JP5059407B2 - Gel, production method thereof, water-absorbent resin, lubricant, and cell culture substrate - Google Patents

Description

  The present invention relates to a gel having a semi-interpenetrating network structure in which another polymer is entangled with a network structure composed of a crosslinked polymer, a method for producing the gel, a water absorbent resin, a lubricant, and a cell culture using the gel The present invention relates to a substrate.

  Gel, which is a two-phase colloidal system of liquid and solid, has excellent properties such as high flexibility and high water retention, and industrial applications have been studied in various ways using these properties. Yes. For example, Patent Document 1 discloses a low friction material in which a linear polymer is mixed or graft polymerized with respect to a gel.

  However, since the conventional gel has a remarkably low mechanical strength, the strength and durability are easily insufficient, and the use application is remarkably limited.

Therefore, various techniques for increasing the mechanical strength of the gel have been studied and developed (for example, Patent Documents 2 to 7 and Non-Patent Documents 1 to 4). Among these, for example, Patent Document 2 discloses that a second polymer is formed by polymerizing and crosslinking a monomer in a network structure composed of a first crosslinked polymer, and the first crosslinked polymer and the second polymer are Techniques for producing hydrogels having interpenetrating or semi-interpenetrating networks intertwined with each other are described. The “interpenetrating network structure” refers to a network structure in which another network structure is entangled with the base network structure, and the “semi-interpenetrating network structure” refers to a linear polymer in the base network structure. Refers to a mesh structure with tangled.
Japanese Patent Laid-Open No. 2002-212453 International Publication No. 03/093337 Pamphlet JP 2004-91724 A JP 2002-053762 A JP 2002-053629 A Japanese Patent Laid-Open No. 57-130543 JP 58-36630 A J. et al. P. Gong, Yoshinori Katsurayama, Takayuki Kuroka, Yoshihita Osada, “Double-Network Hydrogel with Extremely High Mechanical 3D 115-M11”. H. Haraguchi, T .; Takeshita, “Nanocomposite Hydrogels: A Uniform Organic-Inorganic Network, Structured with Extra 1, 1, 1, 1, 120 m, and Swelling / De-well. Y. Okumura, KohzoIto, “The Polyrotaxane Gel: A Topological Gel by FIGure-of-Eight Cross-links”, 13, 485-487 (2001). Long Zhao, Hiroshi Mitomo, Naotsugu Nagasawa, Fumio Yoshii, Tamikazu Kume, "Radiation synthesis and characteristic of the hydrogels based on carboxymethylated chitin derivatives", Carbohydrate Polymers, 51,169-175 (2003)

  However, the present inventors have developed the technique disclosed in Patent Document 2 and continued earnest research to further improve the strength of the gel, and as a result, disclosed in Patent Documents 2 to 7 and Non-Patent Documents 1 to 4. We obtained knowledge that was different from the development concept of the technology. That is, for example, in the technique disclosed in Patent Document 2 or Non-Patent Document 1, the most important factors for improving the strength of the gel are the molar ratio of the second monomer to the first crosslinked polymer and the degree of crosslinking of the second polymer. In particular, in the technique disclosed in Patent Document 2, the second polymer has a very slight cross-linked structure. Specifically, the degree of cross-linking of the second polymer is 0.001 mol% or more. Although there is an optimum condition for increasing the strength of the gel, there is a limit.

  An object of the present invention is to provide a technique capable of dramatically improving the strength of a gel without impairing excellent properties such as high flexibility and high water retention property of the gel, and further utilizing the gel. To provide various uses.

The gel according to the present invention has a semi-interpenetrating network structure in which a non-crosslinked polymer invades and physically entangles into a network structure composed of a crosslinked polymer, and the degree of swelling is 5 or more during equilibrium swelling with a good solvent. and the weight content of the good solvent is at least 80%, and employs a configuration fracture energy is 700 J / ^{m 2} or more 2000J / ^{m 2} or less.

  That is, the second polymer that is not a crosslinked polymer is linear and has a high molecular weight without having any crosslinked structure. And it discovered that the intensity | strength of a gel improved specifically only when the 2nd polymer took a non-crosslinked polymer rather than taking a crosslinked structure.

  According to the present invention, a non-crosslinked polymer having high flexibility satisfying a predetermined condition invades and physically entangles into a rigid network made of a crosslinked polymer and having scattered cavities, which is comparable to a living tissue. A gel with mechanical strength and durability higher than that can be provided.

The figure which shows typically the semi-interpenetrating network structure which the gel which concerns on this invention has The figure which shows typically the cavity part of the network structure which consists of a crosslinked polymer in a semi-interpenetrating network structure At the crack tip of the gel according to the present invention, the semi-interpenetrating network structure is deformed and a non-crosslinked polymer forms a transient network by physical entanglement regardless of chemical crosslinking in a certain speed region. A diagram schematically showing the state of resistance to crack progression The figure which shows typically the velocity area of the external force where the transient network is formed in the non-crosslinked polymer in the concentrated solution state The figure which shows typically the correlation of the fracture energy of the gel which concerns on this invention, and the weight average molecular weight _Mw of a non-crosslinked polymer.

  The gist of the present invention is to form a gel having a semi-interpenetrating network structure in which a non-crosslinked polymer in the form of a random coil having a size satisfying the cavity is entangled with a network structure in which cavities made of a crosslinked polymer are scattered. It is. The size of the random coil depends on the molecular weight of the non-crosslinked polymer.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

  When evaluating the gel according to the present invention, “compressive strength” is used as an index indicating its mechanical strength, and “breaking energy” is used as an index indicating its fracture mechanical strength. “Compressive strength” is the value obtained by dividing the stress required for the fracture of the gel by the initial area, and “Fracture energy” is the work used for steady fracture progression of the gel divided by the fracture area. The value, i.e., the energy required to form a fracture surface. Therefore, as an index indicating the superiority or inferiority of the gel, it is more appropriate to use the fracture energy rather than the compressive strength in view of the gel characteristics that the deformation rate until the fracture is extremely high (Y. Tanaka, K. et al. Fukao, Y. Miyamoto, “Fracture energy of gels”, The European Physical Journal E, 3, 395-401 (2000)).

  FIG. 1 schematically shows a semi-interpenetrating network structure of the gel according to the present invention. The cross-linked polymer that forms the basic skeleton of the gel forms a rigid network structure in which cavities, which are extremely sparse parts of the network, are scattered, while the non-cross-linked polymer is concentrated in the cavities and is flexible. It is physically entangled with the network structure of the cross-linked polymer at its end while maintaining the properties.

  Here, “physically entangled” means a positional relationship in which two or more discontinuous linear objects are not in a coupled state by a covalent bond or the like, but their spatial positions can be constrained. If there is at least one portion taken and both or one of them is not physically destroyed or deformed, it means an unwound state. However, in the case of things that are microscopic and invisible in the first place, use an electron micrograph, etc. There should be at least one. However, the physical entanglement between the polymers present in the solution cannot be confirmed with an optical microscope or the like, but is also physically entangled in such a microscopic part that it cannot be confirmed with an electron micrograph. Therefore, its existence can only be suggested by a dynamic light scattering device or the like. In the following, a structure in which a non-crosslinked polymer is entangled with the void-containing crosslinked polymer may be referred to as a double network (DN).

The network structure in which cavities made of the crosslinked polymer are scattered is formed by radical copolymerization of a vinyl monomer and a divinyl monomer, for example. Since vinyl monomers and divinyl monomers have different reactivity in radical polymerization, when they are copolymerized, a microgel is formed at the initial stage of the reaction, and when it grows, the microgel cross-links to form a non-uniform network structure. (Erik Geissler, “Dynamic light scattering from polymer polymer gels”, Chapter 11 ^th , 471-511, Edited by WYN Brown, “Dynamic Light Scattered. The network structure of the cross-linked polymer formed in this way is spatially non-uniform due to the increase in the density of the network as the degree of swelling increases as the equilibrium swelling is reached by absorbing a large amount of solvent. There is very high (Hidemitsu Furukawa, Kazuyuki Horie, "Swelling-induced modulation of static and dynamic flnuctuations in polyacrylamide gels observed by scanning microscopic light scattering", Physical Review E, 68,031406 (2003), Mitsuhiro Shibayama, "Spatial inhomogeneity and dynamic luctuations of polymer gels ", Macromol.Chem.Phys., see 199,1-30 (1998)). In addition, when comparing the network structure composed of the electrolyte cross-linked polymer and the network structure composed of the non-electrolyte cross-linked polymer, if the degree of cross-linking is the same, the degree of equilibrium swelling and the non-uniformity of the net are more Is significantly larger than Therefore, it is considered that an extremely sparse part of the network, that is, a cavity part is surely scattered in the network structure made of the crosslinked polymer of the electrolyte. Note that the measurement data obtained by the dynamic light scattering method supports this idea.

  On the other hand, the “non-crosslinked polymer” in the present invention refers to a polymer having a degree of crosslinking of less than 0.001 mol%, preferably a polymer that is not crosslinked at all, and the degree of crosslinking is added when polymerizing the non-crosslinked polymer. Calculated from the amount of the crosslinking agent. A polymer having a low degree of crosslinking is soluble in a solvent in a sol state that does not form a gel, has high flexibility, and easily forms a random coil.

FIG. 2 schematically shows a cavity of a network structure made of a crosslinked polymer in a semi-interpenetrating network structure. The non-crosslinked polymer is considered to be a random coil because it can move and deform freely in this cavity, and statistically its diameter dη is the intrinsic viscosity [η] of the polymer solution and the weight average molecular weight M _w. (M.-M. Kulikke, R. Kniewske, J. Klein, “Preparation, Characterization, Solution Properties and Rheologic Behind of Poly68”, Prod. )reference).

When the diameter of the random coil made of the non-crosslinked polymer calculated from this formula is about 10 times or more the average interval of the network made of the crosslinked polymer, the mechanical strength and the fracture energy of the gel having the semi-interpenetrating network structure are specifically determined. Start to improve. That is, the molecular weight of the non-crosslinked polymer in this case is 10 ⁶ or more in terms of weight average molecular weight, and the polymer is present at such a concentration that sufficient physical entanglement can occur. The mechanism by which such a phenomenon occurs is that the random coil made of non-crosslinked polymer becomes larger as the degree of polymerization increases and fills the cavities scattered in the network structure made of cross-linked polymer. When the diameter of the random coil is larger than the diameter of the cavity, the cross-linked polymer and the non-cross-linked polymer become physically entangled, and by forming pseudo cross-linking points due to the entanglement, This is presumed to be because the polymer behaves like a continuous network. On the other hand, if the diameter of the random coil made of the non-crosslinked polymer is smaller than the diameter of the cavity, a pseudo cross-linking point is not formed between the crosslinked polymer and the non-crosslinked polymer. Since the crosslinked polymer is merely swollen by the solvent whose viscosity is increased by the presence of the non-crosslinked polymer, the mechanical strength and fracture energy of the gel are not significantly improved.

  In addition, the mechanism by which the mechanical strength and fracture energy of the gel are specifically improved when the diameter of the random coil made of the non-crosslinked polymer in the semi-interpenetrating network is larger than the diameter of the cavity is explained as follows. You can also That is, the semi-interpenetrating network structure is a higher-order structure having a spatially hard part (a dense part of the crosslinked polymer) and a soft part (an extremely sparse part of the crosslinked polymer, that is, a non-crosslinked polymer in the cavity). However, even if a crack is generated due to the stress concentration point in this hard part, when the crack reaches the soft part, the stress is dissipated at the tip, and the curvature of the crack tip becomes very large, and the crack progresses. It is a mechanism that stops. Therefore, in a gel having a semi-interpenetrating network structure, cracks cannot propagate over long distances unless a very large external force exceeding the stress that can be diffused by the non-crosslinked polymer is applied, causing microscopic fracture. But that doesn't lead to macroscopic destruction. That is, in the case of the gel according to the present invention, the critical value leading to macroscopic destruction is remarkably increased, so that the gel is not broken unless a very large external force is applied. If the network structure of the crosslinked polymer is uniform, the critical value that leads to such macroscopic destruction is not significantly improved.

  FIG. 3 shows a state in which the semi-interpenetrating network structure is deformed at the crack tip of the gel according to the present invention, and a state in which a non-crosslinked polymer forms a transient network in a certain speed region and becomes a resistance to crack progress. And are shown schematically. The gel according to the present invention has a speed dependency on the external force, and the optimum external force speed for increasing the strength of the gel is determined between the non-crosslinked polymers in the cavities scattered in the network structure of the crosslinked polymer in the semi-interpenetrating network structure. Is considered to correspond to a velocity region in which a transient network due to entanglement can be formed.

  FIG. 4 schematically shows an external force velocity region in which a transient network is formed in the non-crosslinked polymer in a concentrated solution state. As shown in FIG. 4, when the crack progress rate at the crack tip is faster than the movement speed of the non-crosslinked polymer, as shown in the lower part of FIG. 3, (B) cutting of the non-crosslinked polymer occurs preferentially from the stretched state. Therefore, it is considered that the mechanical strength and fracture energy of the gel are reduced. On the other hand, when the crack progress rate at the crack tip is slower than the movement speed of the non-crosslinked polymer, the slip of the non-crosslinked polymer (A) occurs preferentially from the stretched state as shown in the lower part of FIG. It is thought that the mechanical strength and fracture energy of the gel also decrease. Such a decrease in the mechanical strength and fracture energy of the gel causes the flow of the non-crosslinked polymer when the rate of external force applied is significantly slower than the rate of motion of the non-crosslinked polymer in a physically entangled concentrated solution. On the other hand, if it is significantly faster than that, the non-crosslinked polymer is considered to be caused by the fact that it loses time to move and deform and becomes glassy.

  However, in the speed range during which the non-crosslinked polymer behaves in a semi-interpenetrating network and flows into a glass state, the non-crosslinked polymer in the concentrated solution state forms a transient network due to entanglement and forms a rubber. Since it is considered that similar physical properties are exhibited, the stress generated at the crack tip can be diffused. In other words, the transient network formed by the non-crosslinked polymer in a concentrated solution state does not have a chemical cross-linking point and can slip when excessive stress is applied (stress concentration occurs). Friction converts stress to heat and diffuses it. Therefore, it is preferable that the non-crosslinked polymer moves slowly while maintaining fluidity in a state close to a high concentration solution. Incidentally, the elastic modulus of this transitional network must be sufficiently smaller than the elastic modulus of a rigid network composed of a crosslinked polymer.

  In short, the cavity made up of the network structure of the crosslinked polymer and the physical entanglement of the non-crosslinked polymer can avoid stress concentration on the crack (crack), can dissipate the energy on the explosion, "become.

  Therefore, the mechanical strength and fracture energy of the gel having a semi-interpenetrating network structure vary depending on the relationship between the speed of movement of the non-crosslinked polymer and the speed of the applied external force, and are added at a speed close to that of the non-crosslinked polymer. Maximum for the external force applied. Therefore, if the kinetic speed of the non-crosslinked polymer is changed by adjusting the temperature of the gel or the viscosity or compatibility of the solvent that swells the gel, the speed range of the external force that maximizes the mechanical strength and fracture energy of the gel can be obtained. Can be changed.

FIG. 5 shows the correlation between the fracture energy and the weight average molecular weight _Mw of the non-crosslinked polymer for a gel having a semi-interpenetrating network structure in which the non-crosslinked polymer is entangled with a network structure in which cavities of the crosslinked polymer are scattered. This is shown schematically. FIG. 5 shows an example in which a non-crosslinked polymer made of polyacrylamide (PAAm) is entangled with a crosslinked polymer formed from acrylamidomethylpropanesulfonic acid (AMPS) and a divinyl monomer. Also, in FIG. 5, it is difficult to take out only the non-crosslinked polymer from the semi-interpenetrating network structure and measure its weight average molecular weight M _w , so the polymerization conditions of the non-crosslinked polymer and its weight average molecular weight M _w The correlation was grasped, and the weight average molecular weight _Mw of the non-crosslinked polymer in the semi-interpenetrating network structure was estimated from the correlation.

As shown in FIG. 5, the breaking energy of this gel rises remarkably from around the weight average molecular weight M _w 1 × 10 ⁶ of the non-crosslinked polymer and reaches a peak at around 4 × 10 ⁶ . This is because when a random coil made of a non-crosslinked polymer reaches a weight average molecular weight _{Mw of about} 1 × 10 ⁶ , it begins to fill cavities scattered in the network structure of the crosslinked polymer and reaches a weight average molecular weight of _{Mw of about} 4 × 10 ⁶ Then, it is estimated that the cavity is almost filled with random coils. Therefore, it is considered that there is an optimum range depending on the size of the cavities scattered in the semi-interpenetrating network structure in the size (degree of polymerization) of the non-crosslinked polymer.

  Here, since the non-crosslinked polymer is also a linear polymer having almost no branch, the degree of polymerization, that is, the length of the polymer is approximately linearly proportional to the molecular weight. Thus, the fact that there is an optimal molecular weight for physical entanglement indicates that for a crosslinked polymer having a network structure, there is a length that is well-suited for the non-crosslinked polymer to be physically entangled. As inferred with reference to FIG. 1, it is expected that the non-crosslinked polymer slips out of the network structure of the crosslinked polymer unless the length of the non-crosslinked polymer is sufficiently long. Alternatively, it can be expected that the non-crosslinked polymer itself cannot constitute a sufficiently wound random coil and cannot form a semi-interpenetrating network structure without being caught by the crosslinked polymer. This may be rephrased that pseudo cross-linking points are not formed. Therefore, the semi-penetrating network structure is a structure that occurs only when the random coil diameter of the non-crosslinked polymer is much larger than the average interval of the network of the crosslinked polymer.

In this way, if the gel has a semi-interpenetrating network structure in which a non-crosslinked polymer having a size satisfying the cavity is physically entangled with a rigid network structure composed of a crosslinked polymer, the cavity is scattered. Even when the swelling degree is 5 or more and the weight content of the good solvent is 80% or more at equilibrium swelling, the non-crosslinked polymer can surely form a transient network when an external force is applied. Therefore, it is possible to realize a high durability which could not have been conventionally achieved that the breaking energy 700 J / ^{m 2} or more 2000J / ^{m 2} or less.

  In addition, this gel has a feature that when a nuclear magnetic resonance measurement is performed during equilibrium swelling with a good solvent, a chemical shift that appears due to the presence of an intermolecular interaction is not observed. This observation means that there is no intermolecular interaction stronger than hydrogen bonding between non-crosslinked polymers. In this way, if there is no intermolecular interaction stronger than hydrogen bonding between non-crosslinked polymers, the fluidity and mobility of the non-crosslinked polymer will not be impaired in the cavities scattered in the network structure composed of the crosslinked polymer. The breaking energy of the gel is effectively improved.

As if to support this, the double network gel exhibiting such high fracture energy cannot be explained by the theory proposed for other mechanisms, such as Lake-Thomas theory. If estimated by Lake-Thomas theory, the fracture energy is only around 10 J / m ² , which is two orders of magnitude lower than the experimental value.

  Further, in this gel, the ratio (b / a) of the transient elastic modulus (b) of the non-crosslinked polymer to the elastic modulus (a) of the crosslinked polymer at equilibrium swelling with a good solvent is 1/100 or more and 1/5 or less. It is preferable that Here, a method for calculating the transient elastic modulus (b) of the non-crosslinked polymer will be described. By observing the strain (e) caused by stepwise increasing the stress on the non-crosslinked polymer solution, the creep compliance (J), which is a coefficient of the linear function of strain “e = Jσ” for small stress (σ), is obtained. obtain. When this creep compliance shows a constant value (steady state compliance) in a certain speed region, the reciprocal of this steady state compliance corresponds to the transient elastic modulus (b) of the non-crosslinked polymer.

Thus, during equilibrium swelling with a good solvent, there is no intermolecular interaction stronger than hydrogen bonding between the non-crosslinked polymers, or the ratio of the transient elastic modulus of the non-crosslinked polymer to the elastic modulus of the crosslinked polymer is 1. If the gel has a semi-interpenetrating network structure of / 100 or more and 1/5 or less, even if a crack occurs, the stress generated at the tip of the crack is converted into heat by the formation of a transient network of the non-crosslinked polymer to be effectively spread is, fracture energy is certainly a 700 J / ^{m 2} or more 2000J / ^{m 2} or less.

  Further, this gel preferably has an equilibrium swelling degree of the crosslinked polymer with a good solvent of 5 to 1000, and the weight content of the non-crosslinked polymer is higher than the weight content of the crosslinked polymer. Moreover, it is preferable that the weight content rate of a non-crosslinked polymer is 10 to 40% with respect to the total weight of the crosslinked polymer and good solvent in this gel.

  The crosslinked polymer constituting this gel needs to have a high equilibrium swelling degree and a high rigidity with a large extension of the polymer chain. Specifically, the equilibrium swelling degree with a good solvent is 5 to 1000 (solvent It is preferably crosslinked so that the content rate is 80 to 99.9 w%. The mechanical strength of the crosslinked polymer itself does not need to be so high. The initial elastic modulus of the gel is substantially determined by the initial elastic modulus of the network structure composed of the crosslinked polymer, and the influence of the non-crosslinked polymer on the initial elastic modulus of the gel is extremely small. Therefore, the initial elastic modulus of the gel can be adjusted by adjusting the degree of crosslinking of the crosslinked polymer.

  The crosslinked polymer is preferably a strong electrolyte. The inventors of the present invention produced a gel having a semi-interpenetrating network structure by combining an electrolyte / non-electrolyte crosslinked polymer and an electrolyte / non-electrolyte non-crosslinked polymer. However, the only combination that significantly improved the mechanical strength and the fracture energy was a combination of a strong electrolyte or a weakly crosslinked polymer that was completely dissociated with a non-electrolyte non-crosslinked polymer. Therefore, in the present invention, it is preferable to use a combination of a strong electrolyte or a completely dissociated weakly crosslinked polymer and a non-electrolyte non-crosslinked polymer. Even if the crosslinked polymer is an electrolyte, the degree of shrinkage of the gel is remarkably small even if the crosslinked polymer is entangled with a non-crosslinked polymer even when immersed in a solvent having a high ionic strength.

  In addition, this non-crosslinked polymer may have characteristics such as being non-electrolyte and high in flexibility, and having no or no interaction such as electrostatic interaction and hydrophobic bond with the crosslinked polymer. preferable. Here, the non-crosslinked polymer is in the form of a concentrated solution or sol in the network structure composed of the crosslinked polymer, and itself has fluidity like egg white and cannot maintain the outer shape.

  In addition, the weight content of the non-crosslinked polymer in the gel according to the present invention should be higher than the concentration at which the high molecular weight non-crosslinked polymer can cause sufficient physical entanglement. The range is preferably 5 to 100 mole times. Moreover, in the gel at the time of equilibrium swelling with a good solvent, the concentration of the non-crosslinked polymer is too low or too high, so that the mechanical strength of the gel does not improve, so 0.5 to 5 mol / L (3 0.5 to 35%). Furthermore, when the non-crosslinked polymer contains no cross-linked structure, the non-crosslinked polymer has a concentration of 0.5 to 5 mol / L (3.5 to 35%) with respect to the solvent, and The molecular weight is preferably equal to or higher than the lower critical molecular weight described below.

The lower critical molecular weight of this non-crosslinked polymer is 10 to 100 times greater than the molecular weight that gives the critical point at which the molecular weight dependence of the concentrated solution viscosity changes from η to M to η to M ^3.4 due to entanglement between the polymers. And the degree of polymerization (number of polymer units) refers to a molecular weight of about 10,000 or more. If the average molecular weight of the non-crosslinked polymer is equal to or higher than the lower critical molecular weight, the mechanical strength and fracture energy of the gel having a semi-interpenetrating network structure are improved with the molecular weight, and if the average molecular weight is equal to or higher than the upper critical molecular weight, The mechanical strength and fracture energy of the gel will be constant. Therefore, in the example shown in FIG. 5, the lower critical molecular weight of the non-crosslinked polymer is around the weight average molecular weight M _w 1 × 10 ⁶ where the breaking energy of the gel starts to improve specifically, and the upper critical molecular weight of the non-crosslinked polymer. Is around the weight average molecular weight M _w 4 × 10 ⁶ where the breaking energy of the gel reaches its peak. Note that the lower and upper critical molecular weights of the non-crosslinked polymer vary depending on the size of the cavities scattered in the network structure composed of the crosslinked polymer.

  The volume occupied by the non-crosslinked polymer is preferably equal to or greater than the volume of the cavities scattered in the network structure composed of the crosslinked polymer, that is, the non-crosslinked polymer is preferably sufficiently entangled with the network structure composed of the crosslinked polymer. In addition, there is a dense part of the network around the cavity part scattered in the network structure composed of crosslinked polymer. If the non-crosslinked polymer is sufficiently entangled with the dense part, it exists in the dense part. A non-crosslinked polymer that acts as a crosslinking point with a significantly slow diffusion rate. Therefore, it is preferable that the non-crosslinked polymer has at least two cross-linking points at both ends across the cavity scattered in the network structure composed of the crosslinked polymer, and further has a volume that completely fills the cavity. . By the way, since the molecular weight of the non-crosslinked polymer is shown by a statistical average value, the non-crosslinked polymer in the case where the cross-linking points are formed across the cavities scattered at both ends of all the non-crosslinked polymers in the network structure composed of the crosslinked polymers. The average molecular weight is the upper critical molecular weight.

  As a raw material monomer constituting such a crosslinked polymer and a non-crosslinked polymer, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AAm), acrylic acid (AA), methacrylic acid, N-isopropylacrylamide, Examples include vinyl pyridine, hydroxyethyl acrylate, vinyl acetate, dimethyl siloxane, styrene (St), methyl methacrylate (MMA), trifluoroethyl acrylate (TFE), styrene sulfonic acid (SS), and dimethylacrylamide. The raw material monomer constituting the non-electrolyte non-crosslinked polymer is a fluorine-containing monomer, specifically 2,2,2-trifluoroethyl methyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate. 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 1H, 1H, 9H-hexadecafluorononimethacrylate, 2,2,2-trifluoroethyl acrylate, 2,3,4,5,6-pentafluorostyrene Or a vinylidene fluoride etc. are illustrated. Moreover, polysaccharides, such as gellan, hyaluronic acid, carrageenan, chitin, or alginic acid, or proteins, such as gelatin and collagen, can also be used for a crosslinked polymer or a non-crosslinked polymer.

  Further, the gel according to the present invention preferably has a water content in pure water of 10 to 99%, more preferably 50 to 95%, and even more preferably 85 to 95%. Thus, if the gel contains a large amount of pure water, the solvent absorption rate of the gel increases, and at the same time, the permeability thereof improves. Therefore, such a gel is used for a superabsorbent resin, soft contact lens or liquid chromatography. This is useful for applications such as a separating frame or applications that require sustained release.

  Moreover, it is preferable that this gel has a volume maintenance rate of 20 to 95%, further 60 to 95%, particularly 70 to 95% when transferred from pure water to physiological saline. In addition, this gel has a feature that even if it is once dried, it can be re-swelled to restore the original physical properties, and the solvent at the time of re-swelling is not limited to water. Therefore, if this gel is used as a water-absorbing agent such as a diaper, it can absorb a large amount of a solution with high osmotic pressure such as urine. Can be provided.

  Further, with respect to this gel, another polymer may be entangled with a semi-interpenetrating network structure constituted by a crosslinked polymer and a non-crosslinked polymer. This semi-interpenetrating network surface layer is predominantly occupied by the last added polymer, so entanglement of other polymers with the semi-interpenetrating network imparts the properties of the other polymer to the gel be able to. Therefore, using the technique disclosed in Patent Document 1, if a free end chain is formed by mixing or graft polymerizing an electrolyte polymer to this semi-interpenetrating network structure, the mechanical strength and the fracture energy are extremely high. A low friction material can be obtained.

  In addition, the side chain of the non-crosslinked polymer constituting the semi-interpenetrating network structure is chemically modified by known means, thereby changing the motion speed of the non-crosslinked polymer, and the swelling property, fracture energy and viscoelasticity of the gel. The characteristics can be adjusted.

  Further, by immersing the gel according to the present invention in a polyvalent ion-containing solution and causing the gel to swell, the specific functional group included in the cross-linked polymer or non-cross-linked polymer constituting the semi-interpenetrating network structure and the polyvalent ion are combined. By reacting, a chelate complex or colloid containing a multivalent ion is formed on the surface and inside of the semi-interpenetrating network structure, and the physical properties of the gel can be changed. In general, when the content of metal ions in a gel increases, the water content decreases and the mechanical strength increases. In the gel according to the present invention, when an external force is applied, the non-crosslinked polymer needs to form a transient network, so that the network structure composed of the crosslinked polymer and the multivalent ions form a complex or a colloid, and The non-crosslinked polymer preferably does not form a complex or colloid with the multivalent ion. In addition, the content of multivalent ions in the gel is preferably 0.01 to 1 mol / L, more preferably 0.03 to 0.3 mol / L during equilibrium swelling with pure water. Further, the kind of the multivalent ion is not particularly limited as long as it is a metal ion capable of forming a complex, and examples thereof include zinc ion, iron ion, nickel ion, cobalt ion, and chromium ion. Examples of the functional group capable of forming a complex with these multivalent ions include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

  In addition, by adjusting the surface potential of the gel according to the present invention, endothelial cells can be attached to the surface and proliferated. Therefore, by selecting the type of non-crosslinked polymer that governs the physical properties of the surface layer of the semi-interpenetrating network structure in the gel according to the present invention, or by chemically modifying the side chain of the non-crosslinked polymer, it is extremely durable. Can be obtained.

  In addition, as described above, the gel of the present invention in which a non-crosslinked polymer having high flexibility satisfying a predetermined condition invades and physically entangles in a rigid network made of a crosslinked polymer and in which cavities are scattered is used. By constituting a water-absorbing resin, a lubricant, a cell culture substrate, etc., the mechanical strength and durability of these industrial materials can be improved.

  The method for producing a gel having a semi-interpenetrating network structure according to the present invention is not particularly limited, but first, a monomer having different reactivity is radically copolymerized to form a crosslinked polymer in which cavities are scattered, and then A sequential polymerization method is preferred in which the cross-linked polymer is entangled in the monomer solution containing no cross-linking agent, and the non-cross-linked polymer is entangled with the cross-linked polymer by radical polymerization from the monomer solution. In addition, in order to enlarge the voids scattered in the network structure composed of cross-linked polymers, radically copolymerize monomers with different reactivity to form a polymer once, and add other cross-linking agents to the polymer solution or add gamma A method in which the polymers are further polymerized by, for example, irradiation with a beam is suitable. Further, the gel having the semi-interpenetrating network structure may be further immersed in another monomer solution, and the third and fourth non-crosslinked polymers may be entangled with the gel.

  In forming a network structure composed of such a crosslinked polymer, it is preferable to add 0.001 to 0.1 mol times divinyl monomer as a crosslinking agent with respect to an electrolyte vinyl monomer having an appropriate concentration, and to radically copolymerize these monomers. . Examples of the crosslinking agent include N, N'-methylenebisacrylamide (MBAA) and ethylene glycol dimethacrylate. Incidentally, when using a weak electrolyte vinyl monomer, it is necessary to start the reaction after increasing the degree of dissociation by exchanging counterions or controlling pH. Moreover, the heterogeneity of the network structure comprised from a crosslinked polymer can be improved by adding the poor solvent to the reaction system which produces | generates a crosslinked polymer. Further, when the crosslinked polymer is radically polymerized, fine particles may be mixed inside the network structure, and the fine particles may be removed by dissolution after the formation of the network structure, thereby increasing the non-uniformity of the network structure. .

  In addition, when the non-crosslinked polymer is entangled with the network structure composed of the crosslinked polymer using the sequential polymerization method, the crosslinked polymer may be removed from the solvent, immediately after synthesis, or in equilibrium swelling. Good. Furthermore, after the crosslinked polymer is immersed in the monomer solution of the non-crosslinked polymer and becomes in an equilibrium swelling state, that is, after the monomer concentration is almost equal between the inside and the outside of the network structure, the polymerization of the monomer is not performed. Preferably. In this monomer solution, the concentration of the crosslinking agent such as divinyl monomer with respect to the monomer needs to be less than 0.001 mol%. According to such a sequential polymerization method, since the non-crosslinked polymer is polymerized in a state where the crosslinked polymer is sufficiently swollen, even if the non-crosslinked polymer is entangled with the crosslinked polymer, the volume increase rate is at most several tens%. . In order to further entangle the third and fourth polymers with this semi-interpenetrating network structure, the same means as the above-described polymerization means of the non-crosslinked polymer may be used.

  In order to form a complex or colloid containing polyvalent ions on the surface and inside of this semi-interpenetrating network structure, the gel produced by the above-mentioned method is once vacuum-dried, and then the dried gel is mixed with a large amount. What is necessary is just to immerse in the containing solution of a valence ion.

  First, as a comparative control of the gel according to the present invention, using the method described in Example 1 of Patent Document 2, a second structure having a cross-linking degree of 0.1 mol% is formed on a network structure in which cavities made of a cross-linked polymer are scattered. A gel having a semi-interpenetrating network structure in which the “polymer of” entered and physically entangled was prepared. Specifically, it is as follows.

(Comparative Example 1)
<Formation of a network structure in which cavities made of a crosslinked polymer are scattered>
A frame having an outer side length of 80 × 80 mm and a width of 5 mm was cut out from a 100 × 100 × 2 mm silicon resin plate with a cutter, and a 3 mm groove was formed in one frame. The silicon resin frame was sandwiched between two 100 × 100 × 3 mm glass plates to assemble a polymerization vessel.

  25 ml of 2 mol / L 2-acrylamide-2-methylpropanesulfonic acid (AMPS) aqueous solution as a monomer, 1 ml of 2 mol / L N, N′-methylenebisacrylamide (MBAA) aqueous solution as a crosslinking agent, and an initiator It was combined with 1 ml of a certain 0.1 mol / L 2-oxoglutaric acid aqueous solution and adjusted with water to obtain 50 ml of an aqueous solution.

  This aqueous solution was deoxygenated using nitrogen gas. Subsequently, the deoxygenated aqueous solution was poured into the opening of the silicon resin plate placed on one glass plate of the polymerization vessel, and the other glass plate was stacked on the silicon plate to seal the periphery of the opening, A gel having a non-uniform network structure with a degree of cross-linking of 4 mol% and interspersed cavities by polymerizing by irradiation with ultraviolet rays at room temperature for 6 hours using a 365 nm UV lamp (22 W, 0.34 A) (semi-finished product) ) Was produced. The calculation of the degree of crosslinking is as follows.

{(MBAA aqueous solution concentration × amount) / (monomer concentration × amount)} × 100
= {(2 mol / L × 1 ml) / (2 mol / L × 25 ml)} × 100
= 4 mol%

<Formation of interpenetrating network structure or semi-interpenetrating network structure>
40 ml of a 5 mol / L acrylamide (AAm) aqueous solution as a monomer, 1 ml of a 0.2 mol / L MBAA aqueous solution as a crosslinking agent, and 1 ml of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator were mixed. The solution was adjusted with water to obtain 200 ml of an aqueous solution (immersion solution). The soaking solution was deoxygenated using nitrogen gas. The initiator concentration at this time was 0.1 mol%. The calculation of the degree of crosslinking is as follows.

{(0.2 mol / L × 1 ml) / (5 mol / L × 40 ml)} × 100
= 0.1 mol%

  Next, the immersion solution and 4 g of the gel (semi-finished product) were placed in a sealed container having a capacity sufficiently larger than the gel. This container was placed in a refrigerator at 4 ° C. for 24 hours, and the monomer, crosslinking agent and initiator in the immersion solution were diffused and permeated into the gel. During this step, the container was gently shaken from time to time for the purpose of uniform soaking solution concentration. In this step, the gel (semi-finished product) is equilibrium swollen to increase its volume by about ten times, the non-uniformity of the network is expanded, and a network structure in which cavities are scattered is formed.

  Next, after the gel (semi-finished product) was taken out from the dipping solution and cut into an appropriate size, the gel was sandwiched between two glass plates of 100 × 100 × 3 mm so as not to mix air bubbles. After sealing the four sides around the two glass plates, ultraviolet rays were irradiated at room temperature for 6 hours using a UV lamp (30 W, 0.68 A) having a wavelength of 365 nm. At this time, a gel having an interpenetrating network structure or a semi-interpenetrating network structure was obtained by polymerization of the AAm monomer diffused in the gel to produce a second polymer. The degree of crosslinking of the second polymer in this gel was 0.1 mol%. The calculation of the degree of crosslinking is as follows.

{(0.2 mol / L × 1 ml) / (5 mol / L × 40 ml)} × 100
= 0.1 mol%

  The gel having the interpenetrating network structure or semi-interpenetrating network structure obtained in this way was equilibratedly swollen in pure water (good solvent). In the gel at the time of parallel swelling with pure water, the weight content of the crosslinked polymer is 1.5%, the weight content of the second polymer is 10.5%, and the weight content of pure water is 88%. Yes, the equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 8.

  And about this gel, the "initial elasticity modulus", "compressive strength", "breaking energy", and "the presence or absence of the intermolecular interaction stronger than a hydrogen bond" were measured with the following means. The composition and measured properties of this gel are summarized in “Table 1” below.

(Example 1) to (Example 3)
A gel having a semi-interpenetrating network structure was produced in the same manner as in Comparative Example 1 except that the following points in <Formation of Interpenetrating Network Structure or Semi-Interpenetrating Network Structure> were changed.

  40 ml of a 5 mol / L acrylamide (AAm) aqueous solution as a monomer and 1/20 ml (50 μl) of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator are mixed and adjusted with water to prepare an aqueous solution (immersion solution) ) 200ml was obtained. The initiator concentration in this immersion solution is 0.005 mol%. The calculation of the initiator concentration is as follows.

{(0.1 mol / L × 1/20 ml) / (5 mol / L × 40 ml)} × 100
= 0.005 mol%

In addition, the gel (semi-finished product) sandwiched between two glass plates after being taken out from the dipping solution was irradiated with ultraviolet rays at room temperature using a UV lamp (30 W, 0.68 A) with a wavelength of 365 nm, and 10 in Example 1. When irradiated for 8 hours in Example 2, and 6 hours in Example 3, the non-crosslinked polymer having a predetermined weight average molecular weight _Mw is formed in the network structure in which the cavities constituting the gel (semi-finished product) are scattered. Was generated and a gel having a semi-interpenetrating network structure was obtained.

  Each of the gels having a semi-interpenetrating network structure obtained in this manner was equilibratedly swollen in pure water (good solvent). In each gel in parallel swelling with pure water, the weight content of the crosslinked polymer is 1.5%, the weight content of the non-crosslinked polymer is 10.5%, and the weight content of pure water is 88%. Yes, the equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 8. The composition and measured properties of these gels are summarized in “Table 1” below.

Example 4
The polyacrylamide (PAAm), which is a non-crosslinked polymer in a gel having a semi-interpenetrating network structure obtained in the same manner as in Example 3, was chemically modified using the following means.

<Chemical modification of PAAm side group by Mannich reaction>
In 150 ml of pure water, 1.2 ml of 35% aqueous formaldehyde solution was dissolved, adjusted to pH 9.0 by adding triethylamine, and heated to 70 degrees. In this hot reaction solution, 25 g of a plate-like (about 5 mm thick) gel that reached equilibrium swelling in pure water was added to initiate the methylolation reaction. After 1 hour from the start of the reaction, this plate-like gel was taken out of the reaction system and swollen in a large excess of cold water to stop the methylolation reaction. When the introduction rate of methylol groups introduced into PAAm by this reaction was calculated by a known method, it was about 30%.

  The methylolated gel having a semi-interpenetrating network structure obtained in this manner was again subjected to equilibrium swelling in pure water. In the gel during parallel swelling with pure water, the weight content of the crosslinked polymer is 1.5%, the weight content of the non-crosslinked polymer is 12.5%, and the weight content of pure water is 86%. The equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 7.4. The composition and measured properties of this gel are summarized in “Table 1” below.

(Comparative Example 2)
<Formation of a network structure in which cavities made of a crosslinked polymer are scattered>
A frame having an outer side length of 80 × 80 mm and a width of 5 mm was cut out from a 100 × 100 × 0.1 mm silicon resin plate with a cutter, and a 3 mm groove was formed in one portion of the frame. The silicon resin frame was sandwiched between two 100 × 100 × 3 mm glass plates to assemble a polymerization container.

  25 ml of a 2 mol / L AMPS aqueous solution as a monomer, 1/8 ml (125 μl) of a 2 mol / L MBAA aqueous solution as a crosslinking agent, and 1 ml of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator were mixed. The solution was adjusted with water to obtain 50 ml of an aqueous solution.

  This aqueous solution was deoxygenated using nitrogen gas. Subsequently, this deoxygenated aqueous solution was poured into the opening of a silicon plate placed on one glass plate of the polymerization vessel, and the other glass plate was stacked on the silicon plate to seal the periphery of the opening, and then the wavelength was 365 nm. A gel (half-finished product) having a network structure in which the degree of cross-linking is 0.5 mol% and cavities are scattered is obtained by polymerizing by irradiating ultraviolet rays at room temperature for 6 hours using a UV lamp (30 W, 0.68 A). Produced. The calculation of the degree of crosslinking is as follows.

{(MBAA aqueous solution concentration × amount) / (monomer concentration × amount)} × 100
= {(2 mol / L × 0.125 ml) / (2 mol / L × 25 ml)} × 100
= 0.5 mol%

<Formation of interpenetrating network structure or semi-interpenetrating network structure>
40 ml of a 5 mol / L acrylamide (AAm) aqueous solution as a monomer, 1 ml of a 2 mol / L MBAA aqueous solution as a crosslinking agent, and 1/20 ml (50 μl) of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator Were mixed and adjusted with water to obtain 200 ml of an aqueous solution (immersion solution). The soaking solution was deoxygenated using nitrogen gas. The initiator concentration in this immersion solution is 0.005 mol%. The calculation of the initiator concentration is as follows.

{(0.1 mol / L × 1/20 ml) / (5 mol / L × 40 ml)} × 100
= 0.005 mol%

  Subsequently, the immersion solution and 0.3 g of the gel (semi-finished product) were placed in a sealed container having a capacity sufficiently larger than the gel. This container was placed in a refrigerator at 4 ° C. for 24 hours, and the monomer, crosslinking agent and initiator in the soaking solution were diffused and permeated into the gel (semi-finished product). During this step, the container was gently shaken from time to time for the purpose of uniform soaking solution concentration. In this step, the gel (semi-finished product) was in equilibrium swell and its volume increased to 250 times or more.

  Next, after taking out the gel (semi-finished product) from the soaking solution and cutting it into an appropriate size, the gel is used to prevent air bubbles from being mixed between the glass plates using two glass plates of 100 × 100 × 3 mm. And pinched. After sealing the four sides around the two glass plates, ultraviolet rays were irradiated for 10 hours at room temperature using a UV lamp (30 W, 0.68 A) having a wavelength of 365 nm. At this time, a gel having an interpenetrating network structure or a semi-interpenetrating network structure was obtained by polymerization of the AAm monomer diffused in the gel.

  The gel thus obtained was equilibrated and swollen in pure water. In the gel during parallel swelling with pure water, the weight content of the crosslinked polymer is 0.1%, the weight content of the second polymer is 5.9%, and the weight content of pure water is 94%. Yes, the equilibrium swelling degree of the crosslinked polymer was 1360, and the equilibrium swelling degree of the gel itself was 17. The composition and measured properties of this gel are summarized in “Table 1” below.

(Comparative Example 3)
In Comparative Example 1, the weight content of AMPS and MBAA used in <formation of a network structure in which cavities made of a crosslinked polymer are scattered> and <formation of an interpenetrating network structure or a semi-interpenetrating network structure> A gel having an interpenetrating network structure or a semi-interpenetrating network structure was obtained in the same manner except that the weight contents of AAm and MBAA were changed.

  The gel thus obtained was equilibrated and swollen in pure water. In the gel at the time of parallel swelling with pure water, the weight content of the crosslinked polymer is 0.7%, the degree of crosslinking of the crosslinked polymer is 2 mol%, and the weight content of the second polymer is 9.3%. The crosslinking degree of the second polymer was 0.1 mol%, the weight content of pure water was 90%, the equilibrium swelling degree of the crosslinked polymer was 103, and the equilibrium swelling degree of the gel itself was 10. . The composition and measured properties of this gel are summarized in “Table 1” below.

(Comparative Example 4)
A gel having a semi-interpenetrating network structure was obtained in the same manner as in Comparative Example 1 except that MBAA was not used in <formation of an interpenetrating network structure or a semi-interpenetrating network structure>.

  The gel thus obtained was equilibrated and swollen in pure water. In the gel at the time of parallel swelling with pure water, the weight content of the crosslinked polymer is 1.5%, the degree of crosslinking of the crosslinked polymer is 4 mol%, and the weight content of the non-crosslinked polymer is 10.5%, The weight content of pure water was 88%, the equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 8. The composition and measured properties of this gel are summarized in “Table 1” below.

(Comparative Example 5)
A gel having a semi-interpenetrating network structure was obtained in the same manner as in Comparative Example 1, except that <interpenetrating network structure or semi-interpenetrating network structure formation> was changed as follows.

<Formation of semi-interpenetrating network structure gel>
40 ml of a 5 mol / L aqueous acrylamide (AAm) solution as a monomer and 1 ml of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator are mixed, and 5.6 μl of 2-methylcaptoethanol is further added as a chain transfer agent. In addition, it was adjusted with water to obtain 200 ml of an aqueous solution (immersion solution). The immersion solution was deoxygenated using nitrogen gas. The initiator concentration in this immersion solution is 0.1 mol%. The calculation of the initiator concentration is as follows.

{(0.2 mol / L × 1 ml) / (5 mol / L × 40 ml)} × 100
= 0.1 mol%

  Next, the immersion solution and 4 g of the gel (semi-finished product) were placed in a sealed container having a capacity sufficiently larger than that gel. This container was placed in a refrigerator at 4 ° C. for 24 hours, and the monomer, crosslinking agent, and initiator in the immersion solution were diffused and permeated into the gel. In this step, the container was gently shaken from time to time to make the concentration of the immersion liquid uniform. In this step, the gel swells and the volume of the gel becomes about ten times larger, so that the non-uniformity of the network structure is expanded and a network structure in which cavities are scattered is formed.

  Next, the gel was taken out from the soaking solution and cut into an appropriate size, and the gel was sandwiched between two glass plates of 100 × 100 × 3 mm so that no air bubbles were mixed between the glass plates. After sealing the four sides around the two glass plates, ultraviolet rays were irradiated for 10 hours at room temperature using a UV lamp (30 W, 0.68 A) having a wavelength of 365 nm. At this time, a gel having a semi-interpenetrating network structure was obtained by polymerization of the AAm monomer diffused in the gel.

  The gel thus obtained was equilibrated and swollen in pure water. In the gel during parallel swelling with pure water, the weight content of the crosslinked polymer is 1.6%, the degree of crosslinking of the crosslinked polymer is 4 mol%, and the weight content of the non-crosslinked polymer is 8.2%, The weight content of pure water was 89%, the equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 8.5. The composition and measured properties of this gel are summarized in “Table 1” below.

(Comparative Example 6)
A gel having a semi-interpenetrating network structure was obtained in the same manner as in Comparative Example 1, except that <interpenetrating network structure or semi-interpenetrating network structure formation> was changed as follows.

<Formation of semi-interpenetrating network structure gel>
40 ml of a 5 mol / L acrylamide (AAm) aqueous solution as a monomer and 1/20 ml (50 μl) of a 0.1 mol / L 2-oxoglutaric acid aqueous solution as an initiator are mixed and adjusted with water to prepare an aqueous solution (immersion solution) ) 200ml was obtained. The immersion solution was deoxygenated using nitrogen gas. The initiator concentration in this immersion solution was 0.005 mol%. The calculation of the initiator concentration is as follows.

{(0.1 mol / L × 1/20 ml) / (5 mol / L × 40 ml) × 100
= 0.005 mol%

  Next, the immersion solution and 4 g of the gel (semi-finished product) were placed in a sealed container having a capacity sufficiently larger than that gel. This container was placed in a refrigerator at 4 ° C. for 24 hours, and the monomer, crosslinking agent and initiator in the soaking solution were diffused and permeated into the gel. In this step, the container was gently shaken from time to time to make the concentration of the immersion liquid uniform. In this step, the gel swells and the volume of the gel becomes about ten times, thereby increasing the non-uniformity of the network structure and forming a network structure in which cavities are scattered.

  Next, after the gel was taken out from the dipping solution and cut into an appropriate size, the gel was sandwiched between two glass plates of 100 × 100 × 3 mm so that no bubbles were mixed between the glass plates. After sealing the four sides around the two glass plates, ultraviolet rays were irradiated for 10 hours at room temperature using a UV lamp (30 W, 0.68 A) having a wavelength of 365 nm. A gel having a semi-interpenetrating network structure was obtained by polymerizing the AAm monomer diffused in the gel to produce a non-crosslinked polymer.

<Chemical modification of PAAm side group by Mannich reaction>
In 150 ml of pure water, 1.2 ml of 35% aqueous formaldehyde solution was dissolved, adjusted to pH 9.0 by adding triethylamine, and then heated to 70 degrees. In this hot reaction solution, 25 g of the gel having the plate-like (thickness: about 5 mm) semi-interpenetrating network structure that reached equilibrium swelling in pure water was put to start the methylolation reaction. One hour after the start of the reaction, 9.5 ml of a 50% aqueous dimethylamine solution was further added to the hot reaction solution. After 30 minutes, the gel was taken out of the reaction system and swollen in a large excess of cold water to stop the reaction. When the introduction rate of the methylol group and the cationic group introduced into PAAm by this reaction was calculated by a known method, each was about 30%.

  The gel having the methylolated and cationized semi-interpenetrating network structure thus obtained was again subjected to equilibrium swelling in pure water. In the gel during parallel swelling with pure water, the weight content of the crosslinked polymer is 2.2%, the weight content of the non-crosslinked polymer is 14.8%, and the weight content of pure water is 83%. The equilibrium swelling degree of the crosslinked polymer was 44, and the equilibrium swelling degree of the gel itself was 6. The composition and measured properties of this gel are summarized in “Table 1” below.

[Measurement of various properties of gel]
For the measurement of the “initial elastic modulus” and “compressive strength” of the gel, TENTICON type RTC-1150A (tester A) manufactured by ORIENTIC or TENSILON type RTC-1150A type RTC-1150A (tester B) manufactured by ORIENTIC An attachment fitting made by Seisakusho was used. The tester A can measure stresses of 250 N or less, and the tester B can measure stresses of 10 kN or less, and they are used depending on the mechanical strength of the gel to be measured.

  First, a compression test is performed, the gel is cut into a cylindrical shape with a thickness of about 5 mm with a circular cutter having a diameter of 9 mm, and the height direction of the gel using an attachment fitting (upper and lower compression plate type) connected to the testing machine A or B The stress generated in the gel was measured at a compression rate of 10% / min (for example, 0.5 mm / min for a 5.0 mm thick gel) with respect to the strain.

  The initial elastic modulus of the gel was calculated from the slope of the curve in the region where the strain of the strain-stress curve obtained by the compression test was less than 10% and high linearity, by the following formula. In addition, the compressive strength of the gel is the stress when the slope of the strain-stress curve output to the monitor changes in real time during measurement due to the destruction of the gel, or the slope of the strain-stress curve output to the monitor. Even if the change did not change, it was calculated by the following formula from the stress and the surface area when the destruction of the gel was confirmed.

(Initial elastic modulus) = (stress) / (strain rate)
(Compressive strength) = (Stress at break) / (Surface area at non-deformation)

  Further, the breaking energy of the gel was also measured using the tester A or B. The breaking energy of the gel is fixed to a 4.0 to 5.0 mm thick gel cut out with a JIS K-6252 trouser type 1/2 size metal cutter with an attachment fitting (fixing device for tensile test). A tear test was performed at a speed of 500 mm / min under conditions in which a general fracture occurred, and the test result was calculated by applying to the following equation.

  Normally, as the destroyed surface, two surfaces on both sides are obtained with reference to the destruction position, such as the left and right or upper and lower sides of the destruction, but here, in order to simplify the discussion, a model with only one side is considered.

(Fracture energy) = (Work required for steady fracture) / (Break area)
= (Average force at steady state failure) / (gel thickness)

  In addition, regarding the “presence / absence of intermolecular interactions stronger than hydrogen bonds” between non-crosslinked polymers or between second polymers, nuclear magnetic resonance measurements should be performed on the gel and should appear due to the presence of intermolecular interactions. Judgment was made by whether or not a chemical shift was observed.

In addition, the weight average molecular weight _Mw of the non-crosslinked polymer in the semi-interpenetrating network structure is obtained in advance based on the correlation between the polymerization conditions of the noncrosslinked polymer and the weight average molecular weight _Mw. It calculated from the polymerization conditions.

As the weight average molecular weight _{Mw of} the non-crosslinked polymer constituting the semi-interpenetrating network is increased by comparing the structures and properties of the gels obtained in Example 1 to Example 3 shown in Table 1, the gel It can be seen that the destruction energy is improved. In Table 1, the weight average molecular weight _Mw of the non-crosslinked polymer (B) is expressed as an exponential function with 10 as the base.

  This specification is based on Japanese Patent Application No. 2004-187754 filed on June 25, 2004. All this content is included here.

  The hydrogel according to the present invention has high mechanical strength and high fracture energy, is transparent, has flexibility, substance permeability and impact resistance, so diapers, hygiene products, release agents, civil engineering materials, building materials, Communication materials (eg bearings, cables and joints), soil modifiers, contact lenses, intraocular lenses, hollow fibers, artificial cartilage, artificial joints, artificial organs (eg artificial blood vessels and artificial skin), fuel cell materials, batteries Stabilizers and thickeners such as separators, bedsores and anti-wrinkle mats, cushions, lubricants, lotions, cell culture substrates, drug delivery systems (DDS), drug carriers, specific substance sensors or catheters It can be used for soft actuators used at the tip of

Claims (19)

It has a semi-interpenetrating network structure in which a non-crosslinked polymer invades and physically entangles into a network structure composed of a crosslinked polymer,
The non-crosslinked polymer has a weight average molecular weight of 4 × 10 ⁶ or more,
At the time of equilibrium swelling with a good solvent for the crosslinked polymer and the non-crosslinked polymer , the degree of swelling is 5 or more, the weight content of the good solvent is 80% or more, and the breaking energy is 700 J / m ² or more and 2000 J / M ² or less gel.   The gel according to claim 1, wherein there is no intermolecular interaction stronger than hydrogen bonding between the non-crosslinked polymers during equilibrium swelling with the good solvent. The non-crosslinked polymer has an equilibrium swelling degree of 5 to 1000 with the good solvent,
The non-crosslinked polymer has a weight content higher than the weight content of the crosslinked polymer.
The gel according to claim 1.   The gel according to claim 1, wherein the non-crosslinked polymer has a weight content of 3.5 to 35% with respect to the weight of the good solvent in the gel.   The gel according to claim 1, wherein a weight content of the non-crosslinked polymer is 10 to 40% based on a total weight of the crosslinked polymer and the solvent in the gel.   Raw material monomers of the crosslinked polymer and the non-crosslinked polymer are 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AAm), acrylic acid (AA), methacrylic acid, N-isopropylacrylamide, vinylpyridine, hydroxy Ethyl acrylate, vinyl acetate, dimethylsiloxane, styrene (St), methyl methacrylate (MMA), trifluoroethyl acrylate (TFE), styrene sulfonic acid (SS), dimethylacrylamide, 2,2,2-trifluoroethyl methyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 1H, 1H, 9H-hexadecafluorononimethacrylate, 2 2,2 trifluoroethyl acrylate, 2,3,4,5,6-pentafluoro styrene, selected from vinylidene fluoride, claim 1 wherein the gel.   The gel according to claim 1, wherein the crosslinking agent used for polymerization of the crosslinked polymer is N, N'-methylenebisacrylamide (MBAA) or ethylene glycol dimethacrylate.   The gel of claim 1, wherein the molar ratio of the cross-linked polymer source monomer to the non-cross-linked polymer source monomer is about 1:20.   The gel according to claim 1, wherein the semi-interpenetrating network surface layer has a free end chain made of an electrolyte polymer.   A water-absorbent resin obtained by removing a solvent from the gel according to claim 1.   A lubricant comprising the gel according to claim 1.   A cell culture substrate comprising the gel according to claim 1. Polymerizing the first raw material monomer together with a crosslinking agent in a solvent to form a crosslinked polymer having a network structure to obtain a semi-finished gel as an intermediate product composed of the crosslinked polymer and the solvent;
After the second raw material monomer is diffused and permeated into the semi-finished product gel, it is polymerized in the presence of 0.005 mol% or less of the polymerization initiator with respect to the second raw material monomer to form a non-crosslinked polymer. Thus, the non-crosslinked polymer is produced by a production method comprising a step of obtaining a gel as a final product including a structure physically entangled with the network structure,
The degree of swelling at the time of equilibrium swelling by the solvent is at least 5, the weight content of the solvent is 80% or more, and fracture energy is 700 J / ^{m 2} or more 2000J / ^{m 2} or less, gel.   The gel according to claim 13, wherein the production method further comprises a step of immersing in a multivalent ion-containing solution to form a colloid therein.   The gel according to claim 13, wherein a weight content of the non-crosslinked polymer is 10 to 40% based on a total weight of the crosslinked polymer and the solvent in the gel.   The raw material monomer is 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylamide (AAm), acrylic acid (AA), methacrylic acid, N-isopropylacrylamide, vinylpyridine, hydroxyethyl acrylate, vinyl acetate, dimethylsiloxane , Styrene (St), methyl methacrylate (MMA), trifluoroethyl acrylate (TFE), styrene sulfonic acid (SS), dimethylacrylamide, 2,2,2-trifluoroethyl methyl acrylate, 2,2,3,3 3-pentafluoropropyl methacrylate, 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 1H, 1H, 9H-hexadecafluorononimethacrylate, 2,2,2-trifluoroethyl acrylate , 2,3,4,5,6-pentafluoro-styrene, are selected from vinylidene fluoride, according to claim 13, wherein the gel.   The gel according to claim 13, wherein the cross-linking agent is N, N'-methylenebisacrylamide (MBAA) or ethylene glycol dimethacrylate.   The gel of claim 13, wherein the molar ratio of the first raw material monomer to the second raw material monomer is about 1:20. In a gel having a semi-interpenetrating network structure in which a non-crosslinked polymer penetrates into a network structure composed of a crosslinked polymer and is physically entangled, the side chains of the noncrosslinked polymer are chemically modified, or the degree of crosslinking of the crosslinked polymer is adjusted. while the by setting the weight average molecular weight of the non-crosslinked polymer 4 × 10 ⁶ or more, to adjust the fracture energy of the gel at 700 J / ^{m 2} or more 2000J / ^{m 2} or less of the range, the production method of the gel.

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