiments are given the same reference numerals, and the description thereof may be omitted.

[0070] [Extraction process (stable structure acquisition process)] In the extraction step S7 of this embodiment, a hydrogen atom model 7H, which is a model of a hydrogen atom, is bonded to the cut model 26 to obtain a stable structure of the cut model 26 (step S74). Fig. 14(a) is a conceptual diagram showing an example of the cut model 26 before it is made into a stable structure. Fig. 14(b) is a conceptual diagram showing an example of the stable structure of the cut model 26.

[0071] In step S74 of this embodiment, based on the valence and hybrid orbitals of the atomic model 7 constituting the cut model 26 (shown in FIG. 14(a)), a hydrogen atom model 7H (shown in FIG. 14(b)) is bonded to the terminal atomic model (atomic model 7 having an unpaired electron) of the cut model 26. As a result, as shown in FIG. 14(b), a stable structure of the cut model 26 in which the radicals are neutralized and which is chemically stable is obtained.

[0072] Then, in step S8 of this embodiment, the interaction energy between the polymer model 5 and the organic molecule model 10 is calculated for the local model 20 (shown in FIG. 11) including the stable structure of the cut model 26. As a result, the analysis method of this embodiment can calculate the interaction energy with higher accuracy.

[0073] [Extraction process (third embodiment)] In the extraction step S7 of the previous embodiment (second embodiment), a stable structure of the cut model 26 is acquired in order to calculate the interaction energy more accurately, but the present invention is not limited to this. Fig. 15 is a flowchart showing an example of the processing procedure of the extraction step S7 of the third embodiment. In this embodiment, the same components as those in the previous embodiments are denoted by the same reference numerals, and the description thereof may be omitted.

[0074] [Extraction process (second cutting process)] In the extraction step S7 of this embodiment, when the monomer model 6 straddles the boundary 23, the monomer model 6 is included in the cut model 26 (step S75). Fig. 16(a) is a conceptual diagram showing an example of the polymer model 5 before cutting. Fig. 16(b) is a conceptual diagram showing an example of the cut model 26 in which the monomer model 6 is included.

[0075] In step S75 of this embodiment, first, among all the cut models 26 (shown in FIG. 12(b)), the cut models 26 in which the monomer models 6 (shown by two-dot chain lines) straddle the boundary 23 in the polymer model 5 before cutting shown in FIG. 16(a) are identified. Then, as shown in FIG. 16(b), for the identified cut models 26, the monomer models 6 straddling the boundary 23 are included in the cut models 26.

[0076] The cleavage model 26 of this embodiment does not include the atomic model 7 having an unpaired electron because it is not cleaved by the monomer model 6. Therefore, a stable structure of the cleavage model 26 that is chemically stable can be obtained.

[0077] Then, in step S8 of the present embodiment, the interaction energy between the polymer model 5 and the organic molecule model 10 is calculated for the local model 20 including the stable structure of the cut model 26. As a result, the analysis method of the present embodiment can calculate the interaction energy with higher accuracy.

[0078] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and carried out in various forms. EXAMPLES

[0079] Interactions between polymers and organic molecules were analyzed (Examples 1 to 3) based on the processing procedure shown in Fig. 3. In Examples 1 to 3, local models were extracted based on the processing procedure shown in Fig. 9 so that polymer models located outside the region were excluded.

[0080] In Example 1, a cut model obtained by cutting a part of a polymer model that straddles the boundary between regions and that is disposed inside the region was included in the local model. In Example 2, a hydrogen atom model was bonded to the cut model of Example 1 based on the processing procedure shown in Fig. 13 to obtain a stable structure of the cut model. In Example 3, a monomer model that straddles the boundary between regions was included in the cut model of Example 1 based on the processing procedure shown in Fig. 15.

[0081] Then, the interaction energy (dispersion energy) between the polymer model and the organic molecule model was calculated based on the fragment molecular orbital method for the local models of Examples 1 to 3. The common specifications are as follows. Polymer material: Polymer: styrene butadiene rubber Organic molecules: phenolic resin Topical Model: Shape: Cube Side length: 4 nm

[0082] The interaction energies of Examples 1 to 3 were approximate to the actual interaction energies between polymers and organic molecules. Therefore, in Examples 1 to 3, the interaction energies between polymers and organic molecules could be calculated with high accuracy. Furthermore, in Examples 2 and 3, the stable structure of the cleavage model was used, so the interaction energies could be calculated with high accuracy compared to Example 1. [Explanation of symbols]

[0083] S6 Calculation of structural relaxation for mixed system models S7 Extracting a local model from the mixed system model S8 Calculate interaction energy for local model

Claims

1. 1. A method for analyzing interactions between a polymer and an organic molecule, comprising: inputting a plurality of polymer models obtained by modeling the polymer into a computer; and inputting at least one organic molecule model obtained by modeling the organic molecule into the computer; The computer, A step of calculating structural relaxation based on molecular dynamics calculation for a mixed system model including the polymer model and the organic molecular model; extracting a local model including one organic molecule model and a plurality of polymer models arranged around the organic molecule model from the mixed system model after the structural relaxation; A step of calculating an interaction energy between the polymer model and the organic molecular model based on a fragment molecular orbital method is carried out for the local model; The step of extracting the local model includes a step of defining a region separated by a predetermined distance from the organic molecular model; extracting the local model such that the polymer model located outside the region is excluded; Methods for analyzing interactions in polymeric materials.

2. A method for analyzing interactions of polymer materials as described in claim 1, wherein the distance is a distance at which the magnitude of interaction between the polymer model and the organic molecular model is zero.

3. A method for analyzing interactions of polymer materials as described in claim 1 or 2, wherein the process of extracting the local model includes a process of including in the local model a cut model obtained by cutting a portion of the polymer model that spans the boundary of the region and that is located inside the region.

4. The polymer model is an all-atom model, The method for analyzing interactions in polymer materials according to claim 3 , wherein the step of extracting the local model includes a step of combining a hydrogen atom model, which models hydrogen atoms, with the cut model to obtain a stable structure of the cut model.

5. The polymer model is an all-atom model defined by connecting a plurality of monomer models each of which is a model of a monomer of the polymer, 5. The method for analyzing interactions of polymer materials according to claim 3, wherein the step of extracting the local model includes a step of including the monomer model in the cut model when the monomer model straddles the boundary.

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