WO2018205350A1

WO2018205350A1 - Nanocomposite hydrogel material and preparation method therefor

Info

Publication number: WO2018205350A1
Application number: PCT/CN2017/088782
Authority: WO
Inventors: 李宗津; 孙国星
Original assignee: 李宗津
Priority date: 2017-05-12
Filing date: 2017-06-16
Publication date: 2018-11-15
Also published as: CN107266692A

Abstract

Provided are a nanocomposite hydrogel material and a preparation method therefor, the nanocomposite hydrogel material being prepared by reinforcing polyacrylamide with calcium hydroxide nanospheres (CNS). The hydrogel is formed by forming CNS by means of the crystallization of calcium ions of tricalcium silicate, dicalcium silicate, Portland cement or other cementing materials containing a calcium component at 0ºC, and uniformly diffusing same into a acrylamide polymer matrix and subjecting same to acrylamide polymer in situ polymerization and crosslinking with CNS. The uniformly dispersed CNS is a hydration product of the calcium-containing component cementing material at 0 degrees and functions as a crosslinking agent in the polyacrylamide polymer network. The nanocomposite hydrogel has superior mechanical strength, elasticity, ultra-high ultimate strain, toughness and recoverability, and maintains the transparency and low cost of traditional PAM hydrogels.

Description

Nano composite hydrogel material and preparation method thereof

Technical field

The invention relates to the technical field of hydrogels, in particular to a nano composite hydrogel material and a preparation method thereof

Background technique

Fatal disadvantages of conventional polymer hydrogels are low strength, high brittleness, low transparency or poor deformability. These unavoidable problems severely limit their industrial and biomedical applications. Although several types of inorganic nanoparticles, such as clay and graphene oxide (GO), have been demonstrated to form polymer nanocomposite (NC) hydrogels with significantly enhanced mechanical properties, complex processing and polymerization of clays The black color of the object/GO hydrogel severely limits their application. Common inorganic nanoparticles, including nano-sized silica and titanium dioxide, do not form polymer NC hydrogels. Therefore, the formation and development of high performance new polymer NC hydrogels has become a major challenge.

For example, Chinese Patent No. CN105419190A discloses a method for preparing a medical polyvinyl alcohol hydrogel, which comprises the following steps: 1) weighing raw materials according to the following parts by weight: polyvinyl alcohol 5-20; humectant 8-12; Water or 1% acetic acid 68-87; preservative 0.1-1; the humectant comprises one of glycerin, propylene glycol, sorbitol or polyethylene glycol; the preservative comprises: sodium benzoate, sorbic acid or nepo One of the golds; the polyvinyl alcohol has a degree of alcoholysis of not less than 88%; 2) adding polyvinyl alcohol to water, soaking at 50 ° C to 70 ° C for 10 to 90 minutes, adding a humectant, a preservative Continue heating to 85 ° C ~ 100 ° C to dissolve, to obtain a solution A; the solution A is separated or discharged by ultrasonic or decompression method; the solution after removing the foam is poured into the mold, placed at -10 ° C ~ - Leave at 20 ° C for 10 to 48 hours, take out, and leave it at room temperature for 0.5 to 10 hours. Seal the hydrogel in a gel, using cobalt-60 irradiation, and irradiate the dose from 50KGy to 150KGy. The prepared water gel is subjected to corresponding research on the light transmittance. However, in the actual use process, it is necessary to fully consider the comprehensive ability of the strength, brittleness, transparency and deformability of the hydrogel.

Further, as disclosed in Chinese Patent No. CN104114591A, a method for preparing water-absorbing polymer particles comprises polymerizing an aqueous monomer solution or suspension containing the following materials to obtain an aqueous polymer gel, a) at least one having a carboxyl group and An ethylenically unsaturated monomer which is at least partially neutralized, b) at least one crosslinking agent, c) at least one initiator, d) optionally one or more may be the ones mentioned in a) a copolymerized ethylenically unsaturated monomer, and e) optionally one or more water soluble polymers, thermally drying the polymerization The gel is gelled, the dried polymer gel is pulverized to obtain polymer particles, and the resulting polymer particles are classified, the method comprising mixing a thermal blowing agent substantially free of inorganic acid anions into the aqueous polymer gel. In the gel polymer, only the swelling rate and the permeability of the gel during the preparation process do not comprehensively take into account the comprehensive capabilities such as gel strength, deformability, and brittleness. Therefore, the hydrogel has a very high use during use. Great limitations.

Summary of the invention

In order to overcome the problems of low elasticity and poor recovery in the prior art, the present invention provides a nanocomposite hydrogel material and a preparation method thereof.

The invention discloses a nano composite hydrogel material, which is innovative in that the composite hydrogel is composed of a polymer as a matrix material, and nano spherulites having a size of less than 10 nm are added as a crosslinking agent; the polymer matrix Polyacrylamide PAM was prepared by using acrylamide AM as a monomer and ammonium persulfate APS as an initiator; and N, N, N', N'-tetramethyl-ethylenediamine was added as a catalyst.

Further, the nanosphere crystal is calcium hydroxide nanosphere crystal; the calcium hydroxide nanosphere crystal has a diameter of less than 10 nm.

Further, the composite hydrogel contains nanospheres in an amount of from 1 to 500 ppm by weight of the hydrogel.

Further, the content of the polymer is from 10% by weight to 50% by weight based on the total weight of the hydrogel.

The invention also discloses a method for preparing a nano composite hydrogel, which is innovative in that the specific steps are as follows:

S1, mixing granules of tricalcium silicate / dicalcium silicate / Portland cement / white cement or a mixture thereof in an ice bath at 0 ° C to form calcium hydroxide nanospheres, the calcium hydroxide nanospheres dispersed Obtaining a translucent aqueous dispersion in deionized water, stirring for 10 minutes under ultrasonic treatment to obtain a uniform dispersion, and the uniform dispersion is a calcium hydroxide suspension;

S2, adding a polymer, an initiator and a catalyst to the calcium hydroxide suspension to form a mixture;

S3, the mixture was kept in an ice bath at 0 ° C for 72 hours to fully hydrate the tricalcium silicate;

S4, forming a nanocomposite hydrogel material by a polymerization method at 0.01 atm;

Among them, the stirring speed is from 10 rpm to 1000 rpm.

Further, the polymer is a water-soluble polymer selected from the group consisting of polyacrylamide, N-isopropylacrylamide, polyvinyl alcohol or a mixture thereof; the initiator is a water-soluble polymer, The water-soluble polymer is ammonium persulfate, potassium persulfate, sodium persulfate or 2,2'-azobisisobutylphosphonium dihydrochloride; a dispersant is added to the mixture in S2 to improve calcium hydroxide nanospheres Dispersion; the dispersant is an anionic surfactant, the anionic surfactant is a polycarboxylate ether, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, an anionic polyacrylamide or hydroxyethyl Sodium sulfonate.

Further, the hydration temperature of the calcium hydroxide nanospheres ranges from -10 °C to 40 °C.

Further, the polymerization method is in situ radical polymerization.

Further, the nanoparticles are added to the mixture in S2 to further improve the mechanical properties of the composite hydrogel.

Further, the nanoparticles are selected from the group consisting of hectorite, montmorillonite, graphene oxide, layered double hydroxide, titanate nanosheets, controllably active nanogels, or mixtures thereof.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The PAM/CNS hydrogel property is obtained by adjusting the CNS concentration to obtain high expansion, elongation, fracture stress and recoverability. In the unpolymerized CNS, it can be obtained by replacing the tricalcium silicate with a Portland cement suspension, and further performance enhancement can be obtained by in-situ polymerization of another polymer hydrogel. The results show that individual dispersed spherulites of less than 5 nm can be obtained by low temperature hydration reaction of tricalcium silicate, which helps the hydrogel to enhance the crosslinked network and properties.

(2) The composite hydrogel modified by 40 ppm CNS has a stress of 430 KPa and a draw ratio of 121,200 ppm. The composite hydrogel of CNS has a stress of 630 KPa at a draw ratio of 65 and under a stress of 100 MPa. , restored to 90% of the original size. At the same polymer content, the composite hydrogel has the same transparency as the original polyacrylamide.

(3) Due to the low polymerization, small size and uniformly dispersed CNS, the transparency of C200 is almost the same as that of the original PAM hydrogel. The coupling between the PAM functional group and the CNS is the acid passing through the initiator ammonium persulfate and calcium hydroxide. The alkali reaction is established.

(4) Size of Porous Structure There are a large number of parallel and crosslinked filamentous structures in the 20-80 nm xerogel. These structures range in size from 50 nm to 2 μm and are regularly distributed in the pores. There is a significant protrusion between the crosslinked wire and the inside of the hole at the joint, indicating that it has a strong bonding force, which plays an important role in the swelling property and mechanical properties of the hydrogel.

(5) The polymer molecules in the hydrogel crosslinked network are free, highly elastic, and mobile, exhibiting a follower image between the CNS.

DRAWINGS

Figure 1 is a TEM image of the release of CNS from a tricalcium silicate particle;

Figure 2 is an electron diffraction spectrum of CNS released from the hydration reaction of tricalcium silicate;

Figure 3 is a TEM image of the dispersed CNS (200 ppm CNS concentration in PAM/CNS) in C200;

Figure 4 is an optical photograph of a cylindrical C200 sample;

Figure 5 is a gelation diagram of a PAM/CNS hydrogel at 0.01 atm after 10 days of standing at 0 ° C and 1 atm;

Figure 6 is a gelation diagram of a PAM/CNS hydrogel placed at 0.01 atm for 3 h after being placed at 0 ° C and 1 atm for 1 day;

Figure 7 is a gelation diagram of a PAM/CNS hydrogel placed at 0.01 atm for 3 h after being placed at 0 ° C and 1 atm for 3 days;

Figure 8 is a gelation diagram of a 3 h PAM/CNS hydrogel placed at 0.01 atm after 5 days at 0 ° C and 1 atm;

Figure 9 is a schematic diagram of CNS in PAM cross-linked tricalcium silicate;

Figure 10 is a bar graph showing the relative peak intensities of negative ions in the (SO ₄ CH ^- and SO ₄ CH ₂ ^- ) terminal groups and the (CN ^- and CNO ^- ) side groups in PAM and C200;

Figure 11 is a graph of relative peak intensity in C200;

Figure 12 is an SEM image of a C40 xerogel;

Figure 13 is a SEM zoom view of the block area of Figure 12;

Figure 14 is a SEM zoom view of the block area of Figure 13;

Figure 15 is an SEM image of a C200 xerogel;

Figure 16 is a SEM zoom view of the block area of Figure 15;

Figure 17 is a SEM zoom view of the block area of Figure 16;

Figure 18 is an optical diagram of the expanded hydrogel after immersion of C40, C100 and C200 in deionized water for 3 weeks;

Figure 19 is a DSC curve of C40, C200 and CA;

Figure 20 is a tensile stress-strain curve of a PAM hydrogel at CNS concentrations of 0, 40, and 200 ppm. Figure

Figure 21 is a graph showing the compressive stress-strain curve of a PAM hydrogel at C40 and C200;

Figure 22 is a five-fold extension of the tensile stress-strain curve of C200 in four cycles;

Figure 23 is a cyclic stress-strain curve of C200 magnified 5 times in four cycles;

Figure 24 is a 10 times extension of the tensile stress-strain curve of C200 in four cycles;

Figure 25 is a cyclic stress-strain curve of C200 magnified 10 times in four cycles;

Figure 26 is a gelation reaction diagram of PAM when mixed with tricalcium silicate and sodium hydroxide at normal temperature;

Figure 27 is a TEM image of a calcium hydroxide microcrystal;

Figure 28 is a TEM image of the CNS in a 500 ppm Portland cement suspension placed at 0 °C for 3 days;

Figure 29 is a SEM image of the dispersion of tricalcium silicate in ethanol at a concentration of 500 ppm.

detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Common inorganic nanoparticles, including nanoscale silica and titanium dioxide, fail to form polymer nanocomposite hydrogels. Therefore, the formation and development of high performance novel nanocomposite hydrogel polymers has become a major challenge. In order to solve the above problem, the calcium hydroxide nanosphere crystal is combined with the polyacrylamide matrix, and the calcium hydroxide nanosphere crystal having a small size functions as a crosslinking agent. This polyacrylamide-based calcium hydroxide nanosphere crystal hydrogel (PAM/CNS hydrogel) exhibits an extremely high stretch at low inorganic content and an uncommon multi-layered pore structure.

For the sake of brevity, in the remainder of this embodiment, we only use calcium hydroxide nanospheres (CNS) instead of C ₃ S, C ₂ S, Portland cement, and white cement.

Example 1

The invention discloses a method for preparing a nano composite hydrogel (PAM/CNS). The preparation steps are the synthesis of tricalcium silicate, the preparation of calcium hydroxide CNS suspension, and the preparation of PAM/CNS nano composite hydrogel material.

Synthesis of tricalcium silicate: calcium carbonate and silica silica were mixed at a molar ratio of 3:1, screened through a 63 um sieve, and then mixed for 1-2 h. The obtained fine powder was compressed into a sheet, placed in a crucible for 5 hours, at a temperature of 1500 ° C, and rapidly cooled to room temperature in 10 minutes. The obtained product is ground into subdivisions, and then One compression and calcination. After repeating 4 times, the final tricalcium silicate size is less than 500 nm.

Preparation of calcium hydroxide CNS suspension:

Mixing hydrated tricalcium silicate/dicalcium silicate/Portland cement/white cement or a mixture thereof to form calcium hydroxide nanospheres, when C ₃ S, C ₂ S, Portland cement or white cement particles are dispersed In water, Ca ^{2+ is} released from C ₃ S (or C ₂ S, Portland cement, white cement) to form calcium hydroxide spherulites in aqueous solution. The hydration temperature is critical throughout the preparation process, with the hydration temperature controlled between -10 and 40 ° C, preferably at a hydration temperature of 0 ° C, mainly due to the release of Ca ²⁺ released from C ₃ S at this temperature. The speed is just enough to form calcium hydroxide spherulites. At the same time, due to the low crystallization temperature, the right calcium hydroxide nanospheres have a diameter of less than 10 nm, preferably less than 5 nm in diameter. Theoretically, the calcium hydroxide nanospheres have good dispersibility and small size. Crystallization improves the performance of new nanocomposite hydrogel polymers. The calcium hydroxide nanospheres are dispersed in deionized water to obtain a translucent aqueous dispersion, and after stirring for 10 minutes under ultrasonic treatment, a uniform dispersion is obtained, and the uniform dispersion is a calcium hydroxide suspension; the stirring speed is 10 rpm. 1000 rpm, preferably a stirring speed of 500 rpm. Further, a dispersant may be added to the mixture to improve the dispersibility of the calcium hydroxide nanospheres. The dispersing agent is an anionic surfactant selected from the group consisting of polycarboxylate ether, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, anionic polyacrylamide or sodium isethionate.

PAM/CNS nanocomposite hydrogel material preparation:

The PAM/CNS hydrogel is prepared by in-situ radical polymerization; the polymer, the initiator and the catalyst are added to the CNS suspension, wherein the polymer is a water-soluble polymer, and the water-soluble polymer is selected from the group consisting of polyacrylamide, N- Isopropyl acrylamide, polyvinyl alcohol or a mixture thereof, polyacrylamide is used in the embodiment; the initiator is selected from ammonium persulfate, potassium persulfate, sodium persulfate or 2,2'-azobisisobutylphosphonium Dihydrochloride, in the present embodiment, ammonium persulfate APS is used; the catalyst is N, N, N', N'-tetramethylethylenediamine TEMED. Nanoparticles are added to the mixture to further improve the mechanical properties of the composite hydrogel; the proportion of each component in the suspension is CNS suspension / AM / APS / TEMED = 60g / 15g / 0.03g / 48μL, of which CNS in CNS suspension The concentration is 40 ppm. For complete reaction of CNS and APS, the mixture was kept at 0 °C for at least 72 hours in an ice bath. The polymerization was carried out in a vacuum environment (0.01 atm) at 0 ° C for 6 hours.

Example 2

PAM/CNS nanocomposite hydrogel material preparation:

The PAM/CNS hydrogel is prepared by in-situ radical polymerization; the polymer, the initiator and the catalyst are added to the CNS suspension, wherein the polymer is a water-soluble polymer, and the water-soluble polymer is selected from the group consisting of polyacrylamide, poly N - isopropyl acrylamide, polyvinyl alcohol or a mixture thereof, the monomer acrylamide AM is used in the present embodiment; the initiator is selected from ammonium persulfate, potassium persulfate, sodium persulfate or 2,2'-azo diiso Butyl hydrazine dihydrochloride, in this embodiment, ammonium persulfate APS is used; the catalyst is N, N, N', N'-tetramethylethylenediamine TEMED; the proportion of each component in the suspension is CNS suspension / AM /APS/TEMED=60g/15g/0.03g/48μL, wherein the concentration of CNS in the CNS suspension is 200ppm. For complete reaction of CNS and APS, the mixture was kept at 0 °C for at least 72 hours in an ice bath. The polymerization was carried out in a vacuum environment (0.01 atm) at 0 ° C for 6 hours.

Figures 1-4 were obtained by comparing the hydrogels of Example 1 and Example 2. Figure 1 is a TEM image of the CNS released in the tricalcium silicate particles. The base of the figure is 100 nm and the base of the illustration is 5 nm. Figure 2 is an electron diffraction spectrum of CNS released from a hydration reaction in tricalcium silicate, which is 51/nm. Figure 3 TEM is a dispersed CNS in C200 (200 ppm CNS concentration in PAM/CNS) with a base gauge of 30 nm. Figure 4 is an optical photograph of a cylindrical C200 sample having a diameter of 2.7 cm, a thickness of 1.2 cm, and a base gauge of 1 cm with respect to the background image. As can be seen from Figure 1, the transparency of C200 is almost the same as that of the original PAM hydrogel.

Example 3

In contrast to Example 1, the calcium hydroxide nanospheres in the PAM/CNS hydrogel in this example were replaced with calcium hydroxide microspheres.

Example 4

In contrast to Example 1, in this example, the polymer in the PAM/CNS hydrogel was 20% by weight and 500 ppm of tricalcium silicate. Placed at 0 ° C and 1 atm for 10 days, gelatinization occurred at 1 atm, as shown in Figure 5.

Example 5

In contrast to Example 4, in this example, the hydrogel was allowed to stand at 0 ° C and 1 atm for 1 day, and after being placed at 0.01 atm for 3 hours, gelation occurred, as shown in FIG.

Example 6

In contrast to Example 4, the hydrogel of this example was allowed to stand at 0 ° C and 1 atm for 3 days, and gelled after standing at 0.01 atm for 3 hours, as shown in FIG.

Example 7

In contrast to Example 4, in this example, the hydrogel was allowed to stand at 0 ° C and 1 atm for 5 days, and after being placed at 0.01 atm for 3 hours, gelation occurred, as shown in FIG.

Example 8

The difference from the embodiment 4 is that the polymer concentration in the PAM/CNS hydrogel of the present embodiment is 20 wt%, no tricalcium silicate is added, and the PAN gelation reaction adds tricalcium silicate at normal temperature. With sodium hydroxide, the gelation time was 20 min. At room temperature, OH ^- reduced the S ₂ O ₈ ^2- in the initiator, so that polymerization was difficult to occur.

Example 9

In contrast to Example 8, in contrast to this example, after adding 500 ppm of tricalcium silicate, the gelation time was extended from 20 minutes to 300 minutes. The gelation reaction did not occur in time after the addition of 500 ppm of sodium hydroxide, indicating OH ^- inhibition at the initial stage of polymerization, as shown in Fig. 9.

Example 10

The morphology and distribution of the CNS of the PAM/CNS hydrogel of Example 1-2 was analyzed by transmission electron microscopy with an energy dispersive spectroscopy system installed. The structure of the gel was scanned by a high resolution scanning electron microscope. The glass transition temperature of the hydrogel is measured by a differential scanning calorimeter. Secondary ion mass spectrometry was used to detect PAM terminal groups and side groups and CNS. The static secondary ion mass spectrum of PAM and hydrogel C200 was obtained by a secondary ion mass spectrometer five-stage spectrometer. A large amount of Bi ³⁺ ions were added to the sample, which was accelerated by an average pulse current of 0.3 Pa, 25 kV. The grating area is 200 μm × 200 μm, and the spectral collection time is 40 s each time, which corresponds to a <4×1011 ion.cm ⁻² ion dose. Three positive and negative spectra of each sample were recorded at different locations, resulting in Figures 10-11.

Example 11

In contrast to the first embodiment, in this embodiment, the polymer matrix is N-isopropylacrylamide, the nanoparticle is selected from hectorite, and the hectorite is 30000 ppm to prepare a hydrogel. The tensile and compression tests were carried out, and the mechanical tests were carried out at 25 ° C using an MTS tester. In the tensile test, a diameter of 30 mm and a diameter of 3.2 mm were used as samples. The extension of the sample was 2.0 mm for C40 and 1.8 mm for C200, and the tensile loading rate of the sample was 50 mmmin ^-1 . A cylindrical sample of the previously prepared hydrogel was used in the compression test. The C40 sample was 11.8 mm in diameter and 6.1 mm high. The C200 sample was 10.3 mm in diameter and 5.7 mm in height. The cycle was subjected to multiple cycles of compression test. The head speed is 1mmmin ^-1 , and when it is loaded to 8400N, the maximum loading force is reached, and then the loading is stopped.

Example 12

In contrast to Example 11, in this example, the polymer used in the present example was N-isopropylacrylamide, and the nanoparticles were selected from hectorite and hectorite at 125000 ppm.

Example 13

In contrast to Example 11, in this embodiment, the polymer used in the present embodiment is polyacrylamide (PAM), the nanoparticles are selected from montmorillonite (MMT), and the montmorillonite (MMT) is 8700ppm.

Example 14

In contrast to Example 13, in this example, the polymer was polyacrylamide (PAM), the nanoparticles were selected from montmorillonite (MMT), and the montmorillonite (MMT) was 80,800 ppm.

Example 15

In contrast to Example 12, in this example, the polymer was polyacrylamide (PAM), the nanoparticles were selected from graphene oxide (GO), and the graphene oxide (GO) was 80 ppm.

Example 16

In contrast to Example 15, in this example, the polymer was polyacrylamide (PAM), the nanoparticles were selected from graphene oxide (GO), and the graphene oxide (GO) was 480 ppm.

Example 17

In contrast to Example 13, the polymer used in the present example is polyacrylamide (PAM), and the nanoparticle-selected layered double hydroxide (LDH), layered double hydroxide (LDH) ) 8000ppm.

Example 18

In contrast to Example 13, the polymer used in the present example was polyacrylamide (PAM), and the additive selected alginate, and the alginate was 110,000 ppm.

Example 19

In contrast to Example 17, the polymer used in the present example was polyacrylamide (PAM), the additive selected alginate, and the alginate was 330000 ppm.

Example 20

The hydrogel prepared in Example 1 was subjected to an expansion test by immersing the hydrogel in deionized water at 25 ° C for 3 weeks, and the deionized water height was higher than the hydrogel height in order to achieve a swelling balance. During this process, the deionized water is periodically replaced. The expanded sample is then lyophilized. The expansion ratio Q is calculated by using Q = Ws / Wd, where Ws is the weight of the expanded sample and Wd is the weight of the sample after drying, wherein the CNS concentration in the PAM/CNS hydrogel is 40 ppm, 100 ppm, and 200 ppm, respectively.

Example 21

The invention provides a nano composite hydrogel material, the composite hydrogel is composed of a polymer as a matrix material, and the nanosphere crystal is added as a crosslinking agent; the polymer matrix is acrylamide as a monomer, and the peroxide is used. Ammonium sulfate was used as an initiator to prepare a polyacrylamide PAM; N, N, N', N'-tetramethyl-ethylenediamine was added as a catalyst. The nanospheres are calcium hydroxide nanospheres; the calcium hydroxide nanospheres have a diameter of less than 10 nm, preferably less than 5 nm; and the composite hydrogel contains nanospheres having a hydrogel weight of 1-500 ppm; It is preferably from 40 to 200 ppm of nanospheres having a polymer content of from 10% by weight to 50% by weight, preferably 20% by weight, based on the total weight of the hydrogel.

In the preparation of the nanocomposite hydrogel material, the hydration reaction of the Portland cement of the main component tricalcium silicate (Ca ₃ SiO ₅ ) is used to prepare the calcium hydroxide nanosphere crystal CNS. When the particles of tricalcium silicate are dispersed in water, divalent calcium ions (Ca ²⁺ ) are separated from the tricalcium silicate to form calcium hydroxide in the solution. 0 ° C is the optimum temperature because at this temperature, the release rate of calcium ions from tricalcium silicate is just enough to form calcium hydroxide crystals, and likewise, the crystal size is also suppressed due to the lower crystallization temperature.

As is clear from Figure 1, a photo of an electron microscope surrounding the hydrated tricalcium silicate particles is shown. The left side of Figure 1 corresponds to a large piece of tricalcium silicate with a height of 500 nm. The right side of Figure 1 and the inserted image show tiny particles with a diameter below 5 nm. Energy spectrum analysis confirmed that these tiny particles contained only calcium and oxygen, and the crystal structures observed in the electron diffraction pattern of Fig. 8 and the inset in Fig. 1 indicate that those are CNS crystals. In an aqueous solution with a concentration of 200 ppm, the electric double layer produced by the counter ion on the surface of the CNS has a potential of -10 mV (determined by dynamic light scattering test); these counter ions ensure that the CNS can effectively diffuse at a concentration of 40 to 200 ppm without any agglomeration. . A nanocomposite hydrogel material comprising an nppm concentration CNS (designated Cn as sample identification) was prepared by in situ free radical polymerization of acrylamide in a CNS suspension. As shown in Figure 5, for C200 (200 ppm CNS samples), particles less than 5 nm in diameter were dispersed very uniformly in the PAM matrix. Due to the absence of agglomeration, the small size and uniform dispersion of the CNS, the clarity of the C200 is almost the same as the original PAM hydrogel (Figure 4). The linkage between the PAM segment functional group and the CNS is established by an acid-base reaction of the initiator ammonium persulfate and calcium hydroxide.

At room temperature, OH ^- causes a decrease in S ₂ O ₈ ^2- in the initiator, so that polymerization is difficult to occur (Fig. 26). However, at 0 ℃, S _² O ₈ ^2- and OH ^- oxidation-reduction reaction between the suppressed; excess OH ^- NH ⁴⁺ and can react NH _{_3,} NH ₃ can be a vacuum pump to remove. Moreover, oxygen is removed during the pumping process. Therefore, polymerization occurs under vacuum (0.01 atm) (Fig. 5-8). The entire preparation of the CNS-prepared PAM/CNS hydrogel process is embodied in the schematic, as shown in Figure 9, where the CNS and PAM end groups are linked by ionic bonds between Ca ²⁺ and S ₂ O ₈ ^2- . To demonstrate this principle, the characteristic ion peaks of the original PAM and C200 were obtained using secondary ion mass spectrometry. In the PAM CH ^- as a reference, when the CN ^- and CNO ^- is a side group, anion SO ₄ CH ^- and the relative peak areas of SO ₄ CH ^2- group is selected to represent the end of the chain PAM. The decrease in relative peak intensity of SO ₄ CH ^- and SO ₄ CH ^2- with the initial PAM indicates a decrease in the terminal group of C200, as shown in Figures 10-11, where curve a represents C200 and curve b represents PAM. Likewise, in vacuum can be generated with the OH side groups -CONH ² ^- ammonia NH ₃ formed in the reaction, and may be attached on the surface of Ca ²⁺ CNS hydrolyzed to -COO-, this reaction path is the CN ^- and CNO ^- relative peak intensity reduction confirmed. The presence of CaSO ₄ CH ^- and CaSO ₄ CH ^2- peaks in the C200 sample strongly suggests a chemical bond between the CNS and PAM end groups (Figure 11). Moreover, their relative strength did not change in the tensile test of 60 times before and after, meaning that there was a strong connection between the CNS and the PAM terminal group.

In the expansion test, C40 (CNS 40ppm concentration sample) was lyophilized by dry gel and swelled in deionized water for 3 weeks before and after, only losing less than 0.1wt% of the weight fraction, indicating that a 40ppm concentration hydrogel formed a Complete cross-linking network. In the same volume content, the CNS particles have a number density size of about 1000, 2000, 200, and 5.0 × 10 ⁵ times higher than that of hectorite, GO, LDH, and TiNS, respectively, due to less than 5 nm. The CNS is more uniformly dispersed as a cross-linking point, and its CNS surface area is less than 78.5 nm ² with respect to a nanosheet having a functional surface of more than 2800 nm ² . The distribution and density of cross-linking points play a key role in establishing a cross-linking network. For example, calcium hydroxide microparticles are cooled from room temperature to 0 ° C from a suspension of calcium hydroxide. CA200 (sample PAM hydrogel containing 200 ppm calcium hydroxide microparticles) was prepared in the same manner as PAM/CNS hydrogel. In the same weight of calcium hydroxide, the number density of cross-linking points in CA200 was only 1/3.8 x 10 ⁶ relative to the hydrogel. Such a low crosslink density produces a poor network structure with limited mechanical properties and will not continue to swell but will dissolve completely in water. Due to the high number density and uniform dispersion of CNS particles, the crosslinked network in the hydrogel can be effectively regulated by the CNS density. The CNS suspension at a concentration of 40 ppm was prepared by dispersing 100 ppm of tricalcium silicate in 0 ° C water for a dispersion time of 3 days. The maximum concentration of CNS is 200 ppm, which is obtained by dispersing 500 ppm of tricalcium silicate in water at 0 °C for 3 days. This concentration does not increase with increasing tricalcium silicate or higher hydration time due to the upper limit of the calcium ion concentration in the suspension of tricalcium silicate. Figure 12 presents a typical SEM image showing the crystal morphology of a dry sample of C40 and a C200 dry gel. Different from NC hydrogel nanosheets, such as PAM/LDH hydrogels have a graded porous morphology, and there are irregular distributions of micron and nanoscale particles. C40 xerogels indicate the presence of a uniform distribution of porous structures of 200-400 microns. . Interconnected nanochannels were found on the inner walls of the porous structure (Fig. 13). Moreover, Figure 14 further shows that most of the nanochannels are less than 300 nm, which means that the crosslinking points are uniformly dispersed at the nanometer level. As the density of the cross-linking agent increases, the size of the porous structure is similar to that of C40 in C200 xerogel, about 20-80 nm, and there are a large number of parallel and cross-linked filament structures, which are between 50 nm and 2 um. It is regularly distributed in the holes (Figure 13). There is a significant protrusion between the crosslinked wire and the inside of the hole at the joint, indicating that it has a strong bonding force, which plays an important role in the swelling property and mechanical properties of the hydrogel.

Compared to C200, the C40 crosslinked network has a large expansion characteristic, mainly due to its larger pore size and less crosslinked filamentary connection. When the C40 was maintained at the initial size, its expansion ratio Q was 253.4, which was about 2.6 and 5.7 times higher than that of C100 and C200 (100S concentration of CNS, which was prepared by standing at 250 °C suspension of 250 ppm of tricalcium silicate at 0 °C for 3 days). Therefore, the Q value can be controlled from a simple adjustment of the CNS concentration in the hydrogel from 44.8-253.4. The string-shaped raised structure can be found in micron-sized C200 dry gel channels (Figures 17 and 16). We believe that the protrusions with a diameter of 100-500 nm are made by PAM. Chain coated CNS. The thickness of the coating (100-500 nm) and the distance of the protrusions (700 nm - 3 μm) indicate that the introduction of CNS has little confinement effect on the fluidity and elasticity of the polymer molecules in the NC gel of the present invention. Another evidence indicates that it is caused by the glass transition temperature Tg, which is detected by a differential scanning calorimeter DSC (Fig. 19). The Tg of the hydrogel (C40: 182.6 ° C and C200: 183.2 ° C) is slightly higher than the linear Tg of the PAM (182.3 ° C), which is dependent on the CNS concentration. In contrast, the Tg of CA200 has a significant increase with a Tg of 196.7 °C, indicating a strong binding between the larger sized particles. Thus, the polymer molecules in the hydrogel crosslinked network are free, highly elastic, and mobile, exhibiting a conformational image between the CNS.

The mechanical properties of the hydrogel are strongly influenced by the CNS concentration, controlling its polymer network structure (as shown in Figure 1), establishing a link between network structure and mechanical properties, and at different room temperature conditions, for water condensation at different CNS concentrations. The tensile test of the rubber, the representative stress-elongation curve shows that the maximum stress of the polyacrylamide-based hydrogel increases from 20KPa to 430KPa, and the elongation at break increases from 10 to 121, as shown in the figure. 20 and FIG. 26, curve III in FIG. 20 represents a stress-elongation curve at a CNS concentration of 0 ppm and r=920%, and curve II represents a stress-elongation ratio at a CNS concentration of 40 ppm and r=905%. Curve, curve I represents a stress-elongation curve at a CNS concentration of 200 ppm and r = 290%.

r is the residual deformation ratio, which is defined as the ratio of the length of the original sample size in the direction of the loading force after the loading force is released, and the residual deformation ratio is regarded as the correction index. After 121 tensile tests, the C40 sample returned to 90.5% of its original size, meaning it had excellent recoverability.

The hydrogel was subjected to compression and tensile tests by Examples 11 to 19, and Table 1, Table 2, and Figs. 21-25 were obtained. The curve i in Fig. 21 represents a compressive stress-strain curve at a CNS of 40 ppm and r = 51.5%. Ii represents the compressive stress-strain curve of CNS200ppm, r=9.6%; curve A in Fig. 22 represents the fracture cyclic tensile stress curve of the fifth cycle, and the first to fourth cycles after the expansion of 5 times in the box area Tensile stress curve; Fig. 23 is a graph of the first to fourth cycle tensile stress curves in the box area of Fig. 22 magnified 5 times, and curve A represents the fracture cycle tensile stress curve of the fifth cycle, curve B The tensile stress curve of the fracture cycle representing the first cycle, the fracture cycle tensile stress curve of the second cycle of curve C, the fracture cycle tensile stress curve of the third cycle of curve D, and the fracture cycle of the fourth cycle of curve E Tensile stress curve; Figure 24 is a cyclic tensile stress-strain curve and a fracture stress curve of the fifth cycle in which C200 is expanded ten times in the fourth cycle, wherein curve A represents the fracture cycle of the fifth cycle. Stress curve, In the box area, the first to fourth cycles of the tensile stress curve after 10 times expansion; Fig. 25 is the first to fourth cycles of the expansion of the box area of Fig. 24 by ten times. Extensive stress curve, curve A represents the fracture cycle tensile stress curve of the fifth cycle, curve B represents the fracture cycle tensile stress curve of the first cycle, and the fracture cycle tensile stress curve of the second cycle of curve C, curve D The fracture cycle tensile stress curve of the third cycle, and the fracture cycle tensile stress curve of the fourth cycle of the curve E.

Among the same volume content and dispensability, the number density of particles less than 5 nm CNS is higher than that of hectorite, graphene oxide, layered double hydroxide, titanate flakes and calcium hydroxide spherulites 1000, 2000, respectively. 200, 5.0 × 10 ⁵ and 3.8 × 10 ⁶ times.

Table 1 shows the elongation at break and the draw ratio of the composite elastic hydrogel prepared by adding different cross-linking agents.

Table 2. Cross-linking nanoparticle size comparison

The elongation at break of C40 is higher than the elongation at break of hydrogels reported in all previous literatures and exceeds the reported maximum stress by four times at the same stage (see Table 1). The fracture toughness of C40 reaches 33.9 MJm ^-3 because it can achieve high stress and high elongation properties in the same time. The tensile properties of C40 can be explained by the following reasons: the unpolymerized CNS size is less than 5 nm, which provides uniform microporosity in the polymer network. The lower the concentration of CNS, the less the connecting fibers, the larger the pore size, the more helpful. Deformation. The stress of C200 reaches 630KPa at a breaking elongation of 65 and the residual deformation ratio reaches 290% (Fig. 20 and Fig. 27), which is equivalent to 2.7 times that of the reported mixed alginate transparent polyacrylamide hydrogel. The draw ratio is 16 times higher, see Table 1). The fracture toughness of C200 is 26.2 MJm ^-3 , which is lower than C40, mainly due to the decrease of the deformation ability of the polymer network. However, for C200, the smaller pore size and the establishment of the fiber structure between the inner walls of the connecting holes provide a high mechanical strength and restoring force. In the compression test, after withstanding a compressive stress of 100 MPa and a strain of 95%, the C200 almost recovered to the original size, and the residual deformation ratio was r = 9.6%. On the contrary, although the C40 can withstand 78 MPa and the strain is 99%. The stress is not broken, but it can only be restored to half of the original size (there is a residual deformation ratio of r = 51.5%).

The excellent recoverability of the C200 is further demonstrated by a cyclic tensile test (Figure 8). When loading from the first loading to the fifth loading, its C200 was extended 5 times, and its cyclic tensile stress-strain curves almost overlaped each other, indicating that the sample was subjected to a slight hysteresis reaction. The residual deformation ratio r was 22.3% in the first cycle and increased by 1.1% in the subsequent four-cycle tensile test, as shown in Figures 22-25. The elongation of the sample in each cycle is calculated by the recovery length, with a slight irreversible deformation during the last stretching. Therefore, due to the irreversible deformation in the previous elongation, the elongation at break of the C200 sample was about 40% in the fifth cycle, with a residual deformation ratio of 205%. The increased tensile stress-strain curve is shown in Figure 23 as the tensile modulus of the first cycle is slightly higher than the rest of the cycle, where the stretch is less than four times and is reduced in further stretching. This indicates that there is a slight irreversible deformation in the crosslinked network during the initial stretching process. Subsequently, the recoverability of the hydrogel is manifested after the deformation adjustment of the initial crosslinked network. The recoverability can also be demonstrated in the stretched C200 hydrogel (Figures 24 and 25). Mainly because the hydrogel obtained a high elongation rate in the first to fourth cycles, and the residual deformation ratio in each cycle was higher than the residual deformation ratio in the five-fold cycle test. However, with a more adequate conformational adjustment, the residual distortion ratio r is reduced to 196% at the fifth pass. This indicates excellent recovery along the direction of the tensile force and is found by the initial slight irreversible shape.

In summary, the PAM/CNS hydrogel can achieve high expansion, elongation, fracture stress and recoverability through CNS concentration adjustment. CNS can also be obtained by replacing the tricalcium silicate with a Portland cement suspension, which greatly reduces the cost of preparation. The results show that CNS nanospheres with uniform dispersion of less than 5 nm can pass through. Per-tricalcium silicate is obtained in a low temperature hydration reaction which helps the hydrogel to enhance the crosslinked network and various aspects of the properties.

The above description shows and describes a preferred embodiment of the present invention. As described above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be construed as being Combinations, modifications, and environments are possible, and can be modified by the teachings of the above teachings or related art within the scope of the inventive concept described herein. All changes and modifications made by those skilled in the art are intended to be within the scope of the appended claims.

Claims

A nano composite hydrogel material, characterized in that: the composite hydrogel is composed of a polymer as a matrix material, and nano spherulites are added as a crosslinking agent; and the polymer matrix is acrylamide AM as a monomer. The ammonium persulfate APS was used as an initiator to prepare a polyacrylamide PAM; wherein N, N, N', N'-tetramethyl-ethylenediamine was added as a catalyst.
The nanocomposite hydrogel material according to claim 1, wherein the nanosphere crystal is calcium hydroxide nanosphere crystal; and the calcium hydroxide nanosphere crystal has a diameter of less than 10 nm.
The nanocomposite hydrogel material according to claim 1, wherein the composite hydrogel contains nanospheres in an amount of from 1 to 500 ppm by weight of the hydrogel.
The nanocomposite hydrogel material according to claim 1, wherein the polymer is contained in an amount of 10% by weight to 50% by weight based on the total amount of the hydrogel.
A method for preparing the nanocomposite hydrogel of claim 1, wherein the specific steps are as follows:

S1, mixing granules of tricalcium silicate / dicalcium silicate / Portland cement / white cement or a mixture thereof in an ice bath at 0 ° C to form calcium hydroxide nanospheres, the calcium hydroxide nanospheres dispersed Obtaining a translucent aqueous dispersion in deionized water, stirring for 10 minutes under ultrasonic treatment to obtain a uniform dispersion, and the uniform dispersion is a calcium hydroxide suspension;

S2, adding a polymer, an initiator and a catalyst to the calcium hydroxide suspension to form a mixture;

S3, the mixture was kept in an ice bath at 0 ° C for 72 hours to fully hydrate the tricalcium silicate;

S4, forming a nanocomposite hydrogel material by a polymerization method at 0.01 atm;

Wherein, the stirring speed is from 10 rpm to 1000 rpm.
The method for preparing a nanocomposite hydrogel according to claim 5, wherein the polymer is a water-soluble polymer, and the water-soluble polymer is selected from the group consisting of polyacrylamide, N-isopropylacrylamide, and polyethylene. An alcohol, a polyacrylate or a mixture thereof; the initiator is a water-soluble polymer, which is ammonium persulfate, potassium persulfate, sodium persulfate or 2,2'-azobisisobutylphosphonium. Dihydrochloride; adding a dispersant to the mixture in S2 to improve the dispersibility of the calcium hydroxide nanospheres; the dispersant is an anionic surfactant, the anionic surfactant is a polycarboxylate ether, twelve Sodium alkyl sulfate, sodium dodecylbenzene sulfonate, anionic polyacrylamide or sodium isethionate.
The method for preparing a nanocomposite hydrogel according to claim 5, wherein the hydrogen and oxygen The hydration temperature of the calcium nanospheres ranges from -10 °C to 40 °C.
The method of preparing a nanocomposite hydrogel according to claim 5, wherein the polymerization method is in situ radical polymerization.
The method of preparing a nanocomposite hydrogel according to claim 5, wherein the nanoparticles are added to the mixture in S2 to further improve the mechanical properties of the composite hydrogel.
The method for preparing a nanocomposite hydrogel according to claim 9, wherein the nanoparticles are selected from the group consisting of hectorite, montmorillonite, graphene oxide, layered double hydroxide, and titanate nanometer. Tablets, controllably active nanogels or mixtures thereof.