KR20190111421A - Method for preparing a temperature responsive hydrogel possible of controlling transmittance by optically bistable switching, the hydrogel prepared by the method and the smart pannel comprising the hydrogel - Google Patents

Abstract

Disclosed by the present invention is a manufacturing method of a temperature sensitive hydrogel, which comprises: a step of making temperature sensitive monomers react sequentially to form a temperature sensitive macromonomer; a step of grafting the temperature sensitive macromonomer to a cellulose derivative; and a step of cross-linking the grafted macromonomer and synthesizing hydrogel having optical bistability. A phase transition state is maintained by hydrophobic junctions between cellulose derivative molecules at a specific temperature range even when the temperature of hydrogel is reduced after the phase transition as the temperature-sensitive macromonomer is grafted onto the cellulose derivative molecule; and a hydrophobic junction decomposes and transfers to the first phase when cooling to room temperature. A smart window produced by using the hydrogel is able to: adjust the section and range of a low critical solution temperature depending on the type of the temperature sensitive monomer constituting the hydrogel, the copolymerization ratio thereof, or the molecular weight of cellulose derivative molecules; adjust a range with optical bistability; and adjust light transmittance according to external environment and needs of a user.

Description

Method for preparing a temperature responsive hydrogel possible of controlling transmittance by optically bistable switching, the hydrogel prepared by the method and the smart pannel comprising the hydrogel }

The present invention relates to a method for manufacturing a temperature sensitive hydrogel which can control light transmittance, and a hydrogel thereby, specifically, a method for preparing a temperature sensitive hydrogel that can control and fix light transmittance through optical bistable, and a hydrogel thereby The present invention relates to a smart window including a smart panel.

One of the most important issues of the 21st century is the severe energy shortage. Therefore, efficient use of finite energy resources is required through low energy consumption, energy collection and energy storage technologies. In this respect, as a new material glass, a smart window in which light transmittance is controlled in response to the external environment has been attracting much attention as a functional alternative in terms of energy economy.

A smart window means the window which can adjust the transmittance | permeability of sunlight freely. Most solar transmittance control technology in the past was a method of mounting a film having a specific transmittance on the window. However, the smart window has the advantage of providing a high level of convenience to the user while significantly increasing the transmittance of solar light compared to the method of mounting a film by developing a material that can freely control the transmittance of sunlight. Thanks to these advantages, smart windows are currently used in various fields such as transportation, construction and information display, and are mainly used for housing interiors such as housing windows, living rooms, verandas, porches, and shower rooms. In particular, developed countries such as Japan, the United States, and Europe continue to develop their applications, and in some fields, they are actually being commercialized, which is expected to expand rapidly in the future.

In addition, smart windows can be practically applied, such as roofs, skylights, architectural or vehicle windows and interior partitions. Since the smart window can appropriately regulate heat exchange from sunlight transmitted into the house, unnecessary use of energy can be suppressed through air conditioning or heating. Smart windows, for example, can be used to reflect large amounts of sunlight in the summer away, suppressing overheating inside buildings, and helping to keep the room warm by absorbing the sun's heat in winter.

As a conventional technique for a window that can variably control the inflow of sunlight indoors, the "smart window device" of the Republic of Korea Patent Publication No. 10-2012-0045915 uses the electrochromic material to the window through the redox reaction generated by the current It has been shown that it can block sunlight by reversibly controlling discoloration. This technology has achieved the goal of variable transmission of sunlight, but has the disadvantage of having a complicated structure and operating only by a user's manual electric control.

Another prior art, Korean Patent Registration No. 10-0310727, "Autonomous-responsive laminate, method for manufacturing the same, and a window using the same" discloses a smart window that is actively operated using a temperature sensitive polymer material. The patent shows that polysaccharide derivatives dissolved in water can coagulate with each other due to an increase in temperature to scatter sunlight and control the amount of sunlight entering the room. That is, the principle is to block sunlight at temperatures above the cloud point where the polymer derivatives aggregate and scatter sunlight, and to transmit light below. This technology enables autonomous active control without an external device except a window, but has a disadvantage in that operation is determined only by a fixed cloud point depending on the material regardless of the intensity of sunlight. If the outside temperature is less than the cloud point, even though the intensity of sunlight is strong, it transmits sunlight, and to overcome this, if the blur point of the material is lowered, the window is opaque even when the temperature is high and the sunlight is weak, making it difficult to view the surrounding landscape. In other words, regardless of the intensity of sunlight there is a problem that the solar light blocking is determined only by the ambient temperature.

Korean Patent No. 10-1535100 "electrochromic smart window and its manufacturing method" discloses a smart window using an electrochromic material. The patent provides a smart window that can be discolored by using oxidation and reduction reactions depending on whether electricity is applied using a metal oxide. However, in the case of using electrochromic materials, in order to maintain a discolored state, a constant energy supply is required to maintain a specific state, and light transmittance is difficult to adjust stepwise.

Accordingly, by developing a hydrogel having optical bistable that can selectively adjust a variety of light transmittance according to the surrounding environment or the user's request, and does not consume external electric energy steadily, and using the hydrogel to transmit the light transmittance by the user's control The situation is that you need a smart window.

In order to solve the above problems, the present invention is to provide a method for producing a temperature-sensitive hydrogel having optical bi-stability that does not consume external electrical energy steadily.

Another object of the present invention is to provide a temperature sensitive hydrogel having optical bi-stability that does not consume external electric energy steadily.

Another object of the present invention is to provide a smart panel in which light transmittance can be adjusted by user's control using the hydrogel.

In order to solve the said subject, this invention is one aspect,

Reacting the temperature sensitive monomers sequentially to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And cross-linking the grafted macromonomer to synthesize a hydrogel having optical bistable stability.

The temperature-sensitive monomer is N - isopropyl acrylamide, N -n- propyl acrylamide, N, N '- dimethyl acrylamide, N, N' - diethyl acrylamide, methacrylic acid, 2-hydroxyethyl methacrylate And at least one monomer selected from the group consisting of N -2-diethylaminoethyl acrylate is copolymerized.

The temperature sensitive monomer addition is characterized in that it consists of a constant rate of 0.01ml / min to 10ml / min.

Forming the temperature sensitive macromonomer is characterized in that at least two or more different temperature sensitive monomers are copolymerized, including chain transfer agents.

The cellulose derivative is a glucose molecule is repeatedly bonded to the hydroxyl group of the glucose molecule is characterized in that the grafted with a vinyl group.

The crosslinking agent used in the crosslinking is N , N , -methylenebisacrylamide, diethylene glycol diacrylate and dimethacrylate, ethylene glycol diacrylate and dimethacrylate, tetra (ethylene glycol) diacrylate, 1 It is characterized in that at least one selected from the group consisting of, 6-hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate, and poly (ethylene glycol) diacrylate.

In order to solve the above other problem, the present invention is another aspect,

Reacting the temperature sensitive monomers sequentially to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And a step of synthesizing a hydrogel having optical bistable by crosslinking the grafted macromonomer, thereby providing a smart panel comprising a temperature sensitive hydrogel.

The content of the photothermal conversion material mixed in the temperature sensitive hydrogel is preferably 0.01 to 50% by weight of the dry weight of the hydrogel.

The smart panel is characterized in that the temperature is adjusted according to the magnitude of the voltage and current applied by the temperature control device and the light transmittance of the panel is adjusted.

The smart panel is characterized in that the light transmittance can be continuously maintained even if the supply of current applied to the panel is removed by the hydrophobic bonding of the cellulose derivative molecules.

According to the present invention, as the temperature-sensitive macromonomer is grafted onto the cellulose derivative molecule, the hydrogel is maintained in a phase transition state by hydrophobic junctions between cellulose derivative molecules at a specific temperature section even when the temperature decreases after the phase transition. Upon hydrolysis, the hydrophobic junction decomposes to the original phase.

In addition, the smart window manufactured by using the hydrogel can control the range and range of the below critical solution temperature according to the type of the temperature sensitive monomer constituting the hydrogel and the copolymerization ratio or molecular weight of the cellulose derivative molecule and has optical bistable stability. The range can be adjusted so that the light transmittance can be adjusted according to the external environment and the user's needs.

FIG. 1 illustrates a process of synthesizing a cellulose derivative molecule grafted with a temperature sensitive macromonomer according to an embodiment of the present invention.
Figure 2 shows in anticipation of the internal molecular structure of the temperature increase and cooling process of the hydrogel prepared according to an embodiment of the present invention.
Figure 3 shows the analysis of the linear swelling ratio according to the temperature of the temperature increase and cooling process of the hydrogel prepared according to an embodiment of the present invention.
Figure 4 shows the analysis by the infrared spectroscopy of the hydrogel prepared according to an embodiment of the present invention and the reactants used to prepare it.
Figure 5 shows a volume change graph for the temperature of the hydrogel prepared by changing the temperature-sensitive macromonomer molecular weight in accordance with an embodiment of the present invention.
Figure 6 shows a graph of the volume change with respect to the temperature according to the copolymerization ratio of PDNV according to an embodiment of the present invention.
Figure 7 shows the volume change graph of the hydrogel according to the type of monomer change in accordance with an embodiment of the present invention.
Figure 8 shows the volume change graph according to the temperature of the prepared PDNV hydrogel according to the comparative example of the present invention.
9 illustrates a manufacturing process of a smart panel having optical bi-stability according to an experimental example of the present invention.
10 illustrates a change in light transmittance according to a supplied current of a smart panel manufactured according to an experimental example of the present invention.
FIG. 11 illustrates light transmittance according to the magnitude of the supplied current and the direction of the supplied voltage of the smart panel manufactured according to the experimental example of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention comprises the steps of sequentially reacting the temperature sensitive monomer to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And cross-linking the grafted macromonomer to synthesize a hydrogel having optical bistable stability.

Cellulose is a polymer composed of β-glucose molecules, and the three hydroxyl groups of the β-glucose molecules greatly affect its characteristics. And a cellulose derivative refers to the thing in which one part of the hydroxyl group which a cellulose has is substituted by another substituent. The kind of the substituent is not particularly limited.

Specifically, vinyl group, carboxyl group, primary, secondary or tertiary amino group, quaternary ammonium group, hydroxyalkyl group, alkyl group, acetyl group, cyanoethyl group, sulfuric acid group, amide group, aldehyde group, nitro group, nitric acid group, The group containing substituents, such as a tosyl group, a phenylcarvanylate group, a trityl group, and the bridge | crosslinking group which couple | bonds at least 2 or more hydroxyl groups, is mentioned.

A cellulose derivative has various characteristics according to the kind of structure to substitute, substitution degree which shows the grade of substitution, etc. Like cellulose, this cellulose derivative is used for various uses utilizing its characteristics.

Specifically, cellulose derivative molecules form strong hydrophobic junctions at high temperatures above a certain temperature, which are not removed and maintain intermolecular bonds even when the ambient temperature is cooled below a certain temperature to form a hydrophobic junction. To remove the hydrophobic junction, it must be subcooled to a temperature below room temperature. That is, there is a heat history phenomenon in the formation and removal of hydrophobic junctions of cellulose derivative molecules.

In addition, there is a hydroxyl group in the cellulose molecule, which can be grafted with a temperature-sensitive macromonomer molecule containing a vinyl group at its end. In addition, by polymerizing with a crosslinking agent, a hydrogel having a cellulose main chain having a network structure can be produced.

When the cellulose derivative is grafted with the temperature sensitive polymer, the larger the molecular weight, the more the contribution to the change of phase transition temperature range. The weight average molecular weight of the cellulose derivative is preferably 14000 to 63000. If the molecular weight of the cellulose derivative is less than 14000, the hydrophobic bonding force between the cellulose derivative molecules in the PDNV-g-MC hydrogel is weak, and thus the thermal hysteresis phenomenon is not strong. In this case, the contribution of cellulose in the phase transition temperature section of the hydrogel is increased so that the phase transition is rapidly made at a high temperature, which is not preferable because the detailed composition of the light transmittance to be achieved is not achieved.

Figure 1 shows a process for producing a hydrogel having a cellulose main chain according to an embodiment of the present invention. Referring to Fig. 1, thermosensitive macromonomer molecules (poly ( N, N' -diethylacrylamide- co - N -isopropylacrylamide- co -1-vinyl-2-pyrrolidinone), poly (NDEAm- co- NIPAm- co -VP, PDNV), cellulose derivative molecules (methyl cellulose, MC), crosslinking agent ( N, N ' -methylenebisacrylamide, N, N -methylenebis (acrylamide), BisAA) It is characterized by producing a hydrogel having a cellulose main chain through the method.

The present invention exhibits a reversible sol-gel phase transition or volume phase transition at a particular temperature, wherein the lowest specific temperature indicative of the phase transition is referred to as the "lower critical solution". temperature, LCST).

The lower critical solution temperature means a specific temperature point, and based on the temperature point, phase separation due to polymer chain aggregation occurs rapidly, and light transmittance is transparent by light scattering of the formed aggregates. Or opaque only.

Specifically, the thermosensitive macromonomer has the characteristic that its properties change according to the external temperature and causes a phase transition in a specific temperature section, thereby showing reversible sol-gel phase transition or volume phase transition. The temperature point at which the phase transition occurs is called the 'critical solution temperature below'. The critical solution temperature below means a specific temperature point and based on this temperature the aggregation of the polymer chains is shown. As a result, phase separation with the swelling liquid is rapidly performed, and light is scattered by the formed aggregate to control the light transmittance.

In addition, the temperature-sensitive macromonomer according to the present invention is characterized by copolymerizing two or more kinds of different temperature-sensitive monomers.

The temperature-sensitive monomer is N - isopropyl acrylamide, N -n- propyl acrylamide, N, N '- dimethyl acrylamide, N, N' - diethyl acrylamide, methacrylic acid, 2-hydroxyethyl methacrylate And at least one monomer selected from the group consisting of N -2-diethylaminoethyl acrylate is copolymerized.

Specifically, the synthesis of macromonomers having different lower critical solution temperatures is obtained by repeating the polymerization process by mixing an initiator and a chain transfer agent with the monomers, and adding the next monomer at a slow rate during the polymerization. The range of the lower critical solution temperature of the polymerized thermosensitive macromonomer varies depending on the type and number of monomers added. The temperature sensitive monomer to be added is synthesized in the form of a multicomponent copolymer as it contains at least two different temperature sensitive monomers.

Immediately after the polymerization of the first temperature sensitive monomer is added, the process of adding the next temperature sensitive monomer is repeated and copolymerized, wherein at least two different temperature sensitive monomers are sequentially added and copolymerized, and the monomer is injected. The speed is characterized in that 0.1ml / min ~ 10ml / min.

The injection rate of the monomer is preferably 0.1 ml / min to 10 ml / min, as well as shortening the time for the polymerization of each of the temperature sensitive monomers having different lower critical solution temperatures by different compositions, as well as thermal properties. By controlling, the macromonomers are synthesized into the multicomponent polymer by successive polymerization of the components having different compositions so that the macromonomers have a critical solution temperature section below.

More specifically, the bottom critical solution temperature of the resulting temperature sensitive macromonomer is between the lowest bottom critical solution temperature and the highest bottom critical solution temperature of the added monomer and by controlling the type and copolymerization fraction of the monomer, the bottom critical solution In addition to widening the range of temperature is characterized in that the temperature range can also be moved.

In addition, in the production of the temperature sensitive macromonomer, the type of initiator and chain transfer agent is commonly used, and is not particularly limited.

In addition, the temperature-sensitive macromonomer is characterized in that it comprises a vinyl group at the end.

Specifically, the synthesized macromonomer includes an amine group or a hydroxyl group at the end by a chain transfer agent, thereby vinylating N-acryloxysuccinimide, acryloyl chloride or methacryloyl chloride at the end of the macromonomer. By doing so, the macromonomer may be crosslinked.

In addition, the cellulose derivative molecule and the temperature sensitive macromonomer are crosslinked by a crosslinking agent to provide a temperature sensitive hydrogel.

In this case the cross-linking agent is not specifically limited, but preferably, N, N '- methylenebisacrylamide, diethylene glycol diacrylate and dimethacrylate, ethylene glycol diacrylate and dimethacrylate Reid, tetra (ethylene glycol) And at least one selected from diacrylate, 1,6-hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate, and poly (ethylene glycol) diacrylate.

In addition, in one aspect of the present invention, there is provided a temperature sensitive hydrogel having optical bi-stability that does not steadily consume external electrical energy produced by the method of manufacturing the hydrogel.

The temperature sensitive hydrogel according to the present invention comprises the steps of sequentially reacting the temperature sensitive monomer to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And a step of synthesizing a hydrogel having optical bistable by crosslinking the grafted macromonomer.

The hydrogel according to the present invention is characterized by having optical bistable stability due to the thermal hysteresis of cellulose.

Conventional thermosensitive hydrogels without optical bistable exhibit phase transitions at the critical solution temperatures below, and must be fixed to maintain a state of hydration / dehydration. That is, in order to maintain the dehydrated state after the phase transition during the temperature increase, the ambient temperature of the hydrogel must be maintained above the critical solution temperature below.

In detail, according to FIG. 2, the hydrogel prepared according to the present invention is stable at a transparent state because the distance between polymer chains is sufficiently far from the wavelength of light at room temperature lower than the critical solution temperature of the macromonomer so as not to scatter light passing through the hydrogel. Keep it. However, if the ambient temperature rises above the critical solution temperature below the temperature sensitive macromonomer through the temperature raising process, the polymer chains undergo a phase transition and close to each other to form aggregates. The light that passes through the hydrogel is scattered to convert the hydrogel into an opaque state. At this time, as the spacing of the cellulose derivative molecules approaches, hydrophobic conjugation occurs, even if the hydrogel temperature drops to a temperature lower than the critical solution temperature below the macromonomer, light is still scattered by the hydrophobic conjugation to maintain an opaque state. The state remains stable.

More specifically, the hydrogel prepared according to the present invention is characterized in that it has an optical bi-stability capable of maintaining a transparent state before the phase change and an opaque state after the phase change even without a continuous supply of external energy.

In addition, the hydrogel retaining opacity by hydrophobic conjugation of the cellulose derivative molecule has a reversible reaction which returns to the initial transparent state when cooled to a sufficiently low temperature (eg, 20 ° C.) to remove the aqueous conjugation. It is done.

In addition, the hydrogel according to the present invention is characterized in that the degree of phase transition, that is, the light transmittance can be adjusted according to the amount of power applied through the Peltier device attached to the inside of the smart panel and the external environment.

Thermosensitive hydrogels have a clouding point and are N -isopropylacrylamide, N -n-propylacrylamide, N , N' -dimethylacrylamide, N , N' -diethylacrylamide, methacrylic acid, 2- One or more monomers selected from the group consisting of hydroxymethacrylic acid, N -2-diethylaminoethyl acrylate may be copolymerized. The monomers are monomers capable of producing a temperature sensitive hydrogel, and monomers which do not exhibit temperature sensitivity may be partially copolymerized. Therefore, other monomers than the above-mentioned monomers may be copolymerized under the conditions of maintaining the temperature sensitivity of the hydrogel.

As temperature-sensitive hydrogels increase in ambient temperature, molecular motion becomes active, resulting in phase separation in which chains are aggregated due to hydrogen bonding between polymer chains. The temperature at which light passing through the hydrogel is scattered and opaque by the aggregated polymer chain is defined as a cloud point of the hydrogel. That is, the hydrogel used in the present invention is in an opaque state due to the phase separation phenomenon above the cloud point, and exists in a transparent state thereafter, and this state change is reversible. The cloud point can be arbitrarily adjusted according to the type or copolymerization composition of monomers constituting the temperature sensitive hydrogel.

The present invention comprises the steps of sequentially reacting the temperature sensitive monomer to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And a step of synthesizing a hydrogel having optical bistable by crosslinking the grafted macromonomer, thereby providing a smart panel comprising a temperature sensitive hydrogel.

The smart panel according to the present invention is composed of a temperature sensitive hydrogel containing a photothermal conversion material inserted between two substrates arranged at arbitrary intervals so as to face each other by at least one spacer. At this time, the hydrogel is a hydrogel containing a temperature-sensitive macromonomer according to the present invention contains a swelling liquid, and may be sealed with a sealant to prevent evaporation thereof and to fix the substrate and the spacer.

The two substrates are used as windows, and various materials can be used that are transparent and can transmit light. Preferably, the substrate may be used as a single or a composite material in a material such as glass, plastic, metal. The spacer is positioned between two substrates to control the thickness of the temperature sensitive hydrogel. In addition to the same material as the substrate, it can be used without limitation as long as it is inserted between the substrates to maintain the gap and does not undergo any chemical reaction with the temperature sensitive hydrogel. The spacing of the substrate can be arbitrarily adjusted according to the installation position, use, and the like.

The smart panel according to the present invention contains a photothermal conversion material in the temperature-sensitive hydrogel, so that the hydrogel can reach the cloud point by heat due to the photothermal conversion effect even below the cloud point. The effect is reflected in the sun protection control of the window. In addition, it can be seen that it is possible to autonomously and actively control the degree of inflow of sunlight according to the external environment, and reversibly repeat the inflow and blocking of sunlight according to the external environment without changing the performance.

The smart panel according to the present invention may further include a photothermal conversion material combined with a temperature sensitive hydrogel. The photothermal conversion material is one selected from the group consisting of graphene, graphene oxide, reduced-graphene oxide, iron oxide (II) nanoparticles, iron oxide (III) nanoparticles, gold nanoparticles, carbon nanotubes and polypyrrole nanoparticles It is preferable that it is above.

At this time, the content of the light-heat conversion material mixed in the temperature sensitive hydrogel is preferably from 0.01 to 50% by weight of the dry weight of the hydrogel. More preferably, the content of graphene oxide is 0.1 to 5% by weight of the hydrogel dry weight. If the content of graphene oxide is less than 0.01% by weight, less heat is emitted from the photothermal conversion effect, so when the temperature of the temperature-sensitive hydrogel is less than the cloud point, the cloud does not reach the cloud point and thus does not achieve the object of the present invention. It is not preferable, and if it exceeds 50% by weight, the smart window is opaque due to the concentration of graphene oxide, which is not preferable.

Smart panel of the present invention is characterized in that the temperature is adjusted according to the magnitude of the voltage and current applied, including the temperature control device and the light transmittance of the panel is adjusted.

In addition, the smart panel of the present invention is characterized in that the light transmittance can be continuously maintained even if the supply of current applied to the panel is removed by the hydrophobic bonding of the cellulose derivative molecules.

Hereinafter, the present invention will be described in detail with reference to Examples, but these Examples should not be construed as limiting the scope of the present invention.

< Example  1> Preparation of macromonomer with wide phase transition temperature range

As monomer 1 N, N '- diethyl acrylamide (N, N' -diethylacrylamide, NDEAm ) 956 mg (7.52 mmol) with the chain transfer agent is 2-aminoethane thiol (2-aminoethanethiol) 8.7 mg ( 0.22 mmol) N, N - dimethylformamide (N, N -dimethylformaide, DMF) was dissolved was added to 20 mL, the initiator 2,2'-azobisisobutyronitrile (2,2-azobis (isobutyronitrile, AIBN )) to the 2.4 mg was added to initiate free radical polymerization in a nitrogen gas atmosphere at 70 ° C.

Next, as the monomer 2 was dissolved in DMF immediately after, 10 mL at which the polymerization reaction proceeds N - isopropylacrylamide (N -isopropylacrylamide, NIPAm) 284 mg (2.51 mmol) of a syringe pump (Legato 100, KD Scientific, USA ) Was injected into the reaction vessel at a constant rate of 0.1 mL / min over 100 minutes.

Next, N as a third monomer dissolved in DMF immediately after, 10 mL of the injection end of the monomer 2-pyrrolidone and vinyl (N -vinylpyrrolidone, VP) 267 mL (2.51 mmol) using a syringe pump, 0.1 for 100 minutes Inject at a rate of mL / min.

After the injection of the monomer 3 was completed, the reaction was further proceeded for 150 minutes, put into diethyl ether, precipitated and filtered to completely remove the dissolution through vacuum drying.

In order to convert the amino-terminal group of the macromonomer with the synthesis of a vinyl group, the macromonomer and 1.2 g N - the acryloxy-succinimide (N -acryloxysuccinimide) 0.5 g In the following, 25 ℃ dissolved in 40 mL of DMF The reaction proceeded by stirring for 72 hours.

After the reaction was completed, the mixture was placed in diethyl ether, precipitated, collected by filtration, and dried in vacuo to obtain a thermosensitive macromonomer (poly (NDEAm- co- NIPAm- co- VP, PDNV) having vinyl end groups. .

< Example  2> cellulose Hydrogel  Produce

9.77 mg (0.11 mM) of PDNV of Example 1, methyl cellulose (MC) (molecular weight 14000 Da, 9.59 mg, 6.85 mM, degree of substitution: 1.5-1.9) and a crosslinking agent, N, N' -methylenebis (acrylic) Amide) ( N, N'- methylenebis (acrylamide), BisAA, 0.003 mg (0.19 mM) was dissolved in 1.0 mL of distilled water.

The precursor solution was degassed and then, under nitrogen atmosphere, 0.6 mL of 10 wt% ammonium persulfate (APS) as an initiator and N, N, N ', N' -tetramethylethylenediamine ( N, N, N ) as a polymerization accelerator. 0.3 mL of ', N' -tetramethylethyldiamine, TEMED) was added to allow free-radical polymerization. As a result, PDNV- g- MC hydrogel having a cross-linked state by grafting PDNV to MC was obtained.

< Example  3> Methyl cellulose  Cellulose with Phase Transition Temperature Controlled by Molecular Weight Hydrogel  Produce

9.77 mg (0.11 mM) of PDNV of Example 1 and 0.003 mg (0.19 mM) of BisAA, a crosslinking agent, were dissolved in 10 mL of distilled water of 9.59 mg of methyl cellulose having different molecular weights. The methyl cellulose used at this time has a molecular weight of 14000 Da, 41000 Da, 63000 Da (6.85, 2.34, 1.52 mM), respectively. The precursor solution was subjected to free radical polymerization in the same manner as in Example 2 by adding APS and TEMED under a nitrogen atmosphere.

< Example  4> Of PDNV  Phase transition temperature range is controlled according to the copolymerization ratio Hydrogel  Produce

The same method as in Example 1 synthesized PDNV, but adjusted the concentration of each monomer. The molar content of NDEAm: NIPAm: VP is 6: 3: 1, 956 mg (7.52 mmol) of NDEAm as monomer 1, 427 mg (3.77 mmol) of NIPAm as monomer 2 and VP 134 mL (1.26 mmol) as monomer 3 ) Was used. Also, PDNV was prepared using 956 mg (7.52 mmol) of NDEAm as monomer 1 and 567 mg (5.01 mmol) of NIPAm as monomer 2 such that the molar content of NDEAm: NIPAm: VP was 6: 4: 0.

9.77 mg (0.11 mM) of PDNV and 0.003 mg (0.19 mM) of a crosslinking agent were dissolved in distilled water together with methyl cellulose (molecular weight 14000 Da, 9.59 mg, 6.85 mM, degree of substitution: 1.5-1.9). . The precursor solution was prepared as a hydrogel through free radical polymerization in the same manner as in Example 2.

< Example  5> The phase transition temperature range is adjusted according to the type of monomer. Hydrogel  Produce

As monomer 1, 1.702 g (15.06 mM) of NIPAm was dissolved in 20 mL of DMF with 17.4 mg (0.22 mmol) of 2-aminoethanethiol, a chain transfer agent, and dissolved in 20 mL of DMF. Free radical polymerization was initiated under.

Next, immediately after the polymerization, 0.468 mL (4.4 mmol) of VP as monomer 2 dissolved in 10 mL of DMF was injected at a rate of 0.1 mL / min for 100 minutes using a syringe pump. Immediately after the end of the injection of monomer 2, 0.708 mg (4.4 mmol) of (2-dimethylamino) ethyl methacrylate (DMA) dissolved in 10 mL of DMF was added using a syringe pump. Inject at a rate of 0.1 mL / min for minutes. Thereafter, poly (NIPAm- co- VP- co- DMA) was obtained in the same manner as in Example 1.

<Comparative Example 1> Preparation of hydrogel with controlled phase transition temperature range not containing methyl cellulose

9.77 mg (0.11 mM) of PDNV of Example 1 and 0.003 mg (0.19 mM) of BisAA, a crosslinking agent, were dissolved in distilled water. The precursor solution was subjected to free radical polymerization in the same manner as in Example 2 by adding APS and TEMED under a nitrogen atmosphere.

Through this, PDNV hydrogel having a crosslinked state that does not contain MC was obtained.

<Analysis>

Analysis 1 Through Infrared Spectroscopy cellulose  Derivative molecules and Temperature sensitivity  Graft confirmation of macromonomers

Infrared spectroscopy was used to confirm that the PDNV vinyl group was grafted by the hydroxyl group of MC in the PDNV- g- MC hydrogels prepared in Examples 1 and 2.

Referring to FIG. 3, the spectra of MC, PDNV, and grafted PDNV- g -MC hydrogels are indicated. The characteristic absorption peaks of PDNV- g -MC hydrogels are observed at 1055 cm ^-1 and 1543 cm ^-1 , which are the absorption of the alkoxy group of the MC and the -NH group of the macromonomer, respectively. Through this, it can be seen that the PDNV is grafted to the MC bonded to, and crosslinked to form a PDNV- g -MC hydrogel.

<Analysis 2> Temperature cellulose Hydrogel  Volume change

In order to confirm the phase transition characteristics of the PDNV- g- MC hydrogel according to temperature, the swelling ratio according to the temperature of the hydrogels prepared in Examples 1 and 2 was measured and shown in FIG. Swelling ratio of the hydrogel was measured through the change in distance between the fluorescent microparticles inserted into the hydrogel. Fluorescence microparticles were observed through a fluorescence microscope (epi-fluorescence microscope, DMI-3000B, Leica, Germany). Observing the swelling ratio change through the movement of the fluorescent microparticles at the time of temperature increase can be seen that the swelling ratio of the hydrogel decreases linearly with temperature.

This is because the lower critical solution temperature is distributed over a wide temperature range by polymerizing three monomers having different lower critical solution temperatures sequentially under the influence of the temperature sensitive macromonomer (PDNV).

Referring to Figure 4, it can be seen that the swelling ratio is kept constant even if the temperature of the hydrogel is cooled to 30 ℃ after the temperature rise. This is because the distance between MC molecules is kept constant by the hydrophobic junction as the temperature rises. Hydrogels prepared in Examples 1 and 2 can be confirmed that the swelling ratio is restored to an initial state from about 29 ℃ during cooling. When it reached about 23 [deg.] C., it was completely restored to its initial state.

Through this, it can be confirmed that the PDNV- g- MC hydrogels prepared according to the present invention have bistable stability, each maintained in a stable state before and after the phase change.

<Analysis 3> Methyl cellulose  Phase transition temperature range is adjusted according to molecular weight Hydrogel  Volume change with temperature

In order to confirm the change of the phase transition temperature range of the PDNV- g- MC hydrogel having adjusted the molecular weight of methyl cellulose, the swelling ratio of the hydrogel prepared in Example 3 was measured and shown in FIG. 5. The swelling ratio of the hydrogels was observed through fluorescent microparticles and fluorescence microscopy in the same manner as in Analysis 2.

Referring to (a) of FIG. 5, the hydrogel using methyl cellulose having a molecular weight of 14000 Da linearly decreases in volume from 25 ° C. to 42 ° C. when heated, and maintains the volume up to 28 ° C. during cooling to an initial volume of 28 ° C. or lower. You can see that it recovers. On the other hand, in Figure 4 b), the hydrogel using methyl cellulose having a molecular weight of 41000 Da shows no volume change from 25 ° C. to about 30 ° C. when the temperature is started, and the volume decreases steeply from 32 ° C. At the time of cooling, it recovers to an initial swelling ratio from about 33 degreeC. Referring to (c) of FIG. 5, when the molecular weight of methyl cellulose is increased to 63000 Da, a sudden volume change occurs from about 35 ° C. Methyl cellulose is a temperature sensitive polymer exhibiting phase transition at 40-50 ° C., and from the results of FIG. 5, it can be seen that the greater the molecular weight, the more contributing to the change of phase transition temperature range when grafted with PDNV.

<Analysis 4> Of PDNV  Phase transition temperature range is controlled according to the copolymerization ratio Hydrogel  Volume change with temperature

Through Example 4, the volume change of the PDNV- g- MC hydrogel using PDNV having different copolymerization ratios was observed and shown in FIG. 6. The swelling ratio of the hydrogels was observed through fluorescent microparticles and fluorescence microscopy in the same manner as in Analysis 2.

A) of Figure 6 shows the volume change according to the temperature of the hydrogel prepared through Example 2 of the present invention. 6) shows the volume change according to the temperature of the hydrogel, in which the molar ratio of NDEAm: NIPAm: VP was adjusted to 6: 3: 1 during the preparation of PDNV prepared in Example 4. Decreasing the fraction of VP with an LCST of 40 ° C. shows that the phase transition temperature range of the hydrogel is moved to a lower temperature as a whole and the change in volume is not constant but appears as a curve. 6) it can be seen that the mole ratio of NDEAm: NIPAm: VP is 6: 4: 0, so that the phase transition curve is steeper than the result of 6: 3: 1 of FIG. .

<Analysis 5> Phase transition temperature range is adjusted according to the type of monomer Hydrogel  Volume change with temperature

By changing the type of the monomer prepared in Example 5 to observe the volume change according to the temperature of the hydrogel adjusted the phase transition temperature section is shown in Figure 7. The swelling ratio of the hydrogels was observed through fluorescent microparticles and fluorescence microscopy in the same manner as in Analysis 2.

Referring to FIG. 7, it can be seen that the poly (NIPAm- co- VP- co- DMA) hydrogel is linearly reduced in volume with temperature from 28 ° C. to 52 ° C. at elevated temperatures. This is because the LCST of DMA has a LCST higher than that of NIPAm and VP at 38-50 ° C., so that the phase transition temperature range of the hydrogel using the copolymer was moved to a high temperature. It was confirmed that the characteristics causing linear phase transition in a wide temperature range can be obtained by a method of injecting the reaction monomer at regular intervals as in Example 1 regardless of the type of monomer.

Through this, it can be seen that the phase transition temperature range of the hydrogel can be arbitrarily adjusted by the user according to the application purpose.

<Analysis 6> Volume change with temperature of hydrogel with controlled phase transition temperature range without methyl cellulose

The volume change with temperature of the PDNV hydrogel containing no methyl cellulose prepared through Comparative Example 1 was observed and shown in FIG. 8. The swelling ratio of the hydrogels was observed through fluorescent microparticles and fluorescence microscopy in the same manner as in Analysis 2.

8, it can be seen that the PNDV hydrogel gradually reaches an equilibrium after decreasing from 37 ° C. to 40 ° C. at elevated temperature. During cooling, the volume gradually increases from 36 ° C. and continues to increase to 27 ° C. before reaching equilibrium.

Compared with the temperature change of the PNDV-g-MC hydrogel containing methyl cellulose of Figure 3 shows a large difference, the volume change at elevated temperature, the hydrogel containing methyl cellulose is a linear volume from 24 ℃ to 43 ℃ Whereas hydrogel without methyl cellulose does not appear linear. It is grafted with PDNV as a thermosensitive polymer with a critical solution temperature of about 50 ° C. below the methyl cellulose to move the critical solution temperature below the hydrogel to a higher temperature.

The PDNV hydrogel without hydrophobic conjugation of methyl cellulose shows a small thermal hysteresis of about 1 ° C. upon cooling and recovers to its original volume.

< Experimental Example >

< Experimental Example  1> optical Bistable  Production of smart panel to have

9 illustrates a manufacturing process of a smart panel according to an embodiment of the present invention. 9, PDNV 123.3 mg (28.8 mM) and MC (molecular weight 14000 Da, 0.12 mg, 8.64 mM, substitution degree: 1.5-1.9) and 0.19 mg (1.2 mM) of BisAA as a crosslinking agent of Example 1 were 1.0. It was dissolved in mL of distilled water.

The precursor solution was degassed, and then free-radical polymerization was performed by adding 6.0 mL of initiator 10 wt% APS and 3.0 mL of polymerization accelerator TEMED under nitrogen atmosphere.

The disclosed precursor solution was then immediately inserted through capillary action between two transparent substrates separated by a spacer 140 mm thick. At this time, the transparent substrate was treated with [3- (methacryloxy) -propyl] -trimethoxysilane, which is an adhesion promoter, to improve adhesion with the hydrogel. The hydrogel inserted between the transparent substrates was polymerized under nitrogen atmosphere for 1 hour. After the polymerization was completed, the edge of the transparent substrate was prevented from evaporation of the solvent using butyl rubber. Peltier modules were attached to both ends of the edge of the panel to control the light transmittance of the smart panel using electrical energy. Through this, a smart panel having optical bi-stability was produced.

< Experimental Example  2> Observation of light transmittance according to current of manufactured smart panel

The Peltier module attached to the smart panel manufactured in Experimental Example 1 can be cooled and heated depending on the direction of the applied voltage. In addition, by controlling the amount of current, the cooling and heating temperature can be adjusted, which allows the light transmittance of the PDNV- g- MC hydrogel to be inserted into the smart panel.

Referring to FIG. 10, the change in light transmittance was observed through a photograph while controlling a current from 0.0 A to 0.8 A while applying a constant voltage of 12 V. FIG. Since no current is supplied at 0.0 A, the initial transparent state is maintained, and when the current is increased to 0.2 A, the light transmittance of the smart panel is gradually decreased.

As the strength of the current increases, the Peltier module's temperature rises and the transmittance of the smart panel decreases gradually, and when 0.8 A is applied, the smart panel becomes completely opaque. Through this, it can be seen that the temperature of the Peltier module is adjusted according to the strength of the current, and the light transmittance is controlled while the temperature of the smart panel is increased by the temperature of the Peltier module.

< Experimental Example  3> Optical of the manufactured smart panel Bistable  observe

 The hydrogel inserted into the smart panel according to the present invention has bistable stability to maintain a stable state before and after the phase transition by the cellulose derivative molecules. Therefore, even without an external continuous energy supply, it is possible to stably maintain the phase transition state, that is, it is possible to stably maintain the light transmittance changed through the phase transition.

Referring to FIG. 11, the smart panel manufactured through Experimental Example 2 can be seen that the transmittance is adjusted when a current of 0.4 A is applied in the state of applying a constant voltage of 12 V. At this time, even if the smart panel is cooled by removing the applied current, the light transmittance is maintained by the hydrophobic bonding of the cellulose derivative molecules. Here, if a current of 0.8 A is applied while applying a reverse voltage of 12 V, the temperature of the smart panel decreases to about 20 ° C and returns to the initial transparent state.

When the temperature is raised by applying a current of 0.8 A while applying a constant voltage of 12 V to the smart panel in a transparent state, the state becomes completely opaque. In addition, even if the current is removed, it can be seen that the transmittance is maintained due to the hydrophobic bonding by MC of the PDNV- g- MC hydrogel. In addition, if a current of 0.8 A is applied again with a reverse voltage of 12 V, the initial state of the transparent state is also restored.

Accordingly, a hydrogel may be prepared by grafting a temperature sensitive macromonomer including a vinyl group using a hydroxyl group of a cellulose derivative molecule, and the manufactured hydrogel may be linearly formed in a wide temperature range by a wide bottom critical solution temperature section of the macromonomer. It can be confirmed that it causes phase transition.

In addition, it can be confirmed that the hydrophobic conjugation of the cellulose derivative molecule has a bistable stability to maintain the state after the phase transition even without constant energy supply. Cooling to a low temperature to remove the hydrophobic junction can be seen to return to the initial volume or clear state.

As mentioned above, although this invention was demonstrated by the limited Example, this invention is not limited by this and is described below by the person of ordinary skill in the art, and the following. Of course, various modifications and variations are possible within the scope of the claims.

Claims (11)

Reacting the temperature sensitive monomers sequentially to form a temperature sensitive macromonomer;
Grafting the temperature sensitive macromonomer to a cellulose derivative; And
Synthesizing a hydrogel having optical bistable by cross-linking the grafted macromonomer; a method for producing a temperature-sensitive hydrogel comprising a.
The method of claim 1,
The temperature-sensitive monomer is N - isopropyl acrylamide, N -n- propyl acrylamide, N, N '- dimethyl acrylamide, N, N' - diethyl acrylamide, methacrylic acid, 2-hydroxyethyl methacrylate And N -2-diethylaminoethyl acrylate in which at least one monomer selected from the group consisting of copolymerized copolymers is prepared.
The method of claim 2,
The method of producing a temperature-sensitive hydrogel, characterized in that the addition of the temperature sensitive monomer is made at a constant rate of 0.01ml / min to 10ml / min.
The method of claim 1,
Forming the temperature-sensitive macromonomer is a method for producing a temperature-sensitive hydrogel, characterized in that at least two or more different temperature-sensitive monomers including a chain transfer agent is copolymerized.
The method of claim 1,
The cellulose derivative is a method of producing a temperature-sensitive hydrogel, characterized in that the glucose molecule is repeatedly bonded to the hydroxyl group of the glucose molecule is substituted with a vinyl group.
The method of claim 1,
The crosslinking agent used in the crosslinking is N , N , -methylenebisacrylamide, diethylene glycol diacrylate and dimethacrylate, ethylene glycol diacrylate and dimethacrylate, tetra (ethylene glycol) diacrylate, 1 , 6-hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate, and poly (ethylene glycol) diacrylate at least one selected from the group consisting of a method for producing a temperature-sensitive hydrogel.
Reacting the temperature sensitive monomers sequentially to form a temperature sensitive macromonomer; Grafting the temperature sensitive macromonomer to a cellulose derivative; And synthesizing a hydrogel having optical bistable by crosslinking the grafted macromonomer.
Smart panel comprising a temperature sensitive hydrogel according to claim 7.
The method of claim 8,
Smart panel, characterized in that the content of the light-heat conversion material bonded to the temperature sensitive hydrogel is 0.01 to 50% by weight of the dry weight of the hydrogel.
The method of claim 8,
Smart panel, characterized in that the temperature is adjusted according to the magnitude of the voltage and current applied, including the temperature control device and the transmittance of the panel.
The method of claim 8,
Smart panel, characterized in that the light transmittance can be maintained continuously even if the supply of the current applied to the panel by the hydrophobic bonding of the cellulose derivative molecules.

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